Thermodynamic analysis of regenerated air-cycle refrigeration in high and low pressure configuration

•Low-temperature air-cycle refrigeration thermodynamic analysis is performed.•Optimal configurations and benefits of regeneration are identified.•High regeneration rate equals the performance of high- and low-pressure cycles.•Staged compression with inter-cooling is mostly ineffective.•Achievable performance of a feasible, highly effective regenerator is assessed.

A thermodynamic analysis is performed on open, regenerated, inverse air-cycles, focussing on low temperature refrigeration, in order to provide general optimization criteria, support for a rational configuration choice and potential performance improvement for this specific application. The effect of high regenerator effectiveness (0.95) is explored, showing that it may double the air cycle COP in the case at hand. Low and high pressure configurations (i.e. featuring only one heat exchanger on the cold or hot cycle side) are compared. High pressure configuration, normally preferred in the field of low temperature refrigeration, has a lower efficiency, but the gap reduces as regenerator effectiveness increases. Avoidance of a cold heat exchanger eliminates frosting problems and power input for the circulation fan, so that the small COP decrease suffered by the high pressure cycle can easily be compensated for and eventually yield higher average plant efficiency. The feasibility of such a highly effective regenerator, already reported in the literature, is demonstrated using classic Kays and London (1964) data.