Multi-Scale Optimization And Performance Analysis Of Micro-Heat Pipe Array Heat Exchanger

As an efficient phase change heat transfer element with high adhesion,microtube array heat exchanger has been widely used in electronic products.The phenomenon of heat transfer and flow inside the micro heat pipe is common in nature and various engineering fields,covering many levels of scale.It is more and more important to simplify the complex physical process and carry out the simulation calculation at different scales and levels.In this paper,the multi-scale research method is adopted to analyze and study the performance of microtube array heat exchanger from the macro level and micro level respectively,and the influencing factors of the heat transfer performance inside the microtube are obtained.The core research contents and results are as follows:1.CFD visual numerical model of micro-heat pipe was established,and VOF model and standard model were used for computational fluid dynamics simulation.The results show that the heat transfer performance of the micro heat pipe is the best under the condition of 30% liquid filling rate.When methanol is the working medium,the heat transfer effect is the best.Compared with other working medium liquid films,they are evenly distributed in the micro-heat pipe and do not dry up.The heat transfer characteristic of rectangular groove structure is better than that of light tube structure and triangular groove structure.2.Set up three types of array structure of micro heat pipe,through the horizontal and vertical comparison study found that overall thermal resistance type Y1 minimum heat pipe,is 0.8% of the conventional heat pipe,heat transfer coefficient was 10 times higher than the conventional heat pipe and heat pipe heat transfer performance of the whole is best,thus concluded that,under the same condition,array of micro heat pipe heat transfer performance was mainly affected by condensation period of structure.3.Molecular dynamics simulation of liquid film phase transition was carried out at the micro-scale level.The results showed that after the calculation was completed,according to the difference in density distribution,the calculation area was divided into three parts: vapor state,vapor-liquid transition surface and liquid state.As the temperature increases,the thickness of the transition surface is proportional to the temperature.The influencing factors of evaporation rate of micro-scale water liquid film are closely related to the thickness of liquid film and ambient temperature.The evaporation rate of water liquid film is proportional to the temperature of liquid film thickness system.However,with the increase of the temperature and the thickness of the liquid film,the growth rate of evaporation rate becomes smaller and smaller.The efficiency of evaporation rate is optimal when the evaporation temperature is 400 K and the thickness of the liquid film is 1nm.4.The stabilization time of condensation and liquefaction becomes shorter and shorter as the temperature decreases.When the temperature is above 298.15 K,the time required increases with the increase of system temperature.When the temperature is below 298.15 K,the time required to achieve stability is less and less with the decrease of system temperature,but the decreasing amplitude is gradually reduced.Interfacial hydrophilicity can affect the rate of condensation and liquefaction and the degree of difficulty of liquid film forming.The applied electric field can effectively increase the hydrophilic energy of the interface.The hydrophilic action energy is in direct proportion to the electric field intensity,but the increase in amplitude is in inverse proportion to the change in electric field intensity.At the same time,the contact Angle between the condensate droplets and the wall gradually increases,which promotes the formation of the wall liquid film.When the electric field intensity is 3V/ ?,the hydrophilic action energy is the optimal to increase the efficiency.