A novel micro-channel heat sink with trapezoid drainage for enhancing condensation heat transfer of dielectric fluid

Abstract

This study experimentally investigates the condensation of dielectric fluid HFE-7100 in a micro-channel heat sink with the hydraulic diameter of 1.21 mm. Tests are conducted at a fixed pressure of 110 kPa, with vapor mass quality (x(in)) ranging from 0.1 to 0.9, mass fluxes (G) from 150 to 250 kg.m(-2).s(-1), inclined angle ( theta) from -90 degrees to +90 degrees. A novel trapezoid drainage design is proposed to enhance the condensation heat transfer by effectively entraining condensation film. When G is lower than 200 kg.m(-2).s(-1), the two phase heat transfer coefficient (h(tp)) for the trapezoid drainage design exceeds the conventional rectangular micro-channel heat sink by 10-26% while the corresponding pressure drop is about 22-45% lower. When G is increased to 250 kg.m(-2).s(-1), the drainage design can still dramatically decrease the pressure drop, however, it shows a negative effect on h(tp) when the x(in) is greater than 0.2. With inclined arrangements, the pressure drop would dramatically increase due to gravity effect. Besides, at the conditions of theta = -45 degrees and -90 degrees, the trapezoid drainage channel can improve the h(tp) by 43-45% when G is lower than 200 kg.m(-2).s(-1). On the contrary, with the arrangement of theta = +45 degrees and +90 degrees, the trapezoid drainage channels may decrease the h(tp) by 8-15%. This phenomenon is especially pronounced at a high z i p. In addition, the heat transfer enhancement and deterioration are both analyzed based on stress distribution at vapor phase and condensation film.