【摘要】 以常压去离子水为工质,对自然循环工况下上升加热段、上升冷却段和下降冷却段3种传热部件内单相水的流动阻力进行了实验研究。实验结果表明,传热部件内工质的物性变化及由浮升力引起的自由流动对摩擦阻力有重要影响。通过分析,提出了计算自然循环工况下不同传热部件内单相水沿程摩擦阻力系数的经验关系式。更多还原

【Abstract】 This paper presents the experimental study of the friction of single phase liquid up flow in vertical heated tube, up flow in vertical cooled tube and down flow in vertical cooled tube in a natural circulation system. The experimental results indicate that free convection caused by buoyancy in the tubes with heat transfer has great influence on the frictional pressure drop in natural circulation with low mass flow rate. When the free convection in the tubes is co-current with the flow in the natural circulation system, the turbulence in the boundary near the tube wall will be reduced, which can lead to the decrease of the friction. If the free convection in the tubes is in reverse direction with the flow in the circulation system, the turbulence in the boundary will be increased, which can lead to the increase of the friction. Based on the experiments, the empirical correlations for the calculation of the friction factors in tubes at different flow and heat transfer conditions have been presented.更多还原