Performance ranking of refrigerants with low global warming potential

Abstract

This article is an evaluation of the cycle performance of 39 refrigerants identified in the AHRI Low Global Warming Potential Alternative Refrigerants Evaluation Program in a typical air conditioner. This program was initiated in response to environmental concerns raised by the use of high global warming potential refrigerants with the intent to identify and evaluate promising alternative refrigerants. The cycle performance of each refrigerant is calculated assuming the same evaporator heat duty and sink temperatures for the condenser. The evaluation included the effects of heat transfer and pressure drop in the evaporator and the condenser. Four performance variables were investigated: (1) the coefficient of performance, (2) the required volumetric displacement of the compressor, (3) the mean temperature difference of the evaporator, and (4) the compressor discharge superheat. Ratios of the above four parameters relative to the refrigerants that are intended to be replaced are provided for each replacement refrigerant. In addition, a methodology was developed using weighting factors to rank the alternative refrigerants either emphasizing the importance of a large coefficient of performance or the importance of reduced system size. The two ranking methodologies produced different rankings of the alternative refrigerants, although the top three ranked refrigerants had at least two refrigerants in common with each other. Both ranking methodologies identified R1234yf, R32, and R1270 as having ranking factors within those of the best three alternative refrigerants.