Microscopic analysis of thin-film evaporation on spherical pore surfaces

Abstract

As electronic systems become miniaturized, it is crucial to implement optimal cooling technologies to dissipate high heat levels. Evaporation cooling for electronics systems has been considered one of the most promising approaches for meeting the demands of high-powered technologies by taking advantage of their latent heat. Integrating microscale or nanoscale features into two-phase microfluidic cooling systems such as porous media can dramatically increase the area of liquid-vapor interfaces where phonons translate thermal energy to fluid enthalpy. To achieve this performance jump, it is essential to understand how the engineered features improve evaporative heat transfer performance. In this study, we investigate thin-film evaporation performance within crystalline pore surfaces by employing simulation models that examine solid-liquid contact lines and liquid-vapor interfaces. The simulation models compute detailed performance parameters including phase volume fraction, temperature, pressure profile, and evaporative mass flux as a function of location, allowing us to calculate local heat transfer performance parameters. Based on local heat transfer performances, we identify thin-film regions and quantify their fractions to the overall evaporation performance. Area-averaged heat transfer coefficients are compared to identify the morphological effects of varying pore diameters and surface wettability. Insights from this parametric study will allow us to understand how evaporative heat transfer is related to the structural details of porous media and assist us to determine guidelines for the design of evaporating surfaces in modern electronics cooling. (C) 2018 Published by Elsevier Ltd.