Diagnostics of coolers with oscillating fluid motion Part I. Single diagnostic quantity

The small regenerative cryocooler is regarded as an instrument for cryorefr igeration whose instrument constant is designated as C-j (j = A, B, C). The cooler is represented by a reversible Carnot refrigerator-irreversible lin k combination. The refrigerator "pumps" the load (Q(L)) from low temperatur e (T-L) to a high (T-H) location. A thermal link, called shunt, carries par asitic heat (Q(p)) from T-H to T-L. All cooler losses, in the 2nd law sense , are assigned to the shunt's Q(p) rate. We find three different, simplest instrument constants C-A ( = truncated single term, the cryocooler case), C -B ( = I-term, truncated, equivalent to the Bejan model) C-C (two-term case represented entropy generation). We compare the three functions with the r ecent data (Radebaugh set of 1996 for Stirling and pulse tube coolers). We conclude that indeed a single instrument constant is useful in distinguishi ng data of similar cryocoolers. (C) 2001 Published by Elsevier Science Ltd.