Research On Optimal Design And Heat Transfer Characteristic Of Vapor Chamber Based On The Fractal Structure Of Vein

With the rapid development of semiconductor electronic devices,the heat dissipation problem of high heat flux devices is also increasingly prominent.As an efficient heat dissipation technology,the vapor chamber has no need of external energy,no moving mechanical parts and no noise.The design is very simple and very effective.The heat transferred is several hundred higher than any solid metal conductor.At the same time,there are many factors affecting the heat transfer performance due to the changing structure of the vapor chamber,and the internal phase change heat transfer mechanism is very complicated.As vapor chamber toward the ultra-thin,miniaturization trend of development,the research problem is becoming more and more important.In this paper,a vapor chamber is designed.Its internal wick structure is developed from the natural vein structure as a blueprint.Firstly,the research background of the heat dissipation technology is discussed,and the research progress is discussed from the structure design,numerical simulation and performance research.Based on the basic theory of Hagen-poiseuille equation and fractal geometry,the bionic vein structure was preliminarily analyzed.FLUENT simulation software was used to simulate the flow state of the liquid suction core of the leaf pulse fractal structure,and the velocity cloud and pressure cloud diagram of the fluid in its groove were obtained.Finally discusses the issues of sample processing technology,and through the experiment got different fractal series,different fractal angle and liquid rate of vapor chamber temperature distributions under different heating power.The heat transfer performance of the vapor chamber with the vein fractal structure and the vapor chamber without the vein fractal structure were compared and analyzed.The main conclusions are as follows:（1）The condition that the structure parameter of the optimal flow resistance is obtained by theoretical calculation is that the length ratio is equal to the width ratio and all is（1/2）^-1/3.At the same time,the condition of fractal angle is obtained to make the whole vein fractal structure unit is symmetrical structure.（2）The speed distribution cloud diagram shows that the flow state in the channel is the worst when the fractal angle is 90°.The pressure distribution cloud shows that with the increase of the fractal series,the maximum pressure increase speed at the 30°and 60°fractal angles is greater than the 90°fractal angle.At the same time,the low-pressure area with the fractal angle of 90°accounted for the highest area ratio of the fractal structure of the entire vein.（3）In the production of samples and experiments,laser processing is the most suitable processing method by comparing different processing techniques.In the experiment,the heat resistance of the vapor chamber is about 0.2K/W when the fractal angle is 60°,and its average temperature is also good,and the maximum input power that can withstand is 90W.Under the condition of the same vein fractal structure,the heat transfer performance is the best when the filling rate is 53.40%.Compared with the vapor chamber with the vein fractal structure,the thermal resistance of the vapor chamber without using the vein fractal structure is 0.7K/W,the heat transfer performance is the worst,and the average temperature performance is also the worst.