Volume of fluid-based numerical modeling of condensation heat transfer and fluid flow characteristics in microchannels

Abstract

The present work proposes a numerical model for the simulation of condensation heat transfer and fluid flow characteristics in a single microchannel. The model was based on the volume of fluid approach, which governed the hydrodynamics of the two-phase flow. The condensation characteristics were governed by the physics of the phenomena and did not include any empirical expressions in the formulation. The conventional governing equations for conservation of volume fraction and energy were modified to include source terms that accounted for the mass transfer at the liquid–vapor interface and the associated release of latent heat, respectively. A microchannel having characteristic dimension of 100μm was modeled using a two-dimensional computational domain. The working fluid was R134a and the vapor mass flux at the channel inlet ranged from 245 to 615kg/m2s. The channel wall was maintained at a constant heat flux ranging from 200 to 800kW/m2. The predictive accuracy of the numerical model was assessed by comparing the two-phase frictional pressure drop and Nusselt number with available empirical correlations in the literature. A reasonably good agreement was obtained for both parameters with a mean absolute error of 8.1% for two-phase frictional pressure drop against a recent universal predictive approach, and 16.6% for Nusselt number against an available correlation. Further, a qualitative comparison of various flow patterns against experimental visualization data also indicated a favorable agreement.