A mixed convection heat transfer benchmark test case: The prismatic-core advanced high temperature reactor

A thermal-hydraulic sub-channel calculation for a Prismatic-core Advanced High Temperature Reactor (PAHTR) design is investigated. In particular, the investigation focuses on the Star-CCM+’s global discretization error order, with this finite volume code, for forced and mixed convection heat transfer cases pertinent to the nuclear industry. To achieve this, the commercial code Star-CCM+ is used to study the flow and thermal hydraulic conditions of a single coolant channel. First the CFD model for a single channel of the PAHTR is benchmarked and validated against existing correlations for developing forced convection flow. This comparison has allowed a Verification and Validation (V&V) of the commercial code Star-CCM+. The obtained results with the reactor’s operating heat flux values reveal that the flow within the PAHTR core remains in the developing mixed convection regime. Nusselt number and friction coefficient profiles along the pipe’s streamwise direction are directly affected by the heat flux magnitude and distribution. In fact, existing correlations either; do not take buoyancy effects in account or are not within the flow conditions range, hence, the CFD predictions are used to produce more suitable correlations taking in account this mixed convection regime. As for the commercial code used, the global numerical error of the Star-CCM+ CFD code is, as expected, approaching the 2^nd order.