Flow Dynamics and Contaminant Transport in Industrial-Type Enclosing Exhaust Hoods

Abstract

The present study concerns the flow dynamics and associated contaminant transport in the near wake of a worker using an industrial-type benchtop enclosing hood. The primary focus is on evaluating the effects on the dynamics of the wake flow and the exposure level of various extraneous factors, such as the strength and direction of cross-drafts and the worker's body heat and shape. Three-dimensional Unsteady Reynolds-Averaged Navier-Stokes simulations were carried out for a model of a simple mannequin and a model of an anthropometric mannequin. Estimated flow patterns and concentrations near the simple mannequin were compared with the observations from concurrent smoke visualization experiments and with the experimental concentration measurements, respectively. Results for both visualizations indicated that the flow in front of the worker is dominated by dynamic vortical structures and that body heat may have negative effects on the exposure level, especially at low flow rates. Using simple rounded shapes to simulate the human form was a fair approximation from the viewpoint of flow structures and exposure trends, which agreed well with the experimental measurements and observations. However, the quantitative values of the predicted concentrations in the breathing zone were sensitive to the mesh resolution.

An Empirical Study on the Wake Around a Squatting Worker in a Confined Space

“…Karaismail 10) mentioned that a worker's movements could be one of the most important factors affecting the level of exposure in real work. For example, a human worker's arm movements can enhance mixing, which may lead to higher exposure 8,12) .…”

“…For example, a human worker's arm movements can enhance mixing, which may lead to higher exposure 8,12) . However, a squatting worker does not seem to make large arm movements like a standing worker using an industrialtype benchtop enclosing hood 10) . Therefore, an experiment with a stationary mannequin and source is thought to be applicable for most cases of a squatting worker.…”