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The world's highest performing fixed vane VAV swirl diffuser. ...Read more

The world's highest performing fixed vane VAV swirl diffuser.

High capacity, high induction, fixed horizontal discharge swirl diffuser with extended VAV operating range, suitable for low temperature supply air (≥ 5°C) allowing turndown to approx 25% @ ?â?ó?é?ê?é?åTsupply-room = -12 K. Enhanced ADPI ≥ 90% from approx. 1 L/s/m2 to approx. 15 L/s/m2.  May be mounted flush with ceiling or free-hanging.

Airflow volume rate

  • 10 – 440 L/s (36 – 1584 m³/h)

Supply temperature

  • ≥ 5°C

Nominal sizes

  • DN250
  • DN355
  • DN500

Discharge height

  • 2.4 – 4.5 m


  • Substantially flush face with 20 off-set radial vanes.
  • High capacity fixed swirl vane VAV diffuser with horizontal discharge
  • Swirl vanes with cambered leading edges reduce noise & pressure loss.
  • Swirl vanes with helical twist for reduced peripheral pitch extend VAV operating range. Patents pending.
  • Bell-mouth extends VAV operating range and provides stable horizontal discharge even with cold supply air  (≥ 5°C, with ?â?ó?é?ê?é?åTsupply-room ≤ 16 K)
  • Optional reducers for reduced airflow rates.
  • Optional blanking segments for 3-way blow (270°) and 2-way blow (2x90° or 180°) discharge
  • Square (standard) or optional round face
  • Installation freely suspended or flush with closed ceiling
  • Clean Screen™ smudge minimser and sweat inhibitor optionally available (patents pending)
  • Similar aesthetic to HSC-AD
  • Perforated square screen available to cover diffuser face


The SMARTEMP Fixed Helical Swirl Diffuser, type HSC-FD, produces highly inductive swirl discharge of the supply air, diffusing the strongly diluted air stream radially with fixed horizontal discharge direction into the space.

Patent pending, offset radial swirl vanes with helical twist and cambered leading edges increase both the maximum airflow rate and the VAV operating range, whilst reducing noise and minimum permissible supply air temperature. 

The diffuser is made of powder coated galvanised steel and may be flush mounted in a ceiling or freely suspended (ie no Coanda attachment to the ceiling required). The swirl vanes form a flush surface with the surrounding diffuser face, which can be round or square, and may be optionally screened by a perforated face.

Optional neck reducers may be inserted from behind (thereby not affecting the aesthetics of the diffuser face) to reduce the diffuser neck size to suit reduced airflow rates, in particular in VAV applications.  Segment covers are available to reduce the discharge pattern from 360° to 270°, 180° or 2 x 90° (ie from four-way blow to three-way blow or two-way blow).

Intense mixing at the diffuser discharge surface strongly dilutes the swirling supply air stream with large quantities of room air.  Rapid temperature equalisation of the diffuser supply air stream with room air is achieved, preventing cold air dumping, thereby ensuring uniform temperature distribution and high comfort levels in the space. Heating performance is also improved. High induction also produces a strong increase in the mass flow rate of the supply air stream, as well as rapid discharge velocity decay. As a result, at any given airflow rate, the SMARTEMP HSC-FD swirl diffuser is suitable both for long throws (due to the high momentum of the swirling supply air stream) as well as short throws (due to its low velocity). 

The SMARTEMP HSC-FD diffuser may be used in CAV systems, as well as VAV systems, including low-temperature supply air systems with ΔTsupply-room < 16 K. Minimum turndown = 22-28% at ΔTsupply-room = -12 K. Due to high induction swirl discharge, the effective air changes per hour in the space are increased, allowing minimum specific airflow rates as low as approximately 1 L/s/m2 when the diffuser is fully turned down, whilst maintaining enhanced comfort of 90% ADPI. Due to the rapid discharge decay characteristics of the swirl discharge, a high maximum specific airflow rate of 15 L/s/m2 may be achieved at 90% ADPI. 

Optionally perforated hub with Clean Screen™ discharge of clean, dehumidified supply air screens the diffuser face from smuding and condensation due to air borne contaminants and humid room air.  Well suited to areas with high infiltration, such as lobbies, especially near busy streets and in humid climates.

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