Study On Heat Transfer Enhancemant And Temperature Uniformity Of Flow Boiling In Mini-channels Under The Synergy Of Electric Field And Phase Separation Structure

With the increasing demand for heat dissipation with high heat flux density in the fields of national defense,energy and medical care,traditional radiators cannot meet the corresponding requirements.In this paper,the heat transfer performance of parallel countercurrent channels under the synergistic effect of electric field and phase separation structure is studied to achieve high heat flux density cooling requirements.The phase separation structure is a PTFE hydrophobic porous membrane,which is placed at the front and rear between the two countercurrent channels.The main research contents are as follows:(1)Research on heat transfer enhancement of micro-channels with phase separation structure.Three phase separation structures PSS1,PSS2,PSS3 micro-channel flow boiling heat transfer studies were carried out.In order to meet the pressure difference conditions required for the gas-liquid phase separation of the PTFE porous membrane with the phase separation structure,the inlet working fluid of the co-current and counter-current channels was set with a period of time.On this basis,the effect of the commutation period on the heat transfer performance of the microchannels of the phase-separated structure was studied.By analyzing the boiling heat transfer curves of the three phase separation structures before and after the cycle,the effects of different phase separation structures on the wall superheat degree and local saturation boiling heat transfer coefficient were explored.In addition,the effect of inlet subcooling degree on the heat transfer performance of microchannels of phase-separated structure was studied.A high-speed camera was used to visualize the flow boiling of the three phase-separated structures,and the changes in the length of the confined bubbles in the visualization were analyzed,and the enhanced heat transfer mechanism of the phase-separated structures was explored.The research results show that: in the range of the experimental conditions,compared with the structure without phase separation,the heat transfer coefficient of local saturated boiling of the phase separation structure is increased by 26% at most.(2)Study on heat transfer enhancement of micro-channels under the synergistic effect of electric field and phase separation structure.Change the phase separation structure and the magnitude of the applied voltage of the electric field to study the flow boiling heat transfer in the microchannel under the synergistic effect of the electric field and the phase separation structure.PSS2 and PSS3,through 12 combinations of these two parameters,combined with a high-speed camera for visual shooting,to explore the enhanced heat transfer mechanism under the synergistic effect of the electric field and the phase separation structure.The effects of three gas-phase separation structures on the distribution of heat flux density for effective heat transfer enhancement by electric field are mainly studied.The saturated boiling heat transfer coefficient is predicted by using the existing six heat transfer models,and the electric field factor and the phase separation structure factor are proposed to modify the heat transfer model.Within the range of experimental conditions in this paper,compared with the case of no external electric field and no phase-separated structure,the heat transfer coefficients of local saturated boiling of the phase-separated structure,the single electric field,and the synergistic effect of the electric field and the phase-separated structure are increased by 26%and 43%,respectively,65%.The phase separation structure effectively improves the enhanced heat transfer effect of the electric field under high heat flux density.(3)Research on the temperature uniformity along the microchannel under the synergistic effect of the electric field and the phase-separated structure.Firstly,the effects of the three phase-separated structures PSS1,PSS2,and PSS3 on the temperature distribution along the wall of the parallel countercurrent microchannel were studied.Then,the temperature uniformity along the microchannel under the synergistic effect of the electric field and the phase-separated structure was studied.The applied electric field voltage ranged are 400 V,800 V,1200 V,1600 V.Through the standard deviation of the wall temperature along the microchannel,the temperature uniformity along the microchannel wall under different phase separation structures,different electric fields and the synergistic action of the two is studied.The standard deviation of the wall temperature along the path,and the phase separation structure without the electric field can significantly reduce the standard deviation of the wall temperature along the path.