Thin-Film Evaporation in a Mesh Screen Wick

Abstract

Abstract Porous capillary wick structures are being employed in two-phase thermal management devices owing to their pumping capabilities and thermal performance enhancement during evaporation of the working fluid. Thin-film evaporation in a porous wick depends primarily on the shape of the liquid–vapor meniscus, especially near the wall. The primary objective of this paper is to study and investigate the thin-film evaporation of the liquid in a unit cell representation (UCR) of a single layer of a metallic wire mesh screen. The volume-of-fluid (VOF) method, which is an interface-capturing technique in multiphase flow modeling, is employed to obtain the steady-state meniscus shape under equilibrium conditions. This paper demonstrates the impact of the equilibrium contact angle (θ) and the initial meniscus height (H) on the steady-state interfacial pressure difference. It outlines a detailed process for estimating 3D interfacial surfaces, obtained from the VOF solution, to generate the final geometry for the thin-film evaporation analysis. A static meniscus heat-transfer model is subsequently solved using the commercial finite volume code, ansysfluent, to obtain the temperature and flow characteristics during evaporation. The relationship of parameters such as the average evaporation mass fluxes and heat transfer coefficients are estimated and presented in this paper. Finally, the relationship between the pressure drop across the liquid–vapor meniscus and the thin-film evaporation rate for screen mesh wicks is discussed.