While most filters are made of pleated fibrous media, almost all existing theories of aerosol filtration are developed for flat media placed perpendicular to the air flow. Expressions developed for flat sheet media do not provide accurate information directly useful for designing a pleated filter, and therefore, most progress made in developing pleated filters is based on empiricism. This study is aimed at establishing an enabling knowledge that allows for a better design and optimization of pleated aerosol filters. This study is focused on developing a predictive simulation method that accounts for the influence of a filter’s micro-scale geometric parameters, such as fiber orientation, as well as its macro-scale features, like pleat shape, in predicting the transient pressure drop and collection efficiency with or without the effects of dust loading. The dual-scale simulation method developed in this work is believed to be the only feasible approach for design and optimization of pleated aerosol filters with the current academic-level computational power. Our study is divided into two major tasks of micro- and macro-scale modeling. Our micro-scale studies are comprised of a series of CFD simulations conducted in virtual 2-D or 3-D fibrous geometries that resemble the internal micro-structure of a fibrous medium. These simulations are intended to isolate the effects of each micro structural parameter and study its influence on the performance of the filter medium. In detail, it is intended to propose a method to predict the performance of micro-structures with fiber size distribution. Also, the effects of micro-structural fiber orientation were investigated. Moreover, we offered methodology to predict the performance of noncircular fibers using available analytical expressions for circular fibers. It is shown that the circumscribed circle for a trilobal shaped fiber gives the best prediction for collection efficiency. In macro-scale simulations, on the other hand, the filter medium is treated as a lumped porous material with its properties obtained via micro-scale simulations. Our results showed that more number of pleats helps better performance of pleated filters, however, if the pleat channel becomes blocked by dust cake then this effect is no longer valid.

The goal of this study is to further advance the state of the art in developing self-sufficient methods to predict the performance of an aerosol filter. The simulation methods developed in this study are based on first principles and consequently, they do not rely on empirical correction factors. These simulation methods can be used to predict the instantaneous collection efficiency and pressure drop of a filter under dust-loading conditions. In the current study, 3-D micro- and macroscale CFD models are developed to simulate the service life of flat-sheet and pleated filters. These CFD micro- and macroscale models are also used to quantify the effects of a fiber’s cross-sectional shape on the performance of the resulting filter. As fiber manufacturing methods are rapidly advancing, these fibers are becoming more accessible. The filtration performance of trilobal fibers is compared with their circular counterparts under dust-loading conditions. Our results show that trilobal fibers do not outperform circular ones except in very limited conditions, revealing no advantage over circular fibers. In addition, a fast but approximate 2-D model is developed to predict the filtration performance of flat and circular pleated filters. The predictions of the model are compared with predictions from the more sophisticated CFD models, as well as with experimental work in the literature. Our 2-D model developed in this study is aimed at providing the aerosol filtration industry with a fast but fairly accurate method of designing pleated filters. With a CPU-time of practically zero, the developed model allows one to conduct a broad parameter study, altering the parameters that affect the filtration performance of pleated filters. Using this model, predictive correlations for dust-loaded pleated filters are presented. These correlations allow one to estimate the instantaneous pressure drop and collection efficiency of pleated filters effectively.