Experimental and numerical investigation of thermal performance of S-shaped manifold microchannel heat sinks

In this work, the S-shaped manifold microchannel heat sink (S-MMHS) with a high surface-to-volume ratio (6690.89 m2/m3) is proposed to dissipate a high heat flux over 150 W/cm2. There are 1550 micro-ribs distributed over a heating area of 3 × 3 cm2, which contributes over 176.13 cm2 of the total heat transfer area. Heat transfer characteristics of S-MMHS of three different structures were experimentally and numerically evaluated with the glycol aqueous solution under a series of heat flux and inlet flow rates. Experimental results depict that the lowest thermal resistance of S-MMHS is 0.22 cm2⋅K/W when the inlet flow rate is 2.89 L/min under a heat flux of 97.6 W/cm2 and the overall convective heat transfer coefficient can reach up to 44,761.1 W/m2⋅K. The heat transfer processes of S-MMHS are divided into two parts: the jet-impingement heat transfer as the fluid flows into S-MMHS and the convection on micro-fins as the fluid flows through S-MMHS. Based on the analysis of heat transfer processes, a correlation for the overall Nusselt number is proposed, including dimensions of the microchannel heat sink and Reynolds number. The proposed correlation is used to optimize the heat sink structure, which achieves a reduction of thermal resistance by 33%.