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Indoor Exposure to Radiation in the Case of an Outdoor Release LBNL-60662

Description: This report quantifies the effectiveness of ''sheltering in place'' in a commercial building in the event of an outdoor radiological release. The indoor exposure to airborne particles is calculated by solving the mass balance equation that ac accounts for the loss of counts particles due to deposition, filtration and exhaust. Quantitative estimates of shelter-in-place effectiveness are provided for typical commercial buildings.
Date: July 7, 2006
Creator: Price, P N & Jayaraman, B
Partner: UNT Libraries Government Documents Department

MINIMIZING DECOMPOSITION OF VAPORIZED HYDROGEN PEROXIDE IN CLEAN GALVANIZED STEEL DUCTING: IMPLICATIONS FOR BIOLOGICAL DECONTAMINATION

Description: This work examined the behavior of vaporous hydrogen peroxide (VHP) in clean, room-scale galvanized steel (GS) and polyvinylchloride-coated steel air ducts, to understand how it might be used to decontaminate larger ventilation systems. VHP injected into the GS duct decreased in concentration along the length of the duct, whereas VHP concentrations in the polyvinylchloride coated duct remained essentially constant, suggesting that VHP decomposed at the GS surface. However, decomposition was reduced at lower temperatures ({approx} 22 C) and higher flow rates ({approx} 80 actual cubic meter per hour). A computational fluid dynamics model incorporating reactive transport was used to estimate surface VHP concentrations where contamination is likely to reside, and also showed how bends encourage VHP decomposition. Use of G. stearothermophilus indicators, in conjunction with model estimates, indicated that a concentration-contact time of {approx} 100 mg/L H{sub 2}O{sub 2}(g){center_dot}min was required to achieve a 6 log reduction of indicator spores in clean GS duct, at 30 C. When VHP is selected for building decontamination, this work suggests the most efficacious strategy may be to decontaminate GS ducting separately from the rest of the building, as opposed to a single decontamination event in which the ventilation system is used to distribute VHP throughout the entire building.
Date: September 7, 2007
Creator: Verce, M F; Jayaraman, B; Ford, T D; Fisher, S E; Gadgil, A J & Carlsen, T M
Partner: UNT Libraries Government Documents Department

Investigation of room ventilation for improved operation of a downdraft table

Description: We report a computational fluid dynamics (CFD) study on containment of airborne hazardous materials in a ventilated room containing a downdraft table. Specifically, we investigate the containment of hazardous airborne material obtainable under a range of ventilation configurations. The desirable ventilation configuration should ensure excellent containment of the hazardous material released from the workspace above the downdraft table. However, increased airflow raises operation costs, so the airflow should be as low as feasible without compromising containment. The airflow is modeled using Reynolds Averaged Navier Stokes equations with a high Reynolds number k-epsilon turbulence model. CFD predictions are examined for several ventilation configurations. Based on this study, we find that substantial improvements in containment are possible concurrent with a significant reduction in airflow, compared to the existing design of ventilation configuration.
Date: May 1, 2004
Creator: Jayaraman, B.; Kristoffersen, A.; Finlayson, E. & Gadgil, A.
Partner: UNT Libraries Government Documents Department

Comparison Between Experiments and CFD Predictions of MixedConvection Flows in an Atrium

Description: This paper compares results from a computational fluid dynamics (CFD) simulation of airflow and pollutant dispersion under mixed-convection conditions with experimental data obtained in our 7m x 9m x 11m high experimental facility. A tracer gas was continuously released from a 1 m{sup 2} horizontal source 0.5 m above the floor. Path-integrated concentrations were measured along multiple short and long sampling paths in three horizontal planes. A steady state CFD analysis was used to model these experiments. The Reynolds Averaged Navier-Stokes (RANS) equations were solved for the flow and temperature field using the commercial CFD software, StarCD. CFD results were compared with the measured path-integrated concentrations. Accuracy of CFD predictions was found to improve with inclusion of thermal effects, and further by using a low-Re turbulence model.
Date: February 1, 2005
Creator: Jayaraman, B.; Finlayson, E.U.; Wood, E.E.; Thatcher, T.L.; Sohn,M.D.; Price, P.N. et al.
Partner: UNT Libraries Government Documents Department