Performance of displacement air distribution in an office room

Two mixing and several low velocity supply air devices for displacement ventilation have been studied in a full scale room model. The cooling loads varied from 0–50 W/m 2 and air change rates from 3–8 m 3/h m 3. Velocity and turbulence intensity were measured in several locations near the floor level. The mean values of turbulence intensity of displacement air flow were slightly lower than with mixing air flow. However, there was no significant difference between minimum values of turbulence intensity of mixing and displacement air flows. The difference was greatest in the maximum values of the turbulence intensity. The vertical temperature gradient in the middle of the room was dependent on the total temperature difference between exhaust and supply air temperature. The limiting factor for displacement ventilation in an office room seemed to be thermal comfort. If the cooling load exceeded 40 W/m 2, either the vertical temperature gradient or air velocity at the ankle level becomes too large.