This paper deals with the description and determination of the purging flow rate, U_P for ventilation systems or equivalent flow systems. The regional purging flow rate and its use are discussed and proposed. By using the mass conservation principle, U_P is embodied in various accessible mathematical expressions in terms of the transfer probability. Some U_P-related parameters are described. A Markov chain model is proposed for determining the transfer probability and exploring several useful ventilation indices.

Computational fluid dynamics may be used to predict the details of airflow in rooms served by displacement ventilation systems, provided a suitable turbulence model can be found. Since buoyant plumes are central to the displacement ventilation strategy, four turbulence models - three eddy-viscosity models (the 'standard' k-s model, a modified k-s model, and an RNG k-s model) and the Reynolds stress model - were applied to simulate airflow in a turbulent buoyant plume.

This paper is concerned with the numerical modelling and investigation of the performance of air curtains employed to reduce air flow and heat transfer across open doors and between conditioned and unconditioned spaces. It has been found that the model based on a commercial Computational Fluid Dynamics software package can successfully predict the critical velocities and efficiencies of air curtains and the influence of external parameters such as wind speed.

It is possible to make high wall inducing vents with low air resistance, combined with natural ventilation or a mechanical exhaust. By means of these vents draughts may be prevented and high efficiencies in fresh air and contaminant removal may be realised, the latter being determined by the position of the outlet. Existing equations related to air flow patterns and Computational Fluid Dynamics (CFD) computer programs can be used, provided that the equations and the CFD program (Phoenics) are modified in order to get better agreement with measurements.

A numerical calculation procedure for an air flow window (AFW) system integrated with a roll screen is presented. Both beat and air flows within the window elements such as the outside pane of glass the outside air space, a venetian blind, the inside air space and a roll screen, are taken into account by considering the thermal and air flow networks. Agreements between measured and calculated results of temperatures and pressure differences through a series of experiments carried out in an environmental test chamber were observed.

The application of computer tools in construction is set for a revolution as integrated software packages come close to fruition. But there are barriers to the increased use of electronic design tools, notably worries over validation, the skills needed both in the design studio and on site and the quality assurance issues of correctly defining product elements and the design criteria. Over the next three articles, we examine the potential for using integrated computer design tools.