Ventilation to Eliminate Oxygen Deficiency in a Confined Space—Part II: Noncubical Models

Abstract

This study investigated characteristics of ventilation to eliminate oxygen deficiency for confined space (CS) models having several noncubical shapes. Variations from a basic cubical shape (studied previously) included sideways expansion (normal to the vertical ventilation axis), depthwise expansion (parallel to the ventilation axis), and expansions in more than one direction. Variable design parameters, in addition to shape, included ventilation mode (exhaust and supply), volume flow rate, inlet/outlet elevation, and location inside the CS model. Regressions of the experimental data supplement a database from previous studies of a cubical model. The oxygen recovery data can be used to calculate ventilation times, subject to consideration of limitations which apply to the results. The findings also suggest general guidelines for CS ventilation design. Progressive sideways and depthwise expansions produced progressive increases in ventilation time for oxygen recovery. This variation was consistent for changes in flow rate and inlet/outlet elevation. Depthwise expansion experienced more rapid oxygen recovery than did sideways expansion. Supply ventilation was generally more effective than exhaust ventilation. Orientation of the ventilation axis parallel to the long sides of noncubical CS models caused faster oxygen recovery than when the ventilation axis was parallel to the short sides. Oxygen recovery for CS locations in direct alignment with the supply ventilation outlet was considerably faster than for other, non-aligned locations. Findings suggest that empirical approximations may be determined for development of a multiparameter predictive design model for CS ventilation.