Experimental Study On The Temperature Uniformity Performance Of Flat Plate Heat Pipe For Cooling Electronic Devices

Due to the integration and miniaturization of electronic products,the problem of high heat flux density is becoming more and more serious,which will damage the electronic equipment.Therefore,the more effective heat dissipation method requires to solve this problem.And the flat plate heat pipe has become a focus of researches in solving this problem for electronic devices,which has very high thermal conductivity,variability of heat flux density,good isothermal characteristics and structural adaptability.In this paper,a new type of anti-gravity flat plate heat pipe for laptop cooling is proposed with a combined wick of gauze and groove.The heat pipe has no adiabatic section,and the ratio of condenser section area and evaporation section area is 127: 1.The performance of the heat pipe are investigated under the condition of different filling ratios,heating power and inclination angles.And then,the optimization is conducted to achieve a better temperature uniformity.And the influence of heating power and ambient temperature on the starting performance of heat pipe are studied on the basis of the optimization.The main research work and the results are as follows:(1)In this paper,the selection of the wick and shell material of the flat plate heat pipe is designed,and the anti-gravity flat plate heat pipe is made by welding.The size of the heat pipe is 300 mm long and 150 mm wide.The deionized water was used as working fluid and the natural convection is applied on the condensation section.(2)In this paper,the temperature uniformity of the flat plate heat pipe is studied on the different heating power and filling ratios.The results show that the trend of the thermal resistance and the standard deviation of the flat heat pipe decreases first and then increases when the liquid filling ratio changes from 25% to 60%.It shows that there is an optimum liquid filling ratio in the operation of the heat pipe,which is 45%,and the thermal resistance and the standard deviation are the smallest,and the smallest thermal resistance is 0.26K/W.With the increase of heating power,the thermal resistance of the heat pipe decreases when the heating power changes from 10 W to 50 W,the lowest resistance can be achieved at 50 W.(3)The influence of the inclination angle on the temperature performance of the plate heat pipe is studied at the optimum filling ratio.The effects of four inclination angles of 0°,15°,30° and 90° on the performance of the heat pipe are studied.The results show that the heat transfer resistance of the heat pipe increases with the angle increasing,and the average thermal resistance of the three angles corresponds are 0.37K/W,0.41K/W,0.46K/W from 10 W to 50 W.The minimum thermal resistance is 0.26K/W when heat pipe is placed flat.(4)In order to make the heat pipe temperature uniformity effect is better and lighter weight,the thickness of the material of the heat pipe is optimized and the thickness reduced from 1.5mm to 0.45 mm,After optimization,the optimum liquid filling ratio is smaller than that before optimization.The optimum filling ratio is 30%.At this filling ratio,when the heating power is 10 W to 40 W,the temperature uniformity effect is particularly good and temperature distribution standard deviation,thermal resistance,the maximum temperature difference is relatively small.The standard deviation from 10 W to 40 W is 2.9℃,1.8℃,1.8℃,1.8℃,the maximum temperature difference is 11.3℃,10.0℃,8.6℃,8.5℃ and the thermal resistance is 0.30℃/W,0.08℃/W,0.05℃/W,0.04℃/W.(5)After the optimization of the heat pipe,the influence of the ambient temperature on the performance of the flat plate heat pipe is studied.The ambient temperature of 15℃,20℃ and 25℃ is studied.The results showed that with the increase of the ambient temperature,the thermal resistance and standard deviation of the heat pipe are all decreased.Taking 30 W as an example,the average temperature of the surface of the heat pipe from 15℃ to 25℃ are 50.9℃,56.6℃,59.1℃.(6)The effects of heating power and ambient temperature on the start-up time are studied.The results show that with the increase of heating power,the start-up time of 30 W is relatively short,start time is 1750s;At 15℃,20℃,25℃ three temperatures,15℃start faster,start time is 1750 s.(7)Cold spraying method is used to strengthen the dissipation of the flat plate heat pipe,after spraying,the temperature uniformity performance is better,and the standard deviation is 1.2℃,thermal resistance is 0.04℃/W.