Laser cooling

Laser cooling is a technique that uses light to cool atoms to a very low temperature.

It was simultaneously proposed by two groups in 1975, the first being David J. Wineland and Hans Georg Dehmelt and the second being Theodor W. Hänsch and Arthur Leonard Schawlow. It was first demonstrated by Wineland, Drullinger, and Walls in 1978 and shortly afterwards by Neuhauser, Hohenstatt, Toschek and Dehmelt. One conceptually simple form of laser cooling is referred to as optical molasses, since the dissipative optical force resembles the viscous drag on a body moving through molasses. Steven Chu, Claude Cohen-Tannoudji and William D. Phillips were awarded the 1997 Nobel Prize in Physics for their work in laser cooling.

Several somewhat similar processes are also referred to as laser cooling, in which photons are used to pump heat away from a material (normally a solid) and thus cool it. The phenomenon has been demonstrated via anti-Stokes fluorescence, and both electroluminescent upconversion and photoluminescent upconversion have been studied as means to achieve the same effects.

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Reciprocating compressor

A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft^{[1] [2]} to deliver gases at high pressure.

The intake gas enters the suction manifold, then flows into the compression cylinder where it gets compressed by a piston driven in a reciprocating motion via a crankshaft, and is then discharged. We can categorize reciprocating compressors into many types and for many applications. Primarily, it is used in a great many industries, including oil refineries, gas pipelines, chemical plants, natural gas processing plants and refrigeration plants. One specialty application is the blowing of plastic bottles made of Polyethylene Terephthalate (PET)

See also

• Centrifugal compressor
• Vapor-compression refrigeration
• Diving air compressor

References

1. ^ Bloch, H.P. and Hoefner, J.J. (1996). Reciprocating Compressors, Operation and Maintenance. Gulf Professional Publishing. ISBN 0-88415-525-0.
2. ^ Reciprocating Compressor Basics Adam Davis, Noria Corporation, Machinery Lubrication, July 2005

Calculation of required cylinder compression for a multistage reciprocating compressor

http://en.wikipedia.org/wiki/Reciprocating_compressor

The Dangers of Second Hand Refrigeration Equipment

Second hand refrigeration equipment is often thought to be good value for money for the small to medium catering or leisure business. Unfortunately, as many will testify, this is a false economy. Commercial refrigeration depends on reliability and quality, and even the best second hand equipment can't offer that with certainty. The only way to personally ensure your business is covered is to invest in new refrigeration equipment. This will largely come with a warranty for a given period, which will afford peace of mind in the face of disaster. If your business depends on refrigeration, it is crucial that you invest in the proper equipment to avoid paying through the nose for repairs and spare parts.

Buying a second hand commercial refrigerator isn't as simple as buying a second hand car or van. With a second hand car, you get the chance to inspect the engine (if you know what you are looking for), look around for the tell tale signs of rust and degeneration, and maybe even take a test drive to determine other aspects of performance that aren't immediately obvious. Additionally, you can generally get a fair idea of the state of the vehicle simply by looking at it, which means you can weigh up your decision effectively, even without a trained eye. Add to that a record of past ownership and an indication of level of use through mileage and you're going to be capable of forming a rounded opinion. Now consider refrigeration equipment. When buying second hand, there's no test drive. There's no opportunity to inspect the engine, or rather the compressor, because you can't see inside the unit. There's simply no way to gauge by looking at the unit, and even with a t

rained eye, you'd find it hard to predict the lifespan of any particular second hand unit. On top of that, there's no way of knowing how old the unit is, or under what conditions it has been used. In fact, you don't even know that the unit is working effectively, and there's no way to tell until it ruins stock. Furthermore, you might find a great price on a second hand unit, but it's likely you will end up spending double or more on repairs within the first six months of use, and you won't find any warranty in place to cover these costs.

With new equipment, you are firstly guaranteed that the unit is clean, in addition to knowing it is up to date technology. You know the compressor is clean and free of any restrictions and dirt, and you know it's running perfectly unless you have to rely on the warranty. In fact with most new units, it's rare to see a need for repairs years beyond any warranty the manufacturers give. Although new equipment might be more expensive in terms of capital outlay, the cost of keeping the machine going will be significantly less over the long term, which will save you money as well as produce better results.
http://www.articlesbase.com/online-business-articles/the-dangers-of-second-hand-refrigeration-equipment-114455.html

Refrigeration 2

Did'nt you know about hermatic compressor?but can be application for Ultra Low Temperature?
for this now we should answer "i don't know".
i have 3 type of compressor common using for Ultra Low Temperature, not just say but i have prove for this case.
list 1. copeland RF41 type
2. danfoss GS type
3. embraco J type

all the compressor at list can be application on Ultra Low Temperature...., operating system is
-40 until -86 C.
just for share if you have any information.
please share with me...............................

Refrigeration 1

A refrigerator (often called a "fridge" for short) is a cooling appliance comprising a thermally insulated compartment and a heat pump—chemical or mechanical means—to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Refrigerators are extensively used to store foods which spoil from bacterial growth if not refrigerated. A device described as a "refrigerator" maintains a temperature a few degrees above the freezing point of water; a similar device which maintains a temperature below the freezing point of water is called a "freezer." The refrigerator is a relatively modern invention among kitchen appliances. It replaced the icebox, which had been a common household appliance for almost a century and a half prior. For this reason, a refrigerator is sometimes referred to as an "icebox"