新型大通量填料的流体力学和传质性能研究及其CFD模拟

发布时间：2018-03-31 13:21

本文选题：新型大通量填料　切入点：流体力学性能　出处：《北京化工大学》2015年硕士论文

【摘要】：本文根据填料的发展规律及工业需求,针对填料的大通量使用条件,结合BH填料成功的设计经验,对传统填料波纹结构进行改进,设计开发出A、B、C三种结构独特的新型大通量规整填料。常温常压下,在冷模实验装置中以空气-水-氧气为介质研究新型填料的流体力学和传质性能,并与传统的大通量填料Mellapak125X对比。实验结果表明,三种新型填料的干塔压降分别比Mellapak125X下降15.3%、23.8%和35%；湿塔压降分别下降26.7%、34.2%和40.3%；液泛气速分别提高7.5%、11.3%和15.1%。在三种新型填料中,A型填料具有最高的传质效率,但通量较小；而C型填料虽然通量最大,但传质效率却有一定程度的下降。计算流体力学(CFD)技术是流体力学理论与现代计算机科学结合的产物,广泛地应用在科研、制造等领域。但由于填料复杂的结构及填料内两相流动的复杂性,填料的CFD模拟尚未得到广泛应用。本文建立了多尺度CFD模型,以局部的VOF模型为基础,对新型填料(A型)的干、湿塔压降进行了模拟计算,并对不同气液速度下填料表面平均液膜厚度及有效接触面积变化进行了阐述。模拟结果表明：采用该多尺度模型计算填料的干塔压降与实验值误差为5.2%；除个别点误差较大外,模拟的填料湿塔压降与实验值误差在20%以内。当气速为0时,填料表面液膜厚度随液体流速的增加呈线性递增变化；有效接触面积随液体流速的增大有增加的趋势,但增加量逐渐减小。固定液体流量,在低气速范围内增加气速,填料表面平均液膜厚度与有效接触面积有增加的趋势,但不明显；当接近液泛区域时,随着气速的增加,平均液膜厚度及有效接触面积有明显的上升趋势。该现象表明,气速较小时,气液两相交互作用较小,气速对液相分布行为影响小；随着气速的增加,气液交互作用逐渐增强,气速对液相分布具有较大的影响。本文提出的多尺度模型计算量较小、精度较高,将填料的宏观和微观性质相结合,在计算填料压降的同时,还得到了填料局部的流场信息,在填料的理论研究和改进设计中具有一定的应用价值。
[Abstract]:In this paper, according to the development law of packing and industrial demand, according to the condition of large flux of packing, combined with the successful design experience of BH packing, the corrugated structure of traditional packing is improved. Three new types of large flux regular fillers with unique structure are designed and developed. The hydrodynamics and mass transfer properties of the new fillers are studied by using air-water-oxygen as the medium in a cold model experimental device at room temperature and atmospheric pressure. Compared with the traditional high-flux packing Mellapak125X, the experimental results show that, The dry column pressure drop of the three new types of packing is 15.33.8and 35% lower than that of Mellapak125X respectively, the pressure drop of wet tower is 26.732% and 40.3% respectively, the liquid gas velocity increases 7.511.3% and 15.1g, respectively. Among the three new fillers, the type A packing has the highest mass transfer efficiency, but the flux is relatively small. Although the fluxes of C type fillers are the largest, the mass transfer efficiency decreases to a certain extent. Computational fluid dynamics (CFD) technology is the product of the combination of fluid mechanics theory and modern computer science, and is widely used in scientific research. However, due to the complex structure of fillers and the complexity of two-phase flow in fillers, the CFD simulation of fillers has not been widely used. In this paper, a multi-scale CFD model is established, based on the local VOF model. The pressure drop of dry and wet tower is simulated and calculated. The variation of average liquid film thickness and effective contact area of packing surface at different gas-liquid velocities are described. The simulation results show that the error between the pressure drop of dry tower and the experimental value of packing is 5.2 by using the multi-scale model, except for some points, the error is large. When the gas velocity is 0, the thickness of liquid film on the packing surface changes linearly with the increase of liquid velocity, and the effective contact area increases with the increase of liquid velocity. But the increase gradually decreased. When the liquid flow rate was fixed, the gas velocity increased in the range of low gas velocity, the average liquid film thickness and the effective contact area on the packing surface increased, but not obvious. The average liquid film thickness and the effective contact area have an obvious upward trend. This phenomenon shows that the gas-liquid two-phase interaction is smaller and the gas velocity has little effect on the liquid phase distribution behavior with the increase of the gas-liquid velocity, the gas-liquid interaction increases gradually with the increase of the gas-liquid velocity. The gas velocity has a great influence on the liquid phase distribution. The multi-scale model proposed in this paper has the advantages of low computational complexity and high precision. Combining the macroscopic and microscopic properties of the packing, the pressure drop of the packing is calculated and the local flow field information is obtained. It has certain application value in theoretical research and improved design of filler.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ050.45

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