Gas Distribution in Shallow Packed Beds.
Available from UMI in association with The British Library. Packed beds have many industrial applications and are increasingly used in the process industries due to their low pressure drop. Obtaining uniform gas distribution in such beds is of crucial importance in minimising operating costs and optimising plant performance. Since to some extent a packed bed acts as its own distributor the importance of obtaining uniform gas distribution has increased as aspect ratios (bed height to diameter) decrease. There is no rigorous design method for distributors due to a limited understanding of the fluid flow phenomena and in particular of the effect of the bed base/free fluid interface. This study is based on a combined theoretical and modelling approach. The Ergun Equation is used to determine the pressure drop over a bed where the flow is uni-directional. This equation has been used in a vectorial form so that it can be applied to maldistributed and multi -directional flows and has been realised in the Computational Fluid Dynamics code PHOENICS. The use of this equation and its application has been verified by modelling experimental measurements of maldistributed gas flows, where there is no free fluid/bed base interface. A novel, two-dimensional experiment has been designed to investigate the fluid mechanics of maldistributed gas flows in shallow packed beds. The results from this apparatus provide useful insights into the fluid mechanics of flow in and around a shallow packed bed and show the critical effect of the bed base. The PHOENICS/vectorial Ergun Equation model has been adapted to model this situation. The model has been improved by the inclusion of spatial voidage variations in the bed and the prescription of a novel bed base boundary condition. The flow in a curved bed section, which is three -dimensional in nature, is examined experimentally. The effect of the walls and the changes in gas direction on the gas flow are shown to be particularly significant. The model and improved understanding of the underlying physical phenomena form the basis for the development of new distributors and rigorous design methods for them. (Abstract shortened by UMI.).
- Pub Date:
- Physics: Fluid and Plasma; Engineering: Industrial