Space-conditioning using triple-effect absorption heat pumps

A triple-effect cycle absorption heat pump was investigated in this study using OSU-ABSIM, a modular steady state simulation program. Ammonia-water solution was used as the working fluid for the upper, high pressure cycle, while ammonia-water and ammonia-sodium thiocyanate solutions were investigated for the lower pressure cycle. The overall system is so configured that the absorber, condenser, and rectifier heat duly from the high pressure cycle is rejected to the generator of the low pressure cycle. The complete absorption system was analyzed, including air-to-hydronic heal exchangers and the natural gas-fired generator. Cycle performance was modeled over a wide range of cooling and heating mode ambients to determine the overall benefits of using this cycle. The effect of high ambient temperatures on the rise in the highest cycle pressures and temperatures (to maintain coupling between the two cycles) was investigated over the range of expected ambients. Parametric studies were conducted on several significant variables that affect cycle performance, such as heat exchanger sizes and different control schemes. The results of this study can be used to determine the merits of this cycle versus other absorption heat pump alternatives, specifically in terms of potential COP benefits for additional system complexity. (C) 1997 Elsevier Science Ltd.