Thermodynamic performance prediction of pulse tube refrigeration with mixture fluids

A refrigeration cycle with two isentropic and two isobaric processes, refer red to as the modified Brayton cycle, is introduced for predicting the ther modynamic performance of pulse tube refrigeration with a binary mixture ref rigerant. The corresponding theoretical expressions of cooling power, therm odynamic efficiency and required work of a refrigeration cycle are establis hed. Based on the prediction calculations for a number of cryogenic fluids, promising mixture pairs of working refrigerants are recommended. The compu ted results show that 9.5% of the coefficient of performance (COP) and 6.7% of the cooling power at 80 K could be gained if a mixture pair of 10% nitr ogen and 90% helium is used instead of pure helium for the pulse tube refri geration. The minor mixture pairs which have a positive effect on pulse tub e refrigeration at temperatures near 80 K, including hydrogen-helium, argon -helium and neon-helium, are also discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.