Performance Analysis and Experimental Study of Quasi-two-stage Heat Pump Cycle

To solve the contradiction between the surplus of low-temperature waste heat resources and the shortage of high-temperature heat demand, this study designed a set of high-temperature heat pump unit based on quasi-two-stage compression. The cycle was analyzed theoretically, and the design was optimized. A combination of a flash tank and an internal heat exchanger was used to improve the performance of the unit, and a performance test of the unit was carried out. The performance of the unit was analyzed under conditions in which the outlet water temperature of the condenser was 85 ℃-120 ℃ and the inlet water temperatures of the evaporator were 50 ℃, 60 ℃, and 70 ℃. Heating capacity, coefficient of performance (COP), exergetic efficiency, condensing pressure, and discharge temperature were taken as the performance indicators. The performance of the experimental unit was consistent with the theoretically calculated performance. The inlet water temperature of the evaporator was 49.8 ℃, and the outlet water temperature of the condenser was 118.1 ℃. The maximum heat produced by the unit, COP, and exergy efficiency were 916.3 kW, 2.51, and 46.3%, respectively. Meanwhile, the condensing pressure of the unit was 1.8 MPa, and the discharge temperature was 137 ℃; these values meet the safety requirements of the unit.