Impact of flow separation on exposure and hood-capture efficiency. Final report

Technical Report · Thu Feb 01 04:00:00 EST 1990

OSTI ID:5480455

Flynn, M R

A mathematical model was developed which could predict breathing zone concentration for a worker operating in the vicinity of a local exhaust hood. As part of the effort, a mathematical model was developed to predict breathing zone concentration for a mannequin when a point source of tracer was located downstream. The model was extended to include the situation with a mannequin positioned in front of a flanged circular hood and to include cross drafts and mannequin position with respect to the hood. The results of the study indicated that where workers hold contaminant generating sources and operate in front of or within large booth type hoods, the phenomenon of boundary layer separation was of major importance in determining exposure. Where possible the worker should maintain an orientation such that the line connecting the source and worker is a right angle to, not parallel to, the air stream. Vortex shedding plays the primary role in contaminant transport from the separated recirculation zone. The author concludes that ventilation when used as an engineering control must be used in conjunction with, and not in exclusion to, work practices.

• Research Organization: North Carolina Univ., Chapel Hill, NC (United States). Dept. of Environmental Sciences and Engineering
• OSTI ID: 5480455
• Report Number(s): PB-91-188615/XAB; CNN: NIOSH-R01-OH-02392
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
AIR FLOW
AIR POLLUTION
AIR POLLUTION CONTROL
BOUNDARY LAYERS
CONTROL
ENVIRONMENTAL TRANSPORT
EXHAUST GASES
FLUID FLOW
FLUIDS
GAS FLOW
GASEOUS WASTES
GASES
INDOOR AIR POLLUTION
LAYERS
MASS TRANSFER
MATHEMATICAL MODELS
OCCUPATIONAL EXPOSURE
POLLUTION
POLLUTION CONTROL
VENTILATION
WASTES