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Applied Air-Conditioning: Beam work takes off

Published: 1 April 2009 - 00:00
Chilled beams offer an energy efficient alternative to fan coil units says Wander ter Kuile technical manager at Waterloo Air Products.
CHILLED beam technology has rapidly evolved since the 70s when its precursor, chilled ceilings offered a low maintenance method of cooling a room. Since then chilled beams have emerged as a major player in the energy stakes and offer an attractive alternative to conventional systems.

With increased demands for energy savings and ever more stringent building regulations aimed at curbing our carbon footprints, opportunities have been created for manufacturers who can design energy efficient cooling systems. Nowhere has this been more evident than in the growth of indoor climate systems.

As building design combines sophistication with environmental issues, the requirements of the building's occupants is also being tempered with aesthetic looks and energy efficiency.

Their popularity has the indirect support of the government who is keen to see the UK's CO2 emissions drop substantially by 2050 and is in turn encouraging manufacturers and end users to look and use 'greener' solutions. This has encouraged architects and consultants to take a fresh look at chilled beams. As a result more and more projects tend to favour chilled beams as energy efficiency is now an important driver in HVAC selection.

There are essentially two types of chilled beam systems: passive and active.
Common to each is a radiator element that provides radiant cooling via circulated chilled water. The primary distinction between passive and active beams is the mechanism by which airflow is directed and fresh air is introduced.

Chilled ceilings were the bedrock of today's developments and offered a low profile cooling system but lack the ability to control the humidity requirements of a room and tended to be paired with a ventilation system.

Passive chilled beams usually sited above perforated metal tiles rely on the principle of natural convection: warm air rises from an occupied area to the ceiling and enters the beam where it is then cooled by contact with a cold coil. The cool air descends into the room through outlets underneath the beam. Primary applications are to supplement a displacement ventilation system or treat a building's perimeter heat gain.

Active chilled beams are so called because they are connected to an air-handling unit and provide ventilation air via induction nozzles. Because they supply primary air into an occupied space they create a pressure differential in the beam across a cooling coil.

This differential induces air flow across the coil thus providing cool, re-circulated air into the space via outlet slots underneath the beam. Unlike passive beams, active beams can provide heating and cooling.

There are also Multi-Service Chilled Beams (MSCBs). These can use either active or passive chilled beam technologies. The cooling unit is integrated into a perforated architectural casing with central or side-mounted lighting and are tested and delivered to site for mechanical and electrical connection. A full range of building services can be incorporated within MSCBs, including: cooling and heating, fresh air supply, uplighting, downlighting and emergency lighting, BMS sensors, control valves and condensation detectors, fire alarms and sprinkler systems, acoustic insulation, pipework, ductwork and compartmental trunking.

Bringing several services together in an integrated MSCB unit means that the physical dimensions of the unit can be optimised, to enable use in spaces where the floor-to-slab height is minimal.
The concept also provides the specifier with a single source of responsibility for the design, supply and integration of all services, ensuring reduced costs and on-site time.

MSCBs offer an alternative to the monolithic ceilings that have become commonplace in office developments, providing attractive yet functional building services installations. The appearance of each beam can be customised in terms of shape, dimensions, colour and perforation pattern to meet the client's particular requirements. Either a passive or an active chilled beam can be made into a multi-service beam that offers a compact single unit combining all the required building operations such as lighting, sprinkler systems security and motion sensors, sprinkler systems and more.

Although chilled beams can, depending on the application, be more costly initially than a fan coil system, their energy saving benefits in the long term make them more attractive.

Advantages

Chilled beams offer a number of advantages over conventional VAV systems including low maintenance, energy efficiency, superior comfort, reduction in overall building costs, ease of installation and low noise.

There are no internal fans or filters that can break down or need cleaning so all maintenance is at the central plant area.

The low fan speeds that deliver air to the outlet diffusers uses little energy. Higher operating temperatures enable the use of free cooling. Chilled beams provide superior comfort over a VAV system and the greater the room's heat loads the greater the energy savings. Room temperatures can be controlled via an individual beam or groups of beams offering flexibility. Assembly takes place off-site and units are delivered ready for easy on-site installation.

The 'fit and go' concept reduces commissioning times and costs. Multi service beams also offer an alternative to suspended ceilings and can reduce building costs if architects, consultants and the customer can work closely together and factor in energy efficiency parameters from the outset.

Active beams on the other hand such as the ABM 600 are ideally suited to refurbishment projects as they can replace standard ceiling tiles. Beams are highly aesthetic with a finish that can suit most environments. Lighting can be integrated and beams can be fully recessed to reduce the appearance of 'ceiling furniture'.

There are of course some disadvantages and the most commonly cited are system flexibility - beams can be inflexible if the layout of an office space changes - and water needs to be piped to every terminal unit, whereas a fan coil can deliver chilled air to several terminal units for with water supply. But the benefits and energy savings far outweigh these.

The market for chilled beams is increasing yearly and the latest figures from BSRIA show that in 2006 the number of units reached 47,600 and 72,800 in 2007. With energy efficiency and sustainable buildings a prerequisite the outlook for chilled beams couldn't be brighter.

Waterloo Air Products
01622 717861

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