湍动浆态床流体力学研究(Ⅴ)带多层水平网格构件的浆态床流体力学模型

Studies on hydrodynamics of turbulent slurry bubble column(Ⅴ) Modeling of bubble column with multi-layer screens

水平布置的多层筛网是最简单的阻尼型内构件,用于改善流动分布。在安装多层筛网的500mm×5000mm鼓泡塔冷模装置中进行了流速分布与气含率分布测定。实验表明,网格型内构件可以有效抑制塔中心区过快上升的流速,改善其分布。网孔越小,流动阻尼效果越明显,同时平均气含率也会有所增大。提出了与列管内构件相似的一维流体力学模型,将网格型内构件对流体的阻尼效果作为体积源来考虑,湍流耗散方程中的参数值c3=2.0、c4=1.3,与列管束内构件略有不同。模型计算与实验数据符合良好,能够定量描述网格型阻尼内构件对流场的影响。

Screen is one of the simplest resistance internals for improving the radial profile of axial velocity in a bubble column.In this paper the profiles of axial liquid velocity and gas hold up along the radius of 500 mm×5000 mm bubble column with multi-layer screens were measured by Pavlov tube and conductivity probe respectively.The experimental observations showed that the lateral screen internals could remarkably reduce the ascending liquid velocity in the core region,resulting in improvement of flow profiles.The smaller the screen hole,the more remarkable the resistance effect,and the higher the average gas hold up.A one dimensional CFD model similar to that of pipe bundle internals was developed,and the damping effect of screen internals on the liquid was regarded as the volumetric source of momentum,turbulent kinetic energy and dissipation.The values of parameters in the turbulent energy dissipation equation were different from the model of pipe bundle internals,and they were estimated as c3=2.0,c4=1.3 by comparison with experimental data.The present model provided an effective tool in simulation of damping effect of multi-layer screens internals in bubble columns.