Enhancement of Heat Transfer to a Non-Azeotropic Refrigerant Mixture in a Horizontal, Spirally Grooved Evaporator Tube

An experiment was performed to investigate the enhancement of local heat transfer to a boiling or evaporating non-azeotropic refrigerant mixture of HCFC22 and CFC114 in a horizontal, spirally grooved tube. There was no notable difference in the enhancement among the mixture and the pure refrigerants at a high flow rate. At a low flow rate, the heat transfer to the mixture in the high quality region was found to be enhanced over the smooth tube as effectively as to the pure refrigerants ; therefore, no features of the mixture were recognized. In the low quality region where the effective enhancement was also achieved for the pure refrigerants, however, the enhancement for the mixture was greatly degraded. This degradation was theoretically explained by taking account of the variation of composition in the meniscus liquid film formed in the grooves on the upper part of the tube perimeter.