Abstract:

Steam direct contact condensation has high efficiency in heat and mass transfer and is widely used in nuclear energy safety and other fields. Compared with the stable condition on land, the swing movement under the marine conditions may exacerbate the oscillation of the auto liquid interface and further affect the safe operation of the equipment. Therefore, the condensation process of low flow rate steam under rolling conditions was studied by numerical simulation, and the changes of pressure, heat transfer characteristics and bubble forces under rolling conditions were analyzed. The results showed that the sharp fluctuations of pressure and heat transfer coefficient mainly concentrated in the phase of bubble shrinkage and separation, when the bubble forces also reached the maximum, and the bubble was mainly affected by the inertia force and condensation force. In addition, it is found that the inertia force partially increases due to the change of bubble velocity under the rolling condition, and the additional rolling velocity brought by the rolling motion strengthens the heat transfer performance of the vapor-liquid interface, and the average heat transfer coefficient is much higher than that under the stationary condition.

Key words: vapor direct contact condensation, bubble force, gas-liquid flow, CFD, transport processes, rolling motion

摘要：

蒸汽直接接触冷凝具有高效的传热传质性能，广泛应用于核能安全等领域。低质量流率蒸汽直接接触冷凝具有低频压力振荡，易引发设备共振。相比陆地稳定工况，海洋条件下摇摆运动可能加剧气液界面振荡，进一步影响设备的安全运行。为此，通过数值模拟对摇摆条件下低流率蒸汽凝结过程进行研究，分析了摇摆条件下压力、换热特性和气泡受力的变化规律，结果表明压力和传热系数剧烈波动主要集中于气泡颈缩和脱离阶段，此时气泡受力也达到最大值，气泡主要受惯性力和凝结力作用。此外，对比静止工况和摇摆工况，发现摇摆条件下由气泡速度变化导致的惯性力部分增大，摇摆运动带来的附加摇摆速度强化了气液界面的换热性能，平均传热系数远高于静止工况。

关键词: 蒸汽直接接触冷凝, 气泡受力, 气液两相流, 计算流体力学, 传递过程, 摇摆运动