湍流状态下垂直降膜波动特性影响因素研究

Research on factors affecting vertical falling film fluctuation characteristics under turbulent state

针对液膜的稳定性和均匀性会直接影响气液两相和气液固三相传热的问题,对影响液膜流动的因素进行研究。从液膜厚度、液膜速度和湍流强度3个参数定量分析槽宽(2~5 mm)、管径(73~113 mm)、气液接触角(0°~90°)、摩擦系数(0.1~0.9)和气速(2~10 m·s^(-1))对高雷诺数下垂直降膜波动特性的影响机理。结果表明,当槽缝宽度大于3.5 mm时,液膜厚度基本不变,湍流强度变化相对稳定。液膜的厚度、速度和湍流强度随管径的增大而显著变化。随着气液接触角的增大,液膜厚度和速度变化不大,但液膜的湍流强度在出口处略微降低。液膜厚度随着摩擦系数的增加略有增加。随着气体速度加快,液膜厚度先急剧减小,然后缓慢增加。气体速度对入口区域的液膜速度具有抑制作用。

Stability and uniformity of liquid film directly affect heat transfer of gas-liquid two-phase and gas-liquid-solid three-phase systems.Therefore,factors affecting the flow of liquid film were studied.Effects of slot width(2-5 mm),pipe diameter(73-113 mm),gas-liquid contact angle(0°-90°),friction coefficient(0.1-0.9),and gas velocity(2-10 m×s^(-1))on vertical falling film fluctuation characteristics at high Reynolds numbers were quantitatively analyzed from the perspective of liquid film thickness,liquid film velocity,and turbulence intensity.The results show that when the slot width is over 3.5 mm,the liquid film thickness remains unchanged,and the turbulence intensity changes relatively stable.The thickness,velocity,and turbulence intensity of the liquid film vary significantly with the increase of pipe diameter.As the gas-liquid contact angle increases,the thickness and velocity of the liquid film has little variation,while the turbulence intensity of the liquid film decreases slightly at the outlet.The thickness of the liquid film increases slightly with the increase of the friction coefficient.As the gas velocity increases,the thickness of the liquid film decreases sharply in the beginning and then slowly increases.Gas velocity has an inhibitory effect on liquid film velocity in the inlet region.