Numerical investigation of heat transfer enhancement and fluid flow characteristics in a microchannel heat sink with different wall/design configurations of protrusions/dimples

The convective cooling associated with Microchannel heat sink (MCHS) devices for electronic components with high power density is a recent topic of cutting-edge research. However, thermal improvement with minimum degradation in hydrodynamic characteristic by extending the effective heat transfer area of different walls of MCHS is still a major challenge. In this regard, the heat transfer enhancement and fluid flow behavior of MCHS with protrusions, dimples and their different wall, geometric and design combinations are numerically studied in the present study. The wall configurations considered for the present analysis includes: Base wall protrusions/dimples (BWP/D), Side wall protrusions/dimples (SWP/D) and all walls protrusions/dimples (AWP/D). While for design configurations, the (AWP/D-Aligned), (AWP/D-staggered) and all wall protrusions and dimples mix (AWPD-Mix) cases are considered. The governing equations are discretized and solved across the computational domain using commercial computational fluid dynamics code with three-dimensional conjugate laminar flow model. The numerical model is then validated with experiment and theory in the literature and reasonable agreement in the results of average Nusselt number (Nuavg) and apparent friction factor (fapp) are observed. The effect of geometric parameters i.e. protrusion/dimple’s diameter (Dfr = 200 - 230 μm) and Pitch (Sfr = 400 - 1200 μm), operating parameters i.e. Reynolds number (Re = 100–1000) and Heat flux (qw = 50–100 W/cm2) on the heat transfer and fluid flow characteristics are examined to provide a better physical understanding of the energy management. The results indicate that the addition of protrusions/dimples to different walls of MCHS significantly improves the heat transfer with reasonable increase in pressure drop. The fluid flow pattern with the addition of the protrusions/dimples to different walls is improved through better mixing and lower pumping power augmentation to transport the same heat load than Straight MCHS. The favorable configuration along with geometric and operating parameters in terms of better thermal and hydrodynamic performance is suggested based on thermal enhancement factors (ƞ) and entropy generation rates (Ṡgen\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\dot{\mathrm{S}}}_{\mathrm{gen}} $$\end{document}). Among the proposed wall configurations, AWP demonstrates superior thermal performance by resulting in maximum improvement of 82% in ƞ compared to BWP configuration. When compared to the straight MCHS, AWP-aligned MCHS achieved maximum enhancement of 115% in Nuavg at the cost of 152% higher fapp at same operating conditions of Re = 1000 and qw = 100 W/cm2 for design configurations. Furthermore, the outcomes of this study is expected to provide some important guidelines for the future experiments on such MCHS devices for energy saving and management.