Displacement ventilation

Displacement ventilation

A method of space conditioning where conditioned air is supplied at or near the floor. Since the air is supplied at very low velocities, a cool layer of air collects in the occupied zone resulting in comfortable conditions for the occupants. Buoyant forces remove heat generated by occupants and equipment, as well as odors and pollutants, all of which stratify under the ceiling and are extracted from the space by return or exhaust fans. Displacement ventilation systems were originally used in industrial facilities and subsequently in office buildings, auditoria, performing arts centers, and spaces with large interior volumes. These systems are effective in improving indoor air quality as well as providing energy savings when compared with a conventional fully mixed system.
References in periodicals archive ?
To compare the ventilation performance of the displacement ventilation cases with 4 ach, this paper shows the averaged contaminant concentrations at the breathing level of sitting and standing positions--i.e., at the breathing levels of a sitting person (3.7 ft [1.1 m] above the floor) and a standing person (5.3 ft or [1.6 m] above the floor).
No or very small and efficient HVAC, depending on the climate, and underfloor displacement ventilation.
Displacement ventilation has received significant attention in building designs in recent years.
In the case of the displacement ventilation system the air is supplied through two displacement diffusers: 30 in x 60 in x 14in) located on the two ventilation shafts in the lobby area with the front and sides of the diffusers as supply areas (Figure 1).
This paper reports a study of indoor environment conditions in an office room equipped with floor heating and displacement ventilation. A CFD model was developed using data from a full-scale experimental model.
A dedicated, 100% outdoor air, ventilation system is used in conjunction with natural and displacement ventilation strategies to reduce the demand on the central plant, while improving ventilation distribution and occupant comfort.
Stratified ventilation, including displacement ventilation (DV) and underfloor air distribution (UFAD), is a means of providing cool supply air directly to the vicinity of occupants in a space.
The ventilation effectiveness measured with PV systems is reported to be higher than the ventilation effectiveness typically encountered when observing mixing or displacement ventilation systems (Melikov et al.
Later, in a study by Chen (2) in 2009, a procedure for verification of CFD analysis was developed, which showed it was possible to accurately predict the performance of displacement ventilation systems.
2)Hybrid ventilation of the mall central spaces, where natural displacement ventilation at higher than minimum volumes can help free-cool these areas until there is a risk of overheating.
We also have a fascinating feature about how a century-old building used displacement ventilation to improve indoor air quality and thermal comfort.
In displacement ventilation systems, as opposed to the traditional overhead supply mixing ventilation systems, cold air which is supplied at low velocity near the floor captures sensible heat from the space, rises due to buoyancy, and creates stratified temperature distribution in the space.