UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, University of New South Wales, Sydney, 2052, Australia.
UNESCO Centre for Membrane Science and Technology, School of Chemical Engineering, University of New South Wales, Sydney, 2052, Australia.
Water Res. 2019 Sep 1;160:60-69. doi: 10.1016/j.watres.2019.05.056. Epub 2019 May 20.
A three-dimensional Computational Fluid Dynamics (CFD) model was developed to study shear stress induced by spherical cap bubbles in hollow fibre (HF) membrane modules configured with a packing density of 38 m/m, to predict the shear profile in a commercial hollow fibre membrane module of 265 m/m. The CFD model's computational effort was minimised by simulating the formation of bubble structures and their rising velocities in modules with packing densities of 1.8 and 38 m/m and validated with experimental calibration of shear profiles via electro-diffusion methods (EDM). Pulse bubbles (300 mL) generated from a single sparger at 0.5 Hz produced more satellite bubbles in the wake zone of the leading bubble in high packing density (38 m/m) than in low packing density modules (1.8 m/m). The bubble rise velocity was approximately 8% lower in the 38 m/m than in the 1.8 m/m module. Increasing packing density reduced the shear profile from a single sparger and the dispersion of the satellite bubbles in the horizontal plane, especially in the upper part of the membrane module. For systems with multiple spargers, the interaction between pulses generated more shear than the pulses from a single sparger, and produced a more uniform shear profile in the module through asynchronous bubble release from adjacent spargers than synchronous release. A 33% increase in the "Zone of Influence", the flow region where the upward velocity >0.2 m/s, was achieved by moving from a synchronous to an asynchronous form of aeration.
建立了一个三维计算流体动力学（CFD）模型，以研究空心纤维（HF）膜组件中球形帽气泡产生的剪切应力，该模型的填充密度为 38m/m，用于预测填充密度为 265m/m 的商业空心纤维膜组件中的剪切分布。通过模拟填充密度为 1.8 和 38m/m 的模块中气泡结构的形成及其上升速度，使 CFD 模型的计算工作量最小化，并通过电扩散方法（EDM）对剪切分布进行实验校准来验证模型。在高填充密度（38m/m）下，单个分散器以 0.5Hz 产生的脉冲气泡（300mL）在领先气泡的尾流区中产生的卫星气泡比在低填充密度模块（1.8m/m）中多。在 38m/m 模块中，气泡上升速度比在 1.8m/m 模块中低约 8%。增加填充密度会降低单个分散器和卫星气泡在水平面上的分散程度的剪切分布，尤其是在膜组件的上部。对于具有多个分散器的系统，脉冲之间的相互作用产生的剪切力大于单个分散器产生的剪切力，并且通过相邻分散器异步释放气泡而不是同步释放气泡，在模块中产生更均匀的剪切分布。通过从同步形式转变为异步形式的曝气，将“影响区域”（向上速度>0.2m/s 的流动区域）增加了 33%。
