A critical review of displacement ventilation.

This paper reviews several aspects of the performance of displacement ventilation: temperature distribution, flow distribution, contaminant distribution, comfort, energy and cost analysis, and design guidelines. Ventilation rate, cooling load, heat source, wall characteristics, space height, and diffuser type have major impacts on the performance of displacement ventilation. Some of the impacts can be estimated by simple equations, but many are still unknown. Based on current findings, displacement ventilation systems without cooled ceiling panels can be used for space with a cooling load up to 13 Btu/(hfr) (40 W!m2). Energy consumed by HVAC systems depends on control strategies. The first costs of the displacement ventilation system are similar to those of a mixing ventilation system. The displacement system with cooled ceiling panels can remove a higher cooling load, but the first costs are higher as well. The design guidelines of displacement ventilation developed in Scandinavian countries need to be clarified and extended so that they can be used for U.S. buildings. This paper outlines the research needed to develop design guidelines for U.S. buildings.