Passive and active chilled beam cooling systems are used for cooling building air. Passive chilled beams cool the inside air without the noise and expense of ductwork and air handler units. Active chilled beams generally have much higher sensible cooling capacities than passive chilled beams.
The passive chilled beam is a building cooling device that circulates air using the principles of convection. The major advantage of a passive chilled beam over more common forced air systems is that it circulates building air without the noise and expense of ductwork and air handlers. Typically mounted overhead near or within a ceiling, the beam is a type of radiator chilled by an external source such as re-circulated water. It cools the space below it by cooling the naturally rising warm air of the space. Once cooled, the air naturally drops back to the floor where the cycle begins again. Using passive chilled beam systems, the ventilation air required must be delivered to the building by a separate air handling system.
Using active chilled beams, the building's primary ventilation air is cooled and continuously supplied to the active chilled beams by the central air handling system. This primary ventilation air is cooled to handle the temperature-driven sensible loads. Secondary air is induced up into the active chilled beam and is cooled by the cooling surface within the beam. The primary air and the induced air is then supplied into the room via slots on the edge of the active chilled beam. The proportions between primary and secondary air is approximately 1:3, which means that active chilled beams generally have much higher sensible cooling capacities than passive chilled beams.
Chilled beams reduce the need for heavy air ducts and save energy due to natural circulation. The cold-water supply works at fairly high temperatures to avoid dehumidification.