Research On Enhanced Boiling Heat Transfer Characteristics Of Distributed Jet Impingement Combined With Microstructure Surface

With the rapid development of electronic chips towards high performance and miniaturization,the heat flux is increasing,and the heat flux of local hot spots will exceed 500 W/cm².Thermal failure has become the main form of electronic equipment failure.The development of efficient and high heat flux heat dissipation technology is an effective solution to thermal failure.As a new heat dissipation technology,jet impingement combined with microstructure surface enhanced boiling heat transfer technology has the advantages of compact structure,high heat transfer coefficient and effective elimination of local hot spots,which can be used as an effective measure to solve the above problems.In this paper,the distributed jet impingement boiling heat transfer system is taken as the research object,and the relevant test platform is established to explore the flow boiling heat transfer characteristics and reveal the heat transfer mechanism in the jet impingement system with different microstructure surfaces（square array pin-finned surface,copper wire mesh surface and Cu-Al₂O₃ porous electrochemical deposition surface）.Firstly,a visual test section for disassembly and assembly was designed and fabricated.Square array pin fins,wire mesh structure layer and Cu-Al₂O₃porous electrochemical deposition layer were prepared on the smooth surface of the test section.The preparation methods were Wire cut Electrical Discharge Maching,atmosphere furnace sintering and electrochemical deposition.Secondly,a visual distributed jet impingement cooling performance test platform was built,and a high-speed camera system is equipped to record the evolution and development of bubbles in real time.Combined with bubble dynamics,the boiling heat transfer mechanism of jet cooling system is analyzed to explore the complex boiling heat transfer mechanism inside the jet cooling system.Finally,with HFE-7100 as the coolcant,the jet boiling heat transfer characteristics of three kinds of microstructure surfaces with various influencing factors were experimentally investigated.The effects of different undercooling degrees,flow rates and jet distances at three jet positions on the heat transfer characteristics of jet impingement boiling were investigated on the square column array surface.The effects of different jet positions on the heat transfer characteristics of jet impingement boiling,bubble dynamics and pressure fluctuation characteristics were mainly studied.The heat transfer performance of the square micro-rib column array surface was compared with that of the smooth surface.When exploring the heat transfer characteristics of the jet boiling on the surface of the porous wire mesh,the influence of the number of layers and mesh of the porous wire mesh on the heat transfer characteristics of the jet boiling was explored,and the heat transfer performance of the porous wire mesh was compared with that of the smooth surface.At the same time,the dynamic change of bubbles and the fluctuation characteristics of inlet and outlet pressure on the surface of the porous wire mesh were also explored.FE-SEM（field emission scanning electron microscope）,XRD（X-ray diffraction）and contact angle measurement were used to characterize the prepared Cu-Al₂O₃ porous deposition layer surface.The effects of current density,deposition time and Al₂O₃concentration on the microstructure morphology,material composition and wettability of the porous deposition layer surface were analyzed.At the same time,the effects of different current density,deposition time and Al₂O₃ concentration on the heat transfer characteristics of jet boiling were explored,and the heat transfer performance of the microstructure surface was compared with that of the smooth surface.The heat transfer performance of the three microstructure surfaces was compared,and the results showed that the wire mesh surface had the best heat transfer performance at high heat flux,and the heat transfer performance was stable.Cu-Al₂O₃ surface has very high heat dissipation capacity at low wall superheat,which can eliminate high heat load instantaneously,but its heat transfer performance will decrease sharply with the further increase of wall superheat.The heat transfer performance of the micro-column array surface is relatively stable,but its heat transfer performance is lower than that of the wire mesh surface and the Cu-Al₂O₃ surface...