汽液直接接触换热过程汽泡湮灭致压力振荡的机理研究

The pressure oscillations in direct contact condensation are very important for the safe and stable operations of relevant equipments. However, because of the coupling effect of turbulent flow and condensation heat transfer, the mechanism of pressure oscillation has not been clearly recognized until now. Therefore, this project investigates the steam bubble annihilation process, omits the effect of turbulent flow. The theoretical analysis, experimental research and numerical simulation methods will be used to observe the evolution of the interface and micro heat and mass transfer in bubble condensation. Meanwhile, the frequency and amplitude of pressure oscillation will be measured. The characteristics and the deep mechanism of condensation heat transfer, pressure oscillation will be investigated. And then, the simplified theoretical calculation models of bubble condensation heat transfer coefficient and pressure oscillation intensity and frequency will be established. Finally, the effect of condensation heat transfer process on the pressure oscillation will be revealed by changing heat transfer coefficient through adding non-condensable gas into the bubble. Through the research of this project, the mechanisms of condensation heat transfer and pressure oscillation can be revealed. The fundamental theory and key technology of controlling the pressure oscillation can be obtained, which will provide the theoretical basis for the design and development of relevant equipments.

汽液直接接触换热中的压力振荡问题对相关工业设备的安全稳定运行至关重要，但由于湍流流动和凝结换热的耦合作用，使得人们对压力振荡的机理还没有清晰的认识。为此，本项目通过研究汽泡的湮灭过程，去除湍流流动的影响，采用理论分析、实验研究以及数值模拟等方法，通过观察汽泡湮灭过程的汽液相界面的演化过程及传热传质微观过程，同步测得汽泡湮灭过程中的压力振荡频率和强度，获得汽泡湮灭过程中凝结换热与压力振荡特性，揭示凝结换热及压力振荡的机理；进而建立汽泡凝结换热系数及压力振荡强度和频率的理论计算模型，获得其定量表征方法；最后通过加入不凝性气体改变凝结换热系数，揭示凝结换热过程对压力振荡的影响，拓宽其工业应用范围。本项目研究可以揭示汽泡在过冷水中凝结换热与压力振荡机理，得到调控压力振荡的基础理论和关键技术，为相关工业设备的设计和开发提供理论依据。

本项目以核电站中鼓泡器蒸汽直接接触凝结换热与压力振荡为研究背景，对汽泡直接接触凝结换热过程和压力振荡机理开展了系统研究，通过设计并搭建汽泡直接接触换热与压力振荡实验系统，对汽泡凝结中的汽泡形态、凝结换热特性和压力振荡特性进行了实验研究和理论分析。建立了压力振荡强度理论分析模型，获得了压力振荡机理；分析了直接接触凝结换热系数与压力振荡主频的内在联系，建立了压力振荡主频和凝结换热系数的实验关联式，为直接接触凝结换热系数的求取提供了一种新的便捷有效的方法；对压力振荡波的空间传播特性进行了研究，为相关设备的设计和应用提供了重要的数据支持；揭示了直接接触凝结能量转化机制，并对汽泡界面演变特性进行了研究，获得了汽液界面形态对凝结换热和压力振荡的影响机理。本项目研究结果进一步丰富了汽液两相流理论体系，为核电站鼓泡器安全稳定运行提供理论和技术基础。基于上述研究结果，发表SCI论文5篇，培养硕士研究生1名。