锥形分布器下竖直圆管降膜的数值模拟

Numerical Simulation of Falling Film of Vertical Circular Tube under Conical Distributor

通过建立竖直圆管内降膜蒸发的物理模型,对锥形分布器管内的气液两相逆流的换热特性进行二维CFD数值模拟,采用VOF方法捕捉两相流的流动界面,分析了管壁上液膜的膜态、膜厚、速度和温度分布。结果表明:液膜的膜态和温度分布与喷淋量紧密相关,随着喷淋量的增大液膜的稳定性逐渐增加,在喷淋量为1.48 kg/(m·s)时液膜的稳定性最好,液膜表面温度逐渐降低;液膜的降膜膜态分布分为上端的稳定段和下端的震荡段;2000<Re<10000时,管壁的平均传热系数呈现逐渐增大的趋势;膜厚的模拟值与Nussult和Brauer的理论计算值吻合较好。

By establishing a physical model for falling evaporation in vertical circular tube of an annular conical distributor,two-dimensional CFD numerical simulation was conducted on heat transfer characteristics of the gas-liquid countercurrent falling film evaporation,and the falling interface of the two-phase flow was captured by VOF method.The film state,thickness,velocity and temperature distribution of the liquid film on the tube wall were analyzed.The results show that the film state and temperature distribution of liquid film are closely related to the spraying amount.With the increase of spraying amount,the stability of liquid film increases gradually.When the spraying amount is 1.48 kg/(m·s),the stability of liquid film is the best and the surface temperature of liquid film decreases gradually.The falling film state distribution of liquid film can be divided into the stable section at the upper edge and the oscillating section at the lower edge.With 2000<Re<10000,The average heat transfer coefficient of the tube wall increases gradually,and the simulated values of film thickness is in good agreement with the theoretical values given by Nussult and Brauer.