In natural ventilation systems fresh air is often provided through opening of windows. However, the knowledge of the performance of windows is rather limited. Computation of natural ventilation air flow through windows is most commonly made using discharge coefficients, that are regarded as being constant. The reported results show that the discharge coefficient for a window opening cannot be regarded as a constant and that it varies considerably with the size of the opening area, the window type and the temperature difference.

A number of new techniques have been developed in recent years, by various researchers, to assist in the sizing and positioning of natural ventilation openings. These may be of considerable assistance in the natural ventilation design process, while still allowing architectural freedom. This paper reviews some of the available techniques. The complexity of the configurations accounted for by the procedures ranges from two openings with the indoor air at a uniform temperature to a technique that allows for multiple openings throughout a multi-zone structure.

In displacement ventilation the airflow pattern in a room is mainly guided by the convection flows from the heat sources present in the room. This implies that the air in the breathing zone mostly comes from the lower parts of the room, where the air often is less polluted by pollutants originating from persons or electrical appliances present in the room.

Wall-mounted air conditioning systems including window-type and split-type air conditioners are widely used in Asian countries. However, these systems blow cold air directly into the working space perpendicular to the mounted wall and may make people affected by these air conditioners experience discomforts such as draught and uneven temperature distribution. Now a wall-mounted air conditioning system is expected to effectively implement the displacement ventilation system for space cooling and cold draught avoiding.

A study is being conducted to assess the performance of displacement ventilation in high-ceiling areas such as commercial and industrial manufacturing facilities. These areas, which can range from 5 to 20 meters in height, often feature high internal heat loads and contaminants associated with heat sources. Very little performance data exists for displacement ventilation installations in high-ceiling areas, particularly any which account for the influence of wall temperature.

The paper presents a comparison between the results of experimental tests airflow pattern forming in a room with displacement ventilation and numerical calculation. The heat source in the room was a heating plate. Quasi-laminar diffusers supplied the air with the ventilation change rate from l to 7 h-1. Temperature and velocity distributions in the plume and in its surroundings as well as the tracer gas concentrations in the background were measured. The airflow in the room was also predicted by means of CFD, using the standard k-E turbulence model and standard log-law wall-functions.

Two-dimensional computational simulations are performed to examine the effect of vertical location of a convective heat source on thermal displacement ventilation systems. In this study, a heat source is modeled with seven different heights from the floor (0.5m, 0.75m, 1.0m, 1.25m, 1.5m, 1.75m, 2.0m) in a displacement ventilation environment. The flow and temperature fields in thermal displacement ventilation systems vary depending on the location of the heat source. As a heat source rises, the convective heat gain from the heat source to an occupied zone becomes less significant.

An isothermal air curtain for isolation of smoking areas in restaurants was designed, built and evaluated in a test facility using oil-smoke visualisation and tracer measurements. The test facility was a ventilation test room set up as a small restaurant, with tables, chairs, person simulators (cylindrical heat sources) and balanced mechanical ventilation. Fresh air was supplied in the non-smoking section of the room, exhaust air drawn from the smoking area, and the air curtain was attached to the ceiling between the two sections.

A three dimensional computational fluid dynamics (CFO) analysis has been used to predict airflow patterns in laboratory fume hoods. The simulation includes bypass fume hood primary operational features including the top and bottom bypasses, front airfoils, and rear slotted baffles. The study included the effects on the fume hood airflow of sash height changes, an operator positioned outside the fume hood, and equipment within the main fume hood chamber.

In the modem office environment there are numerous heat generating equipment. In addition there are loads from solar radiation and heat produced by people. Therefore, the loads will often exceed.the load the ventilation system can cope with. To meet this demand on extra cooling capacity the commercial market provides cooling ceiling panels and cooling beams. A literature review shows that until now the majority of the research has been focused on the cooling performance and only a minor part on the thermal comfort and air quality.