Some Issues in the Use of Refrigerant Mixtures

The use of refrigerant mixtures in refrigeration machines has been proposed in the technical literature. Some but not all of the arguments for and against the use of mixtures as refrigerants are examined in this study. An issue associated with use of blends is the segregation on leakage and the ensuing loss in capacity and performance change on repeated recharging with the original mixture. We have simulated this phenomenon by creating a variable vapor leak in a 30170 mixture of HFC-32/HFC134a, which has been proposed recently as an R-22 replacement. The experiment shows that the fractionation depends on temperature and can give off potentially flammable vapors. The recharging process is simulated and the effect on refrigeration capacity is calculated as a function of leak rate and of numbers of recharging cycles. It is concluded that if leakage for 32-134a system is 10% of more of the charge, continual loss in capacity will occur even with recharging.