English

Industrial buildings, as in the nuclear industry, are equipped with ventilation systems, the main role of which is to ensure pollutant containment inside the facility during normal, damaged or accidental situations. To do this, the ventilation system is designed to maintain rooms at lower pressure with respect to the outside environment. The air, taken from the outside, thus flows from the rooms with the lowest contamination risk to the rooms with the highest contamination risk, before being filtered and released into the atmosphere.

A pilot survey was undertaken from September 2009 to June 2011 in 310 schools and day-care centres distributed in all regions of France including overseas departments. This experimental survey was carried out as part of the preparation of the mandatory control of indoor air quality in public buildings. Three parameters were measured in 896 classrooms or child playrooms: benzene, formaldehyde and carbon dioxide (CO2). The last enables the determination of degree of air ‘stuffiness’ during children occupancy as well as the night-time air change rate.

A quadrature method of moments, based on the population balance approach, was chosen to model nanoparticle coagulation and transport. Such a way has been already validated using experimental results in a homogeneous closed chamber in a steady fluid. In order to model the spatiotemporal evolution of a nano-aerosol, we propose here to couple the population balance equation (PBE) with computational fluid dynamics (CFD) considering a uniform pipe flow. A source term describing coagulation is added in convection-diffusion equations.

The use of supply jet flows is the most common type of air distribution for general ventilation. Usually the supply flow rate is constant or slowly varying (VAV-systems) to cope with a varying load. A novel air distribution method, with the potential to reduce stagnation and to increase the ventilation efficiency, is to introduce rapid flow variations (pulsations). This paper reports on a fundamental study of this type of air distribution.

An urban heat island results in higher urban temperatures than the surrounding area and is considered as the most documented phenomenon of climate change. This increase in urban temperature has a serious impact on the energy consumption for cooling and also contributes to higher urban pollution levels. Athens suffers from high summer temperatures that affect the quality of life of citizens. In response to the problem, a major rehabilitation plan was designed and applied, based on the use of advanced mitigation techniques.

The aim of this paper is to illustrate the impact of urban wind environments when assessing the availability of natural ventilation. A numerical study of urban airflow for a complex of five building blocks located at the University of Reading, UK is presented. The computational fluid dynamics software package ANSYS was used to simulate six typical cases of urban wind environments and to assess the potential for natural ventilation. The study highlights the impact of three typical architectural forms (street canyons, semi-enclosures and courtyards) on the local wind environment.

The prevailing paradigm in indoor environment control of office buildings often excludes natural ventilation, due to the fact that its dynamic nature may not be compatible with the close control of mechanical conditioning systems. Due to the potential magnitudes of wind and buoyancy forces in tall buildings, the challenges are greater. This research is concerned with the prospect of purely naturally ventilated tall office buildings. The naturally available driving forces of wind and buoyancy are investigated separately or in combination.

Stratified ventilation systems use a fundamentally different approach to supply heated or cooled air through a building than the ‘fully mixed and dilution’ ventilation systems found in the majority of non-residential buildings. Stratified air distribution creates a non-uniform environment in terms of temperature and pollutant distribution, and acceptable conditions in the occupied zone. Previous research has shown that this type of system works well for regions where buildings require year-round cooling.

In this work the evaluation of indoor air quality in a classroom equipped with cross-flow ventilation is presented. A numerical methodology, based on comparison with experimental data, used in the evaluation of the air exchange rate, airflow rate and the age of the air, was applied in the first phase of this work. The evolution of carbon dioxide inside spaces, with different airflow typologies, was then predicted in the second part. The study was based on a school located in the South of Portugal. In the experimental methodology the tracer gas decay method was applied.

The accurate prediction of particle deposition in ventilation ducts is an important step in estimating the exposure risk of building occupants to particulate matter. In this paper a mathematical model for predicting particle deposition in rectangular ventilation duct flow by incorporating existing theoretical and experimental results is presented. The influences of Brownian diffusion, turbulent diffusion and gravity on particle deposition are considered. Model equations are presented for calculating the deposition velocities on vertical surfaces and the floor and ceiling of ducts.