基于石墨铝的固态均热板及其传热性能试验研究

Graphite/Al Composites Solid Chamber and Experimental Study on Its Thermal Behavior

针对卫星电子载荷模块发热量激增引起的散热问题,本文提出固态均热板构型,设计了两种不同内部结构的固态均热板模块,并对该两种固态均热板模块的传热性能进行了试验研究。给出定义和评估固态均热板等效导热系数(λe)的方法,该λe可以用于量化评估固态均热板导热性能。研究结果表明,石墨铝固态均热板传热性能优越,内部接触热阻低至1×10^(-5)m^(2)·K·W^(-1)。石墨铝固态均热板为解决卫星电子高热模块的散热问题提供了新的途径。

The thermal powers of electronic modules utilized in satellites continuously increase due to the enhancement of operational capability of the satellites.The vapor chamber is the most widely used structure to solve heat dissipation problems in satellite electronic modules.The key feature of the vapor chamber is the process of phase change in refrigerant during operating,which gives rise to some deficiencies,such as complicated manufacture process,high cost,mismatch between the design criteria of the vapor chamber and those of the printed circuit boards(PCBs).These drawbacks limit the application of the electronic modules on satellites.In order to overcome the shortcoming of the vapor chamber,a novel configuration of solid chamber,which behaves wide application prospect on satellites in the future,is proposed.Solid chamber modules were designed and system tests were carried out to demonstrate the efficiency of the solid chamber.The configuration of the solid chamber was similar to a sandwich structure.The top and bottom layers of the solid chamber were made with commonly used metals.In order to meet the requirements of lightweight,installation matching with electronic modules and the suitability for aerospace environment,aluminum was used for making the top and bottom layers of solid chamber,and solid material with high heat conductivity was selected for the middle layer of the solid chamber to enhance the heat conductivity of the structure.Macroscopically,the developed solid chamber displayed high heat conductivity similar to the vapor chamber.Two solid chamber modules,whose middle layers were made with different materials,were designed,manufactured and tested.The mid layer of one of the solid chamber modules was made with graphite/Al composites Al/Gp 420/40,and that of the other one was made of graphite foil-aluminum foil composites.Other two modules respectively made of 6063 aluminum and copper T2 with the same geometry were produced for comparison.In order to check the suitability of the solid chamber for aerospace environment,heat transfer properties of the four solid chamber modules before and after thermal shock(-55~+100℃,200 times)were tested.The results showed that the heat transfer capability of graphite/Al composite solid chamber module was significantly higher than that of 6063 aluminum module,appearing excellent heat transfer capability.Moreover,the heat transfer capability of graphite/Al composite solid chamber module nearly did not change after thermal shock,behaving good stabilization.It was concluded that graphite/Al composites solid chamber had the potential to be used in aerospace engineering.On the other hand,the heat transfer capability of the aluminum-graphite foil-aluminum foil composites solid chamber module was almost the same as that of 6063 aluminum module,which meant that the mid layer made of the graphite foil-aluminum foil composites nearly did not enhance the thermal conductivity of the solid chamber.To assess the thermal performance of the solid chamber,a method to define and determine the equivalent heat transfer coefficient(λe)of the solid chamber combing the test and numerical simulation was proposed.By means of the proposed method,the determinedλeof graphite/Al composites solid chamber was 290 W·m-1·K-1and that of the aluminum-graphite foil-aluminum foil composites solid chamber was 180W·m-1·K-1,which consistent with the test results.It was seen thatλecould be used to quantify the enhancement of the heat transfer performance of graphite/Al composites solid chamber.In addition,the inner contact thermal resistance between aluminum and graphite/Al composites of graphite/Al composites solid chamber were studied.The heat transfer performance of the modules with different inner contact thermal resistances were numerically simulated.When the inner contact thermal resistance was 1×10^(-5)m^(2)·K·W^(-1),the simulation result was mostly closed to the test result,indicating that the inner contact thermal resistance between aluminum and graphite/Al composites was approximately 1×10-5m~2·K·W-1.Moreover,the numerical simulation reflected that the increments of the temperature at test points were less than 1℃comparing with the case of zero inner contact thermal resistance.Finally,metallographic observation on the cross section of graphite/Al composites solid chamber showed that aluminum layer and graphite/Al composites layer combined closely,consistent with the result of the numerical simulation.Based on the study of this paper,it was shown that the proposed structure of the solid chamber could significantly enhance heat conductivity,which depended on the material used to make the middle layer of the solid chamber and the manufacture process.λeof graphite/Al composites solid chamber arrived at 290 W·m^(-1)·K^(-1),and the inner contact thermal resistance between aluminum and graphite/Al composites was as low as 1×10^(-5)m^(2)·K·W^(-1).Because the operation process of the solid chamber only related to heat conduction in solid phase without phase change,the solid chamber displayed the advantages of easy manufacturing,low cost,easy design and good applicability in satellite electronic modules.The proposed graphite/Al composites solid chamber provided a wide application prospect in cooling satellite electronic devices with high thermal dissipation.