Gekoppeltes Berechnen von Blasengrößenverteilungen und Strömungsfeldern in Blasensäulen

Coupled Calculation of Bubble Size Distribution and Flow Fields in Bubble Columns In this paper the use of computational fluid dynamics (CFD) for the calculation of flow fields in bubble columns is explained. The local bubble size distribution is considered with the aid of a simplified balance equation for the average bubble volume in bubbly flow. Models are developed for the rate of bubble break‐up and coalescence based on physical principals. The flow fields in cylindrical bubble columns without internals are calculated using the Euler‐Euler method. The small and large bubble fraction are considered as pseudo‐continuous phases in addition to the liquid phase. The calculated flow fields are characterised by several large scale vortices. The local volume fractions of gas and liquid are very inhomogeneous and highly time dependent. The calculated volume fractions, velocities and bubble size distributions agree well with experimental results for bubble columns up to 0.3 m in diameter.     

Druckstoßabreinigung textiler und starrer Filtermedien: Abreinigungsrelevante Parameter

Pulse Cleaning of Textile and Rigid Filter Media – Characteristic Parameters To characterize the pulse cleaning of textile and rigid filter media in technical filter houses and test rigs, by now mainly tank pressure and valve opening time have been used as characteristic parameters which are however dependent on the whole geometry of the plant and which therefore do not allow a comparison between different technical systems. Thus, the question is raised which parameters of a cleaning pulse are decisive for its performance. By knowing these parameters, an experimental setup could be adjusted in a way that it shows the same cleaning behavior like a filter house, so that the laboratory filter tests are comparable to technical filter cycles. On a filter test rig which can be used for both textile and rigid filter media as well as on a pilot plant designed for Herding alpha filter candles, experiments concerning the influence of these different parameters on the cleaning behavior were performed. The characteristic figures maximum pressure, pressure integral, and pressure rise velocity of each pressure pulse were determined and compared with the cleaning efficiency achieved. As result of comprehensive regression analyses we found that especially the maximum pressure and the pressure rise velocity during zero‐passage of a cleaning pulse are decisive for the cleaning result. The practical conclusion is that pulse jet systems should be optimized with regard to these parameters.