| The pulsating heat pipe has the advantages of simple structure,high heat transfer efficiency,good environmental adaptability,etc.,and has shown a wide application prospect in the field of high heat density heat dissipation.This thesis mainly explores the flow pattern changes of gas-liquid two-phase flow in the tube under different heat loads during steady-state operation of the pulsating heat pipe,and its influence on the oscillation characteristics and heat transfer performance of the working fluid in the tube.First,under different thermal load conditions,the two-gas plug-liquid plug model can show the evolution of the working fluid two-phase flow pattern and its heat transfer characteristics,so that the model can better reflect the effect of phase change thermal characteristics on the liquid plug oscillation characteristics.The model is solved to obtain the two-phase flow pattern of the working fluid in the tube,the oscillation of the liquid plug,and the overall heat transfer performance of the pulsating heat pipe.Secondly,an experiment was designed and executed to verify the accuracy of the model.The experiment verifies that the model can better respond to the oscillation and heat transfer characteristics of the working fluid in the pulsating heat pipe.According to the experimental results,it is found that the pulsating heat pipe with different kinds of working fluid and different filling rates has different heat transfer performances,50% hydraulic fluid pulsating heat pipe can reduce the overall cost while ensuring the performance of the heat pipe.It is recommended to use it in practical applications.Furthermore,based on the proposed two-phase flow-gas-liquid plug oscillation model,the effects of various factors on the pulsating heat pipe oscillation and heat transfer performance were analyzed in this work.It is found that low heat load is not conducive to the oscillation of the working fluid in the tube,and the heat transfer performance is limited.Under high heat flux,the working fluid in the tube pulsates violently and the heat pipe havethe higher heat transfer efficiency;by comparing the effects of different tube diameters,different numbers of heat transfer units,and different heating methods on the oscillation characteristics of the working medium and the heat transfer performance of the heat pipe,it is found that the tube with the inner diameter is 1.5 mm,the number of heat transfer units is 4,and the top heating factors and other factors are not conducive to the working fluid oscillation in the tube,thereby reducing the heat transfer performance of the pulsating heat pipe.It is recommended that when the inner diameter of the pulsating heat pipe is 2 ～ 3mm and the number of heat transfer units exceeds 5,it is more beneficial for the pulsating heat pipe to achieve heat transmission.The heat transfer performance of the pulsating heat pipe under the top heating condition will be slightly reduced,but it can still maintain high heat transfer characteristics.Compared with other heat pipes,the heat transfer performance is greatly reduced or even fails under the top heating condition,the pulsating heat pipe has a better performance.It shows that the pulsating heat pipe has better environmental adaptability.Finally,a thermal management system for a pulsating heat pipe battery is designed,and the flow and heat transfer characteristics of the pulsating heat pipe are obtained based on the proposed model simulation.The equivalent thermal conductivity of the pulsating heat pipe under battery conditions is calculated,and the overall thermal management system is numerically calculated.It is found that thermal management system with pulsating heat pipe has a good battery temperature control effect and a very good heat transmission capacity in high heat flux density scenarios. |
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