Journal of Advanced Engineering Research ISSN: 2393-8447 Volume 6, Issue 1, 2019, pp.16-22 Research Article 16 www.jaeronline.com Numerical Investigation of Bio-inspired Heat Sink Model with Multiple Outlets for Cooling Rectangular Shaped Electronic Circuits K. Kandassamy 1, *, B. Prabu 2 1 Department of Mechanical Engineering, Annamalai University, Chidambaram-608002, India 2 Department of Mechanical Engineering, Pondicherry Engineering College, Puducherry-600001, India *Corresponding author email: kandassamy@yahoo.com, Tel.: +91 9486366126 ABSTRACT Cooling of electronic circuits is a necessity to ensure reliability and optimum working conditions. In this work a bio- inspired single-inlet flow field having leaf-type branching secondary micro-channel arrays, with aspect ratios 4.3, 8.6 and 12.9 is analyzed. The simulation of the heat sink models is done using finite element based software. The coupling between heat transfer and laminar fluid flow is done using conjugate heat transfer. The heat sinks are subjected to a constant heat flux input and tested for pressure drop of 0.2-0.3 MPa. Validation of simulation results is done by comparing the mixing cup temperature with that obtained by heat balance. The results prove that, bio-inspired model has a low variation in chip surface temperature than traditional micro-channel arrays. Higher aspect ratio models have higher Nusselt numbers for similar pressure drops. The heat sink models with aspect ratio 12.9 at an input pressure 0.3 MPa shows a thermal resistance of 0.126 C/W with pumping power -2.39W. Keywords – Heat sink, Hydraulic Resistance, Micro-channel, Reynolds number, Thermal Resistance. 1. INTRODUCTION Heat sinks are required to dissipate heat fluxes in the range, 1-10M W/m 2 from electronic circuits. As the density of electronic devices per chip increases the heat dissipation also increases. Straight micro channels incur high parasitic power consumption due to higher pressure drops incurred for the power dissipated [1]. Hence it is necessary to find new ways to increase heat- sinking by designing new flow field models that strike a balance between heat transfer and pressure drop. One of the method is to mimic biological flow distribution systems as in the proposed heat sink model. The majorities of the coolants used in heat sinks are air and water [2]. Straight micro channel heat sinks have decreasing temperature gradient in the flow direction due to saturation of fluid thermal capacity, with higher heat transfer rates in the entrance and reduced values near the exit [3]. The split-flow arrangement is recommended in [4] for reduction in flow length, Δp reduction and heat transfer coefficient enhancement. The optimum α recommended in [5] is 8.8-11.4. Biological designs are achieved in nature by variation in branching channel diameters from inlet to outlet. Most of the bio-inspired flow fields encountered in literature are applied in the field of Proton Exchange Membrane fuel cells [6-12]. Arbabi [13] has given a combination of conventional and bio-inspired flow fields in their models. Lung and leaf inspired models have shorter path lengths, uniform species and velocity distribution for large number of parallel and high α channels than ones with longer pathways. Farzaneh et al. [14] uses a square-shaped heat sink flow-fields based on the constructal theory, for a temperature and Δp reduction of 10-20% and- 25-33% respectively in comparison to flow-fields without branches. Parallel micro-channel networks with bio-inspired inlet and outlet manifolds are found [15] to have more surface area, lower Δp, higher C.O.P and ease of manufacturing compared to constructal networks. The angle of the branching channels with the main supply and collecting channels is maintained at 90º as the lower angle branching channels are not able to achieve uniform flow in diagonal corners of the flow field [16]. The reduction in main channel cross section increases R hy forcing fluid in low resistance branching channels giving a uniform velocity field. The supply and collecting channel dimensions are similar and their angles are determined by trial and error to minimize base surface temperature. Recent processors like AMD’s 2990WX [17] are of rectangular cross-section (4.411*10 -3 m 2 ), with a Thermal Design Power -TDP of 250W, dissipating a heat flux of 56700 W/m 2 . The R th requirement for the processor is 0.152 C/W at a maximum operating