Study On Design Of Double-scale Composite Porous Microchannels And Its Enhanced Boiling Properties

With the rapid development of microelectronic information industry,the high heat flux heat dissipation of electronic devices with increasing integration degree brings great challenges to the field of heat dissipation.Among the many heat dissipation schemes,the boiling heat transfer based on the phase transformation heat principle has the advantages of high heat transfer efficiency and strong stability.In order to further enhance the boiling heat transfer efficiency and improve the stability of boiling heat transfer,a double-scale composite porous microchannel structure(DCPM)was proposed in this paper.The forming mechanism of DCPM and its enhanced boiling property were studied systematically.The main contents of this paper are as follows:1.Fabrication and structural characterization of DCPMDouble scale compound porous microchannel was designed and manufactured,and the forming mechanism of interconnect and concave holes in macroscopic scale was analyzed.Analysis of ultrasonic machining mechanism,the surface morphology of micro-scale porous structure produced by ultrasonic machining was characterized,and the processing technology and parameters were optimized.2.Characterization of Capillary Properties of Microscale Porous Structures by Ultrasonic ProcessingA capillary performance evaluation model was established and the capillary performance of the ultrasonically processed sample was characterized by infrared thermal imaging technology,the mechanism of the enhancement of capillary properties by micro-scale porous structure was studied.The influence of ultrasonic machining parameters on capillary properties was studied.3.Study on the boiling performance of DCPMSet up pool boiling test device and combine with bubble visualization research system.Analysis of SUWU enhanced pool boiling heat transfer mechanism.The effects of macroscopic reentrant pores,interconnected pores and microscale porous structures on the boiling performance of DCPM were experimentally studied under different liquid subcooling degrees.The results show that all three porous structures can improve the pool boiling heat transfer performance,reduce the initial superheat degree,and increase the maximum heat transfer coefficient by 625% compared with the flat structure.4.Study on the flow boiling performance of DCPMA flow boiling test device was set up and combined with a bubble visualization research system to study the effects of DCPM’s macro reentrant pores,interconnected pores,and micro-scale porous structures on flow boiling performance and bubble flow pattern transition under different liquid subcooling and mass flow rates.Analysis of SUWU enhanced flow boiling heat transfer mechanism.The results show that the recessed and interconnected pore structures can enhance the enhanced boiling heat transfer performance,and the microporous structure does not significantly improve the heat transfer of flowing boiling.The effects of ploughing parameters,mass flow rate and subcooling on flow boiling pressure drop and temperature fluctuation were studied.The effects of liquid mass flow and subcooling on bubble flow patterns were studied.