At sufficiently high Reynolds numbers, the discharge coefficient Cd associated with a sharplycontracting flow through a square-edged opening is, in general, taken to be constant.

The estimate of actual air change rates considering atmospheric turbulence isintroduced. The starting point is the spectral description of turbulence - Kaimalspectrum was used in order to consider the height above ground. A set of syntheticwind velocity series are generated, out from a modified spectrum. The procedureconsiders an aerodynamic transfer function (a filter) where peculiar and cut-offfrequencies are determined by the general dimensions of the building and of theexternal openings, i. e., the turbulent scales of interest.

This paper discusses how simplified thermal and ventilation tools could be used during thefeasibility study of buildings to demonstrate the advantages of natural and low energyventilation strategies. The paper focuses on local authority library buildings in South-EastEngland and two simplified tools were used; one using a dynamic thermal simulation andventilation method and another based on the admittance method. The prediction of both toolswere compared with measured temperatures from an existing library that has a knownoverheating problem.

This article describes a ventilation system, developed within the framework of aEuropean project supported by the JOULE III programme (NAVAIR project). Theconcept used - natural ventilation assisted by air induction combines the advantages ofnatural ventilation and the performances of mechanical ventilation.

There has been a growing interest in the use of natural ventilation in buildings to supplement orreplace mechanical air supply systems. However, for buildings in busy urban areas the potentialto use natural ventilation can be limited by excessive noise entering through natural ventilationopenings such as windows and trickle ventilators. Such openings tend to have large open areasto enhance air flow while offering a very low resistance to the transmission of external urbannoise.

There has been a growing interest in the use of natural ventilation in buildings to supplement orreplace mechanical air supply systems. However, for buildings in busy urban areas the potentialto use natural ventilation can be limited by excessive noise entering through natural ventilationopenings such as windows and trickle ventilators. Such openings tend to have large open areasto enhance air flow while offering a very low resistance to the transmission of external urbannoise.

The paper presents results from a wider study into providing displacement ventilationin urban areas by taking air into buildings from the top without the use of fans.Results from large scale experimental work are given. These results indicate thatventilation airflows can be induced using gravity chillers and heaters in conditionswhere this type of installation would otherwise fail. The paper also describes initialexperiments undertaken to see how far the same equipment can be used in heatrecovery.One test installation is modelled using a proprietary zonal model.

Knowledge and estimation of the wind speed and air flow characteristics, in a city, is of vitalimportance for passive cooling applications and especially in the design of naturallyventilated buildings. This study is referred to the analysis of the wind characteristics in urbancanyons as a function of the free stream wind. The impact on the airflow rate calculation isdiscussed for an urban canyon. The goal of this study is to get a better insight of the impact ofthe urban environment on the ventilation effectiveness.

In natural ventilation systems, fresh air is often provided through opening of windows, andthere is a wide range of possibilities with regard to selection of window type and position inthe facade. Different window types have quite different characteristics and thereby differentimpact on the thermal comfort conditions in the occupied zone. The thermal comfort is alsovery dependent on the selected natural ventilation strategy, the outdoor conditions and theavailable pressure difference across the window opening.

In this study a series of parametric laboratory measurements were made of the velocitiesoutside, ve, and inside, vi, a full-scale louver positioned in a rectangular opening located in avertical wall forming part of a 1m x 1m x 2m deep model room. The louver parametersexamined, for external incident wind speeds from 0.6 to 2.5 m/s, included louver blade depth(L), aperture (d) and distance from the louver in to room (Rd). For this initial study the bladesof the louvers for each experiment were horizontal with an inclination angle ? of 0.