22 May 2002
Combined solar ejector-vapour compression air conditioning system comprises an ejector cycle operating at the higher pressure-loop powered by solar energy and a low-pressure conventional vapour compression cycle. The combined system harvests the advantages of both the ejector and vapour compression cycles, therefore provides higher COP than conventional cycles. This system has attractive economic and environmental propositions since it uses solar energy as its major energy source. Most working fluids studied for the combined solar ejector-vapour compression cycle are the HCFCs and HFCs. Due to their high global warming potential (GWP), these types of refrigerants are next in line to be phased out following the CFCs. The focus of this paper is to investigate the potentials of some alternative (and natural) refrigerants such as ammonia, hydrocarbons, carbon dioxide and water. Thermodynamic, economic, environmental and performance comparisons were made with several common existing refrigerants. Combined system performance simulations were performed with the refrigerants used in pairs under varying intercooler temperature. Effects of intercooler temperature variation on system performance were pointed out. Refrigerants responses to changing intercooler temperature were also discussed.