The Constructal Theory is applied to obtain better thermal performance from a type of microchannel heat sink. Based on a smooth, straight, rectangular microchannel heat sink (Case 1), three different configurations of constructal multiple bifurcation are designed for the entrance region of each microchannel. These types are one bifurcation (Case 2), two bifurcations with the second placed in the front part (Case 3), and two bifurcations with the second bifurcation placed in the front part (Case 4). The corresponding laminar flow and heat transfer fields are investigated numerically by means of computational fluid dynamics. The effects of the bifurcation number and length ratio on pressure drop and overall thermal resistance are observed. The overall thermal resistance for the four microchannel heat sinks is compared when subjected to pumping power. It is found that designing one or two bifurcations (Cases 2, 3, 4) in the entrance region can improve thermal performance effectively. It is also recommended to place the second bifurcation in the back part (Case 4) of the microchannel heat sinks to obtain good overall thermal performance by proper design of the bifurcation position and number of channels.
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