Implementation of tritium permeation models in the CFD code Fluent

A number of additions have been made to the computational fluid dynamics (CFD) code Fluent in order to model hydrogen permeation. In addition to fluid dynamics, Fluent solves for heat transfer in coupled solid and fluid regions, and solves advection-diffusion equations for scalar quantities such as hydrogen concentration. The latter have been modified with additional code to satisfy Sievert's Law at solid-fluid interfaces and allow for temperature dependent diffusivity and permeability. The method has been employed to model the Tritium Heat Exchanger (THX) experiment at INL, which investigates hydrogen permeation in helium and candidate structural materials for high temperature gas reactor heat exchangers. TheArrhenius law parameters used in Fluent for Inconel 617 are initially determined via a simplified analytical method, and the resulting model predictions compare favorably with experiment data.