@article{gautam_kumar_tafreshi_pourdeyhimi_2024, title={A simple approach to simulate corona-charged electret filters}, volume={176}, ISSN={["1879-1964"]}, url={https://doi.org/10.1016/j.jaerosci.2023.106293}, DOI={10.1016/j.jaerosci.2023.106293}, abstractNote={This paper presents a novel computational model devised to simulate how different ways of corona-charging a fibrous filter can impact its aerosol collection efficiency. The model assigns different bipolar charges to the fibers in the media based on how the corona-generated negative ions impact these fibers they travel from the corona needles towards the grounded surface underneath the media. The charge assignment process is based on observations made from simulating the electrohydrodynamic field around the corona needles. With the fibers virtually charged, the trajectory of positively and negatively charged aerosol particles, ranging in size from 30 to 500 nm, were simulated across the filter thickness to quantify the effect of fiber charge distribution on the filter efficiency. The performance of our virtual filter was found to be better when it was exposed to the corona ions on both the face and back sides. More interestingly, it was found that the filtration efficiency of the filter was dependent on the order by which its face and back sides were charged. The filter was observed to capture smaller particles (less than 150 nm) more efficiently when it was first charged on the face side and then charged on the back side. The opposite effect was observed when the charging order was reversed. This difference in filtration performance was found to arise from the differences in the solid volume fraction of the filter across its thickness.}, journal={JOURNAL OF AEROSOL SCIENCE}, author={Gautam, S. and Kumar, A. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2024}, month={Feb} }
 @article{kumar_gautam_atri_tafreshi_pourdeyhimi_2023, title={Importance of Dipole Orientation in Electrostatic Aerosol Filtration}, volume={39}, ISSN={["1520-5827"]}, url={https://doi.org/10.1021/acs.langmuir.3c02016}, DOI={10.1021/acs.langmuir.3c02016}, abstractNote={Electrostatic charge is a major part of modern-day aerosol filtration media (e.g., N95 respirators and surgical facemasks) that has remained poorly understood due to its complicated physics. As such, charging a fibrous material has relied on empiricism in dire need of a mathematical foundation to further advance product design and optimization. In this concern, we have conducted a series of numerical simulations to improve our understanding of how an electrostatically charged fiber captures airborne particles and to quantify how the fiber's dipole orientation impacts its capture efficiency. Special attention was paid to the role of Coulomb and dielectrophoretic forces in the capture of particles of different charge polarities (e.g., particles having a Boltzmann charge distribution). Simulation results were compared with the predictions of the popular empirical correlations from the literature and discussed in detail. Predictions of the empirical correlations better agreed with the simulation results obtained for fibers with a dipole perpendicular to the flow direction rather than for fibers with a dipole parallel to the flow. This indicates that such empirical correlations are more suitable for filters charged via contact electrification (friction charging), where the dipoles are mostly perpendicular to the flow direction, and less suitable for corona-charged media, where the fiber dipoles are generally parallel to the flow direction.}, number={49}, journal={LANGMUIR}, author={Kumar, A. and Gautam, S. and Atri, S. and Tafreshi, H. V. and Pourdeyhimi, B.}, year={2023}, month={Nov}, pages={17653–17663} }
 @article{singh_singh_kumar_singh_2023, title={Vertical limit reduction of chimney in solar power plant}, volume={217}, ISSN={["1879-0682"]}, DOI={10.1016/j.renene.2023.119118}, abstractNote={The practical feasibility to install solar updraft tower (SUT) for power production require huge capital investment and difficulties in installing tall giant chimney structure. The chimney is the most expensive element of SUT and typically covers one-fourth of the total SUT cost. Previous finding has shown that a divergent chimney shows significant increase in power output than a conventional design for the same height. This paper deals with the unexplored scientific question: for how much height of divergent chimney can be dispensed with for the same or higher performance of a conventional design? Using an experimentally validated numerical model, we systematically investigated height reduction of chimney (and hence substantial cost) of a high performing divergent chimney whose power output is identical with a long unstable costly conventional cylindrical chimney. The conventional cylindrical design was chosen as the conventional SUT prototype installed at Manzanares, Spain in the year 1980. Results show that it is possible to reduce the vertical limit by about 80% of the height of conventional cylindrical chimney. Further, the cost analysis estimated for each SUT designs and the optimum divergent chimney SUT holds payback period 40% less than the conventional SUT. The proposed designs would be useful for floating chimney as well made of fabric material with light density air filled to keep short chimney height upright vertically to resolve the instability issues with the conventional tall chimney structure during high wind speed environmental conditions The present investigation would assist scientific community to develop more advance clean energy-based power generation systems to achieve net-zero carbon emissions targets.}, journal={RENEWABLE ENERGY}, author={Singh, Ajeet Pratap and Singh, Jaydeep and Kumar, Amit and Singh, O. P.}, year={2023}, month={Nov} }