Experimental Investigation On Capillary Performance Of Wick And Heat Transfer Characteristics Of Vapor Chamber

With the advancement of technology,the increase in power and the decrease in the volume of electronic products have led to a significant increase in the heat production per unit area of electronic products.The heat transfer performance of the vapor chamber is high,which can quickly transfer and spread the heat from the heat source to the larger condensation surface,thereby reducing the heat source surface temperature.As the main structure of the vapor chamber,the wick provides the power for the working fluid to flow,making the vapor chamber become a highly efficient heat transfer element.However,the porosity,permeability,and capillary force of the wick affect the mass transfer performance of the wick,which in turn affects the heat transfer effect of the vapor chamber.There are tiny pores in the sintered copper powder wick structure,which makes the wick have a good capillary force.Therefore,the structure of the sintered copper powder wick has become the main form of the wick of the vapor chamber and heat pipe.From the perspective of engineering application,10 types(74)different types of sintered copper powder wicks were prepared by sintering in this study.The effects of copper powder types on the porosity,shrinkage and permeability of the wick were studied through theory and experiments.The surface morphologies of various wicks were observed and analyzed by SEM.By building a capillary rise infrared test system for the wick,the effect of the type of copper powder on the capillary climbing speed of the wick was researched.The calculated permeability and the calculated effective capillary radius of the wick were calculated by MATLAB programming,and then the capillary pressure and capillary performance factor of the wick was obtained.And the influence of different kinds of copper powder on the capillary properties of the wick was discussed.The experimental results show that the shrinkage of the irregular copper powder wick is larger than that of the spherical copper powder wick and the porosity after sintering is also larger than the spherical copper powder wick for the same particle size.The permeability increases with the increase of average copper particle size.For the wick with the same particle size,the permeability of irregular copper powder wick is larger than that of spherical copper powder wick.The simplified method in this study can well predict the permeability and effective capillary radius of the wick.Within the scope of this study,the capillary performance of the wick with the single particle size irregular copper powder I-75?m is the best.In this study,four types of vapor chamber were prepared,and an air-cooling test system for the heat transfer performance of the vapor chamber was built.The influences of copper powder types and the liquid filling ratio on the heat transfer property of the vapor chamber were explored.The experimental results show that the capillary performance of the wick is the dominant factor affecting the heat transfer performance of the vapor chamber with the different types of wicks.In this study,the capillary performance factor of the vapor chamber with I-75?m wick is much higher than other types of vapor chamber.With the increase of power,the thermal resistance of all VCs showed a downward trend,and the decrease of the total thermal resistance at high power is greater than that at low power.The liquid filling ratio and the structure of the wick have a certain effect on the surface temperature of the heat source of the vapor chamber.However,when the wick has a good capillary performance factor,the vapor chamber with this wick is not sensitive to the filling ratio,it is a vapor chamber with I-75?m wick in this study.To achieve high heat transfer efficiency,it is necessary to have the best matching liquid filling ratio for the vapor chamber with a fixed particle size copper powder wick.The height of the steam chamber is an important factor that affects the heat transfer performance of the vapor chamber.The maximum flux density of the vapor chamber decreases as the height of the steam chamber decreases.