The permeable system - also known as a Low Impulse System - applies the displacement principle. The air distribution is created by using thermodynamics (for more information see under Permeable System - Cooling, Heating & Isotherm).
Depending on the ΔT, the cool air will slowly drop towards the ground due to the higher density of cold air. Traditional installations with steel ducts will need a huge amount of grilles or diffusors in order to keep the low impulse system intact.
Typical flow pattern for textile duct handling a cooling application at a ΔT of -3' K.
Since the large surface area is used to dispatch the air into the room, the exit velocities from the textile system are extremely low. Compared with traditional steel ducting it is a common feature to experience much higher air velocities than those obtained by textile ducts.
This is caused by the static pressure generated by the fan that will force the air out into the room at a very low velocity as the entire surface of the duct is used to distribute the air into the room. You can say that the system is having a deliberately leakage or bleeding.
Permeable system - Cooling
The textile is working as one big diffusor as the total surface area of the fabric duct will be active. The cold air will be dispatched underneath the fabric system. Here it will displace the warmer room air underneath the duct.
Depending on the difference in ΔT, the acceleration towards the floor will vary.
Permeable system - Cooling - ΔT below -3°C
Permeable system - Isotherm (ventilation)
If the system is used for ventilation or isothermal temperatures, the inlet air will spread evenly into the room in all directions.
Permeable system - Isotherm - ΔT = 0°C
Permeable system - Heating
A permeable system used for heating cannot be recommended as the lower density of the heated inlet air will move upwards towards the ceiling. If heating is required from the ventilation system it is recommended to use a High Impulse Element to force the air into the occupied zone.
This can be done using either our Inject Light Material or our Hybrid System solutions.
Permeable system - Heating - ΔT above +3°C
Learn more about the advantages of fabric ducting and Euro Air.