Quasi-local condensation heat transfer coefficients at low mass fluxes inside smooth horizontal tubes were investigated both experimentally and analytically. Experiments were performed with refrigerant R134a in a smooth, commercially available copper tube with an outer diameter of 0.5in (12.7mm). The operating conditions were selected such that the two-phase flow in the test section corresponded to a stratified-wavy regime. The heat transfer coefficient was found to be dependent on both the heat flux as well as mass flux levels. Utilising the experimental results, a new correlation is proposed whereby the overall heat transfer coefficient is taken as the sum of the heat transfer due to film condensation in the top portion of the tube and the forced convection of the condensate in the bottom portion of the tube. The correlation is found to predict the experimental data within +/-7.5%. The mean absolute deviation for the data is 2.7%.

KEYWORDS: year 1996, calculating, heat flow, heat transfer coefficient, experiment, pressure drop, horizontal, smooth tube heat exchangers, heat exchangers, R134a, refrigerants, condensation, comparing