Field Study of Diffuse Ceiling Ventilation Performance in a Landscape Office

Performance of diffuse ceiling ventilation with regard to thermal comfort and limits of the cooling capacity of the system was studied in a 97 m2-landscape office. Seven operation scenarios were tested: two for mixing ventilation with ceiling mounted fan coils and five with diffuse ceiling ventilation.

The conditions for ventilation air change rates were 1.2, 11.5 and 17.9 h-1, respectively and temperature differences between supply and exhaust ranged between 5.5 and 10.6 K. The vertical room temperature distribution and the air speed in several points in the room were measured. The results show that diffuse ceiling ventilation has substantial potential for landscape office applications because it can provide important cooling capacity while maintaining an acceptable comfort level in the occupied zone.

It does not generate draught in the occupied zone even at large temperature differences between supply and exhaust and great air change rates, while the same design parameters caused risk of draught in many points in the case with mixing ventilation. Good mixing in the occupied zone in case of both systems resulted in only small vertical temperature gradients.

The results from the study allow extrapolating the design chart q-ΔT for diffuse ceiling ventilation systems for higher ventilation flow rates.