Diagnostics of coolers with oscillating fluid motion: Part I. Single diagnostic quantity Original Research Article

The small regenerative cryocooler is regarded as an instrument for cryorefrigeration whose instrument constant is designated as Cj (j=A, B, C). The cooler is represented by a reversible Carnot refrigerator–irreversible link combination. The refrigerator “pumps” the load (QL) from low temperature (TL) to a high (TH) location. A thermal link, called shunt, carries parasitic heat (Qp) from TH to TL. All cooler losses, in the 2nd law sense, are assigned to the shuntʹs Qp rate. We find three different, simplest instrument constants CA (=truncated single term, the cryocooler case), CB (=1-term, truncated, equivalent to the Bejan model), CC (two-term case represented entropy generation).We compare the three functions with the recent data (Radebaugh set of 1996 for Stirling and pulse tube coolers). We conclude that indeed a single instrument constant is useful in distinguishing data of similar cryocoolers.