The appearance of bubbles used for flow visualisation around bluff bodies in a wind tunnel is illustrated. It is demonstrated that the large diameter and low density properties of bubbles could enable them to represent raindrops in a wind tunnel.
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.
For proper control of the ventilation in a building, it is necessary to know the factors involved. These include (1) the climate, including temperature, wind direction, and wind velocity, (2) the building performance, (the interconnections b
In energy balance of buildings the ventilation losses are a big part, and this part is getting relatively bigger the better the enclosure of the building is insulated. All ventilation that is larger than what is wanted for hygiene and comfort can be regarded as undesired and thus be considered as heat loss. For energy conservation it is therefore essential that ventilation rate can be controlled. This report discusses the current research in Sweden dealing with air infiltration.
Gives detailed results of an extensive programme of wind tunnel testing of a standard scale model of a one-room, flat-roofed building. A major requirement was coverage of those characteristics of window openings or window accessories which were known (or which appeared) to have a significant effect on indoor air flow.
Air-to-air heat exchangers were evaluated as a method of maintaining indoor contaminant concentration levels below acceptable levels. A mathematical simulation of air infiltration and indoor contaminant generation was used todetermine the distribution of contaminant concentrations at various average intervals including hourly and yearly. Both spot generation such as from unvented combustion, and diffuse sources, such as from materials, were considered for four contaminants, nitrogen dioxide, carbon monoxide, carbon dioxide and formaldehyde.
The thermal effects of air flows in building structures have been analyzed by computer simulation. Some laboratory experiments have also been carried out concerning natural convection in closed and semi-open cavities filled with fibrous insulating material. Three different flow systems in building structures have been studied: natural/forced convection in open/semi-open (permeable cold surface) 2-dimensional insulation structures, heating of infiltrating air in cracks and diffusive infiltration.
A pilot test series has been performed to study the possibility of using carbon dioxide produced by the burners of a test furnace as a tracer gas to measure the fire gas leakage of door assemblies. The experiments show that a test method based on tracer gas techniques can be developed avoiding thedrawbacks of the proposed ISO test method DP 5925 Part 3 based on the use of an enclosure. The investigated method works well for leakage measurements in ambient and medium temperature ranges. A special test door suitable for theoretical estimation of leakage rates was used in the test.
A constant concentration tracer gas system was designed and constructed to continuously measure the air infiltration rate in as many as ten zones of a building. The portable, microcomputer controlled system injects a metered amount of tracer
A method has been introduced for the analysis of the hygrothermal behaviour of building materials and construction. The model equations for coupled heat and mass transfer used in the computer code TRATMO and in the determination of hygrotherm
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