A design procedure for displacement ventilation. Part 2 of a two-part how-to series on passive thermal displacement ventilation.

This article concentrates on displacement ventilation design procedures appropriate for rooms with heat- and contaminant-removal requirements. With passive thermal displacement ventilation, supply air is discharged directly into the occupied zone at a low velocity near the floor level and at a slightly cooler temperature than the design room temperature. The air from the diffusers spreads along the floor, creating a relatively cool layer of fresh air near the floor. Heat sources within the room create thermal plumes of rising air that entrain this air and carry it up past the human inhalation zone and , eventurally, up near the ceiling. The warm, contaminated air forms a stratified region in the upper zone of the room, which is exhausted from high-level air returns. This stratification of contaminant levels makes it possible to provide higher-quality air in the occupant breathing zone without increases in system or operating cost. Two approaches are used for passive-thermal-displacement-ventilation design: the first is based on the analytical model, and the second relies on Computational Fluid Dynamics. Covers air diffuser selection, air diffuser and exhaust location, and selecting air diffuser type.