Numerical simulation of cooling performance of heat sink designed based on symmetric and asymmetric leaf veins

Abstract

Abstract Improvements in electrical equipment urgently require corresponding high efficiencies of heat-dissipation devices. The fractal tree-like network inserted in a heat sink to obtain an increased heat transfer coefficient and a lower pressure drop has been widely researched. However, the leaf vein networks as a high efficient transfer structure employed as microchannels in heat sinks have been rarely studied, especially regarding the effect of the tertiary microchannels on heat transfer and fluid flow that has not been mentioned by researchers. In this study, the heat sink with and without symmetric and asymmetric tertiary microchannels are considered for heat transfer when the branching angle between the primary and the secondary microchannels changes. To simulate the reticulate network of the leaf veins, the Voronoi diagrams are employed for comparison with the real Oosmanthus leaf veins. The results show that with the increase of the branching angle of the heat sink with secondary microchannels, the vortex at the branching site is enhanced and the pumping power is increased a little. Comparing with the heat sinks with secondary microchannels, the heat sink with tertiary microchannels has better performance of flow and heat transfer because it has bigger heat transfer area and there is more cooling water flow through the tertiary microchannels. As for the heat sinks with tertiary microchannels, a smaller branching angle is better for water flow through the tertiary microchannels, thereby generating more and stronger vortexes and finally improving the heat transfer performance of the heat sink. In addition, it is found that comparing to the heat sinks with symmetric tertiary microchannels, the heat sinks with asymmetric tertiary microchannels have better performance of water flow and heat transfer, despite their heat transfer area is smaller. A larger density of the tertiary microchannels causes a smaller pumping power and thermal resistance, which is optimal for improving of the flow and heat transfer performance of the heat sink designed by leaf vein structure and the comparison between the simulation and real leaf vein structure indicates that the Voronoi diagram can be employed to simulate the reticulate leaf vein.