Capture efficiency of flanged circular local exhaust hoods.
Ann Occup Hyg 1986; 30(4):497-513
An idealized theoretical model of capture efficiency for Local Exhaust Ventilation (LEV) systems was developed based on the modified potential flow solution. A model was developed for the flanged circular hood operating in the presence of a cross draft perpendicular to the hood centerline. The model was based on computer generated streamline maps and the assumption that capture efficiency depends upon the interaction of three flow fields, generated by the hood, the contaminating source, and due to any perturbing cross drafts. A point source of gaseous contaminant of low strength was assumed. The predicted capture efficiencies were in close agreement with measured values, with a maximal error of about +/-25 percent at the critical distance. The authors identify the need for further research to determine the applicability and accuracy of the theory in estimating adjustments to LEV systems which will facilitate desired levels of control and in accounting for possible effects of flows around objects and people. The authors conclude that models of breathing zone concentration may be derivable from capture efficiency.
NIOSH-Publication; NIOSH-Grant; Control-technology; Ventilation-systems; Ventilation-hoods; Aerosols; Exhaust-ventilation; Exhaust-hoods; Air-contamination; Mathematical-models; Toxic-gases; Toxic-vapors; Workplace-studies
Physiology Department, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115
Annals of Occupational Hygiene
Harvard University, Boston, Massachusetts