Numerical analysis of forced convection heat transfer in first wall rib-roughened channels for liquid lithium lead blanket

The first wall as the key component of the liquid metal blanket must withstand and remove the maximum heat flux from the plasma chamber and high power density LiPb breeder zone. A suitable countermeasure would be artificial roughening of the coolant channel wall facing the plasma for intensifying heat exchange. The rib-roughened coolant channels with high pressure helium gas for FDS series liquid lithium lead blanket were designed to enhance the turbulence heat transfer in comparison with smooth coolant channels. Heat transfer coefficients and friction factors in rib-roughened coolant channels of the first wall are investigated using the computational fluid dynamics code FLUENT, based on the two dimensional physical model and periodic condition. From the results of the numerical analysis, the turbulence heat transfer Nusselt number (N_u) in the rectangular channels of rib-roughened face is higher 200% than those in the smooth channels, and the fraction coefficient (f) between the helium gas and CLAM steel structure is 20% more than those in the smooth channels. The numerically optimized parameters are also presented considering different convexity part height and width as well.