Study On The Flow And Heat Transfer Characteristics Of Microchannel Heat Sinks With Pins And Concave Cavity

With the continuous development of industrial technology,high-performance electronic chips are widely used in advanced engineering fields such as aerospace electronic equipment,high-performance computers,and energy power.Electronic devices are developing towards miniaturization and high integration,with the heat flux of high heat flux micro devices approaching 10⁷W/m².There is an urgent need to design heat dissipation equipment with better heat exchange performance to solve the"thermal problem"of the equipment.Microchannel heat sinks have a simple structure,are easy to package,and have efficient heat transfer capabilities,making them widely used in various heat exchange devices.However,a single structure of microchannel heat sinks is no longer sufficient to meet the heat transfer needs of electronic devices with high heat flux density under high integration.This article first designs four types of microchannel heat sinks with pin structures,namely rectangular pin microchannel heat sink（RPMCHS）,oval pin microchannel heat sink（OPMCHS）,rhombic pin microchannel heat sink（RHPMCHS）,and hexagonal pin microchannel heat sink（HPMCHS）,for different needle rib shapes.The finite volume method was used to numerically simulate microchannel heat sinks with needle rib structures,and the effects of different needle rib shapes and rotation angles on the internal flow and overall heat transfer performance of microchannel heat sinks were analyzed.The results show that the pin fin structure increases the heat transfer area in the finite space,fully enhances the flow disturbance in the channel,destroys the flow boundary layer and promotes its re growth,and improves the friction resistance of the channel and the overall heat transfer performance of the heat sink.At the same rotation angle,the hexagonal and diamond needle rib structures weaken the comprehensive heat transfer performance of the heat sink.The rectangular and elliptical needle rib structures enhance the comprehensive heat transfer of the microchannel heat sink,among which the rectangular needle rib microchannel heat sink has the best comprehensive heat transfer performance.In addition to the elliptical pin fin microchannel heat sink,increasing the pin fin rotation angle can effectively improve the comprehensive heat transfer performance of the other three types of microchannel heat sinks with pin structure.At the same Reynolds number,the rectangular pin microchannel heat sink（RPMCHS-7）with a rotation angle of 7°has the best comprehensive heat transfer performance.Secondly,a combined microchannel heat sink with a triangular concave cavity and a rectangular needle rib structure was designed,with a focus on studying the effects of concave cavity offset,expansion and contraction ratio,and height on the flow and heat transfer characteristics of the heat sink.The friction resistance coefficient,average Nu number,and comprehensive heat transfer performance of the combined microchannel heat sink were compared under five different offset degrees.When the offset of the concave cavity is 0,the frictional resistance coefficient of the combined microchannel heat sink is the smallest.The frictional resistance coefficient of the channel increases with the absolute value of the offset of the concave cavity.The combined microchannel heat sink with an offset of 0.5 has the best comprehensive heat transfer performance.The effect of cavity expansion and contraction ratio on the flow and heat transfer performance of the channel was studied at an optimal offset of 0.5.The results show that changing the expansion/contraction ratio can affect the damage of the cavity to the flow and thermal boundary layer,and the erosion of the fluid to the contraction section.Under the same operating conditions,microchannel heat sinks with an expansion to contraction ratio of 2have the lowest resistance loss and the highest average Nu number,resulting in the best heat transfer effect.Finally,the influence of cavity height on heat sink flow and heat transfer performance was studied.The results indicate that the higher the proportion of cavity height to the overall height of the channel,the lower the average apparent friction coefficient of the channel.The heat transfer efficiency of the T-0.75 microchannel heat sink is always the best among the six structures,with an average Nu number of up to 1.32,indicating the best heat transfer efficiency within the research scope.The maximum Nu/Nu₀ value of the T-0.75 microchannel heat sink is 1.70,and the PEC value can reach up to 1.34.From the perspective of the comprehensive heat transfer performance of the channel,the T-0.75 combined microchannel heat sink is the best choice.In summary,this article conducted extensive numerical simulations on microchannel heat sinks with needle rib and concave cavity structures,obtaining the optimal shape and rotation angle of the needle rib structure,as well as the optimal offset,expansion and contraction ratio,and height of the concave cavity structure.This provides a certain reference value for heat sink design in the field of microelectronic heat management.