The thermal analysis and experimental research of HL-2M vacuum vessel thermal insulation layer

摘要

The vacuum vessel(VV)is one of the core components in HL-2M Tokamak experimental device. Before the plasma operation, the VV can be baked up to 300 degrees C with a baking speed of similar to 4 degrees C/h using nitrogen gas to obtain a ultrahigh vacuum of similar to 10 - 6Pa. During the baking operation, the VV must be assembled a thermal insulation layer (TIL) to raise the efficiency of baking out-gassing, also to reduce the high temperature influence on other components such as PF coils. In this paper, the finite element model including two sector of VV and its corresponding components have been built, and also the experimental research with a 1:2 scale heat performance test device has been carried on to compare with the FE method and the theoretical analysis. Firstly, the simplified model and boundary conditions have been established, and the main heat transfer equations during this transfer process can be identified. It can be inferred that the convective heat transfer coefficient of insulation layer cold surface is about3 W/(m(2).K). And then the results of simulation and prototype TIL heat transfer experimental research show that only when the thermal conductivity of the TIL is under0.038 W/(m.K) at 300 degrees C, and the natural convection heat transfer coefficient of the TIL cold surface is more than 3 W/(m(2).K), the temperature of PF1-4 coils epoxy resin can be controlled less than 70 degrees C, also the total heat loss of VV will not exceed 20kW. Those finite element simulations and the experimental results can help us to choose the suitable thermal insulation layer material and assemble method of the vacuum vessel thermal insulation layer.