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Air Diffusers

Supply air outlets and diffusing equipment introduce air into a conditioned space to obtain a desired indoor atmospheric environment. Return and exhaust air is removed from a space through return and exhaust inlets. Various types of diffusing equipment are available as standard manufactured products

Slot diffusers are deployed primarily in applications in which suspended panel ceilings leave a narrow gap of only 16-120 mm in width.

They are suitable for installation in rooms ranging in height from approx. 2.60 m to 4.00 m. They offer high induction, resulting in swift reduction of the supply air temperature differential and the air discharge velocity. The recommended volume flow range is 25 to l/s · m, while the permissible supply air temperature differential stands at ±10 K. The stable discharge behaviour of slot diffusers makes them suitable for use in systems with constant or variable volume flow. The air discharge direction can be adapted as necessary to the desired room conditions.

Slot diffusers are generally supplied with rear-mounted plenum box, whereby the air duct system is connected via the side-mounted round spigot.

Swirl diffusers consist of a diffuser face with fixed, radially arranged air control elements. They are available in square or round design. Connection to the air duct system is effected via the plenum box, in either vertical or horizontal configuration.

Swirling, horizontal discharge of the supply air at a high induction rate guarantees swift temperature equalisation and fast reduction of the flow velocity. Up to 30 room air changes per hour are attainable at supply air temperatures between +10K and -10K. In order to stabilize the supply air flow, all sizes must be installed flush with the ceiling.

These type swirl diffusers are suitable for deployment in both the industrial and commercial sectors. They are suitable for both large heights (e.g. factory buildings, airports, theatres, banking halls) and lower rooms down to 3.80 m (e.g. assembly halls).
The blades are adjustable, enabling a horizontal discharge direction for cooling mode and a vertical discharge direction for heating mode. Continuous adjustment can be provided by means of appropriate variable-speed motors. Motors can be deployed in pneumatic or electric versions. The diffusers are connected to the air duct system via the plenum box, in either vertical or horizontal configuration
Floor diffusers are produced in aluminium (FBA) and plastic (FBK). Their select variety of surface structures and colours makes them an attractive design element for building owners and architects. The introduction of supply air through false floor systems is ideally carried out at locations in which convection currents are to be supported in occupied zones. Convection or lift currents can be caused by people, machines or electrical devices. Air flow from the floor to the ceiling is becoming increasingly popular in offices equipped with computers and other electronic devices. Local thermal loads are effectively discharged by means of this principle.

Floor diffusers are installed at locations which are not continuously occupied. They can be deployed at distances of as little as 40 cm from seating

Comparisons between outlet locations and patterns also affect the throw, entrainment, and temperature equalization of a jet. Some general characteristics include the following:

• Grilles with straight vanes project the longest throw. When the grille is located close to a ceiling, entrainment is restricted at the ceiling and results in a longer throw. However, when the air pattern is spread horizontally, the throw is reduced and the jet is flatter so its temperature is more uniform.
• Outlets with radial airflow have a short throw and a relatively thin jet, so the temperature in the jet is fairly uniform. Temperature equalizes more readily in a cooling jet, which results in less drop. • Single jets from ceiling outlets have a longer throw and perform like a grille. Outlets with high entrainment characteristics can also be used advantageously in air-conditioning systems with low supply air temperatures and consequent high temperature differentials between the room air and the supply air. Radial pattern ceiling diffusers may be used in systems with cooling temperature differentials as high as 30 to 35°F and still provide satisfactory temperature equalization in the space. Linear diffusers may be used with cooling temperature differentials as high as 25°F. Grilles may generally be used in well designed systems with cooling differentials up to 20°F.

Special diffusers are available for use with low temperature air distribution systems (i.e., those with supply air temperatures of 35 to 45°F and cooling differentials as high as 40°F). Those diffusers include special features that mix the cold supply air with room air at the outlet and effectively reduce the temperature differential between the supply and room air.

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