超临界水在垂直上升圆管中传热的数值分析

利用FLUENT对超临界水在垂直上升圆管内的传热特性进行了CFD研究，计算结果与Yamagata试验结果进行了对比.采用5种不同湍流模型对同一工况进行计算，结果表明RNG k-ε湍流模型所得到的计算结果与试验结果更为接近.在RNG k-ε湍流模型中比较了不同的y+下的计算结果，结果表明当y+≤1时计算结果与试验结果符合较好，y+=0.1时二者相符最好，最大偏差约为13%.最后选用RNG k-ε湍流模型并取y+=0.1计算了不同的热流密度下的传热特性，结果表明在大比热区低热负荷时传热会得到强化，而随着热负荷的增加，传热强化的效果会被减弱直到出现传热恶化现象.

Numerical Analysis of Heat Transfer in Upward Flows of Supercritical Water in Circular Tubes

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.