air flow

Reports results of studies conducted in Switzerland in small apartment buildings. Air change rates were measured in ten different apartment buildings using N2O as a tracer gas. Measurements were taken for various wind conditions andtemperature differences and with the windows partly open. Finds that ventilation rate increased by a factor of 4 when the windows on one facade were opened by only a few centimetres.

BSTRACT Describes test made to determine air flow through entrances to a multi-storey building. Temperature and pressure differences across entrances and outside wind speed were recorded and flow through doors studied using laboratory scale models. 

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.

Notes importance of air motion in shielded buildings in hot and humid climates. Describes wind-tunnel investigations on shielding effect of buildings for a group of buildings comprising parallel rows of identical blocks. Also considers influence of cross-ventilation through shielding building and variations in relative heights of the buildings. Discusses variation of wind speeds inside shielded building related to its distance from shielding building. gives optimum distances of separation for maximum and minimum shielding effect.

Describes the results of an investigation carried out to determine the rate of fresh air infiltration that is experienced during the winter in a modern air conditioned office building. Six different methods were employed to estimate the rate of infiltration through the building, four by direct measurement and two by calculation. The methods of direct measurement were,tracer gas decay, measured air flow through one floor, measured air flow through one air conditioning unit and measured change on power demand.

Describes how a family of simulated neutral atmospheric surface layers was used to determine the response of the wind loads on a building model, as well as the associated flowfield near it, to variations in the characteristics of these 'test boundary layers'. Results include the variation in the size of the horse- shoe vortex at the base of the building, spectra of pressure fluctuations, and documented variations in the wake Strouhal frequency with changing boundary layer characteristics.

Examines air flow into air-conditioned buildings caused by opened external doors in summer. Firstly the wind velocity through open doorways was measured using puffs of smoke inentrance hallways, finding that velocities varied from 104 ft/min to 350 ft/min with a mean of 265 ft/mins. Then tests were made on the air inflow when a swing door was opened and closed. Finally tests were made of the air flow due to operating revolving doors. Results for various types of entrances are displayed in a table.

Describes typical town centre developments in which a problem of wind environment has arisen, and gives a brief account of the investigation of specific cases. Summarises broad conclusions of 20 special cases. Describes series of investigations intoair-flow around small groups of idealised model buildings and compares model with full-scale measurements. Outlines design method for use in planning layout of small groups of buildings. Discusses future research needs.

Points out mistakes in text book formulae for determining the flow rate of fresh air. Provides a new approximate formula for this. Establishes a differential equation for air change rates and derives a generalized equation for ventilation incorporating only three parameters. Provides curves for determining the fresh air flow rate and gives calculated examples.

Discusses current knowledge concerning wind-induced ventilation in buildings. states major difficulty in estimating ventilation and infiltration rates in a building is ignorance of wind pressure distributions around structures. Examines properties of wind with special reference to mean velocity profiles, characteristics of turbulence and wind energy spectrum. Reviews internal and external pressure distributions on an isolated building. Studies effect of grouping of buildings on pressure distribution around a house by considering results of wind tunnel tests.