Experimental study of local thermal comfort and ventilation performance for mixing, displacement and stratum ventilation in an office

Satisfactory thermal comfort and efficient removals of airborne contaminants are crucial to the work efficiency and health of occupants. Different air distributions can generate distinct airflow patterns, thus affecting thermal comfort and ventilation performance. The experiments were conducted to study the performances of three air distribution methods (i.e. mixing ventilation (MV), displacement ventilation (DV) and stratum ventilation (SV)). Local thermal comfort was evaluated for the three air distribution methods with their individual thermally neutral temperatures. Three gaseous point pollutant sources located at the desktop, floor and manikin armpit respectively were applied to study the impact of the pollutant source locations on their ventilation performances. The distributions of air velocity, air temperature and contaminant concentration were measured. Results showed that a vertical air temperature difference of above 3 degrees C between the head and ankle levels appeared with DV, but the draught ratings (DR) under SV were higher than those under both MV and DV. Pollutant source locations exerted different effects on contaminant dispersion and contaminant removal effectiveness (CRE) for the three air distribution methods. SV always removed the contaminants effectively with all the three pollutant source locations to maintain good inhaled air quality, which was superior to MV and DV.