Experimental investigation on NH₃-H₂O compression-assisted absorption heat pump (CAHP) for low temperature heating in colder conditions

The coefficient of performance (COP) and heating capacity of the absorption heat pump (AHP) decreased obviously as the evaporator inlet temperature dropped. Compression-assisted AHP (CAHP) could operate efficiently in colder conditions, and a prototype was constructed for experimental investigation. At a generator inlet of 130°C, as the evaporator inlet decreases from -5°C to -25°C, the COP drops from 1.513 to 1.372, while the heating capacity deteriorates from 77.26 kW to 47.11 kW. Comparisons between CAHP and normal AHP indicated that CAHP can extend the lower limit of evaporator inlet temperature from -10°C to -25°C. Besides, CAHP can enhance the heating capacity by approximately 55.5-85.0% even when AHP can operate normally. Moreover, the improvement contributed by CAHP is greater under much colder conditions. The heating COP and capacity of CAHP are improved in all the conditions, while the primary energy efficiency is advantageous under lower evaporator inlet temperatures.