流速对含不凝气体的蒸汽冷凝的影响

Effect of Velocity on Steam Condensation with Non Condensable Gas

蒸汽在安全壳内壁面上的冷凝是事故发生后安全壳内的气体向壳壁传热的主要方式,是影响钢制非能动安全壳压力响应的重要因素。针对事故后核电厂安全壳内的事故工况条件,在较宽的参数范围内开展了蒸汽冷凝传热过程的试验研究。试验压力为0.11～0.5 MPa（d）,主流空气质量分数为29%～78%、壁面过冷度为26～60℃,混合气体平均流速0.4～1.9 m/s。试验结果表明：在0.9 m/s以下的低流速范围内,试验数据与经验关系式的计算结果符合较好;流速高于0.9 m/s时,流速成为影响含有不凝性气体的蒸汽凝结传热的主要因素之一;主流空气质量分数较低时,流速对含有不凝性气体蒸汽冷凝的传热系数的影响更加显著;对于伴有蒸汽冷凝的对流换热过程,由自然对流向混合对流转变的判据与单相对流换热过程不同。

Condensation on the containment structures during an accident is one of the critical thermal-hydraulic phenomena that would affect the pressure in the containment vessel. Experiment facility was set up to investigate the steam condensation with non condensable gas on a cold plate, focusing on the conditions in the containment. In the experiment, pressure range is 0.11 - 0.5 MPa; mass fraction of air in the bulk flow is 29%- 78%; the wall sub-cooling is 26-60℃. Gas velocity varies from 0.4 to 1.9 m/s. The experimental result agrees with empirical correlations when the gas velocity is up to 0.9 m/s. Gas velocity becomes one of the primary factors influencing the steam condensation in non-condensable gas with higher gas velocity. The promotion effect on the heat transfer of increasing velocity is more significant when the mass fraction of non-condensable gas is lower. The transition criterion from free to mixed convection for steam-gas flow condensing should be different from that of the single phase heat transfer.