Numerical analysis on supercritical water heat transfer in a 2 × 2 rod bundle

CFD analysis is carried out for supercritical water (SCW) heat transfer in a 2 × 2 rod bundle with three turbulence models, i.e. the SSG, the ω Reynolds stress model (ω-RSM) and the baseline Reynolds stress model (BSL-RSM). The CFD calculation results show that the models predict similar cross-flow pattern between the adjacent subchannels. However, there is apparent discrepancy in the predicted turbulent mixing. Due to the strong cross-flow, the bulk parameters predicted by the models agree well. Comparison between the CFD results and the experiment data reveals that the SSG underpredicts the wall temperature, while the ω-RSM and BSL-RSM tend to overpredict the wall temperature remarkably in the region where the buoyancy effect is dominant near the wall. Such difference can be mainly attributed to the modeling approach near the wall. It may be concluded that the appropriate modeling of buoyancy effect is the key factor to improve the prediction when the wall region is resolved with very fine mesh. The bulk flow parameter obtained in the CFD calculation which cannot be easily measured in the experiment are used to evaluate the SCW heat transfer correlation. An uncertainty analysis shows that the uncertainty caused by the selection of turbulence models is negligible for the correlation evaluation.