Performance of heat-transfer irreversible regenerated Brayton refrigerators

The performance of an externally and internally irreversible regenerated Br ayton refrigerator is analysed. Analytical relationships between cooling lo ad and pressure ratio, as well as between coefficient of performance (COP) and pressure ratio of a real closed irreversible regenerated Brayton refrig eration cycle coupled to constant- or variable-temperature heat reservoirs are derived. The irreversibilities considered in the analysis include the h eat transfer losses in the hot- and cold-side heat exchangers and the regen erator, the non-isentropic expansion and compression losses in the compress or and expander, and the pressure drop losses in the piping system. The opt imal performance characteristics of the cycle may be obtained by optimizing the distribution of the heat conductance or heat transfer surface areas am ong the two heat exchangers and the regenerator. The influences of the effe ctiveness of the regenerator as well as the hot- and cold-side heat exchang ers, the efficiencies of the expander and the compressor, the pressure reco very coefficient, and the inlet temperature ratio of the heat reservoirs on the cooling load and the COP are examined and shown by numerical examples.