Air conditioning Effective air
Q.Why does the absence of a suspended ceiling cause problems? A. The air management challenges in spaces without suspended ceilings stem from the inability to harness the Coanda effect, which prevents ‘dumping’ of cold air into the room. In a room which has a suspended ceiling, the low-pressure differential between the jet and the ceiling means supply air ‘attaches’ to the ceiling upon discharge. Air descends into the room at a manageable velocity, delivering air of the desired temperature into the zone without a feeling of gusts or draughts. Without the flat and continuous surface of a suspended ceiling, however, the Coanda effect can no longer operate, leading to near vertical discharge of air into the space. This results in a high temperature differential, draughts and a less comfortable experience for occupants.
Q. Are there other problems associated with exposed ceilings? A. Yes, there are. For example, if you need to heat a room, the absence of a false ceiling allows the warm air to stratify. The space above the diffusers will be heated before the occupied zone. This wastes energy, slows the rate of temperature change, and can cause discomfort for room occupants, due to high temperature gradients between head and ankle.
In addition to this, there can be acoustic
implications. Suspended ceilings are typically constructed from metal tiles incorporating acoustic materials that can absorb sound, minimising noise and reducing the reverberation time within the occupied space. Without these sound-absorbing materials in the vicinity of building services, ambient noise can be expected to increase.
www.heatingandventilating.net
management with exposed ceilings
Exposed ceilings are an increasingly popular feature in today’s buildings, but the absence of a nearby ceiling surface can cause numerous air management challenges. Tim Tanner, product technical manager – ventilation technology, TROX UK, answers your questions
Q. So how can you avoid air management problems? A. In some applications, it may be possible to employ slot diffusers in specific locations, for example at the perimeter of a room. These are not ideal for use in the middle of a room however. A more effective solution would be to install diffusers specifically designed for exposed ceiling applications. For example, the TROX Tellus swirl diffuser has a gap between the diffuser face and the plenum which allows for the air to discharge horizontally and form a ‘Coanda jet’. The air flowing through the swirl pattern face connects to this jet, increasing the throw distance. For high rooms, Tellus can be provided with a centre punched face for vertical air discharge. Another option is the TROX RFD swirl diffuser. This has an increased diameter discharge nozzle (Dx Face), which ensures the diffuser works well in
10 May 2024
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