In this paper, we have designed a compact and efficient liquid-cooled heat sink for mini-sized electronic devices, particularly for very-large-scale integrated (VLSI) circuits. The heat sink can either be an integral part of the silicon (or metal) substrate, or a separate part attached onto the substrate. The heat sink consists of several wavy microchannels, with hydraulic diameter on the order of 100 μm, microfabricated on a silicon or metal substrate. The fluid flow and heat transfer performance of the heat sink are studied using numerical simulations in the steady laminar flow region and the dynamical system technique using Poincare´ sections is employed to analyze the fluid mixing. It is found that when the liquid coolant flows through the wavy microchannel, Dean vortices can develop. The quantity and location of the Dean vortices may change along the flow direction, which can lead to laminar chaos. The chaotic advection greatly enhances the fluid mixing, and thus the heat transfer performance of the present heat sink is much more superior than previous designs which employed straight microchannels. It is also found that the pressure drop penalty is much smaller that the heat transfer enhancement for the present heat sink. Furthermore, the relative wavy amplitude (wavy amplitude/wavelength) of the channels can be varied along the flow direction for various purposes, without compromising the compactness and efficiency of the heat sink. The relative waviness can be increased along the flow direction, which results in higher heat transfer coefficients and renders the temperature for the devices much more uniform. The relative waviness can also be designed to be higher in regions of high heat flux for hot spot mitigation purposes.

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