how it is different from old computer organisation, changes from vaccum tubes to transistorsInformation on the changes in modern computer hardware?
Earliest devices
The Chinese were frustrated with counting on their fingers, so they invented the Abacus.
The Chinese were frustrated with counting on their fingers, so they invented the Abacus.
Humanity has used devices to aid in computation for millennia. One example is a device for establishing equality by weight: the classic scales. Another is simple enumeration: the checkered cloths of the counting houses served as simple data structures for enumerating stacks of coins, by weight. A more arithmetic-oriented machine is the abacus. One of the earliest machines of this type was the Chinese abacus.
Gears are at the heart of mechanical devices like the Curta calculator.
Gears are at the heart of mechanical devices like the Curta calculator.
The Antikythera Mechanism, discovered in the early 20th century, was discovered in the wreck of a Greek vessel believed to have sunk in 65BC. The mechanism is believed to have been used in preparing calendars for religious observance and for planting and harvesting. It had 30 or more bronze gears and a pin-and-slot device connecting two gears varied the depiction of lunar movement.[1] This technology was lost, however, and over 1,600 years would elapse before similarly complex computing machines were again created.
In 1623 Wilhelm Schickard built the first mechanical calculator and thus became the father of the computing era. Since his machine used techniques such as cogs and gears first developed for clocks, it was also called a 'calculating clock'. It was put to practical use by his friend Johannes Kepler, who revolutionized astronomy.
Machines by Blaise Pascal (the Pascaline, 1642)[1] and Gottfried Wilhelm von Leibniz (1671) followed. Around 1820, Charles Xavier Thomas created the first successful, mass-produced mechanical calculator, the Thomas Arithmometer, that could add, subtract, multiply, and divide. It was mainly based on Leibniz's work. Mechanical calculators, like the base-ten addiator, the comptometer, the Monroe, the Curta and the Addo-X remained in use until the 1970s.
Mechanical calculator from 1914
Mechanical calculator from 1914
Leibniz also described the binary numeral system, a central ingredient of all modern computers. However, up to the 1940s, many subsequent designs (including Charles Babbage's machines of the 1800s and even ENIAC of 1945) were based on the harder-to-implement decimal system.
The slide rule, a basic mechanical calculator, facilitates multiplication and division.
The slide rule, a basic mechanical calculator, facilitates multiplication and division.
John Napier noted that multiplication and division of numbers can be performed by addition and subtraction, respectively, of logarithms of those numbers. Since these real numbers can be represented as distances or intervals on a line, the slide rule allowed multiplication and division operations to be carried significantly faster than was previously possible. Slide rules were used by generations of engineers and other mathematically inclined professional workers, until the invention of the pocket calculator. The engineers in the Apollo program to send a man to the moon made many of their calculations on slide rules, which were accurate to 3 or 4 significant figures.
While producing the first logarithmic tables Napier needed to perform many multiplications and it was at this point that he designed Napier's bones.
[edit] 1801: punched card technology
Punch card system of a music machine. Also referred to as Book music, a one-stop European medium for organs
Punch card system of a music machine. Also referred to as Book music, a one-stop European medium for organs
Punch card system of a 19th Century loom
Punch card system of a 19th Century loom
As early as 1725 Basile Bouchon used a perforated paper loop in a loom to establish the pattern to be reproduced on cloth, and in 1726 his co-worker Jean-Baptiste Falcon improved on his design by using perforated paper cards attached to one another, which made it easier to change the program quickly. The Bouchon-Falcon loom was semi-automatic and required manual feed of the program.
In 1801, Joseph-Marie Jacquard developed a loom in which the pattern being woven was controlled by punched cards. The series of cards could be changed without changing the mechanical design of the loom. This was a landmark point in programmability.
Herman Hollerith invented a tabulating machine using punch cards in the 1880s.
Herman Hollerith invented a tabulating machine using punch cards in the 1880s.
In 1833, Charles Babbage moved on from developing his difference engine to developing a more complete design, the analytical engine, which would draw directly on Jacquard's punch cards for its programming.[2].
In 1890, the United States Census Bureau used punch cards and sorting machines designed by Herman Hollerith, to handle the flood of data from the decennial census mandated by the Constitution. Hollerith's company eventually became the core of IBM. IBM developed punch card technology into a powerful tool for business data-processing and produced an extensive line of specialized unit record equipment. By 1950, the IBM card had become ubiquitous in industry and government. The warning printed on most cards intended for circulation as documents (checks, for example), ';Do not fold, spindle or mutilate,'; became a motto for the post-World War II era.[2]
Leslie Comrie's articles on punch card methods and W.J. Eckert's publication of Punched Card Methods in Scientific Computation in 1940, described techniques which were sufficiently advanced to solve differential equations, perform multiplication and division using floating point representations, all on punched cards and unit record machines. The Thomas J. Watson Astronomical Computing Bureau, Columbia University performed astronomical calculations representing the state of the art in computing.
In many computer installations, punched cards were used until (and after) the end of the 1970s. For example, science and engineering students at many universities around the world would submit their programming assignments to the local computer centre in the form of a stack of cards, one card per program line, and then had to wait for the program to be queued for processing, compiled, and executed. In due course a printout of any results, marked with the submitter's identification, would be placed in an output tray outside the computer center. In many cases these results would comprise solely a printout of error messages regarding program syntax etc., necessitating another edit-compile-run cycle.[3]
Punched cards are still used and manufactured in the current century, and their distinctive dimensions (and 80-column capacity) can still be recognized in forms, records, and programs around the world.
[edit] 1835–1900s: first programmable machines
The defining feature of a ';universal computer'; is programmability, which allows the computer to emulate any other calculating machine by changing a stored sequence of instructions.
In 1835 Charles Babbage described his analytical engine. It was the plan of a general-purpose programmable computer, employing punch cards for input and a steam engine for power. One crucial invention was to use gears for the function served by the beads of an abacus. In a real sense, computers all contain automatic abacuses (technically called the ALU or floating-point unit).
His initial idea was to use punch-cards to control a machine that could calculate and print logarithmic tables with huge precision (a specific purpose machine). Babbage's idea soon developed into a general-purpose programmable computer, his analytical engine.
While his design was sound and the plans were probably correct, or at least debuggable, the project was slowed by various problems. Babbage was a difficult man to work with and argued with anyone who didn't respect his ideas. All the parts for his machine had to be made by hand. Small errors in each item can sometimes sum up to large discrepancies in a machine with thousands of parts, which required these parts to be much better than the usual tolerances needed at the time. The project dissolved in disputes with the artisan who built parts and was ended with the depletion of government funding.
Ada Lovelace, Lord Byron's daughter, translated and added notes to the ';Sketch of the Analytical Engine'; by Federico Luigi, Conte Menabrea. She has become closely associated with Babbage. Some claim she is the world's first computer programmer, however this claim and the value of her other contributions are disputed by many.
A reconstruction of the Difference Engine II, an earlier, more limited design, has been operational since 1991 at the London Science Museum. With a few trivial changes, it works as Babbage designed it and shows that Babbage was right in theory.
The museum used computer-operated machine tools to construct the necessary parts, following tolerances which a machinist of the period would have been able to achieve. Some feel that the technology of the time was unable to produce parts of sufficient precision, though this appears to be false. The failure of Babbage to complete the engine can be chiefly attributed to difficulties not only related to politics and financing, but also to his desire to develop an increasingly sophisticated computer. Today, many in the computer field term this sort of obsession creeping featuritis.
Following in the footsteps of Babbage, although unaware of his earlier work, was Percy Ludgate, an accountant from Dublin, Ireland. He independently designed a programmable mechanical computer, which he described in a work that was published in 1909.
[edit] 1930s–1960s: desktop calculators
By the 1900s earlier mechanical calculators, cash registers, accounting machines, and so on were redesigned to use electric motors, with gear position as the representation for the state of a variable. Companies like Friden, Marchant and Monroe made desktop mechanical calculators from the 1930s that could add, subtract, multiply and divide. The word ';computer'; was a job title assigned to people who used these calculators to perform mathematical calculations. During the Manhattan project, future Nobel laureate Richard Feynman was the supervisor of the roomful of human computers, many of them women mathematicians, who understood the differential equations which were being solved for the war effort. Even the renowned Stanisław Ulam was pressed into service to translate the mathematics into computable approximations for the hydrogen bomb, after the war.
In 1948, the Curta was introduced. This was a small, portable, mechanical calculator that was about the size of a pepper grinder. Over time, during the 1950s and 1960s a variety of different brands of mechanical calculator appeared on the market.
The first all-electronic desktop calculator was the British ANITA Mk.VII, which used a Nixie tube display and 177 subminiature thyratron tubes. In June 1963, Friden introduced the four-function EC-130. It had an all-transistor design, 13-digit capacity on a 5-inch CRT, and introduced reverse Polish notation (RPN) to the calculator market at a price of $2200. The model EC-132 added square root and reciprocal functions. In 1965, Wang Laboratories produced the LOCI-2, a 10-digit transistorized desktop calculator that used a Nixie tube display and could compute logarithms.
With development of the integrated circuits and microprocessors, the expensive, large calculators were replaced with smaller electronic devices.
[edit] Pre-1940 analog computers
Before World War II, mechanical and electrical analog computers were considered the 'state of the art', and many thought they were the future of computing. Analog computers use continuously varying amounts of physical quantities, such as voltages or currents, or the rotational speed of shafts, to represent the quantities being processed. An ingenious example of such a machine was the Water integrator built in 1936. Unlike modern digital computers, analog computers are not very flexible, and need to be reconfigured (i.e., reprogrammed) manually to switch them from working on one problem to another. Analog computers had an advantage over early digital computers in that they could be used to solve complex problems while the earliest attempts at digital computers were quite limited. But as digital computers have become faster and used larger memory (e.g., RAM or internal store), they have almost entirely displaced analog computers, and computer programming, or coding has arisen as another human profession.
Since computers were rare in this era, the solutions were often hard-coded into paper forms such as graphs and nomograms, which could then allow analog solutions to problems, such as the distribution of pressures and temperatures in a heating system.
Some of the most widely deployed analog computers included devices for aiming weapons, such as the Norden bombsight and Fire-control systems for naval vessels. Some of these stayed in use for decades after WWII. One example is the Mark I Fire Control Computer, deployed by the United States Navy on a variety of ships from destroyers to battleships.
The art of analog computing reached its zenith with the differential analyzer, invented by Vannevar Bush in 1930. Fewer than a dozen of these devices were ever built; the most powerful was constructed at the University of Pennsylvania's Moore School of Electrical Engineering, where the ENIAC was built. Digital electronic computers like the ENIAC spelled the end for most analog computing machines, but hybrid analog computers, controlled by digital electronics, remained in substantial use into the 1950s and 1960s, and later in some specialized applications.
[edit] Early digital computers
The era of modern computing began with a flurry of development before and during World War II, as electronic circuits, relays, capacitors, and vacuum tubes replaced mechanical equivalents and digital calculations replaced analog calculations. Machines such as the Atanasoff-Berry Computer, the Z3, the Colossus, and ENIAC were built by hand using circuits containing relays or valves (vacuum tubes), and often used punched cards or punched paper tape for input and as the main (non-volatile) storage medium.
In later systems, temporary or working storage was provided by acoustic delay lines (which use the propagation time of sound through a medium such as liquid mercury or wire to briefly store data) or by Williams tubes (which use the ability of a television picture tube to store and retrieve data). By 1954, magnetic core memory was rapidly displacing most other forms of temporary storage, and dominated the field through the mid-1970s.
In this era, a number of different machines were produced with steadily advancing capabilities. At the beginning of this period, nothing remotely resembling a modern computer existed, except in the long-lost plans of Charles Babbage and the mathematical musings of Alan Turing and others. At the end of the era, devices like the EDSAC had been built, and are universally agreed to be digital computers. Defining a single point in the series as the ';first computer'; misses many subtleties.
Alan Turing's 1936 paper proved enormously influential in computing and computer science in two ways. Its main purpose was to prove that there were problems (namely the halting problem) that could not be solved by any sequential process. In doing so, Turing provided a definition of a universal computer, a construct that came to be called a Turing machine, a purely theoretical device that formalizes the concept of algorithm execution, replacing Kurt Gödel's more cumbersome universal language based on arithmetics. Except for the limitations imposed by their finite memory stores, modern computers are said to be Turing-complete, which is to say, they have algorithm execution capability equivalent to a universal Turing machine. This limited type of Turing completeness is sometimes viewed as a threshold capability separating general-purpose computers from their special-purpose predecessors.
For a computing machine to be a practical general-purpose computer, there must be some convenient read-write mechanism, punched tape, for example. For full versatility, the Von Neumann architecture uses the same memory both to store programs and data; virtually all contemporary computers use this architecture (or some variant). While it is theoretically possible to implement a full computer entirely mechanically (as Babbage's design showed), electronics made possible the speed and later the miniaturization that characterize modern computers.
There were three parallel streams of computer development in the World War II era, and two were either largely ignored or were deliberately kept secret. The first was the German work of Konrad Zuse. The second was the secret development of the Colossus computer in the UK. Neither of these had much influence on the various computing projects in the United States. After the war, British and American computing researchers cooperated on some of the most important steps towards a practical computing device.
[edit] Konrad Zuse's Z-series
A reproduction of Zuse's Z1 computer.
A reproduction of Zuse's Z1 computer.
Working in isolation in Germany, Konrad Zuse started construction in 1936 of his first Z-series calculators featuring memory and (initially limited) programmability. Zuse's purely mechanical, but already binary Z1, finished in 1938, never worked reliably due to problems with the precision of parts.
Zuse's subsequent machine, the Z3, was finished in 1941. It was based on telephone relays and did work satisfactorily. The Z3 thus became the first functional program-controlled computer. In many ways it was quite similar to modern machines, pioneering numerous advances, such as floating point numbers. Replacement of the hard-to-implement decimal system (used in Charles Babbage's earlier design) by the simpler binary system meant that Zuse's machines were easier to build and potentially more reliable, given the technologies available at that time. This is sometimes viewed as the main reason why Zuse succeeded where Babbage failed.
Programs were fed into Z3 on punched films. Conditional jumps were missing, but since the 1990s it has been proved theoretically that Z3 was still a universal computer (ignoring its physical storage size limitations). In two 1936 patent applications, Konrad Zuse also anticipated that machine instructions could be stored in the same storage used for data - the key insight of what became known as the Von Neumann architecture and was first implemented in the later British EDSAC design (1949). Zuse also claimed to have designed the first higher-level programming language, (Plankalkül), in 1945 (which was published in 1948) although it was implemented for the first time in 2000 by the Free University of Berlin -- five years after Zuse died.
Zuse suffered setbacks during World War II when some of his machines were destroyed in the course of Allied bombing campaigns. Apparently his work remained largely unknown to engineers in the UK and US until much later, although at least IBM was aware of it as it financed his post-war startup company in 1946 in return for an option on Zuse's patents.
[edit] American developments
In 1937, Claude Shannon produced his master's thesis at MIT that implemented Boolean algebra using electronic relays and switches for the first time in history. Entitled A Symbolic Analysis of Relay and Switching Circuits, Shannon's thesis essentially founded practical digital circuit design.
In November of 1937, George Stibitz, then working at Bell Labs, completed a relay-based computer he dubbed the ';Model K'; (for ';kitchen';, where he had assembled it), which calculated using binary addition. Bell Labs authorized a full research program in late 1938 with Stibitz at the helm. Their Complex Number Calculator, completed January 8, 1940, was able to calculate complex numbers. In a demonstration to the American Mathematical Society conference at Dartmouth College on September 11, 1940, Stibitz was able to send the Complex Number Calculator remote commands over telephone lines by a teletype. It was the first computing machine ever used remotely, in this case over a phone line. Some participants in the conference who witnessed the demonstration were John Von Neumann, John Mauchly, and Norbert Wiener, who wrote about it in his memoirs.
In 1938 John Vincent Atanasoff and Clifford E. Berry of Iowa State University developed the Atanasoff-Berry Computer (ABC), a special purpose electronic computer for solving systems of linear equations. (The original goal was to solve 29 simultaneous equations of 29 unknowns each, but due to errors in the card puncher mechanism the completed machine could only solve a few equations.) The design used over 300 vacuum tubes for high speed and employed capacitors fixed in a mechanically rotating drum for memory. Though the ABC machine was not programmable, it was the first modern computer in several other respects, including the first to use binary math and electronic circuits. ENIAC co-inventor John Mauchly visited the ABC while it was still under construction in June 1941, and its influence on the design of the later ENIAC machine is a matter of contention among computer historians. The ABC was largely forgotten until it became the focus of the lawsuit Honeywell v. Sperry Rand, the ruling of which invalidated the ENIAC patent (and several others) as, among many reasons, having been anticipated by the Iowa work.
In 1939, development began at IBM's Endicott laboratories on the Harvard Mark I. Known officially as the Automatic Sequence Controlled Calculator, the Mark I was a general purpose electro-mechanical computer built with IBM financing and with assistance from IBM personnel, under the direction of Harvard mathematician Howard Aiken. Its design was influenced by Babbage's Analytical Engine, using decimal arithmetic and storage wheels and rotary switches in addition to electromagnetic relays. It was programmable via punched paper tape, and contained several calculation units working in parallel. Later versions contained several paper tape readers and the machine could switch between readers based on a condition. Nevertheless, the machine was not quite Turing-complete. The Mark I was moved to Harvard University and began operation in May 1944.
[edit] Colossus
Colossus was used to break German ciphers during World War II.
Colossus was used to break German ciphers during World War II.
During World War II, the British at Bletchley Park achieved a number of successes at breaking encrypted German military communications. The German encryption machine, Enigma, was attacked with the help of electro-mechanical machines called bombes. The bombe, designed by Alan Turing and Gordon Welchman, after the Polish cryptographic bomba (1938), ruled out possible Enigma settings by performing chains of logical deductions implemented electrically. Most possibilities led to a contradiction, and the few remaining could be tested by hand.
The Germans also developed a series of teleprinter encryption systems, quite different from Enigma. The Lorenz SZ 40/42 machine was used for high-level Army communications, termed ';Tunny'; by the British. The first intercepts of Lorenz messages began in 1941. As part of an attack on Tunny, Professor Max Newman and his colleagues helped specify the Colossus. The Mk I Colossus was built in 11 months by Tommy Flowers and his colleagues at the Post Office Research Station at Dollis Hill in London and then shipped to Bletchley Park.
Colossus was the first totally electronic computing device. The Colossus used a large number of valves (vacuum tubes). It had paper-tape input and was capable of being configured to perform a variety of boolean logical operations on its data, but it was not Turing-complete. Nine Mk II Colossi were built (The Mk I was converted to a Mk II making ten machines in total). Details of their existence, design, and use were kept secret well into the 1970s. Winston Churchill personally issued an order for their destruction into pieces no larger than a man's hand. Due to this secrecy the Colossi were not included in many histories of computing. A reconstructed copy of one of the Colossus machines is now on display at Bletchley Park.
[edit] ENIAC
ENIAC performed ballistics trajectory calculations with 160 kW of power.
ENIAC performed ballistics trajectory calculations with 160 kW of power.
The US-built ENIAC (Electronic Numerical Integrator and Computer), often called the first electronic general-purpose computer, publicly validated the use of electronics for large-scale computing. This was crucial for the development of modern computing, initially because of the enormous speed advantage, but ultimately because of the potential for miniaturization. Built under the direction of John Mauchly and J. Presper Eckert, it was 1,000 times faster than its contemporaries. ENIAC's development and construction lasted from 1943 to full operation at the end of 1945. When its design was proposed, many researchers believed that the thousands of delicate valves (i.e. vacuum tubes) would burn out often enough that the ENIAC would be so frequently down for repairs as to be useless. It was, however, capable of up to thousands of operations per second for hours at a time between valve failures.
ENIAC was unambiguously a Turing-complete device. A ';program'; on the ENIAC, however, was defined by the states of its patch cables and switches, a far cry from the stored program electronic machines that evolved from it. At the time, however, unaided calculation was seen as enough of a triumph to view the solution of a single problem as the object of a program. (Improvements completed in 1948 made it possible to execute stored programs set in function table memory, which made programming less a ';one-off'; effort, and more systematic.)
Adapting ideas developed by Eckert and Mauchly after recognizing the limitations of ENIAC, John von Neumann wrote a widely-circulated report describing a computer design (the EDVAC design) in which the programs and working data were both stored in a single, unified store. This basic design, which became known as the von Neumann architecture, would serve as the basis for the development of the first really flexible, general-purpose digital computers.
[edit] Summary
Defining characteristics of five first operative digital computers Computer Nation Shown working Binary Electronic Programmable Turing
complete
Zuse Z3 Germany May 1941 Yes No By punched film stock Yes (1998)
Atanasoff-Berry Computer USA Summer 1941 Yes Yes No No
Colossus computer UK 1943 Yes Yes Partially, by rewiring No
Harvard Mark I/IBM ASCC USA 1944 No No By punched paper tape No
ENIAC USA 1944 No Yes Partially, by rewiring Yes
1948 No Yes By Function Table ROM Yes
[edit] First generation von Neumann machine and the other works
';Baby'; at the Museum of Science and Industry in Manchester (MSIM), England
';Baby'; at the Museum of Science and Industry in Manchester (MSIM), England
The first working von Neumann machine was the Manchester ';Baby'; or Small-Scale Experimental Machine, built at the University of Manchester in 1948; it was followed in 1949 by the Manchester Mark I computer which functioned as a complete system using the Williams tube and magnetic drum for memory, and also introduced index registers. The other contender for the title ';first digital stored program computer'; had been EDSAC, designed and constructed at the University of Cambridge. Operational less than one year after the Manchester ';Baby';, it was also capable of tackling real problems. EDSAC was actually inspired by plans for EDVAC (Electronic Discrete Variable Automatic Computer), the successor to ENIAC; these plans were already in place by the time ENIAC was successfully operational. Unlike ENIAC, which used parallel processing, EDVAC used a single processing unit. This design was simpler and was the first to be implemented in each succeeding wave of miniaturization, and increased reliability. Some view Manchester Mark I / EDSAC / EDVAC as the ';Eves'; from which nearly all current computers derive their architecture.
The first universal programmable computer in continental Europe was created by a team of scientists under direction of Sergei Alekseyevich Lebedev from Kiev Institute of Electrotechnology, Soviet Union (now Ukraine). The computer MESM (МЭСМ, Small Electronic Calculating Machine) became operational in 1950. It had about 6,000 vacuum tubes and consumed 25 kW of power. It could perform approximately 3,000 operations per second. Another early machine was CSIRAC, an Australian design that ran its first test program in 1949.
In October 1947, the directors of J. Lyons %26amp; Company, a British catering company famous for its teashops but with strong interests in new office management techniques, decided to take an active role in promoting the commercial development of computers. By 1951 the LEO I computer was operational and ran the world's first regular routine office computer job.
Manchester University's machine became the prototype for the Ferranti Mark I. The first Ferranti Mark I machine was delivered to the University in February, 1951 and at least nine others were sold between 1951 and 1957.
UNIVAC I, above, the first commercial electronic computer in the United States (third in the world), achieved 1900 operations per second in a smaller and more efficient package than ENIAC.
UNIVAC I, above, the first commercial electronic computer in the United States (third in the world), achieved 1900 operations per second in a smaller and more efficient package than ENIAC.
In June 1951, the UNIVAC I (Universal Automatic Computer) was delivered to the U.S. Census Bureau. Although manufactured by Remington Rand, the machine often was mistakenly referred to as the ';IBM UNIVAC';. Remington Rand eventually sold 46 machines at more than $1 million each. UNIVAC was the first 'mass produced' computer; all predecessors had been 'one-off' units. It used 5,200 vacuum tubes and consumed 125 kW of power. It used a mercury delay line capable of storing 1,000 words of 11 decimal digits plus sign (72-bit words) for memory. Unlike IBM machines it was not equipped with a punch card reader but 1930s style metal magnetic tape input, making it incompatible with some existing commercial data stores. High speed punched paper tape and modern-style magnetic tapes were used for input/output by other computers of the era.
In November 1951, the J. Lyons company began weekly operation of a bakery valuations job on the LEO (Lyons Electronic Office). This was the first business application to go live on a stored program computer.
In 1952, IBM publicly announced the IBM 701 Electronic Data Processing Machine, the first in its successful 700/7000 series and its first IBM mainframe computer. The IBM 704, introduced in 1954, used magnetic core memory, which became the standard for large machines. The first implemented high-level general purpose programming language, Fortran, was also being developed at IBM for the 704 during 1955 and 1956 and released in early 1957. (Konrad Zuse's 1945 design of the high-level language Plankalkül was not implemented at that time.)
IBM introduced a smaller, more affordable computer in 1954 that proved very popular. The IBM 650 weighed over 900 kg, the attached power supply weighed around 1350 kg and both were held in separate cabinets of roughly 1.5 meters by 0.9 meters by 1.8 meters. It cost $500,000 or could be leased for $3,500 a month. Its drum memory was originally only 2000 ten-digit words, and required arcane programming for efficient computing. Memory limitations such as this were to dominate programming for decades afterward, until the evolution of a programming model which was more sympathetic to software development.
In 1955, Maurice Wilkes invented microprogramming, which was later widely used in the CPUs and floating-point units of mainframe and other computers, such as the IBM 360 series. Microprogramming allows the base instruction set to be defined or extended by built-in programs (now sometimes called firmware, microcode, or millicode).
In 1956, IBM sold its first magnetic disk system, RAMAC (Random Access Method of Accounting and Control). It used 50 24-inch metal disks, with 100 tracks per side. It could store 5 megabytes of data and cost $10,000 per megabyte. (As of 2006, magnetic storage, in the form of hard disks, costs less than one tenth of a cent per megabyte).
[edit] Post-1960: third generation and beyond
Main article: History of computing hardware (1960s-present)
The microscopic integrated circuit, above, combined many hundreds of transistors into one unit for fabrication.
The microscopic integrated circuit, above, combined many hundreds of transistors into one unit for fabrication.
The explosion in the use of computers began with 'Third Generation' computers. These relied on Jack St. Clair Kilby's and Robert Noyce's independent invention of the integrated circuit (or microchip), which later led to the invention of the microprocessor, by Ted Hoff and Federico Faggin at Intel.
During the 1960s there was considerable overlap between second and third generation technologies. As late as 1975, Sperry Univac continued the manufacture of second-generation machines such as the UNIVAC 494.
The microprocessor led to the development of the microcomputer, small, low-cost computers that could be owned by individuals and small businesses. Microcomputers, the first of which appeared in the 1970s, became ubiquitous in the 1980s and beyond. Steve Wozniak, co-founder of Apple Computer, is credited with developing the first mass-market home computers. However, his first computer, the Apple I, came out some time after the KIM-1 and Altair 8800, and the first Apple computer with graphic and sound capabilities came out well after the Commodore PET. Computing has evolved with microcomputer architectures, with features added from their larger brethren, now dominant in most market segments.
An indication of the rapidity of development of this field can be inferred by the Burks, Goldstein, von Neuman, seminal article, documented in the Datamation September-October 1962 issue, which was written, as a preliminary version 15 years earlier. By the time that anyone had time to write anything down, it was obsolete.
Monday, November 22, 2010
How to change address (URL) at You Tube?
How to change address (URL) at You Tube?How to change address (URL) at You Tube?
Your own URL you mean? In short, you can't.How to change address (URL) at You Tube?
u mean like change the url of ur own personal channel? u cant cuz its too complicated for the ppl to use it. so its just youtube.com/ (ur username)
Can I change my YouTube username? (URL)
Currently, you cannot change your username?there is simply too much information tied to each account. You may, however, sign up for a new account with the username that you desire.
--------------------------------------?br>
can i change my video URL?
no you also are not able to change the URL of your video
-Jake
Your own URL you mean? In short, you can't.How to change address (URL) at You Tube?
u mean like change the url of ur own personal channel? u cant cuz its too complicated for the ppl to use it. so its just youtube.com/ (ur username)
Can I change my YouTube username? (URL)
Currently, you cannot change your username?there is simply too much information tied to each account. You may, however, sign up for a new account with the username that you desire.
--------------------------------------?br>
can i change my video URL?
no you also are not able to change the URL of your video
-Jake
How do you prevent bed sores with someone who's paralyzed?
I have an identical twin sister who was in an accident and became paralyzed from the neck down. She's completely helpless and we have to change her diapers and tube feed her and suction her lungs, etc...We're 17 and I take care of her a lot. Just recently my mother and I noticed she's getting a type of red sore on her upper thigh. Does anyone who's knowledgeable know how you would properly treat a bed sore and prevent further sores and rashes?How do you prevent bed sores with someone who's paralyzed?
Turning her to prevent pressure sores is very important, as they develop anywhere the internal skeletal structure places pressure on the skin, such as the heels, backs of the thighs, buttocks and coccyx, under the shoulderblades, and behind the head. A dietary supplement such as Prosource may be recommended to provide her with extra protein to help heal new sores, and careful bathing must be done, with areas susceptible to pressure sores coated with a cream such as A/D ointment, Calazime, or Greer's Goo.
Anytime urine or fecal matter remains on the skin it produces acids and toxins that will continue skin breakdown and must be continually kept cleaned off the skin.
Now if the sore is on her upper thigh, that is not a pressure sore. It is likely a skin infection, perhaps staph aureus. It should be checked by a doctor, but standard treatments can include topical antibiotic creams or internal antibiotics. In any case I would consult a doctor.How do you prevent bed sores with someone who's paralyzed?
Your poor sister has to be moved all the time, about four times a day and the bed sores have to be addressed right away with a cream the doc can give you, Rub it in to prevent bed sores. Once they start your in trouble for infection as her immune system is already in jeopardy.
She should be turned constantly and move so they don't get irritated. There are county courses for this if you check. You can also get compensation from Social security for her care.
Hi! Every time you change the diaper try to a give her a warm towel wash on the areas then pat dry it properly and dust some talcum powder allover it. Hope it will help, if not please do consult your doctor . I have a son 17months old he had also some similar rashes because of long time diapers when i tried these process on him it was really gone within few days.Will pray for your sister to recover soon and best of luck to and your family! You people seems to be very Strong keep it up that's how a real family stands together. God bless you all!
Thank you!
Apply nivea cream
My late wife died due to a brain tumour and the last month of her life was spent lying on her back in our bed. I changed the bed linen daily and she was regularly given a sponge bath, but did not need to regularly change her position because she was on a water bed.
As you may know, a water mattress supports the body's weight evenly, so there are no points where circulation is impaired or the skin is irritated because of pressure.
The nurses who visited on a daily basis to check on how we were doing commented on the fact that there was never any sign of pressure sores developing.
There are, however, several downsides of water mattresses. Firstly, they are a bit ';squidgy';, so changing the bed linen requires learning a new technique. Another disadvantage I can see in your case is that standard water-bed platforms are quite low, which would cause problems for those caring for your sister. Also, they cannot be partly elevated ?raising the head or foot end of the bed ?which I suspect may be something which your sister finds enjoyable.
Contrary to popular myth, they are not so heavy that they are likely to fall through the floor, nor is damage to the mattress likely to result in a catastrophic flood. They are also heated and generally just very comfortable to lie on, so that might be something your sister finds nice.
I'm not sure if a water-bed would a solution to some ?or any ?of the challenges facing you and your family, but you might seek advice on flotation mattresses from the medical experts who are assisting you.
These can be a big problem, and lead to major infection. The first thing is to keep an eye out - so good job on that!
The key is to not let her sit or lay in one position too long. If she uses a wheelchair at all, get some type of gel cushion for the seat, and make sure to shift her around every couple hours. I'm sure you fidget when you sit for a long time - it's because your body needs to adjust. She can't do that for herself, so you'll have to do it for her.
If she's in bed most of the time, the same thing applies. She should spend time lying on her back and both sides, no more than a couple hours between position changes. Use pillows to prop her on one side or the other.
As for the sore that's already started, you might want to have her doctor take a look, just to make sure it's not a major issue already. The doctor may want you to use some kind of prescription cream or ointment. If not, you can use something as simple as A%26amp;D ointment to help heal it and prevent more.
If you need any more help, feel free to send me a message.
Turning her to prevent pressure sores is very important, as they develop anywhere the internal skeletal structure places pressure on the skin, such as the heels, backs of the thighs, buttocks and coccyx, under the shoulderblades, and behind the head. A dietary supplement such as Prosource may be recommended to provide her with extra protein to help heal new sores, and careful bathing must be done, with areas susceptible to pressure sores coated with a cream such as A/D ointment, Calazime, or Greer's Goo.
Anytime urine or fecal matter remains on the skin it produces acids and toxins that will continue skin breakdown and must be continually kept cleaned off the skin.
Now if the sore is on her upper thigh, that is not a pressure sore. It is likely a skin infection, perhaps staph aureus. It should be checked by a doctor, but standard treatments can include topical antibiotic creams or internal antibiotics. In any case I would consult a doctor.How do you prevent bed sores with someone who's paralyzed?
Your poor sister has to be moved all the time, about four times a day and the bed sores have to be addressed right away with a cream the doc can give you, Rub it in to prevent bed sores. Once they start your in trouble for infection as her immune system is already in jeopardy.
She should be turned constantly and move so they don't get irritated. There are county courses for this if you check. You can also get compensation from Social security for her care.
Hi! Every time you change the diaper try to a give her a warm towel wash on the areas then pat dry it properly and dust some talcum powder allover it. Hope it will help, if not please do consult your doctor . I have a son 17months old he had also some similar rashes because of long time diapers when i tried these process on him it was really gone within few days.Will pray for your sister to recover soon and best of luck to and your family! You people seems to be very Strong keep it up that's how a real family stands together. God bless you all!
Thank you!
Apply nivea cream
My late wife died due to a brain tumour and the last month of her life was spent lying on her back in our bed. I changed the bed linen daily and she was regularly given a sponge bath, but did not need to regularly change her position because she was on a water bed.
As you may know, a water mattress supports the body's weight evenly, so there are no points where circulation is impaired or the skin is irritated because of pressure.
The nurses who visited on a daily basis to check on how we were doing commented on the fact that there was never any sign of pressure sores developing.
There are, however, several downsides of water mattresses. Firstly, they are a bit ';squidgy';, so changing the bed linen requires learning a new technique. Another disadvantage I can see in your case is that standard water-bed platforms are quite low, which would cause problems for those caring for your sister. Also, they cannot be partly elevated ?raising the head or foot end of the bed ?which I suspect may be something which your sister finds enjoyable.
Contrary to popular myth, they are not so heavy that they are likely to fall through the floor, nor is damage to the mattress likely to result in a catastrophic flood. They are also heated and generally just very comfortable to lie on, so that might be something your sister finds nice.
I'm not sure if a water-bed would a solution to some ?or any ?of the challenges facing you and your family, but you might seek advice on flotation mattresses from the medical experts who are assisting you.
These can be a big problem, and lead to major infection. The first thing is to keep an eye out - so good job on that!
The key is to not let her sit or lay in one position too long. If she uses a wheelchair at all, get some type of gel cushion for the seat, and make sure to shift her around every couple hours. I'm sure you fidget when you sit for a long time - it's because your body needs to adjust. She can't do that for herself, so you'll have to do it for her.
If she's in bed most of the time, the same thing applies. She should spend time lying on her back and both sides, no more than a couple hours between position changes. Use pillows to prop her on one side or the other.
As for the sore that's already started, you might want to have her doctor take a look, just to make sure it's not a major issue already. The doctor may want you to use some kind of prescription cream or ointment. If not, you can use something as simple as A%26amp;D ointment to help heal it and prevent more.
If you need any more help, feel free to send me a message.
How do you prevent someone who's paralyzed from getting bed sores?
I have an identical twin sister who became paralyzed from the neck down not that long ago. She's helpless and we have to change her diapers and tube feed her and suction her lungs, etc...We're 17 and I take care of her a lot. My mother and I noticed she's getting a type of red sore on her upper thigh. Does anyone who's knowledgeable know how you properly treat a bed sore and prevent further sores and diaper rashes?How do you prevent someone who's paralyzed from getting bed sores?
Bed sores are due to continous pressure in that area. So,keep changing the positions.If bed sores are secondarily infected then treat with antibiotics.How do you prevent someone who's paralyzed from getting bed sores?
To prevent bed sores, you have to move and rotate her daily, so she's not constantly laying in the same position. Ask your doctor about some creams that you could use for treating the sores, and the diaper rash. good luck.
Repositioning is definitely very important as is a quality incontinence product that will draw the moisture away and keep her skin clean and dry. Tranquility offers a superior product that will meet her needs. The super absorbent polymers not only will keep her skin dry but they also neutralize the urine pH creating a healthier skin environment, reducing bacterial growth, and risks of urinary tract infections. They are available online at Dignity With Diapers and delivered discreetly to your home. Read the testimonials and they will assure you that Tranquility is a superior product highly recommended by it's users.
Bed sores are due to continous pressure in that area. So,keep changing the positions.If bed sores are secondarily infected then treat with antibiotics.How do you prevent someone who's paralyzed from getting bed sores?
To prevent bed sores, you have to move and rotate her daily, so she's not constantly laying in the same position. Ask your doctor about some creams that you could use for treating the sores, and the diaper rash. good luck.
Repositioning is definitely very important as is a quality incontinence product that will draw the moisture away and keep her skin clean and dry. Tranquility offers a superior product that will meet her needs. The super absorbent polymers not only will keep her skin dry but they also neutralize the urine pH creating a healthier skin environment, reducing bacterial growth, and risks of urinary tract infections. They are available online at Dignity With Diapers and delivered discreetly to your home. Read the testimonials and they will assure you that Tranquility is a superior product highly recommended by it's users.
How do you prevent bed sores with someone who's paralyzed?
I have an identical twin sister who was in an accident and became paralyzed from the neck down. She's completely helpless and we have to change her diapers and tube feed her and suction her lungs, etc...We're 17 and I take care of her a lot. Just recently my mother and I noticed she's getting a type of red sore on her upper thigh. Does anyone who's knowledgeable know how you would properly treat a bed sore and prevent further sores and rashes?How do you prevent bed sores with someone who's paralyzed?
First, let me say, I AM SO TERRIBLY SORRY TO READ WHAT HAPPENED TO YOUR TWIN. I have done home health care in the past and the best thing to do is reposition her as much as possible and buy as many pillows as you can. Remember, when propping legs, butt, arms, hips, thighs up with pillows it takes the weight off specific areas that cause the pressure points to turn into bed sores. You can take the weight off different parts of her legs and butt just by moving the pillows under her legs in different places. Also propping her on her sides by using pillows will help a lot.
Another thing to always remember is continue to treat your sister as though she is still the same even though she has a disability now. Wash her hair and style it for her, paint her nails, do her makeup, spray her with her favorite perfume, dress her as cute as possible. The key to keeping someone from becoming too depressed in this situation is to try to keep the focus off of them being the patient so much and more on the focus of her being your sister and friend.
I would say go to a home health care store and pick things out that will help her. Rent her favorite movies, and most importantly, be her friend. DONT LET HER DISABILITY PUT A DISTANCE BETWEEN THE TWO OF YOU. She is still your sister and even better your twin. Be there for her. Love her alotHow do you prevent bed sores with someone who's paralyzed?
Awww, I'm sorry to hear that. You should be turning her every few hours or so.. changing her position should help with this. Keep up the good work, It takes someone special to do what you're doing.
Im so sorry to hear that.My neighbor is paralyzed too and she use a little hard bed and she turns around every 3 hours.I don't know how does the hard bed work but it seems that it helps her spine and back
I know how you feel, I've done this twice before with loved ones.
Like the others said, repositioning is key. We did it every 3 hours, and that staved them off, and there is a special ';skin-gard'; skincare product (ask your home nurse or health care provider about it) which can help prevent the formation of bedsores from hotspots like the one you described. Until then, keeping it clean and away from any rubbing or friction is very important.
If bedsores do develop (which I hate to say they likely will despite constant vigilance...usually somewhere you can't immediately see) keep them clean, dry and dress them with guaze and an antibacterial ointment.
Best of luck... my prayers are with you.
I'm sorry to hear.
Get her a really soft matress or consult a doctor, they will tell you what to do.
wow im so sorry thats intense. Thats rough, and I pray the best for you.
http://www.ehow.com/how_2179273_sores-he
This gives a list of ways to prevent bed sores.
Im not an expert but rotate her like every hour or so [=
good luck and stay strong.
';when im afraid i'll trust in thee';-pslams 56:3 both you and your sister are is great hands and god is always there.
Bed sores are a frustrating problem in paralyzed persons. They are caused by the constant pressure of the skin against the bed, and pressure points over the buttocks, upper thigh, shoulders and even the occiput of the head are frequently involved.
Obviously you are turning your sister frequently. Try to keep the skin clean and dry to prevent irritation that makes pressure sores more likely. A special air mattress with many small cells is helpful. An air pump at the bedside alternately fills and releases air in the various cells so that pressure is not always on one spot. Donut cushions surrounding irritated areas help, too.
Do you have a visiting nurse or other therapist come on frequent occasions? Often your insurance will cover such a service. These persons can be very helpful in offering other suggestions.
You can get pads that are like air bubbles that change the pressure points under her body, you may also want to try lambs wool. You can put it on her (once the current sores are healed) at the spots that seem to be the problem. Also make sure she is dry as the moisture can intensify the irritation of the skin. Make sure the current sores are clean %26amp; free from infection. Usually releaveing the pressure point (where the body rubs on a surface, such as the sheets) will allow them to heal naturally, depending on how bad they have gotten. I'm not 100% sure but if memory serves me correctly satin or silk sheets are easier on the skin but also expensive %26amp; harder to clean. I think the lambs wool would be a better solution. Do you have home health care aides where you live? Around here some of the major drugstores have sections that are dedicated to caring for people at home %26amp; may be of help to you.I hope that things get easier for you (once you learn all of the tricks, it will get easier %26amp; not so overwhelming)
ABislamic heaven using lip plumping gloss
First, let me say, I AM SO TERRIBLY SORRY TO READ WHAT HAPPENED TO YOUR TWIN. I have done home health care in the past and the best thing to do is reposition her as much as possible and buy as many pillows as you can. Remember, when propping legs, butt, arms, hips, thighs up with pillows it takes the weight off specific areas that cause the pressure points to turn into bed sores. You can take the weight off different parts of her legs and butt just by moving the pillows under her legs in different places. Also propping her on her sides by using pillows will help a lot.
Another thing to always remember is continue to treat your sister as though she is still the same even though she has a disability now. Wash her hair and style it for her, paint her nails, do her makeup, spray her with her favorite perfume, dress her as cute as possible. The key to keeping someone from becoming too depressed in this situation is to try to keep the focus off of them being the patient so much and more on the focus of her being your sister and friend.
I would say go to a home health care store and pick things out that will help her. Rent her favorite movies, and most importantly, be her friend. DONT LET HER DISABILITY PUT A DISTANCE BETWEEN THE TWO OF YOU. She is still your sister and even better your twin. Be there for her. Love her alotHow do you prevent bed sores with someone who's paralyzed?
Awww, I'm sorry to hear that. You should be turning her every few hours or so.. changing her position should help with this. Keep up the good work, It takes someone special to do what you're doing.
Im so sorry to hear that.My neighbor is paralyzed too and she use a little hard bed and she turns around every 3 hours.I don't know how does the hard bed work but it seems that it helps her spine and back
I know how you feel, I've done this twice before with loved ones.
Like the others said, repositioning is key. We did it every 3 hours, and that staved them off, and there is a special ';skin-gard'; skincare product (ask your home nurse or health care provider about it) which can help prevent the formation of bedsores from hotspots like the one you described. Until then, keeping it clean and away from any rubbing or friction is very important.
If bedsores do develop (which I hate to say they likely will despite constant vigilance...usually somewhere you can't immediately see) keep them clean, dry and dress them with guaze and an antibacterial ointment.
Best of luck... my prayers are with you.
I'm sorry to hear.
Get her a really soft matress or consult a doctor, they will tell you what to do.
wow im so sorry thats intense. Thats rough, and I pray the best for you.
http://www.ehow.com/how_2179273_sores-he
This gives a list of ways to prevent bed sores.
Im not an expert but rotate her like every hour or so [=
good luck and stay strong.
';when im afraid i'll trust in thee';-pslams 56:3 both you and your sister are is great hands and god is always there.
Bed sores are a frustrating problem in paralyzed persons. They are caused by the constant pressure of the skin against the bed, and pressure points over the buttocks, upper thigh, shoulders and even the occiput of the head are frequently involved.
Obviously you are turning your sister frequently. Try to keep the skin clean and dry to prevent irritation that makes pressure sores more likely. A special air mattress with many small cells is helpful. An air pump at the bedside alternately fills and releases air in the various cells so that pressure is not always on one spot. Donut cushions surrounding irritated areas help, too.
Do you have a visiting nurse or other therapist come on frequent occasions? Often your insurance will cover such a service. These persons can be very helpful in offering other suggestions.
You can get pads that are like air bubbles that change the pressure points under her body, you may also want to try lambs wool. You can put it on her (once the current sores are healed) at the spots that seem to be the problem. Also make sure she is dry as the moisture can intensify the irritation of the skin. Make sure the current sores are clean %26amp; free from infection. Usually releaveing the pressure point (where the body rubs on a surface, such as the sheets) will allow them to heal naturally, depending on how bad they have gotten. I'm not 100% sure but if memory serves me correctly satin or silk sheets are easier on the skin but also expensive %26amp; harder to clean. I think the lambs wool would be a better solution. Do you have home health care aides where you live? Around here some of the major drugstores have sections that are dedicated to caring for people at home %26amp; may be of help to you.I hope that things get easier for you (once you learn all of the tricks, it will get easier %26amp; not so overwhelming)
AB
Did you have any changes after you had your tubes tied (tubal ligation) ?
I am curious if there are any women out there that had a lot of changes in how they felt after their surgery? I have had a lot of post tubal ligation syndrome symptoms. Would like to know symptoms someone else has had.
ThanksDid you have any changes after you had your tubes tied (tubal ligation) ?
I had my surgery the day after Christmas 2006 but I also had what is called a Uterine Ablation. The only side effect I seem to experience it what my Gyno calls ';Phantom'; cramps. Not quite like menstrual period cramps, a bit milder. My cramping could be an effect from the other procedure though.Did you have any changes after you had your tubes tied (tubal ligation) ?
sorry but i don't know
hope u luck:D
ThanksDid you have any changes after you had your tubes tied (tubal ligation) ?
I had my surgery the day after Christmas 2006 but I also had what is called a Uterine Ablation. The only side effect I seem to experience it what my Gyno calls ';Phantom'; cramps. Not quite like menstrual period cramps, a bit milder. My cramping could be an effect from the other procedure though.Did you have any changes after you had your tubes tied (tubal ligation) ?
sorry but i don't know
hope u luck:D
How the hell do i change my profile pic on you tube?
i want to change my profile pic the very top box on the left but it shows an image from one of the videos how do i change it? its driving me mad!How the hell do i change my profile pic on you tube?
u have to push account tab which is stood after ur profile name top page than u can change ur pic
u have to push account tab which is stood after ur profile name top page than u can change ur pic
Can BART really Go up to 100MPH (Miles per hour)?
rode the BARt under the transbay tube a few days ago. it feels like it is going very fast. i dont know how fast, but when you ever ride bart, it feels like it is going very fast. i sat in the front before, and looked inside where the bart driver sits and operates the train. near him i saw two flashing numbers. the one that i saw was in green. the one in green saids 00. but then when the train moves, the number changes from 00 to 30-40. then when it goes in the transbay tube, it changed from 30-80.im guessing the numbers tell how fast the train is traveling? do you think im right? if not, tell me why i am not right.Can BART really Go up to 100MPH (Miles per hour)?
BART can do OVER 100mph,but they don't go that fast due to safety/scheduling issues.Can BART really Go up to 100MPH (Miles per hour)?
Sounds right to me. Digital speed recorders are everywhere.
According to BART themselves, maximum speed is 80mph. So the answer to your question, I would assume would be right.
BART can do OVER 100mph,but they don't go that fast due to safety/scheduling issues.Can BART really Go up to 100MPH (Miles per hour)?
Sounds right to me. Digital speed recorders are everywhere.
According to BART themselves, maximum speed is 80mph. So the answer to your question, I would assume would be right.
How many outfits do you have to make in sims 3 for your character?
im going to get sims 3 pretty soon (it's coming in the mail)and i wanted to know how many outfits im going to need to make becuase in the videos on you-tube the sims change really fast. I could see that a box came up that had a choice of outfits and then after they clicked on one the sim would change very quickly but still... how many outfits do you have to make on sims 3?How many outfits do you have to make in sims 3 for your character?
I'm not exactly sure what the question is that you are asking but you don't *have* to make outfits. The game comes preloaded with many different combinations. You select one (the part you are saying goes by too fast) and your sim will change into it. You have the option to modify it with a button that looks like a color palette but you don't have to.
I'm not exactly sure what the question is that you are asking but you don't *have* to make outfits. The game comes preloaded with many different combinations. You select one (the part you are saying goes by too fast) and your sim will change into it. You have the option to modify it with a button that looks like a color palette but you don't have to.
How do i change my video screen on you tube?
when i try to change my video screen on you tube it says copy and paste the embed code when you are done. but what do i paste it on ?and no i am not computer dumb it is just this one thing that confuses me. sorry for shouting.How do i change my video screen on you tube?
You don't seem to understand.
The custom player is for embedding in OTHER websites. Have you ever gone to a blog and it had a player embedded in the page? That's an embedded player.
You can't change the player for Youtube.com. Only on other sites.
Custom players exist because the default Youtube color scheme might not match up well with a lot of websites. So you can give it custom colors if you want. But again, it will NOT work on Youtube.com.
And it won't work in forums, either, because forums generally do not support user HTML. Often, only the makers of websites can embed a player in them.
_____
鈭扐DAMANT 脝VE!
http://img20.imageshack.us/img20/4016/imself employed person social security tax
You don't seem to understand.
The custom player is for embedding in OTHER websites. Have you ever gone to a blog and it had a player embedded in the page? That's an embedded player.
You can't change the player for Youtube.com. Only on other sites.
Custom players exist because the default Youtube color scheme might not match up well with a lot of websites. So you can give it custom colors if you want. But again, it will NOT work on Youtube.com.
And it won't work in forums, either, because forums generally do not support user HTML. Often, only the makers of websites can embed a player in them.
_____
鈭扐DAMANT 脝VE!
http://img20.imageshack.us/img20/4016/im
Jacobsen Snowblower wheel removal?
How do I remove the wheels to change tires and inner tubes?
The pins came out fine but the wheels appear to be rusted to the axle. I applied penetrating oil but no use. Is the axle just round and held in place by the pins or is there a groove the wheel slots onto?. I have no manual, it is a very old machine but runs well.Jacobsen Snowblower wheel removal?
I would try using a puller. Usually on these older machines the wheels were just held in by that pin, usually with a washer as well to avoid wearing into the wheel.
The pins came out fine but the wheels appear to be rusted to the axle. I applied penetrating oil but no use. Is the axle just round and held in place by the pins or is there a groove the wheel slots onto?. I have no manual, it is a very old machine but runs well.Jacobsen Snowblower wheel removal?
I would try using a puller. Usually on these older machines the wheels were just held in by that pin, usually with a washer as well to avoid wearing into the wheel.
How does the size of tube effect the pitch in wind chimes?
i know that you can change how long the tube is and that will change the pitch but i want to know how that will help the pitch.....like how does the change in size of the tube help to change the pitch???How does the size of tube effect the pitch in wind chimes?
The fundamental pitch is based on two basic factors. The mass that is swinging back and forth and the spring stiffness that turns the motion around and sends it the other way. Longer tubes are less stiff and have more mass, so have lower pitches. Shorter tubes have less mass and are stiffer, so produce higher pitches. The mass is proportional to the length, but the stiffness changes as the third power of length. I think the frequency is roughly proportional to the square root of (stiffness divided by mass)
That means that a tube that is half as long as an otherwise similar tube has half the mass, and 8 times the stiffness, for times the resonant frequency of the short tube is about 4 times higher than the one twice as long. Remember that this only works for tubes of the same material, diameter and wall thickness. And only applies to the lowest resonance, not the higher order vibrating modes.
--
Regards,
John PopelishHow does the size of tube effect the pitch in wind chimes?
If you shorten the tube it will have a higher pitch. The vibrating tube will emit a shorter wavelength from a shorter tube.
Also if you are starting with untried tubes the diameter and the thickness of the tube will make a difference.
The fundamental pitch is based on two basic factors. The mass that is swinging back and forth and the spring stiffness that turns the motion around and sends it the other way. Longer tubes are less stiff and have more mass, so have lower pitches. Shorter tubes have less mass and are stiffer, so produce higher pitches. The mass is proportional to the length, but the stiffness changes as the third power of length. I think the frequency is roughly proportional to the square root of (stiffness divided by mass)
That means that a tube that is half as long as an otherwise similar tube has half the mass, and 8 times the stiffness, for times the resonant frequency of the short tube is about 4 times higher than the one twice as long. Remember that this only works for tubes of the same material, diameter and wall thickness. And only applies to the lowest resonance, not the higher order vibrating modes.
--
Regards,
John PopelishHow does the size of tube effect the pitch in wind chimes?
If you shorten the tube it will have a higher pitch. The vibrating tube will emit a shorter wavelength from a shorter tube.
Also if you are starting with untried tubes the diameter and the thickness of the tube will make a difference.
Does any one know how to change your account picture on you tube?
i want to change my pic on my account but i don't know how when i click on the picture it does nothing so please help me!Does any one know how to change your account picture on you tube?
http://youtube-answers.blogspot.com/2008Does any one know how to change your account picture on you tube?
1- go to youtube.com
2- login into your account
3- go to http://www.youtube.com/account
4- you will find under your picture a link (change)
5- click on change a a window will open to brows your computer and upload your new picture
6- save changes
http://youtube-answers.blogspot.com/2008Does any one know how to change your account picture on you tube?
1- go to youtube.com
2- login into your account
3- go to http://www.youtube.com/account
4- you will find under your picture a link (change)
5- click on change a a window will open to brows your computer and upload your new picture
6- save changes
How can i optimize and increase the heat rejection and decrease the coil surface of air cooled condenser?
what should i do to decrease the coil surface of the condenser coil in air cooled condenser unit ? what parameter should i change? material of tube? diameter of tube? material fin? arrangement of coils? what is the best arrangement of condenser coil in air cooled condenser unit? flat or v-type ?How can i optimize and increase the heat rejection and decrease the coil surface of air cooled condenser?
What is this condenser's service? Refrigerant, steam, other? Do you need any sub-cooling.
Materials for the tubes or fins have very little to do with the over all heat transfer rate. Air flow rate and velocity inside the tube have a bigger impact.
If you do not need any sub-cooling, then having a configuration that will get the condensed liquid out of the condenser so more surface is exposed to the condensing process is important.
One important thing that is overlooked many times is air recirculation. Having a forced draft arrangement where the fans push the air across the condenser seems at first to be the most economical arrangement but in fact an induced draft arrangement where the air is pulled across the tubes and then discharged by the fans minimizes an air recirculation and actually results in better performance. You should note that most air conditioning condensers use this principle.How can i optimize and increase the heat rejection and decrease the coil surface of air cooled condenser?
Well ,you can increase heat rejection by increasing the resistsnce which inturn can be done by increasing the length.
Introduction
Refrigeration is technology which makes a major contribution to humanity in many ways including food preservation, control of indoor air quality, gas liquefaction, industrial process control, production of food and drink and computer cooling. Without refrigeration, modern life would be impossible. About 15% of the world’s electricity is used to drive refrigerating and air-conditioning systems. Inefficient use of energy is a waste of valuable resource and contributes to global warming. Most of the global warming effect of refrigerating systems comes from generating energy to drive them. Only a small proportion comes from the release of certain refrigerants. This informatory note describes how the efficiency of refrigerating systems can be maximized thereby minimizing their global warming impact.
Fundamentals
Refrigeration is the science of making heat flow “uphill” from low to high temperatures. A refrigeration system extracts heat from the substance being refrigerated (cold reservoir) and rejects it to the ambient at a higher temperature (hot reservoir) as indicated in Figure 1. This is analogous to the pumping of water to an elevated storage tank. The energy consumption of a refrigerator is roughly proportional to rate of heat extraction (amount of water pumped) and to the temperature lift through which the heat is raised (height water is pumped).
The energy efficiency of a refrigeration system is usually expressed as a Coefficient of Performance (COP) which is the ratio of the heat extraction rate to the rate of energy use.
Whatever type of refrigerating system is being used, it is fundamental to minimize the required heat extraction and to keep the difference between TC (condensing temperature) and T0 (evaporating temperature) as small as possible. Minimizing heat extraction is done by insulating the refrigerated room and low-temperature parts of the refrigeration system, minimizing ambient air infiltration (e.g. door openings and leakage) and reducing energy use in refrigerated applications (e.g. fans and forklifts). Reducing (TC – T0) is done by maximizing condenser and evaporator heat transfer performance and minimizing refrigerant pressure drops in suction and discharge pipelines.
Description of a Vapour Compression Refrigeration System
The standard vapour compression refrigeration system consists of a refrigerant in a closed circuit comprising a compressor, a condenser, an expansion device, an evaporator and interconnecting piping (Figure 2). In the condenser, compressed refrigerant vapour at high pressure is condensed at high temperature by heat transfer to the surroundings. The high-pressure refrigerant liquid is reduced to a low pressure at the expansion valve. At low pressure, the refrigerant will evaporate at a low temperature enabling it to extract heat from the substance to be cooled. To complete the cycle, the low pressure refrigerant vapour exiting the evaporator is compressed to high pressure by the compressor. The total heat rejected in the condenser is the sum of the heat extracted plus the compressor energy use.
Figure 2. Schematic of a Simple Vapour Compression Refrigeration System
Loss of refrigerant from the circuit would have a very detrimental effect on the reliability of the system, so great care is taken to make refrigerating systems as leak-tight as possible. Individual domestic refrigerators, of which there are more than one billion, each contains a very small amount of refrigerant. Such systems are expected to run for more than 20 years without addition of refrigerant. The global warming effect of such refrigerators is significant but nearly all of it is caused by carbon dioxide produced when the electricity to run the refrigerator is generated.
Effect of System Components on Efficiency
Refrigerant
Very few substances have properties appropriate for a refrigerant and, of these, few have stood the test of time and continue to be used as refrigerants. Figure 3 shows some of the substances that have been used as refrigerants and how their use has varied over time.
Figure 3. Typical Refrigerants and Their Historical Use
There is no ideal refrigerant. Selection of a refrigerant is a compromise between many factors including ease of manufacture, cost, toxicity, flammability, environmental impact, corrosiveness and thermodynamic properties as well as energy efficiency. A key characteristic is the pressure/temperature relationship. In general, for energy efficiency it is desirable for the refrigerant critical point (temperature above which the refrigerant cannot condense) to be high compared with the heat extraction and rejection temperatures.
Good transport and heat transfer properties are also important for energy efficiency as they reduce running costs and allow smaller temperature differences to be employed in evaporators and condensers and hence smaller overall temperature lifts. In general, refrigerants of low molecular weight and low viscosity will have the best properties.
Compressor
Compressors will lose efficiency if the temperature lift is higher than necessary and they will also lose efficiency if droplets of refrigerant liquid are present in the suction vapour or if the suction vapour becomes too hot. Compressor maintenance, where possible, and the preservation of lubricant quality are important to retain energy efficiency. For some compressor types (particularly screw and centrifugal), their part-load energy efficiency performance is poor compared with at full load, so sustained part-loaded operation should be avoided. Variable speed drive technology and improved control systems can minimize the energy penalty but increase capital costs.
Condenser
To keep refrigerant heat rejection temperatures as low as possible, condenser heat transfer rates should be maximized and the cooling medium temperature minimized. Evaporative condensers are often the most efficient because they reject heat to the wet-bulb temperature of the ambient air. For instance, humid air at 25°C and 60% relative humidity has a wet-bulb temperature of 16°C. However, they require careful maintenance to avoid Legionella contamination. Water-cooled condensers combined with cooling towers also approach ambient wet-bulb temperature but there is an additional temperature difference to drive heat from the refrigerant into the water, so refrigerant heat rejection temperature is generally higher. Water use can be excessive if a cooling tower is not used. Air-cooled condensers are usually the least efficient method as they reject heat to the air dry-bulb temperature, which is generally significantly higher than wet-bulb or water temperature. However, for small systems they are commonly used because they are cheap, simple and require little maintenance.
It is important to keep all types of condenser clean and free from fouling. Condensers rejecting heat to atmosphere must be allowed plenty of fresh air and protected against any tendency for the air to re-circulate back to the condenser inlet. Systems that operate with refrigerant suction pressures less than atmospheric (e.g. low temperature ammonia or air-conditioning with HCFC-123) should use purgers to remove non-condensables from the refrigerant.
Expansion devices
Many expansion devices require significant pressure difference to allow proper operation. Therefore condensing pressure is often maintained at artificially high levels, even at low ambient temperatures. The biggest culprit in this respect is the conventional thermostatic expansion valve which is often selected because of its very low cost. One solution is to use electronically controlled expansion valves.
Evaporators
As for condensers, evaporators should be designed to operate at minimum economic temperature difference so that the refrigerant heat extraction temperature can be as high as possible for a given substance temperature. Increasing heat extraction temperature also reduces the size of the compressor required.
As well as evaporator size, aspects such as refrigerant distribution, circuiting and velocity, use of enhanced surfaces, air speeds (for air coolers) can all significantly affect energy efficiency. Air coolers that operate at temperatures below freezing must be defrosted regularly to restore performance. Electric defrost is simple but is least efficient and therefore only suitable for small systems. Electric defrost has to be paid for at least twice, to put the electric heat into the cooler and to take it out again. Water defrost, hot gas defrost, and defrost by the circulation of warm fluid through the cooler, are all potentially more efficient. However, whatever the system, it is important to optimize the frequency and duration of defrost to avoid unnecessary defrosting.
Interconnecting piping
Efficiency can be reduced if interconnecting piping is of the wrong size or is arranged in ways that cause unnecessary pressure drop or inhibit oil return (e.g. excessive bends and fitting).
Importance of controls
A refrigeration system with well-designed components will not operate efficiently unless the components are correctly matched and controlled. Energy efficiency has not always been the prime consideration when selecting effective controls. If possible, the following control options should be avoided to maximize energy efficiency:
– slide valve unloading of over-sized screw compressors;
– hot gas bypass of compressors;
– throttling valves between evaporators and compressors;
– evaporator control by starving refrigerant supply;
– too frequent defrosts;
– condenser head pressure controls except when necessary.
Conclusion
Improving the energy efficiency of refrigeration systems is not difficult and should be encouraged because of the environmental benefits. It often involves a trade-off between initial costs and on-going operating costs. There are many situations where economics motivate the equipment supplier to provide the cheapest solution, especially if the supplier does not have to pay for the running costs of the system. Standards should be set for energy efficiency for all types of refrigerating system. Governments should legislate to ensure that suppliers are penalized for supplying systems that do not reach acceptable standards of efficiency and to ensure that users of efficient systems benefit by more than the resulting reduction in running costs. If this were done, it is reasonable to suppose that the energy consumption of refrigerating systems could be reduced by at least 20% in the short term. An objective of 30-50% reduction — depending on applications — by 2020 is a goal which could be achieved.
This Informatory Note was prepared by S. Forbes Pearson, winner of the IIR Gustav Lorentzen Medal awarded at the 21st IIR International Congress of Refrigeration in Washington DC in August 2003. It was reviewed by 24 experts worldwide.
The International Institute of Refrigeration (IIR) is an intergovernmental organization comprising 61 Member Countries representing over 80% of global population.
The IIR's mission is to promote knowledge and disseminate information on refrigeration technology and all its applications in order to address today's major issues, including food safety, protection of the environment and development of the least developed countries.
The IIR provides a wide range of services: organization of conferences, congresses, workshops and training courses, a database (Fridoc) containing 70 000 references, several publications (journals, manuals, technical books, conference proceedings, informatory notes), and a Web site providing a wide range of information (www.iifiir.org).
Technical Note on Refrigerating Technologies
Ice Slurry: a Promising Technology
For centuries, ice has been considered as effective storage material for temperatures around 0°C. Using ice can reduce the size of a water storage tank by a factor of two to ten, depending on the temperature range used for operating the system. The reason for the high energy density is the latent heat of phase change. For a pure substance, under constant pressure, at the freezing temperature, a large amount of energy is required to build up a regular crystalline structure, which leads to the solid phase. In the opposite process of melting, the crystal is destroyed and energy released at the same temperature, now called the melting temperature. For temperatures other than 0°C, other materials that exhibit a change of phase, phase-change materials (PCM), can be used. In technical applications, mixtures are the most used. They show a temperature glide (continuous transition) in the enthalpy function during the phase change.
If a PCM is finely dispersed in a carrier fluid, a phase-change slurry is obtained. The particles need to be stable and should not lead to high stratification effects in the system, caused by the buoyancy force. Phase-change slurries may be micro-emulsions, shape-stabilized paraffins, clathrates, microencapsulated phase-change slurries, etc.1 In April 2003, in Switzerland, an international conference and business forum on the new fields of PCM and energy storage based on these materials was organized.2 In this type of energy storage, PCMs – which have a high thermal energy density and stable temperature due to the phase change – are also used for the transport of cold or heat. Ice slurry is the oldest and most commonly used substance in the phase-change slurries group.
This technical note briefly highlights the state of the art of this promising technology.
Definitions
In early times, to cool their food, the Romans used naturally occurring ice slurries, e.g. snow-water mixtures, crushed ice, flake ice, etc. Last century, ice slurries were created artificially. Initially, these were basically water with large ice particles with a characteristic diameter of one to several centimetres and were mainly used to cool coal and silver or gold mines. The production of fine-crystalline ice slurries then allowed the technique to be applied in small-scale systems, e.g. for the cooling of display cabinets in supermarkets (see Figure 1).
It is difficult to define “ice slurries”. Ice slurries can be classified using the following definitions3:
Definition 1: An ice slurry consists of solid ice particles in a fluid forming a suspension with two phases.
Definition 2: A fine-crystalline ice slurry is a substance comprising ice particles with an average (characteristic) diameter which is equal to or smaller than 1 mm.
Definition 2 is a little arbitrary, but still very useful. This technical note only addresses fine-crystalline ice slurries, produced for example with mechanical scraper-type ice-slurry generators. With this method, the ice particles created have a characteristic diameter of approximately 200 mm.
Application in refrigeration systems and environmental benefits
Experience has demonstrated that conventional direct evaporation systems are usually low-cost and are technically very reliable. However, they use the same fluid – the refrigerant – for “production” and “transport” of cold from the central refrigeration unit to the end users (e.g. display cabinets). As a result, these systems contain large masses of refrigerant and, in the case of permanent or accidental leakage, may lead to high losses with drastic consequences for the environment. Furthermore, high system charges of refrigerants lead to higher costs, because new replacements of CFCs and HCFCs are several times more expensive.
In indirect systems, the production of cold and its transport are separated. Cold is transferred in a heat exchanger from the primary to the secondary circuit. Indirect systems facilitate the use of refrigerants such as ammonia (R-717) or propane (R-290). A large number of fluids are available and used as “secondary liquid refrigerants”. The use of ice slurries is a development in such systems where the phase change is used in order to reduce the required mass flow for a given capacity compared with that obtained using a secondary liquid refrigerant.
The difficult search for alternative refrigerants, due to the phasing out of CFCs and HCFCs, has led to the envisaging of the development of ice-slurry technology.
Production methods
Currently, the most commonly applied techniques are mechanical ones. Usually, the refrigerant is evaporated in a cylindrical double-wall evaporator. In the inner domain, a water-additive mixture leads to the creation of ice crystals on the wall; these are then mechanically removed. As the crystals drop into the fluid, the number of ice particles per volume and, therefore also the ice concentration, increases. Mechanical-scraper type ice-slurry generators with:
bullet
rotating knifes
bullet
rotating cylindrical slabs (see Figure 2)
bullet
rotating brushes
bullet
screws in cylinders
have appeared on the market and are now widely used for experiments and in some installations.
Condenser
Textfeld: Condenser
Figure 1. A schematic drawing of an ice-slurry system, e.g. of a supermarket, is shown. The left part shows the ice-slurry generator
Figure 2. The principle of an ice slurry generator with rotating slabs allows a high ice production rate per volume
Other ice-slurry generators under investigation are:
bullet
vortex-flow type (turbulent fluid eddies remove the ice particles from special treated surfaces with little adhesion)
bullet
direct-injection or direct-heat exchange type (the refrigerant is directly injected into the water)
bullet
fluidized bed ice generator (the flow enables steel or glass spheres to hit the ice crystals and remove them from the wall)
bullet
ice generators using supercooled water with different types of nucleation initiation:
bullet
by a momentum decrease (flow perpendicular to a cold wall)
bullet
by an ultra-sound field
bullet
by bubble nucleation
bullet
vacuum ice generators (the pressure is lowered to the triple point of water)
bullet
hydro scraped generator.
Advantages of ice-slurry technology
The potential advantages of ice-slurry systems, which are listed in this section, are valid in comparison with direct evaporation systems or/and indirect refrigeration systems containing brines as a secondary refrigerant:
bullet
high cooling capacity given by the latent heat
bullet
smaller tube diameters for the piping system (A)
bullet
lower energy demand for the pumps (B)
bullet
practical observations tend to prove that the “quality” of cold produced by ice-slurry systems is improved: better temperature stability, easier moisture and frosting/defrosting management…
bullet
combined with energy storage, the high thermal capacity of the system may bridge small electricity supply cuts
bullet
cheaper electricity and the low nocturnal condensing pressure can be taken advantage of
bullet
increased safety by storing cold in storage tanks
bullet
smaller filling mass of primary circuits
bullet
if the cooling demand of an existing system has to be extended, then the electrical supply does not have to be increased, because cold production can be extended to 24 h
bullet
the peak supply power of cold is many times larger in an ice-slurry system than in a conventional storage system (e.g. an ice-on-coil system).
The system design engineer may choose between (A) and (B) or take partial advantage of both. High heat transfer rates are possible because the ice particles are very finely dispersed in the fluid. Figure 3 shows numerous ice particles in an ice slurry, and Figure 4 the related surface of the total amount of ice particles in one kilogram of ice slurry.
Drawbacks and limits
Ice-slurry systems also show some significant disadvantages, which are listed below:
bullet
additional heat exchanger between the primary refrigerant system and the secondary transportation system for cold
bullet
additional pump
bullet
additional energy demand for the pump to charge the storage tank and for the operation of the mixing element
bullet
additional systems for controlling and monitoring the ice-slurry quality
bullet
not adapted for use in air-conditioning and chiller systems, except where savings offered by this technology offset the thermodynamic penalty due to cooling below 0°C to fulfil a cooling task at only 12-14°C
bullet
ice-water systems are most advantageous at temperatures close to the freezing point of water.
The latter disadvantages have recently led to the development of other PCMs, e.g. use of substances such as paraffins. With such substances the melting point can be continuously adjusted to the requirements dictated by the particular application.
Figure 3. A microscopic photograph of an ice slurry is shown in this figure.3 After their creation, the ice particles grow slightly as a function of time, leading to time-related behaviour of physical properties
Figure 4. The total surface areas A of all the particles in one kg ice slurry, for different ice mass fractions, are presented. These results are valid for spherical particles with a diameter dp
Current applications
Ice-slurry systems can be applied in the following domains:
bullet
refrigeration in supermarkets
bullet
cooling in dairies and cheese production facilities
bullet
cooling in breweries
bullet
fast food cooling
bullet
cooling of planes in airports (transport of cold over long distances to the docks)
bullet
cooling of pharma parks (analogous to technoparks, but for pharmaceutical research)
bullet
direct immersion of food (e.g. shrimps).
bullet
cold storage in the food industry, in air conditioning and in district cooling.
These are some examples that can be spread to many other domains.
Possible future applications
Future applications are expected in the following domains:
bullet
plastics production: temperature stabilization leads to more homogeneous temperature profiles in the plastic extruders. This will increase the product quality
bullet
cooling of chemical processes
bullet
immediate stopping of a chemical process by direct injection of ice slurry into the reactor to absorb as much heat as possible, for safety reasons
bullet
mixing of concrete with ice slurry in a quantity so that after the melting of the ice particles exactly the right mass of water is added to the concrete. The latent heat will be used to absorb the reaction heat. Particularly in the construction of road and train tunnels, the technical cooling system may be reduced in size or even economized.
The IIR Working Party on Ice Slurries, which was set up in 1998, has organized five workshops and published proceedings of the papers presented. The contributions cover all important topics that still need to be investigated in order to favour the development of this technology: from physical properties and their time behaviour to fluid dynamics (e.g. pressure drop calculations in piping systems), heat transfer (Nusselt functions) for laminar and turbulent flows, ice generation, storage, mixing, piping, etc. Special contributions will be published in a Special Issue on Ice Slurries of the International Journal of Refrigeration in 2004. All useful and available practical knowledge will be brought together in an IIR Handbook on Ice Slurries, which will be published in 2005.
Conclusion
Ice slurry is undoubtedly a promising technology that should be encouraged because of its numerous advantages, in particular energy saving and environmental benefits.
Further research and development work needs to be carried out, particularly on how to generate ice slurry in an efficient, reliable and economical way, and on fluid properties and measuring techniques in order to open up this technology for use in a broader range of applications.5
References
1. Inaba H. et al. New Challenge in Advanced Thermal Energy Transportation Using Functionally, Thermal Fluids, Int. J. Therm. Sci., 39, 991-1003, 2000.
2. Proceedings of the Phase Change Material and Slurry Scientific Conference and Business Forum, Editors Egolf P.W., Sari O. Yverdon-les-Bains, Switzerland, April 23-26, 2003.
3. Egolf P.W., Sari O. A Review from Physical Properties of Ice Slurries to Industrial Ice Slurry Applications. Proceedings of the Phase Change Material and Slurry Scientific Conference and Business Forum, 15-25, Yverdon-les-Bains, Switzerland, April 23-26, 2003.
4. Brühlmeier J, Egolf PW. Flüssigeis - ein neuer K?ltetr?ger. Booklet printed in the framework of a special prize donated by the Swiss Bank Association (UBS), 1996.
5. Granryd E. Perspectives on ice slurries, Proceedings of the Fifth IIR Workshop on Ice Slurries, Stockholm, Sweden, 2002.
First, it will depend on how air will be flowing through the condenser. If it is a passive air flow, you might need a large condenser. If it has a fan pushing (or pulling) air through it, it can be smaller. Second, it depends on the K factor of the tubing and fin material. Metals like aluminum and copper transfer heat fairly rapidly, and using these metals will allow a smaller coil. Thirdly, what type of fluid is inside of the coil? If it is a liquid, more heat can be transferred in a smaller area, compared to a gas fluid. Lastly, the shape of the coil will only depend on the way that air will be flowing through it. Look at an air conditioner condenser coil outside of your house, and it is somewhat circular in shape, as it has a fan that pulls air through it. It is designed to maximize area and minimize space occupied. The air conditioner coil on an automobile, however, is flat, as it is designed to take advantage of the forward movement of the car in addition to the fan on the engine. Diameter of tubing and spacing of fins would need to be taken into account, but these parameters would depend on material of the tubes and fins, as well as fluid flowing through.
It might help if you could add a water spray to the cooling air. The unused water could be recirculated so that all the water consumed went to evaporative cooling.
What is this condenser's service? Refrigerant, steam, other? Do you need any sub-cooling.
Materials for the tubes or fins have very little to do with the over all heat transfer rate. Air flow rate and velocity inside the tube have a bigger impact.
If you do not need any sub-cooling, then having a configuration that will get the condensed liquid out of the condenser so more surface is exposed to the condensing process is important.
One important thing that is overlooked many times is air recirculation. Having a forced draft arrangement where the fans push the air across the condenser seems at first to be the most economical arrangement but in fact an induced draft arrangement where the air is pulled across the tubes and then discharged by the fans minimizes an air recirculation and actually results in better performance. You should note that most air conditioning condensers use this principle.How can i optimize and increase the heat rejection and decrease the coil surface of air cooled condenser?
Well ,you can increase heat rejection by increasing the resistsnce which inturn can be done by increasing the length.
Introduction
Refrigeration is technology which makes a major contribution to humanity in many ways including food preservation, control of indoor air quality, gas liquefaction, industrial process control, production of food and drink and computer cooling. Without refrigeration, modern life would be impossible. About 15% of the world’s electricity is used to drive refrigerating and air-conditioning systems. Inefficient use of energy is a waste of valuable resource and contributes to global warming. Most of the global warming effect of refrigerating systems comes from generating energy to drive them. Only a small proportion comes from the release of certain refrigerants. This informatory note describes how the efficiency of refrigerating systems can be maximized thereby minimizing their global warming impact.
Fundamentals
Refrigeration is the science of making heat flow “uphill” from low to high temperatures. A refrigeration system extracts heat from the substance being refrigerated (cold reservoir) and rejects it to the ambient at a higher temperature (hot reservoir) as indicated in Figure 1. This is analogous to the pumping of water to an elevated storage tank. The energy consumption of a refrigerator is roughly proportional to rate of heat extraction (amount of water pumped) and to the temperature lift through which the heat is raised (height water is pumped).
The energy efficiency of a refrigeration system is usually expressed as a Coefficient of Performance (COP) which is the ratio of the heat extraction rate to the rate of energy use.
Whatever type of refrigerating system is being used, it is fundamental to minimize the required heat extraction and to keep the difference between TC (condensing temperature) and T0 (evaporating temperature) as small as possible. Minimizing heat extraction is done by insulating the refrigerated room and low-temperature parts of the refrigeration system, minimizing ambient air infiltration (e.g. door openings and leakage) and reducing energy use in refrigerated applications (e.g. fans and forklifts). Reducing (TC – T0) is done by maximizing condenser and evaporator heat transfer performance and minimizing refrigerant pressure drops in suction and discharge pipelines.
Description of a Vapour Compression Refrigeration System
The standard vapour compression refrigeration system consists of a refrigerant in a closed circuit comprising a compressor, a condenser, an expansion device, an evaporator and interconnecting piping (Figure 2). In the condenser, compressed refrigerant vapour at high pressure is condensed at high temperature by heat transfer to the surroundings. The high-pressure refrigerant liquid is reduced to a low pressure at the expansion valve. At low pressure, the refrigerant will evaporate at a low temperature enabling it to extract heat from the substance to be cooled. To complete the cycle, the low pressure refrigerant vapour exiting the evaporator is compressed to high pressure by the compressor. The total heat rejected in the condenser is the sum of the heat extracted plus the compressor energy use.
Figure 2. Schematic of a Simple Vapour Compression Refrigeration System
Loss of refrigerant from the circuit would have a very detrimental effect on the reliability of the system, so great care is taken to make refrigerating systems as leak-tight as possible. Individual domestic refrigerators, of which there are more than one billion, each contains a very small amount of refrigerant. Such systems are expected to run for more than 20 years without addition of refrigerant. The global warming effect of such refrigerators is significant but nearly all of it is caused by carbon dioxide produced when the electricity to run the refrigerator is generated.
Effect of System Components on Efficiency
Refrigerant
Very few substances have properties appropriate for a refrigerant and, of these, few have stood the test of time and continue to be used as refrigerants. Figure 3 shows some of the substances that have been used as refrigerants and how their use has varied over time.
Figure 3. Typical Refrigerants and Their Historical Use
There is no ideal refrigerant. Selection of a refrigerant is a compromise between many factors including ease of manufacture, cost, toxicity, flammability, environmental impact, corrosiveness and thermodynamic properties as well as energy efficiency. A key characteristic is the pressure/temperature relationship. In general, for energy efficiency it is desirable for the refrigerant critical point (temperature above which the refrigerant cannot condense) to be high compared with the heat extraction and rejection temperatures.
Good transport and heat transfer properties are also important for energy efficiency as they reduce running costs and allow smaller temperature differences to be employed in evaporators and condensers and hence smaller overall temperature lifts. In general, refrigerants of low molecular weight and low viscosity will have the best properties.
Compressor
Compressors will lose efficiency if the temperature lift is higher than necessary and they will also lose efficiency if droplets of refrigerant liquid are present in the suction vapour or if the suction vapour becomes too hot. Compressor maintenance, where possible, and the preservation of lubricant quality are important to retain energy efficiency. For some compressor types (particularly screw and centrifugal), their part-load energy efficiency performance is poor compared with at full load, so sustained part-loaded operation should be avoided. Variable speed drive technology and improved control systems can minimize the energy penalty but increase capital costs.
Condenser
To keep refrigerant heat rejection temperatures as low as possible, condenser heat transfer rates should be maximized and the cooling medium temperature minimized. Evaporative condensers are often the most efficient because they reject heat to the wet-bulb temperature of the ambient air. For instance, humid air at 25°C and 60% relative humidity has a wet-bulb temperature of 16°C. However, they require careful maintenance to avoid Legionella contamination. Water-cooled condensers combined with cooling towers also approach ambient wet-bulb temperature but there is an additional temperature difference to drive heat from the refrigerant into the water, so refrigerant heat rejection temperature is generally higher. Water use can be excessive if a cooling tower is not used. Air-cooled condensers are usually the least efficient method as they reject heat to the air dry-bulb temperature, which is generally significantly higher than wet-bulb or water temperature. However, for small systems they are commonly used because they are cheap, simple and require little maintenance.
It is important to keep all types of condenser clean and free from fouling. Condensers rejecting heat to atmosphere must be allowed plenty of fresh air and protected against any tendency for the air to re-circulate back to the condenser inlet. Systems that operate with refrigerant suction pressures less than atmospheric (e.g. low temperature ammonia or air-conditioning with HCFC-123) should use purgers to remove non-condensables from the refrigerant.
Expansion devices
Many expansion devices require significant pressure difference to allow proper operation. Therefore condensing pressure is often maintained at artificially high levels, even at low ambient temperatures. The biggest culprit in this respect is the conventional thermostatic expansion valve which is often selected because of its very low cost. One solution is to use electronically controlled expansion valves.
Evaporators
As for condensers, evaporators should be designed to operate at minimum economic temperature difference so that the refrigerant heat extraction temperature can be as high as possible for a given substance temperature. Increasing heat extraction temperature also reduces the size of the compressor required.
As well as evaporator size, aspects such as refrigerant distribution, circuiting and velocity, use of enhanced surfaces, air speeds (for air coolers) can all significantly affect energy efficiency. Air coolers that operate at temperatures below freezing must be defrosted regularly to restore performance. Electric defrost is simple but is least efficient and therefore only suitable for small systems. Electric defrost has to be paid for at least twice, to put the electric heat into the cooler and to take it out again. Water defrost, hot gas defrost, and defrost by the circulation of warm fluid through the cooler, are all potentially more efficient. However, whatever the system, it is important to optimize the frequency and duration of defrost to avoid unnecessary defrosting.
Interconnecting piping
Efficiency can be reduced if interconnecting piping is of the wrong size or is arranged in ways that cause unnecessary pressure drop or inhibit oil return (e.g. excessive bends and fitting).
Importance of controls
A refrigeration system with well-designed components will not operate efficiently unless the components are correctly matched and controlled. Energy efficiency has not always been the prime consideration when selecting effective controls. If possible, the following control options should be avoided to maximize energy efficiency:
– slide valve unloading of over-sized screw compressors;
– hot gas bypass of compressors;
– throttling valves between evaporators and compressors;
– evaporator control by starving refrigerant supply;
– too frequent defrosts;
– condenser head pressure controls except when necessary.
Conclusion
Improving the energy efficiency of refrigeration systems is not difficult and should be encouraged because of the environmental benefits. It often involves a trade-off between initial costs and on-going operating costs. There are many situations where economics motivate the equipment supplier to provide the cheapest solution, especially if the supplier does not have to pay for the running costs of the system. Standards should be set for energy efficiency for all types of refrigerating system. Governments should legislate to ensure that suppliers are penalized for supplying systems that do not reach acceptable standards of efficiency and to ensure that users of efficient systems benefit by more than the resulting reduction in running costs. If this were done, it is reasonable to suppose that the energy consumption of refrigerating systems could be reduced by at least 20% in the short term. An objective of 30-50% reduction — depending on applications — by 2020 is a goal which could be achieved.
This Informatory Note was prepared by S. Forbes Pearson, winner of the IIR Gustav Lorentzen Medal awarded at the 21st IIR International Congress of Refrigeration in Washington DC in August 2003. It was reviewed by 24 experts worldwide.
The International Institute of Refrigeration (IIR) is an intergovernmental organization comprising 61 Member Countries representing over 80% of global population.
The IIR's mission is to promote knowledge and disseminate information on refrigeration technology and all its applications in order to address today's major issues, including food safety, protection of the environment and development of the least developed countries.
The IIR provides a wide range of services: organization of conferences, congresses, workshops and training courses, a database (Fridoc) containing 70 000 references, several publications (journals, manuals, technical books, conference proceedings, informatory notes), and a Web site providing a wide range of information (www.iifiir.org).
Technical Note on Refrigerating Technologies
Ice Slurry: a Promising Technology
For centuries, ice has been considered as effective storage material for temperatures around 0°C. Using ice can reduce the size of a water storage tank by a factor of two to ten, depending on the temperature range used for operating the system. The reason for the high energy density is the latent heat of phase change. For a pure substance, under constant pressure, at the freezing temperature, a large amount of energy is required to build up a regular crystalline structure, which leads to the solid phase. In the opposite process of melting, the crystal is destroyed and energy released at the same temperature, now called the melting temperature. For temperatures other than 0°C, other materials that exhibit a change of phase, phase-change materials (PCM), can be used. In technical applications, mixtures are the most used. They show a temperature glide (continuous transition) in the enthalpy function during the phase change.
If a PCM is finely dispersed in a carrier fluid, a phase-change slurry is obtained. The particles need to be stable and should not lead to high stratification effects in the system, caused by the buoyancy force. Phase-change slurries may be micro-emulsions, shape-stabilized paraffins, clathrates, microencapsulated phase-change slurries, etc.1 In April 2003, in Switzerland, an international conference and business forum on the new fields of PCM and energy storage based on these materials was organized.2 In this type of energy storage, PCMs – which have a high thermal energy density and stable temperature due to the phase change – are also used for the transport of cold or heat. Ice slurry is the oldest and most commonly used substance in the phase-change slurries group.
This technical note briefly highlights the state of the art of this promising technology.
Definitions
In early times, to cool their food, the Romans used naturally occurring ice slurries, e.g. snow-water mixtures, crushed ice, flake ice, etc. Last century, ice slurries were created artificially. Initially, these were basically water with large ice particles with a characteristic diameter of one to several centimetres and were mainly used to cool coal and silver or gold mines. The production of fine-crystalline ice slurries then allowed the technique to be applied in small-scale systems, e.g. for the cooling of display cabinets in supermarkets (see Figure 1).
It is difficult to define “ice slurries”. Ice slurries can be classified using the following definitions3:
Definition 1: An ice slurry consists of solid ice particles in a fluid forming a suspension with two phases.
Definition 2: A fine-crystalline ice slurry is a substance comprising ice particles with an average (characteristic) diameter which is equal to or smaller than 1 mm.
Definition 2 is a little arbitrary, but still very useful. This technical note only addresses fine-crystalline ice slurries, produced for example with mechanical scraper-type ice-slurry generators. With this method, the ice particles created have a characteristic diameter of approximately 200 mm.
Application in refrigeration systems and environmental benefits
Experience has demonstrated that conventional direct evaporation systems are usually low-cost and are technically very reliable. However, they use the same fluid – the refrigerant – for “production” and “transport” of cold from the central refrigeration unit to the end users (e.g. display cabinets). As a result, these systems contain large masses of refrigerant and, in the case of permanent or accidental leakage, may lead to high losses with drastic consequences for the environment. Furthermore, high system charges of refrigerants lead to higher costs, because new replacements of CFCs and HCFCs are several times more expensive.
In indirect systems, the production of cold and its transport are separated. Cold is transferred in a heat exchanger from the primary to the secondary circuit. Indirect systems facilitate the use of refrigerants such as ammonia (R-717) or propane (R-290). A large number of fluids are available and used as “secondary liquid refrigerants”. The use of ice slurries is a development in such systems where the phase change is used in order to reduce the required mass flow for a given capacity compared with that obtained using a secondary liquid refrigerant.
The difficult search for alternative refrigerants, due to the phasing out of CFCs and HCFCs, has led to the envisaging of the development of ice-slurry technology.
Production methods
Currently, the most commonly applied techniques are mechanical ones. Usually, the refrigerant is evaporated in a cylindrical double-wall evaporator. In the inner domain, a water-additive mixture leads to the creation of ice crystals on the wall; these are then mechanically removed. As the crystals drop into the fluid, the number of ice particles per volume and, therefore also the ice concentration, increases. Mechanical-scraper type ice-slurry generators with:
bullet
rotating knifes
bullet
rotating cylindrical slabs (see Figure 2)
bullet
rotating brushes
bullet
screws in cylinders
have appeared on the market and are now widely used for experiments and in some installations.
Condenser
Textfeld: Condenser
Figure 1. A schematic drawing of an ice-slurry system, e.g. of a supermarket, is shown. The left part shows the ice-slurry generator
Figure 2. The principle of an ice slurry generator with rotating slabs allows a high ice production rate per volume
Other ice-slurry generators under investigation are:
bullet
vortex-flow type (turbulent fluid eddies remove the ice particles from special treated surfaces with little adhesion)
bullet
direct-injection or direct-heat exchange type (the refrigerant is directly injected into the water)
bullet
fluidized bed ice generator (the flow enables steel or glass spheres to hit the ice crystals and remove them from the wall)
bullet
ice generators using supercooled water with different types of nucleation initiation:
bullet
by a momentum decrease (flow perpendicular to a cold wall)
bullet
by an ultra-sound field
bullet
by bubble nucleation
bullet
vacuum ice generators (the pressure is lowered to the triple point of water)
bullet
hydro scraped generator.
Advantages of ice-slurry technology
The potential advantages of ice-slurry systems, which are listed in this section, are valid in comparison with direct evaporation systems or/and indirect refrigeration systems containing brines as a secondary refrigerant:
bullet
high cooling capacity given by the latent heat
bullet
smaller tube diameters for the piping system (A)
bullet
lower energy demand for the pumps (B)
bullet
practical observations tend to prove that the “quality” of cold produced by ice-slurry systems is improved: better temperature stability, easier moisture and frosting/defrosting management…
bullet
combined with energy storage, the high thermal capacity of the system may bridge small electricity supply cuts
bullet
cheaper electricity and the low nocturnal condensing pressure can be taken advantage of
bullet
increased safety by storing cold in storage tanks
bullet
smaller filling mass of primary circuits
bullet
if the cooling demand of an existing system has to be extended, then the electrical supply does not have to be increased, because cold production can be extended to 24 h
bullet
the peak supply power of cold is many times larger in an ice-slurry system than in a conventional storage system (e.g. an ice-on-coil system).
The system design engineer may choose between (A) and (B) or take partial advantage of both. High heat transfer rates are possible because the ice particles are very finely dispersed in the fluid. Figure 3 shows numerous ice particles in an ice slurry, and Figure 4 the related surface of the total amount of ice particles in one kilogram of ice slurry.
Drawbacks and limits
Ice-slurry systems also show some significant disadvantages, which are listed below:
bullet
additional heat exchanger between the primary refrigerant system and the secondary transportation system for cold
bullet
additional pump
bullet
additional energy demand for the pump to charge the storage tank and for the operation of the mixing element
bullet
additional systems for controlling and monitoring the ice-slurry quality
bullet
not adapted for use in air-conditioning and chiller systems, except where savings offered by this technology offset the thermodynamic penalty due to cooling below 0°C to fulfil a cooling task at only 12-14°C
bullet
ice-water systems are most advantageous at temperatures close to the freezing point of water.
The latter disadvantages have recently led to the development of other PCMs, e.g. use of substances such as paraffins. With such substances the melting point can be continuously adjusted to the requirements dictated by the particular application.
Figure 3. A microscopic photograph of an ice slurry is shown in this figure.3 After their creation, the ice particles grow slightly as a function of time, leading to time-related behaviour of physical properties
Figure 4. The total surface areas A of all the particles in one kg ice slurry, for different ice mass fractions, are presented. These results are valid for spherical particles with a diameter dp
Current applications
Ice-slurry systems can be applied in the following domains:
bullet
refrigeration in supermarkets
bullet
cooling in dairies and cheese production facilities
bullet
cooling in breweries
bullet
fast food cooling
bullet
cooling of planes in airports (transport of cold over long distances to the docks)
bullet
cooling of pharma parks (analogous to technoparks, but for pharmaceutical research)
bullet
direct immersion of food (e.g. shrimps).
bullet
cold storage in the food industry, in air conditioning and in district cooling.
These are some examples that can be spread to many other domains.
Possible future applications
Future applications are expected in the following domains:
bullet
plastics production: temperature stabilization leads to more homogeneous temperature profiles in the plastic extruders. This will increase the product quality
bullet
cooling of chemical processes
bullet
immediate stopping of a chemical process by direct injection of ice slurry into the reactor to absorb as much heat as possible, for safety reasons
bullet
mixing of concrete with ice slurry in a quantity so that after the melting of the ice particles exactly the right mass of water is added to the concrete. The latent heat will be used to absorb the reaction heat. Particularly in the construction of road and train tunnels, the technical cooling system may be reduced in size or even economized.
The IIR Working Party on Ice Slurries, which was set up in 1998, has organized five workshops and published proceedings of the papers presented. The contributions cover all important topics that still need to be investigated in order to favour the development of this technology: from physical properties and their time behaviour to fluid dynamics (e.g. pressure drop calculations in piping systems), heat transfer (Nusselt functions) for laminar and turbulent flows, ice generation, storage, mixing, piping, etc. Special contributions will be published in a Special Issue on Ice Slurries of the International Journal of Refrigeration in 2004. All useful and available practical knowledge will be brought together in an IIR Handbook on Ice Slurries, which will be published in 2005.
Conclusion
Ice slurry is undoubtedly a promising technology that should be encouraged because of its numerous advantages, in particular energy saving and environmental benefits.
Further research and development work needs to be carried out, particularly on how to generate ice slurry in an efficient, reliable and economical way, and on fluid properties and measuring techniques in order to open up this technology for use in a broader range of applications.5
References
1. Inaba H. et al. New Challenge in Advanced Thermal Energy Transportation Using Functionally, Thermal Fluids, Int. J. Therm. Sci., 39, 991-1003, 2000.
2. Proceedings of the Phase Change Material and Slurry Scientific Conference and Business Forum, Editors Egolf P.W., Sari O. Yverdon-les-Bains, Switzerland, April 23-26, 2003.
3. Egolf P.W., Sari O. A Review from Physical Properties of Ice Slurries to Industrial Ice Slurry Applications. Proceedings of the Phase Change Material and Slurry Scientific Conference and Business Forum, 15-25, Yverdon-les-Bains, Switzerland, April 23-26, 2003.
4. Brühlmeier J, Egolf PW. Flüssigeis - ein neuer K?ltetr?ger. Booklet printed in the framework of a special prize donated by the Swiss Bank Association (UBS), 1996.
5. Granryd E. Perspectives on ice slurries, Proceedings of the Fifth IIR Workshop on Ice Slurries, Stockholm, Sweden, 2002.
First, it will depend on how air will be flowing through the condenser. If it is a passive air flow, you might need a large condenser. If it has a fan pushing (or pulling) air through it, it can be smaller. Second, it depends on the K factor of the tubing and fin material. Metals like aluminum and copper transfer heat fairly rapidly, and using these metals will allow a smaller coil. Thirdly, what type of fluid is inside of the coil? If it is a liquid, more heat can be transferred in a smaller area, compared to a gas fluid. Lastly, the shape of the coil will only depend on the way that air will be flowing through it. Look at an air conditioner condenser coil outside of your house, and it is somewhat circular in shape, as it has a fan that pulls air through it. It is designed to maximize area and minimize space occupied. The air conditioner coil on an automobile, however, is flat, as it is designed to take advantage of the forward movement of the car in addition to the fan on the engine. Diameter of tubing and spacing of fins would need to be taken into account, but these parameters would depend on material of the tubes and fins, as well as fluid flowing through.
It might help if you could add a water spray to the cooling air. The unused water could be recirculated so that all the water consumed went to evaporative cooling.
How to change fluorescent light bulb?
We need to change a fluorescent bulb which has two tubes but only one socket. It fits into a standard bulb socket so it is not to be confused with the standard long cylindrical fluorescent lamp. No matter how I try to remove the bulb (by twisting), it does not want to budge.How to change fluorescent light bulb?
A common problem, it sounds like the pins inside the lampholder have pressed deeply into the solder contacts on the lamp cap, which is now 'locked' from turning by the indents. The best bet is to turn it back and forth without forcing it too much, untill the pins smooth off a 'ramp' and then it will come out. This is caused by the heat build up in the cap and pins and the fact that the lamps last so long that they have more time to indent. If this fails you will have to dismantle the lampholder top to remove it.How to change fluorescent light bulb?
Sounds like a standard energy saving bulb, a combination of the two differering technologies.
A problem can be that the base has come undone between the socket and the actual bulb part. you will have to be carefull and gently (or not sogently) push the bulb into the socket while twisting it.
if it wont work then turn off the electric , wrap the glass in a towel and use more force. The glass may break but from experience it will twist open with a little force.
first turn off the power to the light. get some thick gloves and a cloth turn counter clockwise if it doesn't work you can always break the bulb and use a pair of long pliers. TURN OFF POWER!!!!!!
are you sure you're not just turning it in the wrong direction? There might also be a release button that lets go of the bulb.
it sounds like it is ceased up in the socket ,turn the light out or do it in daylight give the socket a few gentle taps , then try again . If all else fails smash the bulb and use plyers to take it out
Get a man! That's what God made them for.
The glass tubes on these end in plastic base, that fit into sort of a square socket. You don't twist these, there is a small tab on the socket that you push in, and pull the bulb straight out. I hope I'm right without seeing this?
try, after you have turned the power off, push and twist anticlockwise,
Yes i think so, i went to Disney world last year! I was in line 2 see micky mouse for 2 hours, How strange? After i went inside the tree of life to see a bugs life 3D! It was well funny, by far the best holiday i ever had! Hope this helps!How do I keep bed sheets tight black circles under my eyes
A common problem, it sounds like the pins inside the lampholder have pressed deeply into the solder contacts on the lamp cap, which is now 'locked' from turning by the indents. The best bet is to turn it back and forth without forcing it too much, untill the pins smooth off a 'ramp' and then it will come out. This is caused by the heat build up in the cap and pins and the fact that the lamps last so long that they have more time to indent. If this fails you will have to dismantle the lampholder top to remove it.How to change fluorescent light bulb?
Sounds like a standard energy saving bulb, a combination of the two differering technologies.
A problem can be that the base has come undone between the socket and the actual bulb part. you will have to be carefull and gently (or not sogently) push the bulb into the socket while twisting it.
if it wont work then turn off the electric , wrap the glass in a towel and use more force. The glass may break but from experience it will twist open with a little force.
first turn off the power to the light. get some thick gloves and a cloth turn counter clockwise if it doesn't work you can always break the bulb and use a pair of long pliers. TURN OFF POWER!!!!!!
are you sure you're not just turning it in the wrong direction? There might also be a release button that lets go of the bulb.
it sounds like it is ceased up in the socket ,turn the light out or do it in daylight give the socket a few gentle taps , then try again . If all else fails smash the bulb and use plyers to take it out
Get a man! That's what God made them for.
The glass tubes on these end in plastic base, that fit into sort of a square socket. You don't twist these, there is a small tab on the socket that you push in, and pull the bulb straight out. I hope I'm right without seeing this?
try, after you have turned the power off, push and twist anticlockwise,
Yes i think so, i went to Disney world last year! I was in line 2 see micky mouse for 2 hours, How strange? After i went inside the tree of life to see a bugs life 3D! It was well funny, by far the best holiday i ever had! Hope this helps!
Aquarium lighting question?
Why and how often do i have to change the flourescent tubes in my aquarium????Aquarium lighting question?
theres all kinds of scientific crap behind WHY u should change ur bulb, but in a language that all of us ';normal'; ppl understand ';english';. the bulbs lose valuable spectrum waves over time. every time u turn on ur light, it decreases the life of the bulb. thats why it is important to change out ur starter for the bulbs frequently. when ur bulb starts to flicker alot b4 turining on completely, then it is time to change the starter. having a bad starter will KILL the life of ur bulb VERY quickly.
again as stated from the answers above. general rule for ur flourescents, change the bulb (with planted aquariums) every 6 months or u will be in a nasty mess. for an ALL fish aquarium, it is always best to change the bulb anywhere between 9 to 12 months. just for the overall health and look of ur tank.
i forgot the website that i found the info on but i googled aquarium lights one time and found this site that had crazy info on light bulbs. the effect that they have and the importance of having the proper lighting. this guy goes into crazy scientic detail (that only nerds such as myself can enjoy. LOL). vvery educational. i will try to post a link if i find it.Aquarium lighting question?
When they burnn out
After about 6 months, they'll have changed in spectrum enough to make them less useful for plants. I replace mine about once every 9 months, but for a tank with only fish, you really only need to change them once they burn out.
Flourescent tubes should be replaced roughly every 12 month, even if they appear to be working. Light output falls and quality changes with age of the tube, and although these changes may be imperceptible, they will stess the plants in the tank if you have plants. But if it is only fish in your tank you should replace it immediantly aftr it burns out.
Hope this helps!
theres all kinds of scientific crap behind WHY u should change ur bulb, but in a language that all of us ';normal'; ppl understand ';english';. the bulbs lose valuable spectrum waves over time. every time u turn on ur light, it decreases the life of the bulb. thats why it is important to change out ur starter for the bulbs frequently. when ur bulb starts to flicker alot b4 turining on completely, then it is time to change the starter. having a bad starter will KILL the life of ur bulb VERY quickly.
again as stated from the answers above. general rule for ur flourescents, change the bulb (with planted aquariums) every 6 months or u will be in a nasty mess. for an ALL fish aquarium, it is always best to change the bulb anywhere between 9 to 12 months. just for the overall health and look of ur tank.
i forgot the website that i found the info on but i googled aquarium lights one time and found this site that had crazy info on light bulbs. the effect that they have and the importance of having the proper lighting. this guy goes into crazy scientic detail (that only nerds such as myself can enjoy. LOL). vvery educational. i will try to post a link if i find it.Aquarium lighting question?
When they burnn out
After about 6 months, they'll have changed in spectrum enough to make them less useful for plants. I replace mine about once every 9 months, but for a tank with only fish, you really only need to change them once they burn out.
Flourescent tubes should be replaced roughly every 12 month, even if they appear to be working. Light output falls and quality changes with age of the tube, and although these changes may be imperceptible, they will stess the plants in the tank if you have plants. But if it is only fish in your tank you should replace it immediantly aftr it burns out.
Hope this helps!
How do I change my user name on You Tube?
I love going on You Tube but stupidly gave myself a real dumb-*** name when I first joined and now I want to change it. Does anyone know if this is possible cos I go to ';user channel'; to change it and nothing happens. Help!How do I change my user name on You Tube?
nope you can't. once u sticked to a name then it has to be that one. the only way if u want to change it is rather make a new account.How do I change my user name on You Tube?
not possible
but you can change your channel name
make a new account. sorry, thats the only way
You can't you'll have to make a new one. If you already have subscribers I'd just tough it out.
go to youtube, log in then go to my account/ Personal info/ Channel Info and there you can change you name
GREAT QUESTION...Contact the messenger help line using the link.
u cant
the only way to change it is to make a new account.
Sorry, you will have to make a new account. But what you can do is put a link to your new account on your old one and the link to your old account on your new one so people can see your previous videos. Also notify all you friend and subscribers to subscribe to your new account. Hope this helps!
You can't.. =\
You have to start a new account with youtube.
nope you can't. once u sticked to a name then it has to be that one. the only way if u want to change it is rather make a new account.How do I change my user name on You Tube?
not possible
but you can change your channel name
make a new account. sorry, thats the only way
You can't you'll have to make a new one. If you already have subscribers I'd just tough it out.
go to youtube, log in then go to my account/ Personal info/ Channel Info and there you can change you name
GREAT QUESTION...Contact the messenger help line using the link.
u cant
the only way to change it is to make a new account.
Sorry, you will have to make a new account. But what you can do is put a link to your new account on your old one and the link to your old account on your new one so people can see your previous videos. Also notify all you friend and subscribers to subscribe to your new account. Hope this helps!
You can't.. =\
You have to start a new account with youtube.
How much should It cost to get coolant tubes in radiater changed ?
I recently took my car for servicing and the mechanic told me that the coolant was leeking and needed fixing, though I had not noticed anything I still agreed and got it done and he charged me $450 just after two weeks of getting it serviced and fixed I actually noticed coolant leaking in my driveway. I took the car back to the mechanic this time he told me that the coolant tubes in the radiator were corroded and needed replacement and gave me a quote of $1500. I am finding it hard to trust him. What should I do? does it really cost this much to get them replaced.How much should It cost to get coolant tubes in radiater changed ?
I would suggest that you try a couple of other garages for quotes or you could try one of the large motoring organisations for advice.
Unless you personally know this ';Mechanic'; and know him to be genuine then get it checked out. I got ripped off a good many years ago by a so called mechanic, i got most of my money back after a friend of mine had a chat with him, but you might not be so lucky.
As i said check it out and good luck.How much should It cost to get coolant tubes in radiater changed ?
it will be a whole lot cheaper to just buy a new radiator. someimes you can find one still in good shape at the junk yards. but it is defenatly not worth 1500
It doesnt cost that much to get a new raidiator put in I suggest you find a new mechanic or an even better idea is take it to a raidiator shop and have them put a new core in it a couple of hundred at the most and your good
I don't know what country you're in but I live in the US and when my radiator is leaking, I call down to Auto Zone for a replacement. My truck radiator was $150 new. I priced one for my Mercury Villager and it was $199. Be serious. Take your business away from this guy, run don't walk. Know what the job should be worth before you walk into a repair shop.
Well there really isn't enough info for me to answer this question. What kind of car do you have?
I have never heard of replacing the ';Coolant Tubes'; are you sure he wasn't meaning to replace the whole radiator? Depending on what type of car you have you could always go to AutoZone.com and find out how much a new radiator would cost. Without knowing what type of car you are fixing it's really tough to give you a good answer. Good Luck.
it is cheaper by far to simply replace the radiator. most radiators, brand new run between 100-290 plus the installation charge. get yourself to a new service provider. this guy is giving the rest of us a bad name
a new radiator costs $100 to 300 labor to install between $50 and 200
so the total is .$1950?????..i hope that includes a rebuilt engine too ..get away from that rip off mechanic.....
I would suggest that you try a couple of other garages for quotes or you could try one of the large motoring organisations for advice.
Unless you personally know this ';Mechanic'; and know him to be genuine then get it checked out. I got ripped off a good many years ago by a so called mechanic, i got most of my money back after a friend of mine had a chat with him, but you might not be so lucky.
As i said check it out and good luck.How much should It cost to get coolant tubes in radiater changed ?
it will be a whole lot cheaper to just buy a new radiator. someimes you can find one still in good shape at the junk yards. but it is defenatly not worth 1500
It doesnt cost that much to get a new raidiator put in I suggest you find a new mechanic or an even better idea is take it to a raidiator shop and have them put a new core in it a couple of hundred at the most and your good
I don't know what country you're in but I live in the US and when my radiator is leaking, I call down to Auto Zone for a replacement. My truck radiator was $150 new. I priced one for my Mercury Villager and it was $199. Be serious. Take your business away from this guy, run don't walk. Know what the job should be worth before you walk into a repair shop.
Well there really isn't enough info for me to answer this question. What kind of car do you have?
I have never heard of replacing the ';Coolant Tubes'; are you sure he wasn't meaning to replace the whole radiator? Depending on what type of car you have you could always go to AutoZone.com and find out how much a new radiator would cost. Without knowing what type of car you are fixing it's really tough to give you a good answer. Good Luck.
it is cheaper by far to simply replace the radiator. most radiators, brand new run between 100-290 plus the installation charge. get yourself to a new service provider. this guy is giving the rest of us a bad name
a new radiator costs $100 to 300 labor to install between $50 and 200
so the total is .$1950?????..i hope that includes a rebuilt engine too ..get away from that rip off mechanic.....
How can I change my video settings on my PS3 without the right tv.?
My PS3 is set to HDMI but my Television is no longer working and I only have a regular tube tv. I need to change it to av from HDMI. If someone could get on their PS3 and write down the steps of getting to the right menu so I can just do this without the tv in a way.How can I change my video settings on my PS3 without the right tv.?
turn your ps3 off. make sure its connected with the composite cables (red/white/yellow). Then hold the power button to turn it on (it should beep a few times) then your audio/video settings will be reset.How can I change my video settings on my PS3 without the right tv.?
You have to do a video reset:
It may be necessary for you to change the Video Output Settings on the PLAYSTATION 3 in order to see a picture.
Reset Video Output
If you are changing cables or cannot see an image on the screen, you may need to reset the video output to default settings. To reset the video output:
While the PLAYSTATION 3 system is in standby mode (red light on the front of the system), hold down the touch-sensitive On/Off button on the front of the system until the PLAYSTATION 3 beeps twice (approximately 5 seconds), then release it.
The PLAYSTATION 3 will power up, the Video Output Settings will automatically reset to the standard resolution (or detect the current display output settings of your TV/monitor).
There's no way you can change the video settings without the TV display. You have to find an HDTV and hook up with your PS3 and then you can change the video settings to AV.
Do what Adidas said.
turn your ps3 off. make sure its connected with the composite cables (red/white/yellow). Then hold the power button to turn it on (it should beep a few times) then your audio/video settings will be reset.How can I change my video settings on my PS3 without the right tv.?
You have to do a video reset:
It may be necessary for you to change the Video Output Settings on the PLAYSTATION 3 in order to see a picture.
Reset Video Output
If you are changing cables or cannot see an image on the screen, you may need to reset the video output to default settings. To reset the video output:
While the PLAYSTATION 3 system is in standby mode (red light on the front of the system), hold down the touch-sensitive On/Off button on the front of the system until the PLAYSTATION 3 beeps twice (approximately 5 seconds), then release it.
The PLAYSTATION 3 will power up, the Video Output Settings will automatically reset to the standard resolution (or detect the current display output settings of your TV/monitor).
There's no way you can change the video settings without the TV display. You have to find an HDTV and hook up with your PS3 and then you can change the video settings to AV.
Do what Adidas said.
How do you change your username on a you tube account?
Thanks.. just want to know. I can change my password but not username. It's annoying!How do you change your username on a you tube account?
Currently, you cannot change your username?br>
there is simply too much information tied to each account. You may, however, sign up for a new account with the username that you desire.How do you change your username on a you tube account?
There's no wayblocked myspace advice how
Currently, you cannot change your username?br>
there is simply too much information tied to each account. You may, however, sign up for a new account with the username that you desire.How do you change your username on a you tube account?
There's no way
How to change your picture on your You-tube profile?
I am wondering how to change it! I just made a youtube and wanna set a picture to it! Please let me know!!
Thanks!How to change your picture on your You-tube profile?
home page %26gt; under your username click account %26gt; under the picture you currently have, click change %26gt; browse through file pictures or use something...just follow the directions that's on thereHow to change your picture on your You-tube profile?
Go to your channel. Find your Username in the upper-right hand corner and hover your mouse over it until a menu pops up. click on account. from there, you will see ';change'; under your picture.
Go to this link, http://www.youtube.com/account and under the picture it says change, you can either upload your own or use a video still.
Thanks!How to change your picture on your You-tube profile?
home page %26gt; under your username click account %26gt; under the picture you currently have, click change %26gt; browse through file pictures or use something...just follow the directions that's on thereHow to change your picture on your You-tube profile?
Go to your channel. Find your Username in the upper-right hand corner and hover your mouse over it until a menu pops up. click on account. from there, you will see ';change'; under your picture.
Go to this link, http://www.youtube.com/account and under the picture it says change, you can either upload your own or use a video still.
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