English

This paper describes the development of a simplified tool which should be used at the early design stage for predicting air ventilation rates in a building. The method is based on the assumption that the air flow rate may be calculated as a function of two independent parameters. The first, called effective pressure difference, takes into account the local weather data, surrounding terrain, and building typology. The second is the overall building permeability, and accounts for permeable components (geometry and permeability), including vents.

The characteristics of a hybrid air-conditioning system, utilising natural and mechanical 'task' ventilation, are investigated in an office setting. The characteristics of the indoor environment are examined by means of CFD (Computational Fluid Dynamics) simulations under various conditions of incoming outdoor air. The control of the task air conditioning system (VAV system) is included in the calculation through changing the supply air volume to keep the task zones temperature at a target temperature.

This study, which formed part of the Annex 35 Hybrid Ventilation in New and Retrofitted Office Buildings project, was completed at LEPTAB and supported by the French Research Ministry and the ADEME (Agence De lEnvironnement et de la Matrise de lEnergie). It consisted of modelling a typical classroom and comparing different control strategies to estimate the performance of a hybrid ventilation system for different climates.

The demand for buildings with high quality indoor environments is growing, especially in developing countries, where more and more energy will be consumed in the near future. Air flow pattern, air temperature and humidity are among the main parameters that contribute to indoor thermal comfort. Care must be taken to design the most energy-efficient air distribution system that provides comfort for the occupants. To achieve this it is very helpful to know the air flow patterns and the temperature and humidity field in a building at the design stage.

Creating a computer model that is able to simulate different ventilation scenarios within a structure is essential for improving the understanding of passive designs that are both sustainable and environmentally acceptable. The purpose of this investigation was to build a prototype model that could be heated from both the outside and inside to duplicate an occupied structure during the morning hours. Two Computational Fluid Dynamic (CFD) models were created for this study to firstly compare and then validate results obtained from experimental data.

The basic mechanism for natural ventilation in a building involves air flowing through purpose-made ventilator openings. These ventilators must be carefully designed as natural ventilation driving forces are weak compared to the dynamic forces created by mechanical systems. This paper describes a series of experimental parametric studies that investigated how components within a ventilator (in this case louvers and wire mesh screens) interacted. Air flow measurements through the individual louver and mesh components were compared to the air flow through mesh / louver combinations.

This paper describes an analysis using the BRE Pollution Dispersion Wind Tunnel to estimate pollution concentration patterns on buildings in urban arrays due to local line sources of pollution, typical of vehicular traffic emissions. The experimental procedure involved measurements of both pressure and concentration patterns on building forms in urban arrays, intended to provide information on the ingestion of pollutants into buildings in urban areas.

Buildings are aired to evacuate indoor pollutants, in particular those produced by the occupants. CO2 is a good indicator of occupancy, as long as there is no other significant source. This is the case in most buildings. Cheap, portable analysers and loggers that allow easy recording of the CO2 concentration in a room or in the exhaust duct of a ventilation system are available on the market. The peak value of CO2 concentration during occupancy is an indicator of the minimum air flow rate per person.

The problem of the hygienic state of air-conditioning installations in many countries is still treated with limited attention and, in general, this issue is disregarded both when systems are designed and when the maintenance of already operating system is performed. In order to highlight problems resulting from contamination of the installation, microbiological assessment of air conditioning systems in a hospital was carried out. The measurements particularly pointed to increased microbiological contamination of air and dust deposited in the system just downstream of the sound attenuators.

It is well known that iterative solution processes can lead to divergence when dealing with coupled airflow and thermal analyses for buildings ventilated either naturally or by a mixed-mode system. The Newton-Raphson method or its variants are used in almost all existing multi-zone airflow models. This paper discusses the qualitative features of the iterative solution processes of the Newton-Raphson method when used for coupled thermal and ventilation analyses of a simple one-zone building with two openings.