Low GWP refrigerant R1234ze(E) falling film evaporation on a single horizontal plain tube and enhanced tubes with reentrant cavities

Experimental results of falling film evaporation heat transfer on horizontal copper tubes of low GWP refrigerant R1234ze(E) are presented. A plain tube, an integrated condensation-enhanced fin tube and three boiling enhanced tubes with 3-D different reentrant cavities are tested in this study. Experiments are carried out at saturation temperatures of 6, 10 and 16?, heat fluxes from 10 to 120 kW·m^-2 and film flow rates from 0.014kg·m^-1s^-1 to 0.12kg·m^-1s^-1. It is found that R1234ze(E)'s heat transfer performance is slightly inferior to that of R134a. Effect of film Reynolds number on HTCs of enhanced tubes can be separated into two regimes, a quasi-plateau regime and a sharp decrease regime. HTCs increase with heat flux. Increase of saturation temperature has little effect on HTCs for the plain tube. The integrated fin tube performs best among the tubes tested. Tube positioned below the top row, possesses the similar variation trend of HTCs with that of the top row but suffers an earlier dryout.