Performances Study of Eco-friendly Binary Azeotropic Mixtures Used as Working Fluid in Three Refrigeration Cycles

Abstract

According to the European (F-gas) regulation, all refrigerants with a global warming potential (GWP) above 150 will be out by 2030. Searching for alternative refrigerants that are environmentally friendly has become an urgent challenge for the refrigeration and air-conditioning sector. Based on their environmental advantages and good thermo-physical properties, azeotropic mixtures have recently gained special interest as substitutes for conventional refrigerants. This study aims to compare the performance of three eco-friendly azeotropic mixtures with the common refrigerant R134a in three refrigeration cycles: the basic cycle (BC), the ejector-expansion refrigeration cycle, and the ejector sub-cooled cycle. The mixtures under study are R1234ze+R600a, R1234yf+R600a, and R1234yf+R290. These mixtures have global warming potential (GWP) of 5.668, 3.8688, and 3.2865 respectively, whereas R134a has a GWP of 1430. To reach this objective a numerical program was developed using MATLAB software to evaluate the coefficient of performance (COP), and the cooling capacity of the three refrigeration cycles using the studied eco-friendly mixtures and were compared with those of the commonly used R134a refrigerant. The entrainment ratio was also compared for the two ejector cycles using these refrigerants. The simulation was realized for condensing temperatures (Tc) selected between 30 and 55°C and evaporation temperatures (Te) ranging between -10 and 10°C. The results have shown that the eco-friendly azeotropic mixture R1234yf+R290 (GWP=3.51) has the best performances compared to the two other mixtures and they are close to those of R134a. On the other hand, the ejector expansion refrigeration cycle has exhibited a high coefficient of performance compared to the basic cycle and ejector sub-cooled cycle, and a high entrainment ratio compared to the ejector sub-cooled cycle for all used refrigerants. However, the ejector sub-cooled cycle gave a better cooling capacity than the other cycles. According to the obtained results, the azeotropic mixture R1234yf+R290 apart from its excellent environmental properties yields better performances in most of cases, this confirms that it could be a suitable substitute for conventional working fluid R134a which has a great global warming potential.