Frenger’s Active Chilled Beams can Achieve Coanda Effect at Low Pressure / Low Air Volume

Unlike other Chilled Beams on the market, all Frenger's Active Chilled Beams feature our “Turn Down” facility as standard, which allows them to create a full Coanda effect at an air pressure even as low as 15Pa.

They are able to achieve this due to our Patented ‘Burst Nozzle Technology’, which is featured as standard on all of our Active Chilled Beams, and also helps to reduce noise levels and encourage greater induction.

The video above was filmed in one of our in-house climatic test laboratories and demonstrates how our active chilled beams are still able to achieve a full Coanda effect, which is crucial for maintaining Good Thermal Comfort, even when the static pressure in the air chamber of the Active Chilled Beam is as low as 15Pa, when room areas not populated to full design occupancy and you want to reduce the fresh air supply accordingly (lower the pressure = lower fresh air supply volume).

Coanda Effect

The Coanda effect is a phenomenon that causes a moving stream of fluid that comes into contact with a curved surface to follow the curve of the object. In the case of Active Chilled Beams, as air behaves like a fluid, the air will follow the curvature of the air discharge profile allowing it to entrain across the ceiling (or the discharge extrusion on Exposed Chilled Beams and Multi Service Chilled Beams), reducing the air velocities in the occupied zone.

The interaction between the fresh air from the discharge nozzles and air discharge profile on all Frenger’s Active Chilled Beams has been designed to give the perfect conditions to allow the Coanda effect to be generated.

An image detailing the working principles of an Active Chilled Beam

Turn Down

Frenger’s Turn Down facility allows rooms to have lowered fresh air supply volume, for example when not required for maximum occupancy, while still maintaining good thermal comfort. This is difficult to achieve with normal active chilled beams and other HVAC items, as usually when the fresh supply air volume is reduced, the supply pressure is reduced below the designed setting as the air introduced into the room from the active chilled beam will no longer produce the desired Coanda effect. The air will stop entraining across the ceiling and instead dump into the occupied space, causing discomfort / draughts.

As with all Frenger’s products, our Active Chilled Beams have undergone extensive in-house and third party testing, allowing us to develop the optimal way of introducing fresh air to a room without causing draughts or excessive noise.

The ability to ‘Turn Down’ the fresh air supply pressure, whilst still providing induction and Coanda on discharge maintains, Good Thermal Comfort and allows for a more energy efficient and flexible way of building management. This reduces strain on the HVAC systems, in particular AHU’s, therefore lowering running costs and extending the life of the buildings systems.

The graph below shows how the waterside cooling of Frenger’s Active Chilled Beams is reduced during the ‘Turn Down’ facility, allowing the flexibility to match the requirements relative to the number of occupants in the space.

A graph showing the Turn Down relationship between supply air and waterside cooling in Frengers Active Chilled Beams

Turn Down Performance Examples:

  • At 100Pa Active Chilled Beam Static Pressure:-

Design Air Volume = 100%
Waterside Cooling 100%

  • At 60Pa Active Chilled Beam Static Pressure:-

Design Air Volume = 79%
Waterside Cooling 89%

  • At 40Pa Active Chilled Beam Static Pressure:-

Design Air Volume = 63%
Waterside Cooling 76%

  • At 15Pa Active Chilled Beam Static Pressure:-

Design Air Volume = 39%
Waterside Cooling 48%


When room spaces have less occupants than 100% of design, a lower supply air volume a lower waterside cooling should still meet the respiratory requirements (8-15 ltrs/sec per person) and waterside cooling to maintain the design room temperature

The above information is to help enable engineers to calculate the possible Turn Down for their particular projects.