Boiling heat transfer coefficient of R22 and an HFC/HC refrigerant mixture in a fin‐and‐tube evaporator of a window air conditioner

Abstract

The commonly used refrigerant in unitary type air conditioners is R22 and its phase out schedule in developing countries is to commence from 2015. Many alternatives to R22 are found in published literature in which R407C has similar characteristics to those of R22 except for its zeotropic nature. However, R407C which is an HFC is made compatible with the mineral oil lubricant in the system compressor by the addition of 20% of HC. This HFC/HC mixture called the M20 refrigerant mixture is reported to be a retrofit refrigerant for R22. Though its latent heat value is greater than that of R22, its refrigerating capacity is lower when it is used to retrofit R22 window air conditioners. Hence, a heat transfer analysis was conducted in the evaporator of a room air conditioner, for practically realized heat flux conditions during standard performance testing. The tests were conducted as per the BIS and ASHRAE standards. Kattan-Thome-Favrat maps are used to confirm the flow patterns, which prevail inside the fin-and-tube evaporator in the tested operating conditions. It is revealed that the heat transfer coefficient/heat fluxes are poorer for M20 because of the lower mass flow rate and higher vapor fraction at the entry of the evaporator than that of R22 in the prevailing operating conditions. The heat transfer coefficients of the M20 refrigerant mixture under various test conditions are lower in the range of 14% to 56% than those of R22.

Performance study on the evaporation and pressure drop of low‐temperature refrigerant blends in porous media

“…Nonaka et al evaluated the performance of the heat exchanger used in heat pump‐type room air conditioners using the alternative refrigerant R407C. Herbert et al investigated the boiling heat transfer coefficient of R22 and a hydrofluorocarbon (HFC)/hydrocarbons (HC) refrigerant mixture in a fin‐and‐tube evaporator of a window air conditioner. Uhía et al conducted an experimental study on vapor condensation of R22 retrofit substitutes R417A, R422A, and R422D on Cu‐Ni turbo C tubes.…”

Investigation of the effect of superheating on the performance of a refrigeration system using low temperature different refrigerant blends in porous media

“…Raja et al conducted an experimental investigation on the flow boiling heat transfer of R‐134a/R‐290/R‐600a mixture in smooth horizontal tubes. Herbert Raj and Mohan Lal studied boiling heat transfer coefficient of R‐22 and hydrofluorocarbon (HFC)/hydrocarbons (HC) refrigerant mixture in a fin‐and‐tube evaporator of a window air conditioner. Herbert Raj and Mohan Lal investigated the performance variation of R‐22 window‐type air conditioner retrofitted with HFC/HC refrigerant mixture under different ambient conditions over a range of charge quantities.…”