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The computational study reported here is motivated by a desire to develop a computer model for predicting and analyzing experimental screen collection efficiency of wire-mesh filters for microparticles (up to 100 µm). The operational parameters include the particle size of 0.3 to 100 μm, screen opening size of 11 to 160 μm, fiber diameter of 33 to 60 μm and superficial velocity of 0.48 cm/s. We use a simplified 2-D model with the hybrid lattice-Boltzmann Lagrangian method to describe flow crossing a single fiber in a periodic cell of a wire screen. The newly proposed formula of the screen collection efficiency representing particle deposition on two crossed fibers in each screen cell effectively predicts the experimental data with good accuracy. The quality factor analysis that determines a filter performance is adopted to evaluate the interplay between the energy needed for gas transport and collection efficiency. In addition, the detailed analyses are given for particle deposition pattern and transport behavior in terms of particle fraction profiles and flow fields. Finally, the degree of individual forces acting on each particle traveling in the gas flow is revealed. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

While previous experimental studies revealed the existence of optimal heat transfer performance in natural convection of magnetohydrodynamic (MHD) nanofluid flows, it is believed that this phenomenon is not unique in different levels of magnetic flux density. In order to prove this speculation, we numerically investigate the influence of the magnetic field on steady natural convection of aluminum-oxide (Al2O3) nanofluids inside an enclosure. The MHD flow model without the consideration of nanofluids is well validated against theoretical, numerical, and experimental results. The nanofluid in the present investigation has temperature-dependent physical properties and is modeled by a two-phase mixture considering thermophoresis and Brownian diffusion. While varying the volume fraction of nanoparticles from 0 to 6%, we methodically examine the effect of the Hartmann number on the heat transfer performance through the thermal behavior map in terms of the Hartmann–Rayleigh plane. Depending on the combination of magnetic intensity and buoyancy-induced flow, the nanofluid heat transfer with the addition of various concentrations of nanoparticles can be categorized into two patterns separated by a critical Hartmann number: the presence of a maximum Nusselt number (Type A) and continuously increased heat transfer rates (Type B) over a wide range of the Rayleigh number from 103 to 106 and the Hartmann number from 0 to 300. Described by a piecewise-defined function, the critical Hartmann number is exponentially proportional to the Rayleigh number from 104 to 106 and rises linearly in a logarithmic scale with elevating the Rayleigh number from 103 to 104. [ABSTRACT FROM AUTHOR]

Transport of aerosol particles is a fundamental phenomenon in many environmental and industrial applications. Among the several computational fluid dynamical schemes used to study this problem, the lattice Boltzmann methods (LBMs) have shown great promise. Using a 2-D LBM model coupled with a Lagrangian formalism, this study investigates an early stage of particle–surface collisions in a free-stream flow over a semi-infinite array of staggered obstructions at operating conditions of woven-wire screens. After an initial validation of the model, the particle–surface collision efficiency with different diameters is then examined as functions of the number of staggered obstructions, obstruction morphology, and separation distance between two center points of obstructions. Particle motion mechanisms include drag, lift, and Brownian forces. Enhanced collision efficiency of particles to obstructions due to the presence of multiple staggered cylindrical obstructions is identified and highlighted. Based on these insights, our work also explores the possibility that collision efficiency of particles to obstructions can be enhanced by a change of obstruction morphology. Finally, the results highlight the range where particle–surface collision efficiency is sensitive to the longitudinal spacing between two cylindrical obstructions. Copyright 2014 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]