Investigation Of Enhancement Of Heat Transfer And Flow Characteristics Of Microchannel Heat Sinks Based On Topology Optimization Method

With the increasing integration of electronic devices and their increasing power density,the heat dissipation of electronic devices has become a key issue limiting their further development.Microchannels,as an efficient means of heat dissipation,have great potential for application in high heat flow density electronic device heat dissipation scenarios.An important mean for improving the heat dissipation capability of microchannels is to arrange ribs within the channel,however,this often results in a significant increase in the pressure drop across the microchannel.Therefore,the flow and heat transfer properties of the microchannel need to be considered in the design process.Most of the current methods of rib arrangement in microchannels are based on the experience and basic analysis of researchers and lack certain theoretical and mathematical methods to guide them,which makes it difficult to obtain the optimal arrangement for the target operating conditions.Therefore,this paper introduces a topology optimisation method in the design process of the rib arrangement in the microchannel,and obtains a topology optimised structure of the microchannel heat sink for different channel shapes and different heat flow distribution patterns,and introduces porous ribs in the microchannel heat sink to further reduce the pressure drop and improve its comprehensive performance of flow heat transfer.The specific research contents and main results of this paper are as follows:(1)The new rib arrangements for straight channels,wavy channels and fan-shaped recessed channels are obtained respectively by topology optimization method.The flow and heat transfer performance is evaluated comparing conventional structured microchannels and the intrinsic mechanism of the topology optimised structure in terms of optimised flow and enhanced heat transfer is clarified.The new structured microchannels were found to save 64%,39%and 28%of the pressure drop respectively compared to conventional microchannels,and to reduce the average microchannel substrate temperature by 5.3℃,11.6℃ and 1.9℃ at the same pumping power,providing an optimal combination of flow and heat transfer performance.Further,trapezoidal,crescent-shaped and teardrop-shaped rib structures and repeated left-right rib arrangements were found in the three microchannels,respectively,whose effects of interrupting boundary layer growth and promoting flow mixing contributed to the improved heat transfer performance of the microchannels.(2)The optimal rib arrangement form of the microchannel heat sink is obtained for different non-uniform heat flow conditions,respectively,and the heat transfer performance and flow state of this structure are investigated.The main arrangement characteristics of the topology optimised structure are further summarised,providing a new optimization direction for the design of ribs for conventional microchannels.It is shown that the topology optimised microchannels achieve a 23%,17%,20%and 22%reduction in thermal resistance for the four heat source distribution modes,respectively,with the best overall performance of flow heat transfer.This is due to the special arrangement of the ribs in the topology optimised structure,the front of the ribs in contact with the fluid has a certain angle of sharpness,and the ribs are gradually encrypted in the direction of flow.(3)Porous ribs are arranged within the microchannel heat sink to further reduce pressure drop losses and optimise its flow heat transfer performance.Topology optimization methods are obtained for the arrangement of porous and solid ribs and the flow heat transfer performance is evaluated by comparing the conventional structure of the microchannel heat sink.It is shown that the porous ribs reduce the pressure drop by 87%compared to the solid ribs for the same arrangement,and that the topology optimised porous and solid ribs reduce the heat transfer thermal resistance by 10.1%and 13.6%respectively,and provide a better Comprehensive flow heat transfer performance.This is attributed to the herringbone structure of the ribs within the porous topology optimised structure and the staggered and increasing arrangement of the ribs within the solid topology optimised structure.This study will provide guidance for the improved design of microchannels with porous ribs and solid ribs in conventional structures.