Modified Theoretical Models of Film Condensation in Horizontal Microfin Tubes.

Abstract

The previously proposed theoretical models of film condentation in helically grooved, horizontal microfin tubes have been modified to describe the characteristics of condensing two-phase flow more accurately. The stratified flow regime and the annular flow regime were considered. For the stratified flow regime, the previously proposed theoretical model was modified to take account of the curvature of vapor-liquid interface due to the surface tension force. For the annular flow regime, a more accurate expression for the interfacial shear stress was incorporated in the previously proposed theoretical model. Generally, the modified theoretical models predicted a lower circumferential average heat transfer coefficient than the previously proposed ones. Comparison of the theoretical predictions of the circumferential average heat transfer coefficient with available experimental data for six tubes and five refrigerants revealed that a good agreement (r.m.s. error of less than 21.1%) was obtained for all cases when the higher of the two theoretical predictions were adopted as the calculated value.