Publications Search Results

Now showing 1 - 10 of 34
  • Publication
    Flow-induced deformation of nonwoven filter media: Experiments, modeling and simulation
    ( 2023) ; ;
    Puderbach, Vanessa
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    Antonyuk, Sergiy
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    Henkelmann, Nicola
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    Weirich, Marc
    During operation of filter elements, it is observed that the fluid flow causes deformations of the filter media which can lead to well-known (and undesired) effects like pleat collapse, pleat crowding etc. In such cases, filter designers are facing the additional challenge to provide stabilizing countermeasures such as spacers, supporting ribs and pleat holders without sacrificing too much available media surface area. Finding a good design by building and testing prototypes can become very costly, so it seems natural to use computer simulations to optimize countermeasures like those mentioned above. However, most simulation models assume “rigid” filter materials. Therefore, suitable models and simulation methods for the Fluid-Porous-Structure Interaction (FPSI) are desired to obtain more realistic predictions of the filter media deformation for a given design variant. This requires a better understanding of the mechanical properties of nonwoven filter media. More precisely, the material laws governing their behaviour when subjected to volumetric forces need to be known. To investigate this, several media used in liquid filtration were characterized in terms of air permeability and structural mechanics. For the in-situ measurement of the deformation caused by stationary, laminar flow, a suitable test bench was designed and built. The experimental data are used to identify suitable mechanical material laws and the corresponding parameters. These serve as input for the simulation of the flow-induced deformation. The simulation approach is a coupling of Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM), using the fluid pressure gradient as the mechanical load acting on the filter material. Recent experimental data obtained on the test bench are presented and simulation results are compared to the measurements. The respective advantages of the approaches for practical applications are discussed.
  • Publication
    Vom Prozess bis zur Multiphysik: Digitale Zwillinge für die Filtration
    Die Digitalisierung ("Industrie 4.0") gewinnt auch im Bereich der Filtration und Separation an Bedeutung. Die Vernetzung von Sensortechnik an Filterbauteilen mit der IT-Infrastruktur ermöglicht eine automatisierte Überwachung und Steuerung von Anlagen sowie eine digital unterstützte Planung von Wartungsintervallen, sodass Ausfallzeiten im Betrieb minimiert werden. Bei der Produktentwicklung ermöglichen modellbasierte Simulationstechniken eine rechnergestützte Vorhersage wichtiger Eigenschaften und reduzieren den Bedarf an Prototypen. Im Beitrag von Herrn Kirsch und Herrn Schmeißer vom Fraunhofer ITWM wird ein Überblick gegeben, wie modell- und simulationsbasierte Methoden von der Herstellung der Filtermedien bis hin zu ihrem Verhalten im Betrieb bei der Erstellung von digitalen Zwillingen für die Filtration eingesetzt werden.
  • Publication
    Influence of material compression on the mechanical and electrostatic capturing efficiency of filter media
    ( 2023)
    Mercier, Christian
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    ; ; ;
    Kerner, Maximilian
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    Antonyuk, Sergiy
    One of the main design goals for filter media is a high separation performance while the pressure drop is low. During manufacturing processes such as the pleating of the filter media or during operation, the nonwoven material is locally compacted which is of importance for the above-mentioned quality characteristics. The compaction leads to a local increase of the fiber volume fraction and therefore, to a non-uniform distribution of flow resistance and filtration performance. In this work, the influence of compression on the performance of flat filter media is examined by experiments, both for “classical” materials, for which the deposition is only based on mechanical phenomena, and electret media. To this end, an electrostatic charged media made of 100 % polypropylene (PP) is investigated. After the characterization of the media by the thickness, basis weight and airflow for a given pressure drop, properties like the solid volume fraction and flow resistivity can be deduced. For the present media, compression levels up to 27 % are achieved using cyclic deformation. In order to avoid effects due to material relaxation, the thickness of the compacted media samples is measured over time until a steady state is reached. Measurements of the fractional efficiency are carried out with the prepared samples under variation of the flow speed. In the case of electret media, the samples are discharged by isopropyl alcohol (IPA) treatment and the fractional efficiencies are measured again. This allows for studying the impact of the material compaction on the electrostatic contribution to the efficiency, too. The test dust used for all measurements consists of airborne sodium chloride particles with diameters ranging between 15 nm and 460 nm. The experimental data obtained allow for a prediction of the change in filter performance with respect to deformation. In addition, the data are the basis for deposition models that consider local effects such as the degree of material compression, flow speed and deposition.
  • Publication
    Multiscale modelling and simulation of coolant particle filters and ion exchangers in electric mobility
    For both fuel cells and battery systems, the components of the cooling system are essential to maintain an economic usage and to ensure the desired lifetime of propul-sion technologies in electric mobility. In this work, models and simulations for different components of the cooling system are presented. First, an ion exchanger is investigated. It mostly consists of microporous beads which are combined to a resin. The resin of the ion exchanger can be modeled using a multiscale approach. On the element scale, only the geometry of the ion ex-changer itself is considered using an effective description of the resin. More detailed, also the microporous nature of a single bead can be taken into account. Using these models, the required capacity of a resin and the lifetime of the ion exchanger can be estimated. Another multiscale model is presented for coolant particle filter elements. On the ele-ment scale, the entire housing is considered and the filter medium is modeled as an effective material, characterized by its permeability and its porosity (or open surface). The geometric properties of the medium (weave pattern, fiber diameter(s), and spac-ings) are usually provided by the manufacturer. It is therefore straightforward to create a digital twin of the filter medium on the microscopic length scale. Amongst others, the permeability of the woven filter medium can be obtained from flow simulations. This is used on the element scale to compute the flow field in the housing and through the medium. The velocity distribution at the upstream face of the filter medium is of special interest since in general, the filtering efficiency depends on the face velocity. For this velocity range, the (fractional) efficiencies are computed using particle-based simulations on the microscale. The filtration properties of the medium are upscaled by translating the efficiency into an absorption coefficient, which depends on the face ve-locity. Using the obtained values, the evolution of the pressure drop and the fractional efficiencies of the filter element can be obtained. It is shown that simulation can assist the development and optimization of different components of the cooling system. Moreover, it can give further insights into the transport processes and reveal optimization potentials.
  • Publication
    Efficient simulation of flow-induced deformation of woven filter media
    In more and more areas of filtration, the flow-induced deformation of filter media is a phenomenon that has to be taken into account when optimizing the design of filter elements. Computer simulations can accelerate the development and optimization, but since most state-of-the-art simulation models for the flow in filter elements assume rigid media, the computed results can differ a lot from experiments. A common problem in the modelling of woven filters is the huge ratio of length scales due to the comparatively large bulk fluid domains and the thin filter media with complex microstructure. Direct numerical simulation with the fibres resolved in the computational grid require a tremendous amount of hardware resources, if practical at all. By design, woven filters feature a periodic structure on the microscopic scale, and it seems straightforward to use this fact for the replacement of the resolved microstructure by an effective, 2D poroelastic plate, such that the computational effort reduces drastically. In the presented work, a model-order-reduction based model for the interaction of stationary incompressible flow with deformable woven filters is derived. The novelty of the work lies within the highly efficient computation of the filter’s mechanical properties based on the description of its microstructure as well as in the inclusion of strain dependent permeability coefficients, accounting for locally increasing open surface area due to the filter’s deformation. A complete algorithmic workflow for the efficient simulation is presented. The splitting of the solving process into two phases is proposed: In an offline phase, effective model parameters, namely permeability and effective bending-elasticity coefficients, are predetermined by simulations on the smallest periodic unit of the filter structure. The computed parameters serve as a look-up table for the online phase which solves the fluid-structure-interaction problem with the effective 2D plate model. In the online phase, fluid and structure solvers are decoupled which further simplifies the model-inclusion in existing workflows. The algorithmic workflow is exemplified for a plain-woven filter sample and details on the generalization to arbitrary woven filters are given.
  • Publication
    Influence of an inhomogeneous material distribution on the overall filtration efficiency of fibrous media
    It is well known that the level of uniformity of nonwoven filter materials is related to their filtration efficiency and therefore, this feature is an important subject to quality control (QC). The COVID19 pandemic has once again revealed the importance of efficient manufacturing processes for high-quality nonwovens, such as they are required for face masks that provide sufficient protection. While specialized 3D computer simulations have shown to be very helpful for the design and optimization of nonwovens, their computational cost is (in general) too high to allow for a quick assessment of the properties of a filter material. In addition, the acquisition of images of the microstructure created during production is not practicable.
  • Publication
    Flow-induced deformation of filter media - part 2: Modeling and simulation
    ( 2022) ;
    Antonyuk, Sergiy
    ;
    Puderbach, Vanessa
    ;
    Deshpande, Ruturaj
    The majority of simulation models for filter elements assume that the filter media are "rigid bodies". In reality, it is observed that the fluid flow causes deformations which can lead to well-known (and undesired) effects like pleat collapse, pleat crowding etc. Several works were devoted to the development of models and methods to take into account this Fluid-Porous-Structure Interaction (FPSI) in order to obtain more realistic simulation results. This is accomplished by suitable coupling of Computational Fluid Dynamics (CFD) with Computational Structural Mechanics (CSM).