Study on Flow and Heat Transfer Characteristics of Different States of Water Under Natural Circulation

Software CFX is used to build a typical natural circulation loop to study flow and heat transfer characteristics of water vapor, the vapor-liquid two-phase and supercritical water under natural circulation. During the process of natural circulation, the variation of parameters, heat transfer coefficient and mass flow is compared. It is found that when formed a natural circulation, the steam has a lower mass flow and heat transfer coefficient, while the two parameters of two-phase and supercritical water are higher. Indicates that the heat transfer capability of steam is weak, the steam cannot transfer heat out opportunely when serious accidents take place. The two-phase water is of high heat transfer coefficient. Supercritical water is of strong exchange capacity, supercritical water under natural circulation is a promising flow pattern.