Influence of thermophysical properties on two-phase flow convective boiling of refrigerant mixtures

In this paper, an analytical study on the influence of thermophysical properties on heat transfer characteristics of two-phase flow boiling of some refrigerant mixtures in air/refrigerant horizontal enhanced surface tubing is presented.Correlations were proposed to predict the thermophysical properties of refrigerant mixtures such as thermal conductivity and viscosity as well as their impact on the heat transfer characteristics such as average heat transfer coefficients, and pressure drops of R-507, R-404A, R-410A, and R-407C in two-phase flow boiling inside enhanced surface tubing. In addition, it was found that the refrigerant mixture's pressure drop is a weak function of the mixture's composition.It was also evident that the proposed improved correlations for predicting the thermophysical properties were applicable to the entire heat and mass flux, investigated in the present study. The deviation between the experimental and predicted value using new and improved correlations for the heat transfer coefficient and pressure drop were <±20 %, for the majority of data.