Comparison of the solar-operated two-stage and single-stage LiBrH2O absorption cycles

Abstract

Analysis of a solar operated two-stage LiBrH₂O cycle is presented. The cycle has the advantages that it can operate at a higher ambient temperature and at a lower generator temperature than those required by the single stage cycle. The performance of the cycle is predicted and compared to the performance of the single stage cycle at various design conditions. Four design parameters are identified to control the performance of the cycle. These parameters are the heat sink temperature, the evaporator temperature, the generator temperature, and the intermediate pressure. Numerical correlations are developed to specify the minimum allowable sink temperature, the minimum and maximum allowable generator temperature and the coefficient of performance of both the single-stage and the two-stage cycles. By defining a system thermal ratio for the combined absorption machine and a flat plate collector, the performances of the integrated systems are evaluated and compared when using both cycles. Conditions at which the performance of the solar operated two-stage cycle is superior to that of the solar operated single stage cycle are defined.