| With the continuous miniaturization of microelectronic components,traditional heat dissipation has been unable to meet the demand for heat dissipation,and the problem of heat dissipation with high heat flux in narrow space has become increasingly prominent.The flat heat pipe is a heat conducting element that transfers heat by means of phase transition.It is expected to solve the heat dissipation problem with high heat flux,because it works without external energy supply,without moving parts,and its heat transfer capability by phase change is much higher than the common high thermal conductivity metal materials such as copper and aluminum.The compactness of the electronic device requires that the heat pipe should be designed to be thinner,and the structure of the heat pipe can be adjusted according to the installation space.Therefore,ultra-thin heat pipes and flexible heat pipes are currently the main research hot spots in the field of heat pipes.In this paper,a"Y"shaped channel structure suction core is designed at the condensation end and the overall thickness of the ultra-thin flat-plate heat pipe is 2mm.A complete set of flat heat pipe production platform is designed and manufactured.Finally,the overall heat transfer performance of ultra-thin flat-plate heat pipes with"Y"shaped channels with fractal angles of 60°,70°,80°,and 90°is studied,and the following conclusions are obtained:（1）The overall structure of the"Y"channel wick is determined by the ratio of length,ratio of width,fractal Angle and fractal series.From the bifurcation theory,the optimum length ratio and width ratio are 2-1/3.The capillary force of the rectangular channel bifurcation structure is affected by the type of working medium and the hydraulic radius of the channel.The width of the"Y"channel structure changes at each stage,so the capillary pressure difference is formed.It is found that the pressure drop in the channel with 90°bifurcation angle is the largest,the pressure drop at 60°is the second,and the pressure drop at 70°and 80°bifurcation angle is smaller.（2）Through the design and optimization of the test platform,the error of the test results can be reduced.Through simulate to optimization the heat source,so reducing the radial thermal resistance that lead to test thermal resistance is bigger,by experiment and simulation with optimization of heat resistance heating rods and the optimal distance between the heating surface is 14 mm,at this point heat source on the surface of the maximum temperature of 2.64℃.The total error of the test platform is less than 7%.（3）The bifurcate structure is applied in the flat heat pipe condensation,from the start time,extreme heat transfer power and temperature performance concluded the Angle of 80°bifurcate flat heat pipe at a rate of 35%is the best perform,the worst rate of liquid thermal resistance is 45%.Under the heat power is 5W the rate of 25%,35%,two kinds of liquid flat heat pipe charging rates start time is respectively 800 s and 700 s,35%is faster.Under the conditions of 15℃and 20℃water cooling temperatures,at the highest temperature not exceeding 70℃,the limit power of the four fractal angles is greater at 15℃than at 20℃,and the limit power of the 80°fractal angle is 35W,which is 140%of that of water cooling at 20℃.However,the temperature uniformity of the four bifurcated Angle flat heat pipes is better at 20℃.The thermal conductivity of 70°fractal Angle is stronger during the condition of natural cooling.With the same heating power,the highest temperature of the monitoring points is the smallest,and the temperature uniformity is good.When the liquid filling rate is 35%,the water cooling temperature is 20℃,and the heating power is 20W,the thermal resistance value is only 0.475K/W,and the condensation thermal resistance accounts for 19.8%of the 80°fractal Angle thermal resistance. |
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