Simulations for L-STAR experimental gas-cooled system

Abstract

Turbulent heat transfer through gas-cooled systems is a key factor for the improvements of the gas-cooled fast reactors. Within the FP7 European projects GoFastR (European Gas Cooled Fast Reactor) [1] and THINS (Thermal-hydraulics of Innovative Nuclear Systems) [2], numerical tools for the simulation of the thermal-hydraulics of next generation reactor systems were developed, applied and validated for innovative coolants. One of their objects was the L-STAR (Luft - STab, Abstandshalter, Rauheiten) facility, which has been designed and erected at the Karlsruhe Institute of Technology to study turbulent flow behaviour and its heat transfer enhancement characteristics in gas-cooled annular channels under a wide range of conditions. The test section consists of a hexagonal cross-section channel with an inner electrical rod heater placed coaxially. This design represents the flow domain around a single fuel rod in a future GFR. In this paper experimental results of the fluid flow with uniform heat release conditions for the smooth heater rod are considered. Design of the facility allows using various values of heating power and fluid mass flow rates depending on the chosen scenario. The purpose of this study is to create CFD models for the L-STAR facility, which are capable of reproducing the results of reference measurements. The other aim is to find an applicable turbulence model for the GFR relevant cases. Steady-state simulations are performed for selected cases. We also present mesh, structural element and turbulence model sensitivity studies during this work. With these model results it becomes possible to validate our CFD models to be applicable for the ALLEGRO gas-cooled reactor fuel assemblies.