Performance
The performance of the cooler is determined mainly by the quality of the regenerator. It has to satisfy conflicting requirements: it must have a low flow resistance (so it must be short with wide channels), but the heat exchange should also be good (so it must be long with narrow channels). The material must have a large heat capacity. At temperatures above 50 K practically all materials are suitable. Bronze or stainless steel is often used. For temperatures between 10 and 50 K lead is most suitable. Below 10 K one uses magnetic materials which are specially developed for this application.
The so-called Coefficient Of Performance (COP) of coolers is defined as the ratio between the cooling power and the compressor power P. In formula: . For a perfectly reversible cooler, is given by the famous relation
| (1) |
which is also called the Carnot COP. However, a pulse-tube refrigerator is not perfectly reversible due to the presence of the orifice, which has flow resistance. Therefore equation (1) does not hold. Instead, the COP of an ideal PTR is given by
| . | (2) |
Comparing relations 1 and 2 shows that the COP of PTR’s is lower than that of ideal coolers.
Read more about this topic: Pulse Tube Refrigerator
Famous quotes containing the word performance:
“They say all lovers swear more performance than they are able, and yet reserve an ability that they never perform; vowing more than the perfection of ten, and discharging less than the tenth part of one.”
—William Shakespeare (1564–1616)
“Having an identity at work separate from an identity at home means that the work role can help absorb some of the emotional shock of domestic distress. Even a mediocre performance at the office can help a person repair self-esteem damaged in domestic battles.”
—Faye J. Crosby (20th century)
“Just as the performance of the vilest and most wicked deeds requires spirit and talent, so even the greatest demand a certain insensitivity which under other circumstances we would call stupidity.”
—G.C. (Georg Christoph)