【摘要】 对垂直上升φ31.8×6mm六头内螺纹管内超临界压力水的传热特性进行了比较系统的实验研究。试验参数范围:压力p=22.5～29.0 MPa,管内质量流速G=650～1200 kg/(m~2·s),内壁热流密度q=200～660 kW/m~2.根据试验结果,细致地分析了质量流速和压力对超临界水传热特性的影响,并探讨了大比热容区传热强化和传热恶化的发生机理。通过与亚临界压力下传热特性的比较,表明超临界压力下的对流换热不同于亚临界压力下的单相对流换热;超临界压力下的传热存在三种模式:(1)正常传热;(2)传热恶化;(3)强化传热。同时发现,超临界压力下的传热恶化类似于亚临界压力下的膜态沸腾。更多还原

【Abstract】 In the present paper,heat transfer characteristics of water in vertically-upward internallyribbed tubes at supercritical pressures are investigated experimentally.The internally-ribbed tube is made of SA-213T12 steel with the outer diameter of 31.8 mm and the thickness of 6 mm.The experimental parameters are as follows.The pressure at the inlet of the test section ranges from 22.5 to 29.0 MPa,and the mass flux is from 650 to 1200 kg/(m~2·s),and the inside wall heat flux varies from 200 to 660 kW/m~2.According to experimental data,heat transfer characteristics of water in the vertically-upward internally-ribbed tubs at supercritical pressures is obtained,and the mechanism of heat transfer enhancement and heat transfer deterioration are thoroughly analyzed.It is found the heat transfer characteristics of water at supercritical pressures is greatly different from the singlephase convection heat transfer at subcritical pressures.There are three heat transfer modes of water at supercritical pressures:(1)normal heat transfer,(2)deteriorated heat transfer,and(3)enhanced heat transfer.Based on the analysis of experimental data,it is found that the heat transfer deterioration at supercritical pressures is similar to the DNB(departure from nucleate boiling)at subcritical pressures in mechanism.更多还原