Introduction to Chilled Beams
A Chilled beam refers to an air distribution device with an integral coil that can be installed within a space to offer sensible cooling and heating. Chilled beams are classified into two main categories- active and passive.
Active chilled beams
An active chilled beam is made of a fin and tube heat exchanger contained in a housing that is suspended from the ceiling. These chilled beam systems consume less energy, decrease HVAC equipment costs and in a majority of the cases reduce construction expenses as compared to conventional HVAC systems.
Active beams should be used in places where there is a need of sensible cooling, heating and ventilation air. In case the design demands supplementary cooling only or the ventilation needs of a building’s design is fulfilled by some other means, passive beams can be utilized. Areas that may have moderate to highly sensible heat ratios such as private and public office buildings, classrooms, meeting facilities, health care facilities and other environments where there are limited spaces for new mechanical equipment, active chilled beams are a suitable option.
Passive chilled beams
Passive chilled beams are mainly a cooling coil that is attached or suspended from the ceiling. Under this system, chilled water is passed through the coil that ultimately cools down the air inside the room. The cooling procedure is done by the natural convective movement of air through the coil and to the occupied space.
Both passive and active chilled beams are built to offer sensible cooling only and that is why there must be a separate dedicated outdoor unit for dehumidification. In the case of active chilled beam systems, these dedicated outdoor air units provide the primary air to the chilled beam. As the chilled beams offer sensible cooling only, the chilled water supply temperature to the chilled beams has to be increased up to several degrees above the design space dew point temperature to prevent compression on the chilled beam.
Advantages of chilled beams
- Chilled beams have no terminal unit fan, which is why the overall system fan energy remains lower than the other systems that require terminal equipment fans.
- The maintenance requirements of chilled beams are comparatively less as they do not have any condensate pan or filter like other systems with terminal equipment filters or condensate pans
- This particular system needs minimal airside infrastructure as the systems are only needed for outdoor air ventilation/primary air. Due to this it requires less floor space for central air handling equipment and vertical duct risers.
- Chilled beams remain quiet as there is no terminal equipment fan noise
Disadvantages of chilled beams
- As mentioned above the temperature of the chilled water entering has to be several degrees above the space dew point and that is why the water side delta T remains lower than a fan coil unit or variable volume air handling unit delta T. As a result it increases pumping energy for the chilled beam system compared to those systems.
- In order to control humidity during the cooling season, chilled beams are dependent on a dedicated outdoor unit. This is crucial for the performance of the chilled beam. The job of a dedicated outdoor air unit is to supply subcooled/low dew point ventilation air continually to the building spaces to maintain favorable humidity levels and restrict condensation at the chilled beams. Any condensation can be identified by the occupants and it can permanently damage adjacent building finishes.
- Both the chilled beams are less effective when it comes to heating than cooling. This is the reason why often supplementary heating systems are required.
- A single chilled beam is incapable of serving multiple rooms like a variable air volume terminal or fan coil unit. At least one chilled beam is needed for each room.
- In a heating dominated climate, a separate heating system is often required with a chilled beam technology. Chilled beams utilize the reduced density of cold air in order to encourage flow and this is the reason why they are less effective at heating a particular space.
How chilled beam works?
A chilled beam aims to reduce excessive fan energy and reliance on reheat and it plays the role of a radiator chilled by recirculated water. Chilled beams cool down the warm air that rises and it falls back to the floor where the cycle begins.
Passive chilled beams depend on ventilation air to be delivered by a separate air handling unit. On the other hand, in case of active beams the ventilation air is delivered to the beam with the help of a central air handling system through ductwork.
Where are the chilled beam used?
Eb Air Control OKNI Chilled beams are a good choice for places where thermal comfort is prioritized.