Describes how multizone tracer gas analysis techniques can provide a complete description of office ventilation. Treats the concept of ventilation effectiveness to characterise internal air distribution. Discusses the measurement of whole building ventilation rates and ventilation effectiveness in mechanically ventilated office buildings.
A survey of mathematical models of air flow and of ventilation efficiency. Measuring equipment for laboratory experiments is described and the limitations and potential uses of the models are discussed.
Discusses guidelines produced for the Nordic Ventilation Group. Explains how the designer can select an effective ventilation system on the basis of information on ventilation rates and ventilation efficiency.
To make an evaluation of ventilation systems, numerical computation was carried out for three dimensional, isothermal, and turbulent flow schemes. It was found that there exists an optimum position for an inlet in relation to an outlet whereby the most effective ventilation can be attained. In addition, similar to the results for the two dimensional computation, the slope of the concentration decay is virtually constant and independent of the position in the room, so the mixing factor derived from this slope can be used as an index of the ventilation efficiency.
Evaluates results of the 'Ventilation in Residential Buildings' research programme of the German Federal Ministry for Research and Technology. It was found that conventional ventilation methods based on infiltration and window opening cannot secure proper air quality and at the same time provide energy conservation and user comfort, nor can intelligent ventilation habits be expected of the average user, for subjective and objective reasons. All ventilation systems evaluated had shortcomings.
Displacement flow has been found to be the best flow principle for ventilation, with ventilating air being supplied to the occupied zone. The design procedure should, amongst other things, contain an analysis of contaminant source in order to design the ventilating system to create the most favourable flow pattern for the contaminants. This paper deals with design principles and problems related to displacement ventilating systems.
Substantial work on ventilation effectiveness has been carried out in Norway and Sweden using tracer gas techniques based on fundamental physical and mathematical concepts. The nature of, and how to characterize by using tracer gas techniques, the flow of ventilation air and contaminants through a ventilated room is known. Displacement flow has been proved to be the best flow principle for ventilation, and in general ventilation air should be supplied to the occupied zone.
Measurement of air exchange rates, ages of air, and nominal and local ventilation efficiencies in large buildings is often complicated by the building size and compartmentalization, and by the presence of multiple ventilation systems. To allow characterization of the ventilation process in such buildings, a unique experimental system, that employs multiple tracer gases, is being developed at Lawrence Berkeley Laboratory. The tracer gases are sulfur hexafluoride and five halocarbons. The system is designed to be non-obtrusive, highly automated, and relatively easy to ins tall in buildings.
The filtering effects of three types of air control systems at two wastewater treatment plants on viable particles were investigated. Aspergillus fumigatus and other thermophilic organisms were used as monitors for viable particles. The indoor concentrations of viable particles were found to be affected by building design and the use of conventional mechanical air systems. Viable particles of approximately 4.0 microm and greater in aerodynamic diameter were filtered from the air while respirable size particles less than 4.0 micromwere not filtered as well.
Mechanical ventilation systems in large office buildings are designed to meet space conditioning loads and to maintain acceptable indoor air quality. In order to achieve acceptable air quality, the ventilation systems are designed to bring in a mlnimrm amount of outside air whenever the building is occupied.
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