Numerical Study of the Temperature Effects on Heat Transfer Coefficient in Mini-Channel Pin-Fin Heat Sink

Abstract

Pin-fins are frequently used to increase the heat transfer surface and promote turbulent motion, which improves the devices cooling process by enhancing heat dissipation, as in hydrogen fuel cells applications. The application has burst out this last decade and became vital in several industrial devices. The present study is a numerical investigation of flow and heat transfer in rectangular mini-channels (RMC) and pin-fin heatsinks (PFHS). The pin-fins have a diamond shape arranged in segregated disposition (corrugated channel). In order to adequately calculate the heat transfer coefficient within this complex thermal system; several parameters, such as mass flow rate, geometry dimensions, heat flux and reference temperature are extensively examined. The importance in way the reference temperature was calculated was highlighted. A correct estimation of the heat transfer coefficient led to a better optimisation of the cooling process performances. The aim of this study was to elaborate a technique to correctly estimate the temperature difference between the cooler fluid and the heat sink wall, leading to a better approach for heat transfer coefficient estimation. For this purpose, an approach with variable reference temperature (VRT) has been adopted in the calculation of the wall-fluid temperature difference. Flow field and heat transfer are analysed qualitatively (visualisations of sensible zones) and quantitatively (profiles of heat transfer coefficient, heat flux, wall and fluid temperatures...). The numerical procedure has been validated by experimental measurements. The results showed that the proposed approach to calculate the reference temperature leads to a better presentation of the heat transfer coefficient. In addition, new fit function was involved, in particular the variation of the averaged heat transfer coefficient against Reynolds number.