Analysis and Improvement of Flow Field Calculation in Thermal Hydraulic Program for High Temperature Gas-Cooled Reactor

The flow field calculation plays a crucial role in thermal-hydraulic calculation of High Temperature Gas-cooled Reactor (HTGR). While using the thermal-hydraulic program for HTGR to calculate the low-flow condition, the calculation of the helium pressure field distribution in the reactor core is difficult to converge, which may lead to the non-physical pressure oscillation. The analysis and improvement of flow field calculation to alleviate this non-physical oscillation is of great significance for HTGR thermal-hydraulic design. In this work, the factors affecting the flow field calculation are analyzed. The approximation assumptions of horizontal cavity modeling and the using of Gauss-Seidel (GS) partition point iteration method leading to the flow field calculation is sensitive to round-off error. For the reason of GS partition point iterative method suffers from the slow convergence rate, and may even non-convergence in some conditions, a global direct method is developed in this paper to solve the whole flow field directly to pursue strong stability and high convergence rate. Compared with original method, the numerical results show that the newly developed algorithm achieves faster convergence rate and stricter convergence results.