Investigation On Capillary Flow And Evaporation In Silicon-Based Microchannel

With the development of miniaturization of science and technology,the problem of heat dissipation becomes more and more serious.Among the methods of chip cooling,the microchannel cooling technology is developing rapidly due to its excellent heat dissipation performance.Therefore,the basic research on the flow and phase change of cooling medium in microchannel is of great significance.In the field of electronic device cooling and space thermal control equipment,the loop heat pipe is widely used due to its advantages of high heat transfer efficiency,high reliability and flexible layout.The capillary flow and evaporation in the key part——the wick is the focus of many researchers,which is still of great significance to study on.In this paper,a series of silicon-based microchannel is designed and fabricated by the method of triple thermal oxidation and silicon-glass anodic bonding.Theoretical and visualization experiments were carried out to study the capillary flow and evaporation of different liquid working mediums in single-diameter and variable-diameter microchannels,so as to provide basic data support for the design of microchannel cooling stystem and the selection of capillary wick parameters in the loop heat pipe.The main research contents and conclusions of this paper are as follows:1.The research status and progress of capillary flow and capillary evaporation in microchannels and porous media were reviewed,the deficiency of this research field was analyzed as well.2.The experimental platform for visualized capillary flow and evaporation in silicon-based microchannels was set up.A series of silicon-based microchannel chips containing Pt micro-heating resistors were designed and manufactured,the design of the experimental scheme was completed,the processing method of experimental data was determined and the uncertainty of experimental data was analyzed.3.Experiments on capillary flow in silicon-based microchannels were carried out.The general law of the relationship between h-t and h2-t of capillary flow in single-diameter microchannel was studied,the results were compared with the theoretical calculation results of the L-W model,the influencing factors that may cause the difference between them were analyzed one by one.The general law of h-t relationship of capillary flow in microchannel with variable-diameter was studied,and the reason for the change of flow velocity after the change point was theoretically analyzed.The influence of the position of the change point and different specifications of changing diameter on flow velocity was studied as well.4.Experiments on capillary evaporation in silicon-based microchannels were carried out.The temperature distribution of single-diameter microchannel and the capillary evaporation phenonmenon inside the channel were investigated when the heat flux density changed.The effects of different working conditions and working fluids on the capillary evaporation process were analyzed.Investigations on the temperature distribution of variable-diameter microchannel and the variation law of capillary evaporation in the channel were studied.The effects of working fluids and the location of change point on capillary evaporation were analyzed.