Construction and testing of a wet-compression absorption carbon dioxide refrigeration system for vehicle air conditioner

The environmental benefits of the transcritical carbon dioxide (CO2) refrigeration cycle are considerable. But its application is greatly challenged by the high operation pressure, which could be as high as 120 bar. A wet-compression absorption (WCA) CO2 refrigeration cycle was constructed by adding a non-volatile liquid into a CO2 refrigeration cycle. CO2 is highly soluble in the liquid and easily absorbed and desorbed by it. In the WCA CO2 refrigeration cycle, the high side pressure was less than 35 bar, which was tremendously reduced compared to the transcritical CO2 refrigeration cycle. In this paper, following a thermodynamic analysis of working fluid, a WCA CO2 refrigeration demonstrator plant was constructed within the restricted physical and operational envelope of an existing vehicle refrigeration unit. This unique plant operated satisfactorily, delivering sustainable cooling for refrigerated vehicle. The relationship between system performance and the cycle ratio and IHX (internal heat exchanger) efficiency was tested. The components used in the demonstrator were entirely based on existing components and not optimized and considerable potential exists for efficiency improvements.