Effects of mannequin and walk-by motion on flow and spillage characteristics of wall-mounted and jet-isolated range hoods.

Laser-assisted flow-visualization experiments and tracer gas concentration tests were conducted for the wall-mounted and jet-isolated range hoods to examine the physical mechanisms and relative magnitudes of hood spillages. The effects of a mannequin standing in front of the test rig and walk-by motions (which are situations always encountered in kitchens) were emphasized. The results showed that a mannequin (or a cook) standing in front of the counter would attract oil fumes toward the mannequin's body, induce large turbulent flows, and cause a significant dispersion of oil fumes into the environment through the front edge of the hood. Very high tracer gas concentrations were detected around the breathing zone of the mannequin. Increasing the suction flow rate did not reduce the spillage levels of the wall-mounted range hood but could moderately lower those of the jet-isolated hood. Serious spillages from both the wall-mounted and jet-isolated range hoods were detected as the simulated walk-by motion was performed. The jet-isolated range hood presented a much lower robustness in resisting the influence of people's walk-bys than did the wall-mounted range hood. In summary, both the wall-mounted and jet-isolated range hoods were vulnerable to the influences of a cook's presence and a cook's walk-by motions. Increasing the suction flow rate might not obtain satisfactorily low spillages of pollutants but might increase noise level and energy consumption.