Abstract

The hydrodynamic performance of turbulent flows in circular pipes equipped with screen-type static mixers is numerically assessed in this study. A three-dimensional computational fluid dynamics model is used to study the effect of changing the operating conditions and reactor configuration on the flow field. The accuracy of the numerical results is validated by comparing pressure drop predictions to empirical correlations where a maximum relative error of 13.3% is recorded. The macro-mixing performance of screen type static mixers is also assessed using residence time distributions. The study shows that the flow through screens is three-dimensional by nature with secondary flows being prominent near the pipe walls. Moreover, the presence of the screen has a major impact on the turbulent velocity profile both up- and down-stream. The flow field and velocity gradients are interpreted using strain rate and vorticity. These parameters also show that the flow through screens is highly dispersive where 39.3% of the reactor volume has an extensional efficiency value greater than 0.6. This explains their good performance in processing multiphase flows and gives an insight on how to design systems that maximize this dispersive effect in their volume. The residence time distribution study shows that the presence of screens renders the flow closer to plug flow with the effect being more pronounced using finer mesh screens operating at high flow velocities.

摘要

在这项研究中，数值评估了配备有筛网式静态混合器的圆形管道中湍流的水动力性能。三维计算流体动力学模型用于研究改变操作条件和反应器配置对流场的影响。通过将压降预测与经验相关性进行比较来验证数值结果的准确性，其中记录的最大相对误差为 13.3%。筛式静态混合器的宏观混合性能也使用停留时间分布进行评估。研究表明，通过滤网的流动本质上是三维的，在管壁附近二次流动很明显。此外，屏幕的存在对上游和下游的湍流速度分布有重大影响。使用应变率和涡量解释流场和速度梯度。这些参数还表明，通过筛网的流量是高度分散的，其中 39.3% 的反应器体积具有大于 0.6 的延伸效率值。这解释了它们在处理多相流方面的良好性能，并提供了关于如何设计系统以最大限度地提高体积中的这种分散效应的见解。停留时间分布研究表明，筛网的存在使流动更接近活塞流，使用在高流速下运行的更细网眼筛网效果更明显。6. 这解释了它们在处理多相流方面的良好性能，并深入了解了如何设计系统以最大限度地提高体积中的这种分散效应。停留时间分布研究表明，筛网的存在使流动更接近活塞流，使用在高流速下运行的更细网眼筛网效果更明显。6. 这解释了它们在处理多相流方面的良好性能，并深入了解了如何设计系统以最大限度地提高体积中的这种分散效应。停留时间分布研究表明，筛网的存在使流动更接近活塞流，使用在高流速下运行的更细网眼筛网效果更明显。