Heat transfer deterioration to supercritical water in circular tube and annular channel

In order to ensure the safety of operation in Supercritical Water-Cooled nuclear Reactor (SCWR), heat transfer deterioration (HTD) must be avoided. In this paper, HTD was numerically studied in circular tube and annular channel using eight low-Reynolds-number models to provide detailed information on flow and turbulence structure. All models considered are able to predict HTD phenomena, while SST model performs better than other models quantitatively. Numerical results indicate that acceleration effect is significantly important for HTD at high mass flux while buoyancy effect at low mass flux. The increase of tube diameter leads to the aggravation of HTD phenomena, which is more obvious at low mass flux. At high mass flux, HTD phenomenon in circular tube is severer than that in inner-wall-heated annular channel. However, with both walls heated in annular channel, HTD phenomenon is similar to that in circular tube.