A new multizone airflow and contaminant dispersal model CONTAM93 is described, along with a demonstration of its application in a study of ventilation and contaminant control in single-family residential buildings. While CONTAM93 is based on existing theory of network airflow analysis and contaminant dispersal, the model employs a unique graphic interface for data input and display. The interface uses a sketchpad to describe the connections between zones and icons to represent zones, openings, ventilation system components, and contaminant sources and sinks.
After a short description of the physical phenomena involved, unified expressions are worked out describing net airflow and net heat flow through large vertical openings between stratified zones. These formulae are based on those of Cockroft for bidirectional flow, but are more general in the sense that they apply to situations of unidirectional flow as well. The expressions are compatible with a pressure network description for multizone modelling of airflow in buildings. The technique has been incorporated in the flows solver of the ESP-r building and plant energy simulation environment.
In the UK the increased use of natural ventilation in buildings is being encouraged, particularly during hot weather as an alternative to air conditioning or mechanical ventilation. In order to take advantage of this option building designers need to be able to estimate potential air flows. Conventional calculation methods assume windows to be simple openings, however in practice the situation is more complex since during hot weather the opening is likely to be shielded by some form of solar shading device.
The airflow between a warm room and cool exterior can be significantly affected by an external headwind. Pollutant concentrations within the space depend on the relative sizes of the wind and the undisturbed stack driven flow. Two scenarios are described. Firstly, a space is filled initially with buoyant polluted air. The space is then naturally ventilated through a single opening. In the "no wind" case, a gravity current of external air flows into the space. All the polluted air is expelled from the room.
The paper summarises an approach to determining the equations governing the air flow through simple cracks subject to fluctuating pressures. To this end, an experimental arrangement has been developed that enables the laboratory simulation of fluctuating driving pressure signals. A standard straight crack was subjected to this signal, which fluctuates in both magnitude and frequency. An air control system permits a high level of fluctuating pressure control.
BRE have experimental data for the flows found in Passive Stack Ventilation (PSV) ducts from a test house in Garston. These data cover different duct diameters, number of bends and roof terminals, all measured over a variety of weather conditions. In the first part of this paper the data are analyzed to separate temperature and wind effects, and to see how well they fit well to the expected model of duct flow. The second part gives a comparison of the same data with predictions from the single zone ventilation model BREVENT.
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