The combined use of CFD and zonal modelling techniques to aid the prediction and measurement of ventilation effectiveness parameters.

In order that sampling points may be strategically located, it is desirable to have knowledge of the spatial variation of ventilation eflectiveness parameters prior to measuring them using tracer gas sampling techniques. The research described in this paper is being carried out to establish a tracer gas sampling strategy as well as to facilitate the prediction of ventilation effectiveness parameters. The procedure developed requires the division of the internal space into a large number of cells and, by the application of CFD, the mass flow rates between adjacent cells to be established. Software developed at the University to predict interzonal flows has now been interfaced with the CFD software allowing the ventilation effectiveness parameters within each cell of the CFD model to be established. Investigation of the computed values of the parameters reveals that the characteristics of many adjacent zones are almost identical. A method has been developed to combine small adjacent zones possessing similar characteristics thus allowing the model to be reduced to one of a small number of zones each possessing significantly different properties. It is demonstrated in this paper that, in the simple mechanically ventilated buildings to which the research has at present been restricted, it is possible to produce reliable contour diagrams of ventilation parameter variations from a small number of properly defined large zones. The large zones found in this way may be used both as a guide to the location of tracer gas sampling points and as the basis of a simplified model for design calculations.