竖直圆管内超临界压力氟利昂传热试验研究

深入研究超临界压力下流体特殊的对流传热特性,对超临界水冷反应堆的堆芯设计至关重要。在上海交通大学SMOTH氟利昂回路上开展了压力4.3~4.7 MPa、质量流速600~2 500kg/(m2·s)、热流密度20~180kW/m2参数下的圆管内超临界上升流传热试验。远离拟临界温度区间内换热系数和Dittus-Boelter公式计算值很接近,热流密度越大,近拟临界区换热系数越小,小质量流速大热流密度下,发生显著传热恶化。加速效应无量纲数和浮升力无量纲数对传热特性显示了强烈的相关性。提出了氟利昂工质传热试验的传热恶化起始点关系式。Bishop关系式计算换热系数和试验值之间标准差很小,但整体略偏大;Jackson关系式计算值和试验值之间平均偏差很小,但标准差偏大。

Experimental Study on Heat Transfer of Supercritical Freon Flowing in Vertical Tube

The in-depth study on heat transfer characteristics of fluids under supercritical pressure is crucial to the core design of supercritical water-cooled reactor (SCWR). Heat transfer experiments of supercritical Freon R134a flowing upward in a circular tube were carried out with pressure of 4.3-4.7 MPa, mass flux of 600-2500 kg/(m²•s) and heat flux of 20-180 kW/m². The heat transfer coefficient is close to the value calculated by Dittus-Boelter correlation in the region far from the pseudo-critical temperature. However, it is much smaller than the value calculated by Dittus-Boelter correlation with larger heat flux in the region approaching pseudo-critical temperature. The heat transfer deterioration occurs at the condition of small mass flux and large heat flux. It is shown that the heat transfer coefficient is of significant relevance with both acceleration effect dimensionless number and buoyancy dimensionless number. The correlation of onset of heat transfer deterioration is proposed based on experimental data. The heat transfer coefficient calculated by Bishop correlation shows a small standard error but an overall overestimate. The value calculated by Jackson correlation shows a small average error but a larger standard error.