自然循环加热段内摩擦阻力及对流传热的实验研究

以常压去离子水为工质,对自然循环工况下上升加热段内单相水的摩擦阻力及对流传热特性进行了实验研究.结果表明,自然循环工况下加热段内由浮升力引起的自由流动对摩擦阻力及对流传热特性有重要影响,自然循环与强制循环二种工况下加热段内的摩阻系数及对流换热系数存在明显差别;并且,自然循环工况下加热段内的摩擦阻力存在滞后现象.通过实验提出了计算自然循环工况下加热段内单相水的摩阻系数及对流换热系数的经验关系式.

INVESTIGATION ON FRICTION AND HEAT TRANSFER IN A TUBE WITH NATURAL CIRCULATION

The friction and convective heat transfer of single phase water flow in a vertical heated tube at natural circulation condition were experimentally investigated. The experimental results indicate that free convection caused by buoyancy in the heated tube has great influence on the friction and convective heat transfer under natural circulation condition. The friction factors and convective heat transfer coefficients in the tube obtained from the experiments carried out respectively at natural circulation and forced flow conditions were quite different. Besides, it is found that the friction in the tube at natural circulation was also affected by the method of heat import to the tube. Based on the experimental results, the empirical correlations for the calculation of friction and convective heat transfer in the tube at natural circulation condition have been presented.