Microfin, condensation, zeotropic, refrigerant, mixture
This paper compares the condensation heat transfer and pressure drop for zeotropic refrigerant R454C and its individual components, R32 and R1234yf, in a horizontal microfin tube. The microfin tube has a 4 mm outer diameter, 0.18 mm wall thickness, and a surface area ratio of 1.56. HFOs and HFC/HFO blends like R454C have low global warming potential and can be alternatives to HFC refrigerants when retrofitting a system or producing new equipment. However, there is an additional mass transfer resistance present during phase change for a zeotropic mixture, which results in reduced heat transfer performance. Microfin tubes enhance heat transfer through multiple mechanisms: they increase the internal surface area of the tube, the fins drain condensate from the fin tip to the trough region, and they produce secondary flow structures. Presently, there is limited data of HFO/HFC mixtures in microfin tubes. Thus, experiments are conducted for complete condensation of R454C, R1234yf and R32 for saturation temperatures of 40, 50 and 60 °C and mass fluxes from 100 to 600kgm−2s−1. Experimental heat transfer and pressure drop measurements are compared to wellestablished correlations from the literature. Heat transfer enhancement factors and pressure drop penalty factors are calculated for each refrigerant.