Improvements to ventilation systems for the purpose of saving energy may also affect the provision of good air quality. Measurement of ventilation effectiveness may be used to determine whether or not good fresh air distribution and satisfactory contaminant removal has been achieved in a specific case. However, for such measurements to be useful, it is necessary to establish recommended values of the parameters and to check the reliability of the measurement procedures. This paper is concerned with the second of these problems.
This paper describes a laboratory model for the testing and validation of tracer gas measurement techniques. Previous attempts at experimental validation have often been limited to two zones, or a particular measurement strategy, or a particular range of flows. The model consists of four zones, each of 1m³ internal volume. The zones are connected so that all possible inter-zone flow paths exist. The flow down each path is driven by a pump and monitored by a flow meter. A control panel enables any combination of interzone flows to be set, within the capacity of the pumps.
The air distribution in a room is investigated using computational fluid dynamics. Four common methods of supplying air to a room are compared. The effect of air change rate on the ventilation effectiveness for contamination is small, however the effect of room heating or cooling load can be very significant. It was found that air turbulence has a major influence on the air movement, air velocity and dispersion of contaminants in the room.
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