Modeling and study of pressure-dependent boiling crisis in membrane-based heat sink

Abstract

A theoretical model is developed to study the pressure-dependent boiling crisis of membrane-based heat sink. It has been reported that the critical heat flux of this heat sink can be increased to 1.8 kW/cm2 by using a piece of hydrophobic membrane to promote bubble departure. In the modeling, two boiling crisis mechanisms are applied. The free energy and the forces acting on the bubble are considered in the calculations of the bubble's geometric dimensions, the vapor venting rate, and the pressure drop for driving the wicking flow. Wetting and the evaporating rate beneath the bubble are computed based on the reported coupled wicking and evaporation model. The modeling explains why there exist two regions in the profile of the critical heat flux against the pressure drop. The time for rewetting the dry spot is obtained with the modeling to establish the correlation between the critical heat flux and the pressure drop at higher heat flux. When the boiling surface has a relatively high area ratio, the modeling error is 3 % with the suggested membrane permeability and critical temperature rise of the dry spot.