Obtaining High-temperature Thermal Conductivity Of Graphite Fiber Material And Simulation Of Temperature Field In Vacuum Sintering Furnace

Graphite has become a widely used material by virtue of its electrical conductivity,corrosion resistance and high temperature resistance.China has rich graphite mineral resources,accounting for more than 50%of the world's graphite resource reserves.Therefore,the development of graphite has great prospects in China.And the study of graphite is also of great significance.Purification is an indispensable and extremely important part before the application of graphite.The purity of the extracted graphite determines the industry of its application.The more high-tech industries require higher purity of graphite materials.Simultaneously,the production capacity is also crucial for China to seize market resources.The graphite fiber material studied in this paper is used as a thermal insulation material in the vacuum sintering furnace for purifying graphite.The thermal conductivity has a great influence on the purification process of graphite.The traditional thermal conductivity test method is not suitable for high temperature vacuum in the sintering furnace environment.And domestic research on this area is less,so this paper proposes a method of combining experiment and simulation to obtain the thermal conductivity of graphite fiber material under high temperature and vacuum conditions.Firstly,the small vacuum sintering furnace is used as a test furnace.And four types of graphite fiber materials to be tested are installed in the furnace.There are four groups texts except the verification text.And then each group of tests is arranged with temperature measuring points on the inner and outer walls of the graphite fiber materials.The temperature values at different powers are measured.By the analysis of the temperature results of the tests,it is found that the temperature of the inner and outer wall surfaces showed a linear function relationship.And the thermal conductivity increased with increasing temperature.Besides,through observing the the power of same furnace temperature,the size relationship of the four graphite fiber materials is preliminarily presumed.Secondly,establish the CFD simulation model of the test furnace is necessary.And the boundary conditions can be determined according to the power,the inlet and outlet temperature of the cooling water in the test.An initial value of the thermal conductivity of the graphite fiber material should be given.The next job is to observe whether the simulation temperature is the same as test temperature.At last,by the method of iteration,the thermal conductivity of the graphite fiber material can be calculated,regressed and verified.In addition,through the analysis of the thermal conductivity of the four materials,the effect of temperature and density on the thermal conductivity of the graphite fiber material can be explored.It is found that the thermal conductivity increases as the temperature increases and the magnitude of the increase becomes larger.When the temperature increases,the graphite fiber material with higher density has a suppressive effect on thermal radiation relative to the lower density material.Finally,a large-scale vacuum sintering furnace simulation model for batch purification was established to simulate and study the temperature field.The temperature gradient of the muffle tube with graphite raw materials placed was determined.And the size of its average temperature zone was also determined to provide experience for practical production.In order to solve the problem of time-consuming and energy-consuming in the cooling process of large vacuum sintering furnaces,this paper also studies and analyzes measures to shorten the cooling time.The results show that the advancement of protective gas can effectively shorten the cooling time.And the greater the amount of gas,the shorter the cooling time,but the effect of optimization is not as good as the former.