THERMAL SHOCK PROTECTION BASED ON MICROTUBE AND MICROPOST ARRAY SURFACE

To prevent primary pump shaft and the piping system from crack caused by the thermal shock of cold water at the nuclear power facilities, a new method for thermal shock protection is proposed. The proposed thermal shock protection technique is based on bionic surface with microstructure covered with a layer of water film. Due to the low thermal diffusivity of the water film,the thermal stress at the surface caused by the thermal shock is reduced and the probability of the thermal fatigue failure of the structure will be decreased. In the present paper,using COMSOL multifield coupling analysis software,the temperature field and thermal stress distribution of microstructure at the solid surface are analyzed combining finite elements method and infinite elements method. Effects of thermal shock time, the transition corner between microstructure and bulk material, the thickness of viscous boundary layer and the boundary temperature di erence on the surface thermal stress are studied. Based on the simulation results,it is found that the surface thermal stress is remarkably reduced contributed to the surface microtubes and microposts array structure, and there is an optimal shape of transition structure between microstructure layer and bulk material for minimizing thermal stress.