Condensation heat and mass transfer characteristics of zeotropic refrigerant mixture R1234yf/R32 inside small-scale tube: Flow patterns observation and non-equilibrium film model calculation

Abstract

Minichannel heat exchanger has been more and more widely used in refrigeration industry and other fields due to its high heat transfer efficiency, lightweight and low carbon emissions and other advantages. And, the zeotropic mixture R1234yf/R32 with low global warming potential (GWP) is a promising substitute for R410A in commercial refrigeration. In this study, the experiment investigation of condensation heat and mass transfer characteristics of R1234yf/R32 in minichannel test tube (inner diameter (ID) 2 mm) were conducted. The influencing factors including mass flow rate, vapor quality, mass fraction and tube diameter on the mass transfer and heat transfer coefficient (HTC) were discussed in detailed. The flow pattern was taken during condensation experiment. Meanwhile, based on the discussion of flow pattern, thermophysical properties, tube diameter and composition variation in the liquid film and at the vapor-liquid interface, the effects on heat transfer and mass transfer during condensation were analyzed. The calculation results using the non-equilibrium film model considering the mass transfer on both the liquid and vapor sides were compared and agreed well with the experimental HTC with an average deviation of 14.9%. In addition, the heat transfer degradation coefficient (HTDC), vapor-liquid interface temperature and diffusion flux of R32 were reasonably evaluated by the calculation model, and the comparison analysis were conducted with that of ID 4 mm in the previous study.