Simulation Analysis Of Heat Transfer And Flow Characteristics Of Miniature Flat Heat Pipe

With the continuous development of the electronics industry,the heat flux density of electronic components and equipment continues to increase.The heat dissipation of electronic devices is crucial to the development of electronic technology,so it is important to adopt efficient heat dissipation methods to promote the development of the electronics industry.The flat heat pipe has the advantages of good environmental adaptability,strong heat transfer capability,good temperature uniformity,accurate control of heat flow,and easy bonding with chips.It is widely used in the thermal design of electronic equipment.However,at present,the capillary effect in the flat heat pipe is relatively simple,and the liquid flow in the wick can not be driven by surface tension.There are many numerical simulations on the bubble formation process in the heat pipe,there are few simulations on the relative movement of the gas-liquid two phases between the evaporation section and the condensation section in the heat pipe phase change process.Therefore,the heat transfer and flow in the wick and the phase change in the vapor chamber of a flat plate heat pipe are numerically simulated,the impact of the structure of the microchannel and vapor chamber on the heat transfer performance is analyzed for practical applications.The specific studies include the following aspects:Numerical simulation of heat pipe radial heat conduction process.Relevant theories of numerical heat transfer are introduced.Based on the basic principles of heat transfer,a simplified two-dimensional fluid-structure coupling model is constructed in the radial direction.Using the software Fluent to simulate the temperature distribution in the heat pipe,the effects of the shapes and sizes of microchannels and working fluid on the radial heat transfer ability of the heat pipe have been studied.The results show that the rectangular wick has the strongest heat transfer ability.The shorter distance and the deeper wick can improve the heat transfer capability of the heat pipe.Among the three working fluids of water,ethanol and acetone,water is most benefical to the radial heat transfer ability of the heat pipe.Numerical simulation of the capillary effect in the wick.Based on the principle of capillary effect,the CSF model of Fluent software was used to simulate the capillary effect in the wick,the effects of the shapes and sizes of microchannels and working fluid on the capillary effect in the wick have been studied.The results show that the capillary effect in the rectangular wick is the most significant.The deeper,wider wick can improve the capillary effect.Among the three working fluids of water,ethanol and acetone,the capillary effect produced by water is the most significant.Numerical simulation of the phase change in the heat pipe.The basic formula of energy transfer in the phase transition process of working fluid is introduced,a two-dimensional simplified model of the flat heat pipe is established in the axial direction,and the evaporation and condensation of the working fluid in the vapor chamber is simulated using the compiled UDF(User-Defined Function).The temperature field in the heat pipe is obtained and compared with the pure aluminum plate.after that,The effects of heat source power and vapor chamber height on the heat transfer characteristics of the heat pipe are studied.The results show that the heat transfer ability of the heat pipe is stronger than that of the pure aluminum plate.The smaller the height of the steam chamber is,the better the heat transfer ability of the heat pipe will be.The higher the heat source power is,the higher the overall temperature of the heat pipe will be.But the temperature difference between the two ends of the heat pipe basically does not change with the increase of the heat source power.