Air principles
How air behaves.
You don’t choose a diffuser by its looks. You choose it by what the air does once it leaves the outlet: mix, displace, reach far or cool in silence. Six principles, each with its own limits, as Krantz sets them out in its datasheets.
The basics
Mix or displace.
Almost every outlet belongs to one of two families.
Mixing. Supply air enters with momentum, entrains room air and mixes before it reaches the occupied zone. The whole room ends up at roughly the same temperature.
Displacement. Air enters cool, slow and low, and spreads as a layer across the floor. Heat sources lift it; the warm, used air leaves at the ceiling.
turbulence intensity
- mixing · approx. 40 % · TB 69 p. 3
- displacement · approx. 20 % · TB 69 p. 3
maximum allowable air velocity in the occupied zone, at 26 °C
| Comfort category (EN ISO 7730) | Mixing | Displacement |
|---|---|---|
| A · draught rating < 10 % | 0.15 m/s | 0.18 m/s |
| B · < 20 % | 0.25 m/s | 0.32 m/s |
| C · < 30 % | 0.33 m/s | 0.45 m/s |
TB 69 E 2013, p. 2 (table 1) and p. 3 (table 2).
The six principles
| Principle | What the air does | Typical | Link |
|---|---|---|---|
| Swirl · mixing ventilation | Vanes give the air a twist; radial jets along the ceiling mix quickly with room air | swirl diffuser, radial swirl diffuser in the ceiling | Read → |
| Induction | Many thin jets or nozzles entrain room air, also through a heat exchanger | linear induction diffuser, active chilled beam, façade unit | Read → |
| Displacement · comfort and industry | Cool air, low and slow; the heat sources do the rest | displacement outlet, step outlet, hall outlet | Read → |
| Jet · long throw | One concentrated jet that reaches far and mixes on the way | nozzle, swivel jet outlet | Read → |
| Radiation and convection · chilled ceilings | A cool surface absorbs heat, silently and without a jet | chilled ceiling, chilled sail | Read → |
| Laminar displacement · clean air | A low-turbulence flow in one direction that pushes contaminants ahead of it | laminar outlet, HEPA outlet | Read → |
Before you choose
Five numbers decide the outlet.
- Temperature difference. How much cooler or warmer the supply air is than the room. Every type has a maximum.
- Discharge height. Where the outlet sits decides whether the air reaches the occupied zone properly.
- Cooling load per m². It sets the air volume, and whether a principle can still cope.
- Comfort category. A, B or C to EN ISO 7730, agreed between consultant and client (TB 69 p. 2).
- Sound. The permissible sound level in the room.
Above 50 W/m², category A is only achievable with a chilled ceiling plus an air distribution system for the hygienic air change. (TB 69 p. 3)
About the images
Cool supply air is blue to turquoise; warm air and heat sources are orange to red.
Your host
Tell Pia about your space.
Pia is Peek's digital host. Describe your hall or building, and she will show you the Krantz components that fit.
I'm Pia. Shall I show you around?
Pia is an AI avatar, not a person.
with sound and microphone
Your voice and the conversation go via Runway in the United States, where privacy protection is weaker than in the EU; we do not yet have a data processing agreement with them. By clicking the start button you give your explicit consent to this (see the privacy statement).
Not live. Pia only starts when you click.
Click the start button in Pia's window. Your browser will then ask for your microphone.
Prefer a call? Leave your name and number and we'll call you back. Or chat with Pia using the button at the bottom right.
Or call us: +31 (0)73 820 02 88
