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)
“To vote is like the payment of a debt—a duty never to be neglected, if its performance is possible.”
—Rutherford Birchard Hayes (1822–1893)
“There are people who think that wrestling is an ignoble sport. Wrestling is not sport, it is a spectacle, and it is no more ignoble to attend a wrestled performance of suffering than a performance of the sorrows of Arnolphe or Andromaque.”
—Roland Barthes (1915–1980)