Experimental investigation of enhanced spreading and cooling from a microgrooved surface

Abstract

A heat transfer cell is specifically designed to analyze the heat spreading capacity of a microgrooved surface. V-shaped microgrooves are etched on silicon wafers using standard lithographic process. The shapes of the liquid menisci in the microgrooves are accurately measured using image analyzing interferometry as functions of heat input and opposing body force (angle of inclination). The relevant parameters that govern the spreading and cooling process of an evaporating curved microfilm, e.g., the adsorbed film thickness, contact angle, and curvature at the thicker end of the meniscus are accurately measured. The trends in these values are found to be consistent with the physics of the process. The temperature profiles are measured for the microgrooved and non-grooved silicon substrates under identical conditions of heat input and inclination and the enhanced spreading of the film in presence of microgrooves toward the hot region is quantified. The axially average values of a dimensionless temperature, defined for this study, are used to quantify the enhanced cooling and temperature homogenization potentials of microgrooved surfaces along with the effect of opposing body forces. The study clearly indicates the beneficial effects of change-of-phase heat transfer from an evaporating microfilm on microgrooved surfaces and its potential use in a miniature passive cooling device.