Experimental And Simulative Study On Performance Of Loop Heat Pipe With Plate Evaporator

With the rapid development of science and technology,electronic devices gradually develop towards the trend of high frequency,miniaturization and high integration,which leads to the decrease of effective heat dissipation area and the constant increase of heat flux.The heat transfer efficiency of traditional heat dissipation method and its reliability is poor,so it is not suitable for heat dissipation of high heat flux electronic devices.The loop heat pipe(LHP)with a flat evaporator has been widely concerned and applied in the heat dissipation field of high heat flux electronic devices due to the advantages including:(1)excellent heat transfer capability;(2)long distance heat transmission;(3)excellent anti-gravity capability;and(4)long service life.First,a novel LHP with flat evaporator is designed,compared with the conventional LHP,the LHP has no compensator,and the end of the liquid line is filled with wick,which can reduce heat leak,blocking the vapor from entering into the liquid line,and because of this,it stabilizes the vapor-liquid phase-change interfaces in the evaporator and condenser.Secondly,the experimental platform is built to study the influence of heat load and the sink temperature on the start-up performance,cycle operating performance,temperature distribution and thermal resistance of the LHP.The experimental results show that:(1)the LHP can start up smoothly under low heat load,and the start-up time is shorter,moreover,the highest temperature does not exceed 85 ? when the system reaches stable operation;(2)the LHP can maintain stable heat transfer performance under variable heat load;(3)the smaller the heat load is,the smaller the temperature variation range of each characteristic point is,that is,the bett er the thermal homogeneity of the LHP is,while the influence of sink temperature on the thermal homogeneity of the LHP is smaller;(4)when the heat load is below 50 W,the LHP is in the process of variable thermal conduction,and the system thermal resistance and loop thermal resistance both decrease sharply with the increase of heat load;when the heat load is exceed 50 W,the LHP enters a constant thermal conduction process,and the system thermal resistance and the loop thermal resistance remain basically unchanged.In addition,the system thermal resistance and loop thermal resistance basically decrease with the increase of sink temperature,while the evaporator thermal resistance does not change obviously with heat load and sink temperature.Finally,the steady-state mathematical model is builded based on steady-state energy and momentum conservation equations and thermodynamic relationships.Modeling the heat transfer in the evaporator was particularly considered,and the evaporation heat transfer coefficient is determined from a dimensionless correlation which is developed on the basis of experimental data.Then calculate the operating temperature of the LHP under steady state.By comparing the simulation results with the experimental data,the relative error is within 15%,indicating that the model can effectively predict the operating temperature of the LHP under different heat loads.