Finding a solution to the problem of draughty buildings can be fraught with difficulty. Very often only the symptoms are apparent and the root cause can be difficult to identify. All too often a 'try and see' approach is adopted until finally, if luck prevails, a successful solution is found. The design team addressing the problem of a draughty mall at a shopping centre in Shrewsbury adopted a different approach. The possible causes were identified using site knowledge and Computational Fluid Dynamics. A 'blind' analysis of site data was then undertaken by an independent statistician ie.
This paper discusses two complementary techniques for modeling human exposures to airborne contaminants with a focus on control decisions involving ventilation. Particular attention is given to: (I) the use of empirical-conceptual models with dimensional analysis and (2) computational fluid dynamic simulations. Both techniques provide valuable information. An empirical -conceptual model is formulated with dimensional analysis for a spray painting operation.
Application of industrial painting is often carried out by air-atomization. In this case, health hazards arise from the exposure to solid and liquid aerosols as well as to solvent vapors. Control of these airborne pollutants may be achieved through the use of a spray booth, whose effectiveness depends also on the number and dimension of the openings, on the main air flow rate, as well as on the direction and flow rate of secondary air streams.
Thermal anemometers with heated velocity sensors are mostly used for low-velocity measurements in rooms. The heated velocity sensor generates an upward, free convection flow that interacts with the airflow where measurements are to be performed and, thus, has an impact on the accuracy of the velocity measurements. Tests were performed with four anemometers available on the market to identify this impact in an airflow with a constant velocity and in an airflow with a periodically fluctuating velocity.
A hybrid ventilation system combines both mechanical and natural ventilation modes. The natural ventilation mode, especially, causes some challenges for analysis tools since the varying nature of naturally driven flow means that transient calculations should be used to predict the flow fields. Analysis tools based on CFD have some advantages for detailed investigations since, in addition to evaluating the flow and temperature fields, it is possible to use CFD methods to calculate air exchange efficiency and other flow indices.
This paper presents a study of the dynamics of the turbulent mixing of a hot or cold air stream with the air in the interior of a building zone. Observations and CFO results of transient temperature behaviour in a fully developed jet flow field are presented. A simple model for the characteristic time-constant of the mixing process in a room is derived. The mixing of a turbulent jet, as a function of position inside the room, is also discussed. This mixing time-constant plays an important role in total system dynamic behaviour and stability.
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