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Mixing of a Point Source Pollutant by Natural Convection Flow within a Room
Author(s) -
Baughman A. V.,
Gadgil A. J.,
Nazaroff W. W.
Publication year - 1994
Publication title -
indoor air
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.387
H-Index - 99
eISSN - 1600-0668
pISSN - 0905-6947
DOI - 10.1111/j.1600-0668.1994.t01-2-00006.x
Subject(s) - mixing (physics) , natural convection , helium , smoke , convection , sulfur hexafluoride , isothermal process , airflow , environmental science , mechanics , chemistry , volumetric flow rate , meteorology , atmospheric sciences , nuclear engineering , thermodynamics , physics , organic chemistry , quantum mechanics , engineering
Indoor air quality models are commonly based on the assumption of instantaneous and complete air mixing within a zone. Such an assumption is not appropriate for all circumstances, such as investigating the utility of segregating smokers to reduce nonsmoker exposure to environmental tobacco smoke. This experimental study characterizes quantitatively the rate at which smoke from a cigarette disperses within an unoccupied, 31‐m 3 , low air‐exchange rate room under natural convection flow conditions. Sidestream smoke from a smoldering cigarette was simulated with a pulsed release of a tracer gas – a neutrally buoyant mixture of sulfur hexafluoride (SF 6 ) in helium – above an electrically heated coil. During each experimental run, sequential air samples were collected remotely, using gas‐tight syringes, from 41 locations within the room. After each run, these samples were analyzed for SF 6 content using a gas chromatograph with an electron‐capture detector. Duplicate runs were conducted under three conditions: nearly isothermal surfaces; convection from a 500–watt heater; and convection from incoming solar radiation. Characteristic mixing times ranged from 7–10 minutes for the solar radiation case to 80–100 minutes for the nearly isothermal case.