Conference Year



COP, zeotoropic mixture, R1234yf, R32, R744


     Hydro-fluorocarbons (HFCs) are widely used as working fluids (refrigerants) in air-conditioning and refrigeration systems. However, at the 1997 Kyoto Conference (COP3), it was determined that the product and use of HFCs should be regulated due to their high global warming potential (GWP). In the above mentioned situation for the air-conditioning and refrigeration systems, recently, R1234yf having extremely low-GWP was nominated as one of the alternates of HFCs. Some literatures reported that the heating capacity of heat pump cycles using R1234yf is less than R410A because of its smaller vapor density and latent heat. To achieve the performance comparable to R410A, much larger unit is required. Therefore, in this present study, mixing with R32 of larger latent heat and relatively low-GWP into R1234yf was attempted. Additionally, R744 having higher vapor density and extremely low-GWP was added into R32/R1234yf.  The R32/R1234yf and R744/R32/R1234yf are zeotropic mixtures that cause temperature change during the phase-change, typically called temperature glide. When this temperature glide is utilized effectively to decrease the irreversible loss in heat exchanger, the cycle performance can be improved. The degree of temperature glide is determined by the composition of refrigerant mixtures. The composition of the test refrigerants are selected from the criterions of GWPs just below 300 and 200.Experiment was conducted with a vapor compression heat pump cycle using a compressor developed for R410A. The condenser and the evaporator are tube-in tube heat exchangers of counter-flow configuration.  At compositions with GWP200 and a given heating capacity, the COP of R32/R1234yf and R744/R32/R1234yf are lower than that of R410A. The main causes were that R32/R1234yf of GWP200 has lower vapor density and R744/R32/R1234yf of GWP200 has lager temperature glide. At compositions with GWP300, R32/R1234yf and R744/R32/R1234yf exhibit comparable COP and heating capacity to R410A. Using R32/R1234yf and R744/R32/R1234yf of compositions with GWP300, as the alternatives of R410A, is feasible idea.