Measures to minimize entropy production in compression-resorption heat pumps

Compression-resorption heat pumps (CRHP) enhanced by wet compression are considered a very promising option to upgrade low grade waste heat from the industry. This is especially true for applications where the heat source and/or sink have a large temperature glide. But commercial solutions using wet compression are not yet available on the market. Compared to the classically used vapor compression heat pumps (VCHP), CRHP can provide much better performance but only if the efficiency of the compressor exceeds 0.7. In this respect, a twin screw compressor has been identified as a potential solution to reach this efficiency goal. This study makes use of the entropy production minimization to identify where the major irreversibilites are located in a CRHP system operated with an ammonia-water mixture. A detailed model of the wet compressor and the resorber are coupled with simplified models of other components of the HP cycle to analyze where potential improvements can be made. The results show that significant benefits can be obtained using CRHP.