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.

Temperature efficiency is an important index to estimate the ventilation effectiveness. Usually ,the temperature efficiency is determined through field or model tests such as gas-tracing technology. The heat source structure(location, size, heat emission, etc) has a strong effect on the temperature efficiency. The heat sources present themselves or may be arranged in three basic models:(A)heat sources uniformly distributed in the space; (B) heat sources uniformly distributed on the floor; (C)concentrated heat sources at the bottom of a room.

This paper investigates the relationship between the neutral height for air distribution and the ventilation load in a room with displacement ventilation. An environmental chamber equipped with a displacement ventilation system has been used to carry out the neutral height measurements with the presence of a heated mannequin and other heat sources in the chamber. The total room load used was varied from 104 W to 502 W, i.e., corresponding to a ventilation load from 10 W/m2 to 60 W/m2. The prediction of the neutral height was based on plume theory.

As the climate in the Nordic countries is cold for several months a year, windows are crucial parts of building envelopes. The current trend to reduce the heat losses by building- components has resulted in many modifications of the design work of windows in order to improve the thermal performance and the indoor climate. The improvements of window constructions have resulted in a higher surface temperature on the inner pane and considerably lower downdraught, which in turn has created an opportunity to introduce unconventional design of the heating and ventilation systems.