Experimental comparison of thermal conditions in office rooms: diffuse ceiling ventilation, chilled beam system and chilled ceiling combined with mixing ventilation

Thermal environments generated by diffuse ceiling ventilation (DCV), chilled beam (CB) and chilled ceiling with mixing ventilation (CCMV) systems were compared at different heat gains. Experiments were carried out in two test chambers, in which a double office layout was investigated near heated windows. The heat gain strength was increased from a normal level of 37-40 W/floor-m² to a peak load level of 57-64 W/floor-m2 to observe effects on indoor air thermal conditions and draft discomfort. The target indoor air temperature was 26 ± 0.5 °C in the occupied zone. The results show that the air temperature, air speed and draft risk levels were reasonable at the normal load and increased slightly at the peak load conditions. The CCMV system provided the smallest share of locations, in which the draft risk level was higher than 10 %. None of the studied systems achieved the category A defined by EN ISO 7730. However, all the systems fulfilled the demands of category B, except for CB which felt to category C at the peak load conditions by exceeding the draft risk limit in one location. Thermal conditions were at a same level with the studied systems. However, CCMV may reduce slightly the draft discomfort.