Experimental Study on Falling Film Evaporation of Refrigerant Mixture R32/R1234ze(E) on a Horizontal Smooth Tube

Abstract

This study measured the heat transfer coefficients and visualized flow patterns of falling film evaporation using refrigerant mixture R32/R1234ze(E) as test refrigerant on a horizontal smooth tube with outer diameter of 19 mm. The experiments were carried out at a test pressure of 0.52 MPa and film Reynolds number range of 50–1000. In this experiment, the droplets, disturbed columns, and discrete droplets were observed. Also, there was no difference in the transition of the flow patterns due to the difference in heat flux. The heat transfer coefficients of refrigerant mixture dramatically decreased due to the increase in the dry patch area at the lower film Reynolds number region. At a film Reynolds number of 800, no dry patch occurs even under high heat flux conditions, and the heat transfer coefficients of refrigerant mixture increased monotonically with increasing heat flux.