Experimental investigation and modeling of the flow resistance of compressed nonwoven filter media

A major goal of filter media design is to achieve an optimal balance between high filtration efficiency and minimal pressure drop. However, during manufacturing, filter media experience both local and global compression, e.g., due to calendering and/or pleating. The local change in fiber volume fraction significantly alters the material properties and impacts the overall performance. This paper proposes a novel methodology for an accurate prediction of the flow resistance based on a minimal experimental effort. The method is successfully applied to nonwovens for different fields of filtration.
The air permeability of the considered materials is measured for several levels of compression at different volumetric flow rates to determine whether their flow resistance behavior corresponds to the Darcy or the Darcy-Forchheimer law. The prediction is based on the scaling of the flow resistance of the uncompressed material by using the analytical permeability model by Happel. It is seen that only the absolute minimum of measurements is required to apply the method. The results are compared with those obtained using alternative approaches, which are based to varying degrees on experimental data, namely the method of least squares regression applied to the full series of measurements and linear regression based on a subset of experimental data.
The proposed method combines good prediction accuracy with a significant reduction in testing effort. Therefore, it can serve as a useful tool to consider the influence of the processing of the nonwoven on the quality of the final product.