Performance characteristics of pulse tube refrigerators

Abstract

In the present study experiments were carried out to investigate the performance characteristics of pulse tube refrigerators. It was found that the cool-down time t c during the transient or start-up period is dominated by the time constant of the pulse tube wall τ pt and that the dynamics of a basic pulse tube (BPT) refrigerator approaches that of a first-order system. For steady state operation, the cold-end temperature T L was found to vary with τ pt, and the cooling load Q L increases monotonically with increasing τ pt. This indicates that heat pumped by the gas from the cold to the hot end increases with decreasing h pt (i.e. less energy exchange between the gas and wall). The process of heat storage or release of the pulse tube wall is thus shown to have a negative effect on the performance of a BPT refrigerator. It was thus found experimentally that the gas compression/expansion process inside the pulse tube, which is similar to a Brayton cycle but lies between isothermal and adiabatic, can explain the performance of BPT refrigerators. The present experiment also shows that the performance of a pulse tube refrigerator at transient and steady states is mainly dominated by the time constant of the pulse tube wall τ pt.