Traditionally, prediction of ventilation systems performance has been based on deterministic approach, which implies that the spread of the input parameters values is zero. The deterministic approach is valid if the effect of fluctuations in the forcing functions (wind speed and direction, temperature, radiation, occupants' behavior, etc.) is negligible when compared to the mean value.

The "step-down" tracer gas technique was used to evaluate experimentally in a mechanically ventilated test room the effect of varying thermal boundary conditions, inlet flow rates, and inlet - exhaust grids position on the Air Change Efficiency (ACE) values. The paper shows that the measured global ACE values are strongly correlated to the Archimedes number (Ar).

The present study deals with indoor air quality and is mainly based on an experimental work. The experimental set up is a full scale test cell with a ventilation system which comprises a fixed air supply and a mobile extract. A source of pollutant continuously supplies tracer gas at the centre of the cell. We carried out 12 tests under steady state and with various conditions. The test parameters were the exhaust location, the fresh air now rate and the supply air temperature.

There are many ventilation and air conditioning systems, having their own set of advantages, disadvantages and applications. Inadequate control on ventilation rate for the case of natural ventilation system can lead to indoor air quality problems or excessive energy loss, while mechanical system is often expensive for the installation, operational and maintenance costs.

An important element in the natural ventilation design procedure is the flow-pressure characteristics of a window with a given opening area. The flow in the room is another important element that is often ignored in the design phase due to lack of relevant information on the air movement. This paper shows the outcome of experiments with the room air distribution. The results show that the velocity distribution in the occupied zone can be described by a semi empirical model.

Natural ventilation driven by a solar chimney attached to a single-room building is investigated experimentally with a small-scale model using a recently developed fine bubble technique. Parameters studied in the experiments are the cavity width of the solar chimney, the solar radiation intensity, the height of the solar chimney, the room inlet area and the solar chimney inlet area. Results showed that for given building geometry and inlet areas, there is an optimum cavity width at which a maximum ventilation flow rate can be achieved.

This paper briefly outlines the development of a design tool for ascertaining thermal comfort in high rise buildings in the tropics. The design tool, based on wind tunnel studies and computational fluid dynamic (CFD) simulations, was then applied to four cities in the tropics: Kuala Lumpur, Singapore, Jakarta and Hong Kong. Can thermal comfort be achieved using solely natural ventilation? The overall conclusion was that natural ventilation alone cannot generally provide thermal comfort in high rise buildings in the tropics.

The characteristics of a hybrid air-conditioning system, utilizing natural and mechanical ventilation, is investigated in an office setting. The characteristics of the indoor environment are examined with CFD(Computational fluid Dynamics) simulation under various conditions of incoming outdoor air. The control of the room air conditioning system (VAY system) is included in the calculation through changing the supply air volume to keep the task zone's temperature at a target temperature.

For indoor thermal environment engineering and heating system dimensioning, naturally ventilated spaces impose difficulties due to the interaction of indoor and outdoor air flows and due to their variation in time and space. Thermal building simulation models basically assume mixed air flow conditions in the individual zones, but are able to dynamically model the building masses and the heat exchange between them and the zone air.