Unified Modeling Framework for Thin-Film Evaporation from Micropillar Arrays Capturing Local Interfacial Effects.

Thin-film evaporation from micropillar array porous media has gained interest in a number of fields including energy conversion and thermal management of electronics. Performance in these applications is enhanced by leveraging the geometries of the micropillar arrays to both optimize flow through these arrays via capillary pumping and increase the curved liquid-vapor interface (meniscus) area for active phase-change heat transfer. In this work, we present a unified semi-analytical modeling framework to predict the dry-out heat flux accurately for thin-film evaporation from micropillar arrays with precise prediction of (i) the pressure profile along the wick achieved by discretizing the porous media domain, and (ii) the local permeability that depends on the local meniscus shape. We validate the permeability model with 3D numerical simulations and verify the accuracy of the thin-film evaporation modeling framework with available experimental data from literature. We emphasize the importance of predicting an accurate liquid-vapor interface shape on the prediction accuracy for both the permeability and the associated governing equations for liquid propagation and phase-change heat transfer through porous materials. This modeling framework is an accurate non-CFD based methodology for predicting the dry-out heat flux during thin-film evaporation from micropillar arrays, and will serve as a general framework for modeling steady liquid-vapor phase-change processes (evaporation and condensation) in porous media.