Experimental study on film condensation heat transfer characteristics of R1234ze(E) and R1233zd(E) over horizontal plain tubes

In this study, experimental investigations were carried out to evaluate the film condensation heat transfer characteristics of R1234ze(E) and R1233zd(E) over horizontal plain tubes. Experiments were conducted at saturation temperatures of 36, 38 and 40 °C with different surface sub-cooling temperatures in the range of 3∼18 °C. Experimental results showed that the film condensation heat transfer coefficient decreased with increase in the surface sub-cooling temperature. The effect of tube diameter on film condensation heat transfer coefficient was also examined, and it was found that the smaller the tube diameter, the higher the film condensation heat transfer coefficient. In the present study, experimental correlations of the Nusselt number for R1234ze(E) and R1233zd(E) were also proposed respectively, with ±20 % of error band.