ENERGY SAVING EQUIPMENT
to prevent the conditioned air from entering the occupied zone prematurely. As an approximate guide, the discharge jet expands away from the ceiling at approximately 200 – 250mm per metre throw length. Therefore, for a 4.5m throw, the ceiling height should be a minimum of 2.8m to ensure the discharge jet remains outside of the occupied zone.
Slot diffusers are typically installed around the perimeters of commercial buildings/offices, and are often used to direct cooled air against glazing to offset solar gain, particularly in buildings with glazed facades.
As the air direction of the slot diffuser can be altered on site, without recommissioning, they are ideal where space is frequently reconfigured, for example, due to office churn. There are two main types of deflection devices in slot diffusers: blade and barrel. These can be specified to suit the application, with barrel-style models recommended for greater induction potential.
Jet diffusers
Jet diffusers are designed specifically for handling large air volumes and long throws. This makes them ideal for buildings with high ceilings such as airport terminal buildings, hotel reception areas,
atriums, shopping arcades, museums, sports centres and department stores. Jet nozzles are perfect for applications where the supply air has to travel a large distance to the occupied zone and where the supply of air via ceiling diffusers is not possible. Jet diffusers are relatively low induction devices which maintain velocity and throw lengths of between 5m and 30m. When the temperature differential between the supply air and room air changes, the air stream is deflected upwards for cold air, downwards for warm air or horizontally (isothermal).
As the direction of the air stream can be affected by other factors, such as local convection effects or draughts within the room, jet nozzles are designed so that they can be adjusted to meet requirements for both heating and cooling.
The size and geometry of the jet diffuser’s air outlet lends itself to long throw applications as the core jet remains protected from surrounding room air (low induction rate). This ‘protected’ core retains its initial velocity to provide long, directional throws which enable the supply air to be directed to a specific area.
As well as retaining its core velocity, the discharge air from a jet diffuser also retains its temperature differential, hence its suitability for longer throw applications.
Manual or electronic adjustment of the airstream angle provides control over temperature differential.
J&E Hall
www.acr-news.com
August 2016 33
Trox Xarto swirl diffuser.
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