Experimental investigation on NH3-H2O absorption refrigeration: from single-stage to two-stage, from water-cooled to air-cooled

Experimental prototypes have been built to investigate NH3-H2O absorption refrigeration. The experimental researches are carried out from single-stage to two-stage, from water-cooled to air-cooled. The experimental data of single-stage water-cooled cycle shows the cycle performances and its limitations. Air-cooled mode should be adapted for residential uses of solar cooling, meanwhile two-stage cycle could use low-grade solar energy efficiently. A novel two-stage air-cooled NH3-H2O absorption refrigeration has been built to test the theory. The system can work as both single-stage and two-stage according to different ambient temperatures. The system is without cooling water tower and rectifier. 70-85°C solar hot water is enough to drive the system. Thermal COP ranges from 0.2 (two-stage) to 0.45 (single-stage). Electrical COP ranges from 5 to 12 respectively. Variable working conditions are performed and compared with the simulation results. The main drawback is that the efficiencies of fluid machineries are too low which limit the electrical COP. The experimental studies show that two-stage air-cooled NH3-H2O absorption refrigeration is technically feasible in practical solar cooling applications and low-grade heat utilization.