Abstract: Heat transfer in upward flows of supercritical water in circular tubes is numerically investigated by using the commerical CFD code FLLUENT.The numerical results were compared with the well-recognized experimental results of Yamagata.Five tubulence models were selected to carry out numerical simulations and the results of RNG k-ε model give a better prediction to the heat transfer than the other models.The comparison of results for different y+ showed that y+ which is no more than 1 would gives a better prediction to the heat transfer.The deviation of results for y+=0.1 is confined to 13%.The heat transfer performance for different heat flux was compared using RNG k-ε model with y+=0.1.The results showed that in the region with high specific thermal capacity and low heat flux the heat transfer would be enhanced.However,the impact of enhancement is weakened with the increase of the heat flux and the deterioration would occur at the critical heat flux.

Key words: supercritical, CFD, turbulence model, circular tube