Heat Transfer And Fluid Flow Characteristics Of Microchannel With Oval-shaped Micro Pin Fins

Microchannel heat exchangers have been widely used in many fields such as aerospace,biological equipment and microcomputer electronics due to their advantages of simple structure,easy packaging and high efficiency heat transfer capacity.However,with the increasing integration of microelectronic devices in a finite volume,its heat load poses a new challenge to the heat exchange equipment.Microchannel heat exchangers with simple structure have been difficult to meet their heat dissipation requirements.Therefore,it is urgent to design microchannel with better heat transfer performance to solve the current chip heat dissipation problem.In this paper,a microchannel heat exchanger with a new oval-shaped pin fin is proposed and Fluent software is used to simulate the flow and heat transfer process of the microchannel.It mainly includes the following parts:Firstly,the optimum shape and size of the ribs were determined by changing the geometric parameters such as the ratio of the long axis to the short axis(α),the relative rib width(β)and the relative rib height(γ).The results showed that: The shape of oval-shaped pin fins can make the fluid separation point move back under the condition of large disturbance,reduce the volume of the free-body area at the tail of the ribbed column,reduce the pressure difference resistance before and after the ribbed column,and increase the contact area between medium and high velocity fluid and solid wall surface,so as to improve the heat transfer ability.Then the effect of the bias mode and distance of the rib column on the heat transfer characteristics of the micro-channel flow is studied and thermodynamic analysis is carried out by using the entropy generation principle and the theory of entransy dissipation.The calculation results show that: After rib column offset arrangement,near the flow cross-sectional area is small,lateral offset of fluid flow is small,on the sidewalls of the micro channel scouring effect is abate,the bias side although large flow,but the rib column of fluid out of the side effect is abate,smaller disturbances,makes the fluid flow and thermal boundary layer of microchannel wall,weakened the heat transfer effect.In addition,the greater the number of bias,the greater the entropy generation,the greater the distance of bias,and the lower the efficiency of entransy product transfer.Finally,the flow heat transfer capacity of the double-layer micro-channel in downstream and countercurrent is compared,and the relative temperature deviation is introduced as an index to evaluate the temperature uniformity of the bottom surface of the micro-channel,and the upper and lower inlet differential velocity configuration is used to optimize the high bottom temperature caused by the countercurrent type.The specific results are as follows: The better the perturbation effect(first-stage heat transfer)of the bottom channel is,the better the performance of the double-layer channel will be.In addition,the downstream flow mode can lower the bottom temperature of the microchannel,but the temperature uniformity is poor.The underside temperature of the channel with countercurrent flow is higher,but the underside temperature distribution is more uniform.After differential configuration,the average temperature of the bottom surface of the countercurrent microchannel will be lower than before.