ADIABATIC LOSSES IN STIRLING REFRIGERATORS

The Stirling cycle has been used very effectively in cryocoolers; but efficiencies relative to the Carnot limit are typically observed to pe ak for absolute temperature ratios of about two which makes it less su itable for low-lift refrigeration. The adiabatic loss appears to be re sponsible for poor performance at small temperature differences. In th is paper, adiabatic losses are evaluated, for a temperature ratio of 2 /3, taking into account the effect of phase angle between pistons, of volume ratio, of the distribution of the dead volume necessary to redu ce the volume ratio, and of the distribution of displacement between e xpansion and compression spaces. The study is carried out numerically, using an adiabatic Stirling engine model in which cylinder flow is as sumed to be stratified. Results show that the best location for the cy linder dead volume is on the compression side. Otherwise all strategie s used to trade off refrigeration for coefficient of performance are f ound to be roughly equivalent.