Novel intermittent absorption cooling system based on membrane separation process

The present work analyses an intermittent absorption cooling system using a hydrophobic porous membrane unit as desorber/condenser and powered by thermal solar energy. Experimental test runs were carried out in a membrane unit to experimentally determine the amount of refrigerant produced at different operating temperatures. With the obtained information, an intermittent absorption cooling system was modelled at a larger scale using information from real solar collectors and considering a 1 m2 membrane area. According to the experimental performance of the desorber/condenser unit, after 4 h of operation, the total amount of refrigerant produced was 14.50, 11.59 and 7.20 kg for desorber temperatures of 95.1, 85.2 and 75.1 °C, respectively. The designed solar system was composed of a 0.3 m3 storage thermal tank, and 30.2, 25.6 and 20.9 m2 of solar collector area for each desorber thermal level. According to the simulation of the absorption cooling system, evaporator temperatures of 18 and 14 °C were achieved for desorber temperatures of 75.1 and 85.2 °C, while evaporator temperatures of 17 and 12 °C were obtained at 95.1 °C. The COPs were 0.15, 0.21 and 0.26, which increased according to the increase in the desorber temperatures. Based on the clear desorber/condenser tendencies obtained from the refrigerant production, additional absorption conditions were calculated and may be useful for future designs. The lowest evaporator temperature was 6 °C when the initial LiBr concentration was 54.83% w/w, instead of 50.30% w/w at a temperature of 95.1 °C; however, the COP decreased 33%.