A comparison of predictive techniques for natural displacement ventilation of buildings.

Previous work by Linden, Lane-Serff and Smeed (1990) has developed a simple mathematical model for natural displacement ventilation of an enclosure. The work also introduced the experimental salt-bath technique, which uses salt solutions and fresh water to generate buoyancy forces that are analogous to those found in naturally ventilated buildings. The work claims that a good correlation exists between the predictions of the simple mathematical model and the results obtained using the salt-bath technique. The present paper reports further, independent experimental work using a test enclosure with air as the working fluid. A Computational Fluid Dynamics computer package is also used to predict the flow through the enclosure. The potential of each of the predictive techniques investigated is discussed. Although a simple mathematical model would be desirable, the conclusion of this paper is that such a model is not suitable for use in a design situation, and that alternative predictive techniques are preferred.