Verification of a CFD-Class Software Tool as Applied to Modeling the Fuel Assemblies of Liquid Metal Cooled Reactors

Methodical approaches to verification of a CFD-class code for modeling fluid dynamics and heat transfer processes within the boundaries of a fuel assembly (FA) used in liquid metal cooled reactors are proposed. For verifying the code, experiments that take into account the specific features pertinent to the flow of and heat transfer in liquid metal coolants in the fast reactor FAs with spacer grids were selected. The experiments cover the following regimes: turbulent flow of and heat transfer in liquid metals in the stabilized and nonstabilized sections in simple and complex shaped channels for which the flow structure in the near-wall region is the determining one; turbulent flow in channels containing elements that cause flow separation and redistribution of the flow rate over the cross section, and flow in channels containing abrupt flow constriction/expansion. Proceeding from the need to save computation resources in solving practical problems, the high Reynolds number turbulence model was used, which does not pose the requirement of fulfilling the y⁺ ≈ 1 criterion for the dimensionless distance from the first computational node to the wall. The computations were carried out with the use of the high Reynolds number Realizable k–ε turbulence model with the standard near-wall function. The local Weigand model for the turbulent Prandtl number Pr_t, applied in a wide range of Pr number values, including those for liquid metals, was used. The maximum deviations of the calculated values from the experimental data for the practically important parameters are estimated.