简谐摇摆运动下窄通道内空气-水两相流摩擦阻力

Frictional resistance of air-water two-phase flow in a narrow duct in harmonic rolling motion

矩形窄通道广泛应用于紧凑式换热器设计中,其内空气-水两相流动摩擦阻力受简谐摇摆运动影响而与稳定状态不同。笔者通过实验研究了摇摆运动条件下矩形窄通道内绝热两相流摩擦压降特性。结果表明:层流区(分液相雷诺数Rel<800)及过渡区(800≤Rel≤1400)摇摆条件下摩擦压降波动周期等于摇摆周期;湍流区(Rel>1400)摩擦压降没有明显的周期性波动。Lee-Lee模型能较好地用于摇摆条件下平均摩擦压降的预测,但不能用于周期性变化摩擦压降的动态预测。通过分析大量实验数据的变化规律,基于奇斯霍姆C(Chisholm)关系式,拟合得到了摇摆条件下瞬时摩擦压降经验关系式,其预测值与实验值有较好的一致性。

Narrow rectangular ducts have extensive application in compact heat exchangers design.The frictional resistance of air-water two-phase flow in narrow rectangular ducts under rolling condition is different from that under steady condition.The present work experimentally investigated the characteristics of frictional pressure drop of air-water two-phase flow in a narrow rectangular duct under rolling condition.The results show that the frictional pressure drop fluctuates with the same period of the rolling motion in laminar flow region（Rel800）and transition flow region（800≤Rel≤1400）,whereas it is nearly invariable in turbulent flow region（Rel 1400）.Although the Lee-Lee model is well applied to predict the time-averaged frictional pressure drop under rolling condition,but inapplicable when the transient frictional pressure drop fluctuates periodically due to the rolling motion.A new correlation was achieved by modifying the Chisholm correlation on the basis of analyzing a large quantity of experimental pressure drop,showing good agreement with transient experimental data in rolling motion.