Investigation On Phase Change Cooling Enhancement In Microchannel By Using Micro Pin-fin Cluster Array

The third-generation wide bandgap semiconductor has the characteristics of high frequency,high power,low loss and high anti-interference ability,and has broad development prospects in high-end applications such as modern lasers,military radars,5G radio frequency,and optoelectronics.However,this kind of semiconductor chip generates a large amount of heat flow during normal operation.For example,the local heat flow of GaN high electron mobility transistor amplifiers can even reach 30kW/cm2,and the chip-level heat flow can reach 1kW/cm2.The thermal management problem caused by such a high heat flux has become one of the main bottlenecks restricting its performance improvement.The traditional heat dissipation modes such as air cooling and air cooling can no longer meet such huge heat dissipation needs.Silicon-based microstructures made of MEMS The channel size is small,and it can be integrated and embedded with the heating chip,reducing the intermediate heat transfer resistance,realizing efficient cooling,and meeting the needs of chip miniaturization and integration.It has good applications in the field of high heat flux chip cooling prospect.However,in traditional silicon-based microchannels,due to the smooth surface of the channel,there are fewer effective nucleation holes for the working medium.During the cooling process of the heat exchanger,the working medium is prone to metastable state under high superheat.Once the bubble core appears The bubbles will grow rapidly until they fill the entire microchannel.The gas-liquid interface expands rapidly under high superheat.In severe cases,the working fluid may even flow back,which will adversely affect the heat transfer of the microchannel.Aiming at the problems of high boiling superheat and instability of flow and heat transfer in microchannels,this paper innovatively proposes two types of micro-needle rib cluster array microchannel designs with different arrangements,using the nucleation cavity reduction provided by microneedle rib clusters.Small phase transition initial superheat,using the optimized array arrangement of microneedle rib clusters to enhance the gas-liquid two-phase mixing and convection heat transfer.At the same time,the capillary adsorption effect of the microneedle rib clusters on the liquid is used to delay evaporation and greatly improve the microchannels.Heat transfer performance.In this research,we designed and built a micro-channel phase-change heat and flow pattern visualization experiment platform,and through comparative experiments,studied ordinary parallel silicon-based microchannels,sparse micro-needle-rib cluster silicon-based microchannels And dense micro-needle-rib cluster silicon-based microchannel internal working fluid flow and heat transfer characteristics,combined with the images taken by high-speed camera and infrared thermal imaging camera,reveals that the micro-needle-rib cluster structure enhances the heat transfer performance of the microchannel mechanism.Experimental studies have found that the sparse micro-needle-rib cluster area and the dense micro-needle-rib cluster area have similar heat transfer mechanisms.The micro-needle-rib cluster area provides a large number of gasification cores,and the heat transfer is mainly nucleate boiling;In the micro-channel area between clusters,the working fluid flow pattern is mainly two-phase gas-liquid mixing flow,and its heat transfer is mainly gas-liquid two-phase mixing convection heat transfer;capillary liquid absorption and liquid recapture of microneedle rib clusters.The effect makes the interface evaporation effect of the resident liquid still exist under the higher heat flux density,maintains a larger heat transfer coefficient,and delays evaporation.Under the working condition with a small working fluid flow,the comprehensive heat transfer enhancement effect of the dense micro-needle fin cluster is stronger,and its strengthening factor comprehensively considering heat transfer and pressure drop reaches 1.61;under the working condition with a large working fluid flow,The sparse micro-needle fin cluster has a strong comprehensive heat transfer enhancement effect,and its enhancement factor that comprehensively considers heat transfer and pressure drop reaches 1.49.The micro-needle rib cluster array structure proposed in this study significantly strengthens the phase-change heat in the micro-channel,and provides a new idea for the optimal design of a new type of high-efficiency micro-channel phase-change cooler.