Performance evaluation of a generator-absorber heat-exchange heat pump

A generator-absorber heat-exchange (GAX) heat pump was modeled in this study using OSU-ABSIM, a modular steady-state simulation program. While the thermodynamics of GAX cycles have been investigated in the past, a comprehensive implementation-related performance evaluation of this cycle is not available. Therefore, in the present study, the complete absorption system was analyzed for the heating and cooling modes, including air-to-hydronic heat exchangers and a natural gas-fired generator. Several significant variables that affect cycle performance were systematically investigated. The effect of ambient temperature on system COP was determined for the cooling and heating modes. The system cooling COP at the rating point was maximized by varying the heat-exchanger UA values. The decrease in GAX overlap at low ambients, and the corresponding transformation to the absorber heat-exchange cycle was also modeled; and the implications on system COP were investigated. Furthermore, the role of an additional solution-solution heat exchanger at the low ambients in enhancing COP was quantified. The results of this study can be used to determine the merits of this cycle versus other absorption heat-pump alternatives. The comprehensive investigation of performance (including off-design conditions) allows the evaluation of year-round performance, which can be used in conjunction with climate data to establish the applicability to different geographic locations. Copyright (C) 1996 Elsevier Science Ltd