OVERALL HEAT TRANSFER COEFFICIENT OF R407C/HC290/HC600a REFRIGERANT MIXTURE FLOWING THROUGH A FIN-AND-TUBE EVAPORATOR

Abstract

R22 has been used as a refrigerant in residential air-conditioners and heat pumps for many decades. Even as the Montreal protocol set the phasing out of R22 due to its ODP, many alternatives to R22 are found in published literature. The M20 refrigerant mixture is one such alternative with specific advantages. This paper presents the heat transfer characteristics of the M20 refrigerant mixture, flowing through a fin-and-tube evaporator, experimentally studied in an appliance tested in a psychrometric test facility. The experimental setup consisted of a window air-conditioner fixed in a psychrometric room with instruments to measure the temperatures/pressures of the refrigerant and mass flow rate of the refrigerant as well as air. The experiment was carried out in accordance with the Bureau of Indian Standards (BIS) and American Society of Heating Refrigerating Air-Conditioning Engineers (ASHRAE) test conditions. M20 being considered as an alternative for R22, the overall heat transfer coefficient of the M20 refrigerant mixture has been evaluated, and compared with that of R22. It can be observed that the heat transfer coefficient of R22 is better than that of the M20 refrigerant mixture, for the prevailing flow conditions in the evaporator. The reduction in the overall heat transfer coefficient of the M20 refrigerant mixture as compared to R22, ranges from 7.3% to 20.7%.