Experimental investigation on NH₃-H₂O compression-assisted absorption heat pump (CAHP) for low temperature heating under lower driving sources

The absorption heat pump (AHP) heating system is an efficient alternative to the conventional fuel-based heating systems, with energy saving rate reaching 20-50%. However, the coefficient of performance (COP) and heating capacity of normal AHP decreased obviously as the available driving source temperature dropped. Compression-assisted AHP (CAHP) could operate efficiently under lower driving sources, and an experimental prototype was constructed for performance investigation. At an evaporator inlet of -10 °C, as the generator inlet decreases from 130 °C to 115 °C, the COP changes from 1.442 to 1.271, while the heating capacity drops from 68.21 kW to 31.28 kW. At an increased evaporator inlet of -5 °C, as the generator inlet decreases from 130 °C to 110 °C, the COP changes from 1.511 to 1.103, while the heating capacity drops from 78.72 kW to 21.71 kW. Comparisons between CAHP and normal AHP indicated that CAHP can extend the lower limit of generator inlet temperature from 125-130 °C to 110-115 °C. Besides, CAHP can enhance the heating capacity by 96.4% even when AHP can operate normally at a generator inlet of 130 °C. Moreover, performance improvement contributed by CAHP is greater under lower-temperature driving sources.