A study of aerosol dispersion was conducted in a university classroom using a CO2 tracer gas emitted from three source locations in a steady release, one source location per test. The tracer gas emitted from the single source location represented the potentially infectious aerosol droplets emitted from a single student and was thus a way to examine the influence of one sick student on the rest of the class. Two parameters were adjusted during the testing—the spacing of the desks, which included a spread and compressed configuration, and the inclusion of three-sided clear dividers attached to the student desk surfaces. Tracer dispersion was measured through the use of monitors in 13 locations within the classroom, with eight monitors representing seated student locations, four monitors representing a standing instructor along the classroom front, and one monitor at the return vent in the ceiling. As expected, spacing strongly influenced concentration levels at desks adjacent to the source location. The use of dividers reduced overall student and instructor location tracer concentrations when compared to desks without dividers in most cases. Finally, the influence of air change differences on the results was noted with consistent trends. The experimental construct provides a systematic means for classroom testing that may be broadly applicable to various configurations of classrooms beyond the one tested. Graphic abstract
A tracer gas study coupled with numerical modeling inform selection of teaching location to minimize exposure to aerosols.
Understanding the dispersion of potentially infectious aerosols released from breathing and speaking is critical to maintaining a healthy indoor environment. This study used a low-cost commercial off-the-shelf flow simulation tool (SolidWorks Flow Simulation) to model aerosol dispersion within a university classroom and assessed its utility by comparing results to those from physical experiments. A SolidWorks model of a university classroom was created using parameters from a series of full-scale carbon dioxide tracer gas release experiments previously conducted in the physical classroom at both low (520 cfm) and high (900 cfm) flowrates. Steady state concentrations at 13 monitoring points throughout the room were obtained from the flow simulation tool and compared to the experimental results using four performance measures for dispersion model evaluation [15]. The performance measures for the baseline model fell within published acceptance criteria for Fractional Mean Bias (FB), Normalized-Mean Square Error (NMSE), Fraction of Cpredicted within a factor of two of Cobserved (FAC2), and Normalized Absolute Difference (NAD). A sensitivity analysis revealed that the most critical boundary condition for creating an optimum model in both cases was the student heat flux. Adding a simulation of body heat from the silhouettes improved the FAC 2 in the low flow case from 0.08 to 1.0, the NMSE from 1.19 to 0.14, the FB from 0.91 to 0.30, and the NAD from 0.45 to 0.15. Given the ability of SolidWorks Flow Simulation to function as a viable first pass modeling method at a low cost, this accessible tool could be used by a variety of interested parties to quickly predict the spread of aerosols, gases, and other passive scalars under a variety of ventilation and physical arrangement conditions. This software tool may already be available to many academic institutions and provides a reasonable expectation of accuracy.
This article is a review of the scientific literature published in 2019 on topics relating to bioenergy from biofuel residues and waste. This literature review is divided into the following sections: Feedstocks, Biodiesel, Bioethanol, Hydrogen, Biohydrogen, Biofuel Residues, Microalgae, and Lignocelluloses.
This section presents a review of the scientific literature published in 2019 on topics relating to distributed treatment systems. This review is divided into the following sections: constituent removal, treatment technologies, planning and treatment management, and other topics. © 2020 Water Environment Federation • Practitioner points • Highlights changes and innovation in removal techniques and technologies in water treatment. • Reviews management systems of distributed treatment systems. • Discusses point-of-use treatment systems.
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