Experimental study on compression/absorption high-temperature hybrid heat pump with natural refrigerant mixture

This research concerns the development of a compression/absorption high-temperature hybrid heat pump that uses a natural refrigerant mixture. Heat pumps based on the compression/absorption cycle offer various advantages over conventional heat pumps based on the vapor compression cycle, such as large temperature glide, temperature lift, flexible operating range, and capacity control. In this study, a lab-scale prototype hybrid heat pump was constructed with a two-stage compressor, absorber, desorber, desuperheater, solution heat exchanger, solution pump, liquid/vapor separator, and rectifier as the main components. The hybrid heat pump system operated at 10-kW-class heating capacity producing hot water whose temperature was more than 90°C when the heat source and sink temperatures were 50°C. Experiments with various NH ₃/H₂O mass fractions and compressor/pump circulation ratios were performed on the system. From the study, the system performance was optimized at a specific NH3 concentration.