A Second-Order Accurate Convection Heat Transfer Discretisation Scheme for a Systems Simulation Reactor Model

Nuclear reactor behaviour is determined by the relation between the temperature and the effective neutron reaction cross-sections of the materials in the reactor core. In order to accurately calculate the material temperatures, heat transfer to the reactor coolant is of critical importance. To increase the accuracy of heat transfer calculation, this paper presents a second-order accurate convection heat transfer discretisation for application in two or more dimensions in a finite-volume discretisation. This discretisation is compared to a first-order accurate scheme by means of a grid dependence study on representative reactor geometry. To obtain a certain level of accuracy, the use of second-order accurate convection discretisation reduced the solution time by up to 60 percent, as the second-order accurate scheme required fewer grid points than the first-order accurate scheme. This is of particular importance for systems simulation reactor models, as they use the minimum number of grid points and have to run at the highest possible simulation speed. This study was done using the systems simulation code Flownex.