The BRE has examined the suitability, effectiveness and potential energy savings of retrofitting natural and low energy ventilation systems in UK offices during refurbishment projects.
Constant injection of tracer gas was used to determine the airtightness of a straight length of300 X 300 mm square duct in a laboratory setting. Holes are performed in the ductwork which is connected to a fan with variable speed control to simulate leakages. The holes can be sealed with rubber bungs to simulate an airtight ductwork. 'Stationary' and 'mobile' methods have been developed. The stationary method is suitable for conditions where the locations of the leaks in the ductwork is known.
Particle loss augmentation in turbulent flow was studied experimentally. Experiments were performed in a I SO mm square ventilation duct. Small tracer particles of size ranging from 0.7-7.l μ.m were used to study deposition enhancement with streamwise-periodic disturbances mounted on one of the principal walls, under turbulent flow. A new and highly sensitive analytical technique was adopted to determine the spatial mass flux along the ribbed duct. On some surfaces, particle deposition enhancement as much as seven times higher than on .smooth surfaces was observed.
The properties of particulate filters and gas adsorption filters have been studied to determine the opportunities available for effectively cleaning the outdoor air supplied to buildings located in urban environments. Class F85 fine filters were studied to determine their collecting efficiency for both atmospheric dust and particulate P AH. Activated carbon adsorption filters were tested to establish their collecting efficiency for toluene, m-xylene and benzene in the concentration range of 1-10 ppm. Long-term tests were also run on a carbon filter in a building in central Stockholm.
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