| Item | Mixing Ventilation | Displacement Ventilation |
| Goal | to achieve even room temperature and humidity | comfort in working zone |
| Driven by | fluid dynamics | buoyancy |
| Principle | strong mixing of airflow | diffusion of airfow and lift of buoyance |
| Working Character 1 | large temperature difference and high air speed | small temperature difference and low air speed |
| Working Character 2 | inlet up, outlet down | inlet down and at side, outlet up |
| Working Character 3 | turbulence coefficient at outlet is high | turbulence coefficient of air supply is low |
| Working Character 4 | good mixing performance at air outlet | good diffusion at air vent |
| Flow Regime | reflux zone, turbulent zone | air supply zone, laminar flow zone |
| Distribution | up and down in even | temperature and concentration lamination |
| Performance 1 | eliminate load of entire room | eliminate load of working zone |
| Performance 2 | air quality is cloce to return air | air quality is close to air supply |
Fig2. Flow Regime of Displacement Ventilation in Air Conditioning System
