Ventilation by displacement - characterization and design implications.

Ventilation by displacement is described in terms of ventilation efficiency and quantified by means of a two-zone flow and diffusion model. The practical procedure is by means of adequate diffusers firstly, to 'hit' the persons with the ventilation air and secondly, to displace both air and contaminants out of the zone of occupation and avoid recirculation. This procedure has a firmbasis in the research work on ventilation efficiency that is carried out inNorway and Sweden during the last years as well as in current theory practice. The paper describes practical design implications as well as calculation procedures based on the two-zone model. A system evaluation model is also treated.