Theoretical model of evaporation heat transfer based on stratified flow of horizontal micro-fin tube

The stratified flow model of evaporation heat transfer in helically grooved, horizontal micro-fin tubes has been developed. The profile of stratified liquid was determined by a theoretical model previously developed for condensation in horizontal micro-fin tubes. For the region above the stratified liquid, the meniscus profile in the groove between adjacent fins wad determined by a force balance between the gravity and surface tension forces. The thin film evaporation model in the thin film region of the meniscus previously proposed by the authors was applied. Heat transfer through the stratified liquid was estimated by using an empirical correlation proposed by Mori et al. The theoretical predictions of the circumferential average heat transfer coefficient were compared with available experimental data for four tubes and three refrigerants. A good agreement was obtained for the region Fr₀ < 2.5 as long as partial dry-out of tube surface did not occur.