R407C AS AN ALTERNATIVE TO R22 IN REFRIGERATION SYSTEMS

摘要

A refrigeration test facility was constructed to examine the performance of potential alternatives to R22. For the purpose of this paper, the performance of R407c (a zeotropic mixture of R134a, R125 and R32 in a 52% 25% 23% composition by mass) was compared to that of R22. It was found that the performance of R407c approached that of R22 at higher evaporator temperatures, but reductions in evaporator capacity and COPc were found with decreasing evaporator temperature. The effects on evaporator performance of a 32 cSt polyol ester compressor lubricating oil were also noted. It was seen that while R22 and this oil responded in typical fashion for a soluble refrigerant-oil pair (reduced capacity, increased evaporator pressure drop and fall-off in capacity at low superheats), R407c displayed a two-stage performance decline occurring over a greater range of superheat. The combined effect of differential solubility of the individual components of the mixture in conjunction with a more gradual solubility effect due to the presence of a temperature glide in the evaporator lead to a minor change in composition of the circulating refrigerant mixture resulting in a drop in evaporator capacity and COPc.