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.
To predict the thermal and indoor air quality performance of vertical displacement ventilation systems using two-zone modeling, it is necessary to account for the different nature of the air flow due to thermal and contaminant mixing within these zones. Two zone modeling of vertical displacement ventilation was performed assuming piston flow in the clean zone, uniform mixing in the dirty zone, and no recirculation between the zones except via heat source plumes.
The momentum balance on a centrifugal fan, supplemented by a complete energy balance for rigorous interpretation of power-pressure interactions, relates these variables to flow rate and fan speed. Non ideal behaviour is modeled by direct mechanical interpretation and by engineering correlation, leading to more general expressions than provided by the fan laws. First attempts to fit these expressions to measured data show promise but reveal limitations of current practice in the data collection and reporting process.
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