Thermal stress prediction in divertor cooling finger using the local heat transfer distribution

An approach that combines computational fluid dynamics (CFD) and structural mechanics simulation is used for evaluating stresses in a divertor cooling finger. Local distributions of heat transfer coefficient (HTC) between the helium and inner surface of the thimble are used as a boundary condition for the structural mechanics analysis. Stresses calculated with a realistic non-homogeneous HTC distribution are compared with the results where averaged HTC values in three representative zones of inner thimble surface are used. The obtained maximum stresses are considerably higher in the case of realistic non-homogeneous HTC boundary condition. The highest thermal stresses in the tile–thimble assembly are obtained on the thimble inner surface, in the region where the highest thermal gradients due to jet cooling can be observed. The results also show that tetrahedral based finite element model underestimate the computed stresses, especially when a coarse mesh is used.