Reports investigation of the relative effectiveness of wall gratings and flues as means of naturally ventilating unheated closed rooms. Ventilation rates of several rooms were measured using carbon dioxide as tracer gas and wind speed and direction were recorded. Presents results and finds for the flue, ventilation increased with wind speed irrespective of direction. For grating, ventilation rate increases slowly with size of grating and is dependent on both wind speed and direction. Concludes flue with base opening of 15 sq.ins. is as efficacious as grating having 50 sq.ins.
Due to the complicated flow phenomenon in urban areas, the assessment of wind pressure forces as well as the rates of natural ventilation for groups of low rise buildings is complex. As a result, the current design methods for the prediction of these forces are oversimplified and lead to inaccurate estimates of wind forces and ventilation rates in buildings. A survey of previous studies regarding wind properties and their influence on pressure forces along with work related to natural ventilation, wind loading and air flow round buildings was carried out.
This paper is a general survey of work done on natural ventilation of dwellings. Discusses ventilation of houses with both natural and mechanical ventilation. Reviews experimental investigations, quoting air-change-rates found. Discusses ventilation requirements and methods for investigating different factors. Outlines suggested experimental method for investigating air infiltration of mechanically ventilated houses.
Briefly outlines the causes of natural ventilation which are wind and stack effect. Gives calculation of ventilation rates for a simple building. Discusses the effect of a more complex building plan.
A supply of fresh air is necessary in any dwelling to ensure a comfortable, safe and hygienic environment, but the heat loss to this air, during the heating season, may represent a substantial proportion of the total heat loss. This points to the need forgreater control of domestic ventilation, either by using a mechanical system or by better design for natural ventilation. This paper touches upon both of these possibilities. Gives simple method for assessing approximately the possible reduction in heat loss achieved by the use of a mechanical ventilation system.
Discusses the mechanisms which govern natural ventilation. These are wind speed, flow, characteristics of openings in buildings and pressures generated at building surfaces by wind and temperature difference. Gives formulae for simple cases. Outlines ways of determining natural ventilation rates. Gives brief account of the effect of turbulence and openings in one wall only.
States that to obtain accurate estimates of wind induced natural ventilation of buildings the pressure distribution over the building is required. Reviews the available information for isolated buildings and groups of buildings. Gives the results of wind tunnel measurements made on a cuboid when surrounded by buildings of the same shape. Results are presented statistically and indicate that the pressure distribution on a building can be fairly accurately determined provided the density of the built form and the roughness fetch are known.
Surveys existing studies of natural ventilation which are of two types; full scale studies of small domestic buildings and analogue studies, mainly electronic digital analogues. Gives simple nomograms, deduced from the analogue studies which are useful for estimating gross building infiltration rates underextreme meteorological conditions. States that none of the analogue studies have been carried out in conJunction with simultaneous full scale or model scale studies in order to check their performance.
Describes a computer program written in 1900 fortran which is suitable for computing natural ventilation rates in multi-storey buildings. Lists the assumptions made, the data requirements and output available. Gives a print-out of the program.
Analyses theoretically the natural ventilation of buildings. Derives fundamental formula for the amount of ventilation due to temperature difference from Bernouilli's theorem considering buoyancy. Explains physical meaning of friction loss and theneutral zone, derives pressure distribution due to wind from the shape of buildings and the location of openings. Obtains total expression for amount of ventilation due to both temperature difference and wind.
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