An investigation of some heat transfer and gas flow problems relevant to miniature refrigerators
The performance of regenerative miniature refrigerators is governed by heat transfer and pressure drop losses, particularly in the regenerator. Steady flow experiments have been performed on various regenerator matrices at cryogenic temperatures and heat transfer from helium gas to the matrix, and pressure drop across the matrix have been determined. These data have been found to be in reasonable agreement with data obtained by other workers using transient flow techniques. In order to determine the applicability of such data to the performance of a cooling engine, experimental methods have been developed to measure the performance and losses in a working Stirling-cycle miniature refrigerator. These techniques have led to the analysis of pressure drop and shuttle heat transfer losses, regenerator efficiency, and to the measurement of other losses in the refrigerator. An energy balance is performed on the machine. These novel techniques, which allow the factors determining poor performance of a working refrigerator to be measured in situ, may be applied profitably to other cyclic machines.