Design and analysis of an ammonia-water absorption heat pump

This study focuses on the improvement of the efficiency of an absorption heat pump for high heating temperatures with ammonia-water as working pair, based on experimental investigations. For this purpose, the absorber and the solution heat exchanger are designed. Furthermore, a new generator assembly, consisting of a plate heat exchanger (PHX), a storage tank and a separator, is implemented in the absorption heat pump. In comparison to a vessel-type generator, the weight of the residential size absorption heat pump with a total heating power of about 20 kW in OP1 was decreased from 300 kg to 180 kg. The ammonia filling quantity was also reduced from 15 kg by at least 9.5 kg compared to a vessel-type generator. Experimental investigations are carried out at different operating points where each operating point represents a specific loading condition in the building heating system. An efficiency up to COPh = 1.42 is achieved. Even at challenging conditions like a low external evaporator inlet temperature of - 10 degrees C or a high external condensator outlet temperature of 63 degrees C, a COPh of 1.10 and 1.05 respectively is reached. The solution heat exchanger is working excellently with an efficiency of 0.972 < 0.996. Furthermore, improvements like an integration of a condensate separator or an absorber with internal heat recovery are presented.