低功率条件下低高度差开式自然循环流动模式研究

开式自然循环系统广泛应用于能源和化工领域。在一些特殊条件下，低高度差自然循环系统应运而生，但目前研究并不充分。本文采用蒸汽加热方式，对这类的低高度差开式自然循环系统在低功率水平下的流动模式进行了实验研究，并对其流动模式以及存在物理现象进行了详细的分析。研究发现，在不同功率水平下，因受不凝性气体和过冷沸腾的影响，该自然循环系统主要存在4种流动模式。最后，对不同流动模式转变点的加热段进出口温度进行分析，结果表明加热段出口温度可作为系统流动模式的判定依据。 

Study on Flow Patterns of Open Natural Circulation with Low Height Difference under Low Power Conditions

Open natural circulation systems are widely applied in the field of energy and chemical industries. Under some special conditions, open natural circulation systems with low height difference have to be applied, but little research focused on this type of systems. In this paper, the flow patterns of such a natural circulation system were experimentally studied at low power level by adopting the steam heating. In addition, the flow patterns and physical phenomena of the natural circulation system were analyzed in detail under different heating power conditions. It is found that there are four flow patterns under different power levels for the natural circulation system, because of the influence of non-condensable gas and subcooled boiling. The inlet and outlet temperatures of the heating section are analyzed in different flow patterns. The result shows that the outlet temperature of the heating section can be used as a judgment criterion of different flow patterns.