A two-scale approach for the computation of flow through pleated filters based on real image data

M. Kabel, R. Kirsch*, S. Osterroth, S. Rief, Fraunhofer Institute for Industrial Mathematics (ITWM) , Germany

Pleated filters have been the subject of a lot of research and development activities for decades. In order to optimize pleated panels and cartridges in terms of pressure loss, efficiency and dust holding capacity, it turned out that in many cases, the geometrical design of the pleated filter can be compared in significance to the selected filtering media. Consequently, numerous experimental studies were (and still are) devoted to the modelling of the influence of pleat length, pleat distance, cartridge height etc. on the pressure drop and the evolution of efficiency and flow resistivity during loading. Thanks to more powerful computer hardware and significant advances in the development of numerical methods for filtration, Computational Fluid Dynamics (CFD) is well-established in this field of research, too.

In the majority of models and simulation studies, the filter pleats are considered in a rather simplified or idealized way in terms of both shape and material distribution (see Fig. 1, left). Properties such as solid volume fraction and permeability distribution are frequently assumed to be uniform for the entire pleat, or, in the case of multi-layered or graded media, for each filter material/layer. Even if this assumption does not hold, homogenization by using effective properties is a common approach to reduce the number of grid cells required in the computation. Clearly, this reduction is important for the computational cost of simulations of entire filter elements, including the geometric features of the housing, the inlet and outlet ducts, etc.

Fig. 1: Left: Pleat scale: Example of an idealized 3D model of a pleat as used in simulations and a reconstructed CT image of a real filter pleat.

There are relatively few works on flow simulation for pleated filters addressing the impact of variations of shape and/or material distribution caused by the manufacturing of the pleats, e.g. local material deformation due to embossing and the pleating process itself. In cases in which these phenomena cannot be neglected, it would certainly be helpful to enhance the CFD by using experimental data from real filter pleats, more precisely...

Session: F5 - Filter Media - Numerical Methods for Optimized Media Design II
Day: 14 March 2018
Time: 16:45 - 18:00 h

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