A Correlation for Forced Convective Boiling Heat Transfer of Nonazeotropic Refrigerant Mixtures of HCFC22/CFC114 in a Horizontal Smooth Tube

An experimental study is reported on convective boiling heat transfer for nonazeotropic refrigerant mixtures of HCFC22/CFC114 inside a horizontal smooth tube. The test evaporator is of the double-tube type in which the heating water flows in the outer annulus, and the local heat transfer coefficients are measured for both counter and parallel flow. Based on the equation, which correlates the heat transfer coefficient for pure refrigerants as the sum of forced convective contribution aCv and nucleate boiling contribution anb, an empirical correlation equation for the mixture is developed with the data corresponding to the annular flow pattern. The mean deviation between the calculated and measured heat transfer coefficients is 8.9% for the present experimental data and 7.1% for data obtained by Jung. The equation reveals that the contribution of the nucleate boiling to the total heat flux is much smaller than that in pure refrigerants, while the convective heat transfer coefficient is almost the same.