Last edited 29 Feb 2016

Chilled beam

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[edit] Introduction

Chilled beams are used to provide cooling to the internal spaces of buildings.

They were first used in the Shell headquarters in London in the 1960’s, but have only recently become popular as energy efficiency has become more important and buildings services have been better integrated into the early stages of the design process.

Typically, chilled beams are distributed regularly across the ceiling of a space. They include chilled water pumped through copper cooling coils bonded to aluminium fins that cool air by convection.

Very broadly, chilled beams can be passive or active.

[edit] Passive chilled beams

Passive chilled beams rely on buoyancy to create air movement through the beam. As air in the space heats up, it rises to the ceiling level, where it is cooled by the chilled beam and descends back into the occupied space. This requires a greater open area for air circulation than active chilled beams, and care must be taken to avoid creating draughts.

Separate systems are required to provide ventilation, heating and if required humidity control. Passive chilled beams are not effective at heating as the hot air will rise rather than falling into the occupied space.

Passive chilled beams can typically deliver 300 to 500 watts of cooling per linear metre.

[edit] Active chilled beams

Active chilled beams are an integral part of a building’s mechanical ventilation system. ‘Fresh’ air is supplied to the beam, either through ductwork or a plenum, and injected into the beam through nozzles which induce air flow from the room below. This mixed (or diluted) air is cooled by passing through the beam fins and then discharged into the space below.

Active chilled beams may also include a heating coil so that the supply air can be heated when required. They can also include other services. Multi-service chilled beams (MSCB), or Integrated Service Modules (ISM) can include lighting, speakers, sprinklers, cables, PIR detectors, and so on. See integrated service module for more information.

Active chilled beams can typically deliver 500 to 800 watts of cooling per linear metre.

[edit] Radiant chilled beams

Radiant chilled beams work on a similar principal, but the chilled fins remain exposed, and so provide additional radiant cooling. Radiant chilled beams can be visually concealed behind perforated panels, or may be exposed. The addition of a radiant component to the cooling process can reduce the reliance convection and so reduce the risk of draughts.

[edit] Radiant chilled ceilings.

Radiant chilled ceilings typically incorporate a network of chilled water coils in ceiling panels with insulation above. In some systems, pipework may be incorporated into plasterboard, but this is less efficient as plaster is an insulator. The ceiling surface then cools the occupied space by both radiation and convection. This provides even temperatures throughout the space and avoids draughts.

Very little space is required for chilled ceilings, which may be installed with a depth of just 100mm. In some systems, small bore cooling coils can be embedded in plaster ceiling finishes themselves.

Where this network is designed as a series of panels suspended from the ceiling they may be described as ‘rafts’ or ‘sails’.

Convective chilled ceilings are a variation on this, in which the network of chilled water pipes incorporates fins, increasing the proportion of cooling that is provided by convection.

More recently, chilled ceilings are being developed that incorporate phase change materials. See phase change materials for more information.

Typically, chilled ceilings will deliver 60 to 90 watts of cooling per square metre.

[edit] Benefits

Chilled beams and chilled ceilings are generally considered to be more energy efficient that conventional heating ventilation and air conditioning (HVAC) systems. They include fewer (or no) moving parts and so tend to be quiet and require little maintenance. They are generally space efficient, allowing lower floor to floor heights and flexibility of layout below.

If properly designed, they can be aesthetically pleasing and can create an even, draught-free thermal environment.

However, they can be expensive and complex to install, with complex space requirements and the need for a support structure that is independent of any suspended ceiling.

They can also place some restrictions on the flexibility of layout of the spaces that they serve.

Care must be taken to ensure that chilled water temperatures do not induce condensation, and supply pipes should be insulated. Chilled beams may not be suited to spaces with high humidity.

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