Theoretical Analysis of Hydrocarbon Refrigerant Mixtures as a Replacement for HCFC -22 for Residential Uses

This paper investigates the feasibility of hydrocarbon refrigerant mixtures as a replacement for HCFC-22 in residential air-conditioning and heat pump systems. The COP and the seasonal performance factor (SPF) were calculated using a UA-model for single component refrigerants and refrigerant mixtures. Simulations were run for pure propane and the mixtures of propane/i-pentane, propane/n-butane, and propane/i-butane. The simulation results obtained with the hydrocarbon refrigerants were compared to the results with pure HCFC-22 and the mixture of HFC-32/HFC-125 (50/50 wt. %) a mixture of HFC-32/HFC-l25/HFC-134a (23/25/52 wt. %). 1.0 Introduction HCFC-22 is widely used as a refrigerant, both for commercial and residential heating and cooling applications. However, based on its ozone depletion potential of 0.055 Ill, as compared to the refrigerant CFC-11 (ODP of CFC-11 = 1.0), HCFC-22 will be phased out in the future /2/. Currently no acceptable pure fluid has been identified as a drop-in substitute for HCFC-22. However, binary and ternary mixtures of HFC's such as HFC32/HFC-125 (50/50 wt. %) /3/ and HFC-32/HFC-125/HFC-134a (23/25/52 wt. %) /4/ are currently being promoted by the refrigerant manufacturers. The disadvantage of these mixtures is the relatively high direct global warming potential which can be significantly reduced by utilizing hydrocarbon refrigerants. Therefore, the objective of the work presented here is to evaluate the COP and seasonal performance factor (SPF) of several hydrocarbons and their mixtures, and compare them to the currently proposed replacements, which are mixtures of HFC's . 2.0 Thermodynamic Properties of Hydrocarbon HCFC-22 Alternatives The thermodynamic benefits of the hydrocarbons can be appreciated by examining the properties in Table 1. The hydrocarbons studied are propane (HC-290), n-butane (HC600), isobutane (HC-600a) and isopentane. In this case, the critical temperature is of