Working domains of a novel solar-assisted GAX-based two-stage absorption-resorption heat pump with multiple internal heat recovery for space heating

Ammonia-water absorption-resorption heat pumps have great potential in efficiently utilizing low-temperature heat for space heating or hot water supply. However, single-stage absorption-resorption heat pumps have disadvantages of poor low ambient temperature adaptability and low heat supply temperature over conventional absorption heat pumps, which limit their applications in cold regions. In this paper, a novel GAX-based two-stage absorption-resorption heat pump cycle with multiple internal heat recovery is proposed aiming to expand the application scope at lower ambient temperatures, to raise the heat supply temperature and more significantly to utilize solar heat for space heating for longer solar working time with higher contribution. Feasible operation pressure combinations to enable the cycle were investigated. Coefficient of performance, ambient air temperature restrictions, heat source temperature demand, heat supply temperature level, heat inputs/outputs and solution circulation ratios of generators in terms of different operation pressure combinations were revealed by comparing with those of the single-stage cycle. Under given operation conditions, maximum COP value of 1.367 and heat supply temperature of 46.1 degrees C can be obtained and the cycle could be operated at ambient air temperatures above (-)15.6 degrees C. The heat supply temperature is generally above 42 degrees C, which is suitable for building floor heating or fan coil heating. The cycle can be driven by heat source above 73 degrees C, highlighting the possibility of integrating it with more economical solar collectors for high efficiency space heating.