| The high energy consumption and high heat flux density of the data center put forward higher requirements for the safe heat dissipation of the data center server.The separate heat pipes have a good application prospect in solving the problem of high heat flux density dissipation of server CPU.Based on the standard 19-inch 2U server,this paper designed separate heat pipe exchangers with maximum heat dissipation of 500 W,the performance of the heat pipes and the effect of cooling temperature were experimentally studied,and then improved the separate heat pipes.In this paper,aluminum 6063 and R134 a were used for the heat pipes,and two heat pipes based on the principle of excellent heat transfer performance,cost saving,easy installation,and reliability were designed.The two heat pipes(1-SHP and 2-SHP)respectively adopt the condensers of horizontal and vertical condensing pipe structures,the experiment tested the performance of heat pipes when the heating power was from 100 W to 500 W at each filling rate from 20% to 70%.The heat source was metal ceramics heater,and the condenser was cooled by direct contact with the cold plate.The effects of liquid filling rate and heating power on the heat transfer performance were studied experimentally.Under the premise of comprehensive consideration of the temperature uniformity and the heating power,it was found that the optimal liquid filling rate of both heat pipes were 50%.With the increase of power,the thermal resistance of 1-SHP decreases first and then increases,and the thermal resistance of 2-SHP decreases first and then gradually stabilizes.Under the optimum rate,with the cooling temperature was 20 ℃,and heating power was 500 W,the thermal resistance and heat source surface temperature of 1-SHP were 0.040 ℃/W and 68.30 ℃,and of 2-SHP were 0.035 ℃/W and 61.34 ℃.Compared with the 1-SHP,the 2-SHP had better performance.At the optimal liquid filling rate,with the power increases,the time required to reach equilibrium for the surface temperature of the heat source gradually increases,and 2-SHP had excellent performance when the server CPU was working at variable power.When the cooling temperature was from 14 ℃ to 26 ℃,the relationship between the surface temperature of the heat source and the cooling temperature was almost linear,but it had little effect on the temperature uniformity of the separate heat pipe.The heat pipe was improved by reducing the height of the evaporator and mechanically treat to the evaporation surface,the optimum filling rate of the improved heat pipe was 35%.With the cooling temperature was 20 ℃ and the heating power was 500 W,the heat resistance of the heat pipe and the surface temperature of the heat source were 0.021 ℃/W and 55.91 ℃,compared with 2-SHP,it was reduced by 40% and 8.85% respectively.With the heating power was 100 W,200 W,300 W,400 W and 500 W,the improved heat pipe took 130 S,160 S,200 S,210 S and 260 S to reach equilibrium,compared with the 2-SHP,it was reduced by 90 S,100 S,100 S,90 S,70 S,respectively.In this paper,a separate heat pipe with excellent heat transfer performance,cost saving,easy installation,and reliability was designed.With the cooling temperature was 20 ℃ and the heating power was 500 W,the heat source surface temperature could be controlled to 55.91 °C,and reached the heat dissipation requirements of high heat flux density CPU. |
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