Enhancement of condensation heat transfer on grooved surfaces: Numerical analysis and experimental study

Abstract

The present paper reported numerical analyses and experimental studies on fluid flow and heat transfer for laminar film condensation on various grooved surfaces. Different from the previous literatures, the coupled non-linear governing equations for the fluid flow, mass transfer and two-dimensional thermal conduction were developed base on some reasonable assumptions. Through analyzing the influences of groove shape parameters on film thickness and heat flux, we found that both of them were significantly influenced by the pitch, height and profile radius of the groove. The velocity distributions on the condensate-vapor interface and distributions of wall temperature on various grooves were also studied systematically. The calculations indicated that the surface tension gradient of the liquid film drove the liquid to flow from the crest into the trough. The horizontal velocity decreased first and then increased gradually on the crest and reached a maximum value on profile, and then decreased to zero in the trough region. On the contrary, the condensate flowed at very low vertical velocities on the crest and profile of groove, but in trough region these velocities increased rapidly to a relatively high level. The results of comparison showed that both the distributions of wall temperature and heat flux on involute groove were more favorable to reduce thermal resistance and enhance heat transfer than other grooves. In order to validate the feasibility and reliability of the present analyses, experiments were carried out with some involute grooved surfaces for various physical dimensions, a trapezoid grooved surface and a smooth surface respectively. Both the numerical results and experimental data indicated that involute groove can provide a better heat transfer performance, and the heat flux of involute grooved surface was at least 20% and 50% higher than that of trapezoid grooved and rectangular grooved surfaces. The present analyses were feasible, and could be used in the parameter design and heat transfer calculation of involute grooved surfaces as well as trapezoid grooved surfaces.