| With the development of 5G technology,the surge of data volume has put forward higher requirements for data centers,and the heat dissipation of server CPU has become a key factor restricting the development of data centers.Because of the CPU heat dissipation problem of pedestal server,combined with the characteristics of low thermal resistance of vapor chamber and strong heat dissipation ability of water cooling technology,a liquid cooling integrated roll bond vapor chamber is designed according to pedestal server.The main works of this paper are as follows:(1)The liquid cooling integrated roll bond vapor chamber with different flow channel structures was designed.The stable operating conditions and working principles of the vapor chamber were analyzed.It detailedly described the structure that the working medium flow channel and water cooling channel at the condensing end.The numerical heat transfer model is established through the corresponding simplified process.Further,the simulation model analysis was carried out in Fluent.(2)It described the manufacturing process of liquid cooling integrated roll band vapor chamber in detail.According to characteristics of the liquid cooling integrated roll band vapor chamber,the bending die and forming craft were designed,and the samples with different bending angles were prepared.The heat transfer performance test platform of the vapor chamber was built,and the corresponding heat transfer performance evaluation indexes were put forward.(3)Based on the experimental platform,the key factors(flow structure of working medium,bending Angle,working medium injection rate)affecting the heat transfer performance of liquid cooling integrated roll band vapor chamber were analyzed.The experimental results show that the time to reach the steady-state of the liquid cooling integrated roll band vapor chamber is longer.The temperature difference mainly occurs between T6～T8 and T9～T11,and is tiny in the adiabatic section,which reducces with heating power improving.The working fluid flow channel structure does not influence the heat transfer limit.The working medium flow channel structure of VC2 has the best heat transfer performance and the best start-up performance at low power.(4)The effect of bending angle on heat transfer performance of liquid cooling integrated roll band vapor chamber is as follows:the lower the bending Angle,the greater the heat transfer limit of power,but the bending angle of 150~o and 135~o between difference is small,and when the heating power is less than the limit of heat transfer power,bending Angle has no effect on heat transfer performance.When the heating power is greater than the limit power,the larger the bending angle,the poorer heat transfer performance is,but between 150~o and 135~o is it almost no difference;The larger the bending Angle,the less likely the oscillation is to occur in the low heating power state.(5)When the working medium injection rate is less than 18.6%,the limitation of the heat transfer power increases with increasing of the injection rate.However,when the injection rate exceeds 18.6%,the limitation of heat transfer power does not change with increasing of injection rate.When the power is low,the average temperature of heat source T_a add with the increase of working medium injection rate,and the heat transfer performance decreases.When the power is high,as working medium injection rate improving T_a is decreasesing,and when the liquid injection rate increases from 6.2%to 12.4%,the decreasing trend becomes more severe with the increase of power.The higher the injection rate,the more likely it is to show start-up performance at low heating power.(6)To modify the numerical model,relevant parameters were obtained by building a numerical simulation model verification experimental platform.The revised numerical model was used to simulate.By comparing the numerical simulation with experimental,it was shown that the relative error was small than 7%,which verified the accuracy of the heat transfer numerical model. |
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