Performance investigation of a solar hot water driven adsorption ice-making system

A solar hot water driven solid adsorption ice-making system with heat storage was designed and constructed. The finned-tube absorbent bed in the water tank, which also acted as heat storage unit, was heated by the hot water from the solar vacuum tube collector in desorption process. The water in the tank was also auxiliary heated by electric heater to keep at the set desorption temperature. Activated carbon-methanol was utilized as the working pairs in the system. Effects of heat source temperature on system performance were experimentally investigated under four conditions: maintaining the water temperature in the tank at 94 °C (boiling point), 85 °C, 75 °C, respectively, and heating the water to reach 94 °C then naturally cooling the hot water without maintaining heating in desorption process. The experimental results showed that the temperatures around the finned-tube of the adsorbent bed was homogeneous, which was beneficial for desorption of the adsorbate. The maximum daily ice-making capacity of 8.4 kg and the lowest temperature of −8.6 °C were achieved when the hot water temperature was maintained at 94 °C. The maximum refrigeration cycle coefficient of performance (COP) of 0.139 was obtained under the condition of heating the water to reach 94 °C then cooling naturally the hot water without maintaining heating. The system heat utilization efficiency decreased with the increase of heat source temperature due to the greater heat loss in desorption process.