Dilution_vs_Displacement_Ventilation

Dilution_vs_Displacement_Ventilation - Displacement...

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Dilution Ventilation versus Displacement Ventilation Dilution Ventilation Supply (diffuser) Return or Supply (diffuser) Return Mixing is enhanced (typically assume well-mixed conditions) Typical in USA in all construction (office, home, and industry) Used for both heating and cooling
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Displacement Ventilation Supply Return Natural convection Mixing is suppressed (air is not well-mixed) More common in European countries Works best with cooling; less effective for heating
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Definition of Displacement Ventilation Definition: “ Buoyancy-assisted forced ventilation .” Cool, fresh air introduced near the floor; warm, contaminated air removed from the ceiling. The displacement effect acts like a “piston” pushing the air upward. Assumes stratified (horizontal) layers of air in the room (warm air near ceiling, cool air near floor). Relies on natural convection (due to buoyancy) from people and/or objects to remove contaminated air locally where needed . (For a good general reference, see H. Skistad,
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Unformatted text preview: Displacement Ventilation , 1994, Research Studies Press, Ltd.) Usefulness of Displacement Ventilation Useful only for cooling rooms, not for heating rooms. Useful for removing air contaminants from concentrated sources (contaminants must be warmer and/or lighter than the surrounding air). For the same amount of ventilating air, displacement ventilation provides better air quality than does dilution ventilation. Dilution ventilation mixes contaminants throughout the room Displacement ventilation allows contaminants to naturally convect upward only where required . Example Application of Displacement Ventilation Cool air Supply Outlet Research Cimbala, Garanich, Settles, & Miller (1998) Cimbala, J. M., J. S. Garanich, G. S. Settles, and J. D. Miller. 1998. (abstract) Combined Schlieren Imaging and Numerical Analysis of Displacement Ventilation. Bulletin of the American Physical Society , Vol. 43, No. 9, p. 2016....
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Dilution_vs_Displacement_Ventilation - Displacement...

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