Heat transfer correlations of refrigerant falling film evaporation on a single horizontal smooth tube

Falling film evaporation heat transfer of R134a and its potential substitutes R290 and R600a outside a single horizontal plain tube is experimentally investigated, and the effects of the saturation temperature, film flow rate and heat flux on heat transfer coefficient are studied. Heat transfer performance of R290 is slightly superior than that of R134a, while R600a is inferior than that of R134a. The threshold film Reynolds number is determined to separate the variation trend of HTC with film Reynolds number into full wetting and partial dryout regimes. Increase of heat flux benefits the heat transfer in both full-wetting and partial dry-out regimes. New heat transfer correlations based on the present data and data for R32 and R1234ze(E) in the authors' group are suggested for two regimes. The correlation for full wetting regime fits 96.7% of the total 542 correlated data within +/- 30% while fits 73.4% of the total 289 data in references from -30% to +15%, the correlation for partial dryout regime fits 97.5% of the total 162 correlated data within +/- 30% while fits 76.8% of the total 95 data from references within +/- 30%. (C) 2018 Published by Elsevier Ltd.