Displacement Ventilation is the concept of Supplying air near the floor level rather than at the ceiling and it has significant design implications. To avoid creating uncomfortable drafts for occupants situated near the diffusers. The choice to employ DV instead of conventional mixed-flow ventilation should be a team decision, with the owner, engineer, and architect all on board. Each approach has strengths and weaknesses. Displacement ventilation takes advantage to temperature stratification within high spaces and allows a gradient of temperature to develop above the occupied zone.
Displacement Ventilation system diffuser selection will be with very low air velocity to eliminate occupant discomfort from air movement. The floor diffusers will be selected to a maximum velocity of 0.20-0.30m/s.
Advantages .
1.Energy efficient
1. The lower velocity of air delivery reduces pressure requirements and allows fans to run more slowly, consuming less energy and producing less noise. This makes DV an excellent choice when lower noise levels are desired.
2. DV provides better acoustics and better air quality than mixed-flow systems. Mixed-flow systems tend to be louder because of the higher velocity required from diffusers. Diffuser noise can be difficult to attenuate.
3.If 100% outdoor air and exhaust is used, the heat gain due to the lights and roof can be eliminated from building cooling loads.
4.Ideal for space like Auditorium with large ceiling height
Disadvantages
1. DV adds complexity to supply air ducting because of the integration of low supply air devices within the programmed space. The architectural design needs to incorporate these large air devices.
2. DV diffusers are more expensive than mixed-flow diffusers.
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