In general, chilled beams are considered a more energy-efficient solution compared to conventional HVAC systems. Additionally, they have little to no moving parts, and they even operate quietly and demand little maintenance.
If designed properly, they can complement the aesthetics of a space and even create a draught-free environment. Chilled beams could be classified as either active or passive.
An active chilled beam (ACB) is considered an integral part of a mechanical ventilation system within a building. It lets fresh air in through a ductwork which is then injected to the beam via nozzles, thereby inducing air flow from the room below. After that, the air then passes through the beam fins where it is cooled and distributed afterwards.
Due to this process, an active chilled beam is considered more efficient in terms of cooling capacity compared to its passive counterpart, delivering around 500-800 watts of cooling for every linear meter. In some cases, it might also include a heating coil to heat up supply air when necessary.
Meanwhile, a passive chilled beam (PCB) tends to rely on buoyancy for creating air movement. As chilled water passes via the tubes, warm air will then rise toward the ceiling where it’s cooled by the beam and returns to the occupied space. Due to this, a passive chilled beam is capable of cooling without the need to use a fan. However, its cooling capacity is lower to that of an ACB, delivering only around 300-500 watts of cooling for every linear meter.
Aside from active and passive beams, chilled beams can also be classified into the following:
Active beams are ideal for the following applications:
- Hospital roomsu
- Spaces with sensible heating and cooling requirements
- Spaces that require low noise levels
- Spaces that have limited floor-to-ceiling height
On the other hand, passive beams work best on the following:
- Conference centers
- Spaces that require additional cooling
To make sure we can create the right chilled beam design for your building, we normally examine the following considerations:
Passive, and even active, chilled beams can be considered self-regulating. As there is an increase in heat gain, the mean water temperature difference will progressively increase as well, thereby increasing overall cooling capacity.
Chilled beams are designed to use the dry cooling principle to eliminate the risks of condensation by choosing the chilled water flow temperature, supply air conditions, and ventilation rate. The dehumidification of the primary air supply is a major factor for preventing humidity levels from surpassing the dew point, hence preventing condensation.
To guarantee the dehumidification of supply air during high outdoor temperatures, it is important to size the air handling unit’s cooling cool to dehumidify outdoor air and allow for internal latent gains. Additionally, the humidity ratio must be low to allow ventilation airflow to compensate for the internal humidity loads.
Since the primary airflow rate is based on fresh air requirements, ducts are designed to be relatively small. In a traditional ACB, the ductwork is proportionally balanced. If not, constant-pressure control dampers are necessary.
It’s also important to take note that PCBs that work with separate supply air systems tend to operate at minimum ventilation rates. As a result, smaller duct dimensions are used. In the same manner, ACBs can also operate at minimum ventilation rates to create enough induction of secondary air, thereby providing the necessary waterside cooling.
Chilled beams normally operate at temperatures between 14 and 18 degrees Celsius. If ACBs are used for both cooling and heating purposes, then they’ll have to use two separate water circuits.
Due to the difference between the flow water and room air’s temperature in a dry cooling system, the sizes of the pipes used will be larger compared to the ones in condensing systems. Additionally, distribution pipework is sized to a 50 to 100Pa/m pressure drop as a means of balancing the pipework system via small pressure drops within the balancing valves. This is designed to avoid or prevent noise generation.
The choice of pipes could either be plastic, copper, or steel. However, they have to be properly insulation in order to reduce overall energy consumption. Since chilled beams work above the dew point, a vapor barrier is no longer necessary as long as the inlet water temperature is maintained above the room and void’s dew point temperature.
Meanwhile, the primary distribution pipework must be installed at a higher location than the beams.
Ventilation rates can be computed in accordance with the local building regulations within your area. For example, if you’re from Chicago, you need to comply with the local building regulations in the city.
ACBs typically use constant airflow. However, it’s also possible to use lower supply air temperature as long as the room system can heat the cold supply air to prevent the room from overcooling.
If the active chilled beams’ length is predetermined, you’ll have to follow the primary air flow rate that your manufacturer specified. This way, you’ll be able to achieve optimal cooling performance and ensure effective heat transfer. Make sure you don’t set the primary airflow rate too high as it will only result in excessive induced airflow which could lead to droughts.