Optimum staging of multistage exo-reversible refrigeration systems

A general staging model is developed to optimize multistage exo-reversible refrigeration systems affected solely by internal irreversibilities. Under some reasonable assumption, the same high to low temperature ratio is found at each stage so as to maximize the coefficient of performance of a multistage combined refrigeration system, where each stage is subjected to an independent refrigeration subcycle. This model is then applied to the optimum staging of two configurations of multistage thermoelectric coolers, which are the ones with different and identical electrical current flowing through each stage, respectively. For both the two cases, the optimum stage temperatures are numerically proved to follow from the ideal staging well. Detailed optimum staging parameters of both types of thermoelectric coolers are calculated with commercially available thermoelectric (TE) materials. The temperature dependence of TE properties has been taken into account. (C) 2003 Elsevier Science Ltd. All rights reserved.