Research On Flow And Heat Dissipation Performance Of Metal Foam Heat Pipe Radiator

Modern electronic devices usually integrate a large number of components in a very limited space,resulting in high power density.Therefore,solving the heat dissipation problem is one of the main factors to improve the reliability and service life of electronic devices.Heat pipe radiator can meet the requirements of compact,reliable,flexible and efficient heat dissipation device of electronic devices,so it is increasingly widely used in all kinds of electronic devices cooling system in recent ten years.But the heat transfer from the condensor of the heat pipe to the ambient air greatly limits the heat dissipation performance of the heat pipe radiator.In view of the fact that metal foam can effectively enhance the flow heat transfer,this thesis uses metal foam instead of fins to solve this problem,and proposes a new type of metal foam heat pipe radiator.The flow heat transfer performance under natural convection and forced convection conditions is studied.In this thesis,the connection technology of metal foam and heat pipe is firstly explored,and successfully produce a new type of metal foam heat pipe radiator.Natural convection and forced convection experiments are carried out under different heating power and air velocity.The flow and heat transfer characteristics of metal foam heat pipe radiators are systematically analyzed from the aspects of junction temperature,thermal resistance,convective heat transfer coefficient,pressure drop,friction factor and comprehensive performance evaluation parameters of flow and heat dissipation.For further optimization and analysis,10PPI,20PPI and 40PPI metal foam heat pipe radiators are prepared.The flow and heat dissipation characteristics of these radiators are analyzed under different heat loads and air velocity,and the effects of pore density on thermal resistance,pressure drop and comprehensive performance of flow heat dissipation are discussed.It is found that compared with the traditional finned heat pipe radiator,the heat dissipation performance of the metal foam heat pipe radiator is greatly improved,and the total heat resistance of the heat pipe radiator can be significantly reduced.It predicts that the decrement of the overall thermal resistance can be up to 58%by adopting advanced connecting technology.However,the metal foam heat pipe radiators can significantly increase the pressure drop of the system.Therefore,it is necessary to balance the flow and heat dissipation performance comprehensively in practical applications.The function of Colburn j-factor and friction factor(j/f^1/3)is used as a parameter to evaluate the advantages of improving heat transfer and disadvantages of increasing flow resistance,which provides a direct criterion for its practical application.It finds that the j/f^1/3 of metal foam heat pipe radiator can be four times that of the traditional fin heat pipe radiator,which indicates that its flow and heat dissipation performance is superior to traditional fin heat pipe radiator For the metal foam heat pipe radiator with different pore densities,it is found that the heat dissipation of 10PPI metal foam heat pipe radiator is the largest under natural convection and same junction temperature,which indicates that the increase of pore density is not conducive to the heat dissipation by natural convection.Under forced convection,the maximum cooling load of 20PPI is 18.4%and 47.2%higher than that of 10PPI and 40PPI,and the thermal resistance is reduced by 15%and 31%.However,when considering the flow and heat disspation performance comprehensively,the j/f^1/3 of 20PPI is slightly 2%lower than that of 10PPI,due to the rapid increase in pressure drop while significantly improving the heat dissipation capacity.Therefore,it is speculated that the best pore density is between 10PPI and 20PPI,which can provide high heat dissipation performance while ensuring low pressure drop.In addition,the fitting empirical equations of friction factor are given for further theoretical analysis and numerical calculation.The metal foam heat pipe radiator studied in this thesis can effectively improve the airside heat dissipation performance of the heat pipe radiator,effectively reduce the overall heat resistance and improve the heat dissipation under the premise of not increasing the pressure drop.At the same time,it has a lighter weight.The further optimization design of the heat pipe radiator through the pore density provides a new idea for solving the thermal management problems of electronic devices,and has certain reference value and guiding significance in its practical application.