Experimental Study on the Impact of Passive Chilled Beam in a Room with Displacement Ventilation

Previous studies have demonstrated that displacement ventilation (DV) can provide better air quality than mixing ventilation (MV), and may save energy in buildings. However, since DV introduces supply air to the occupied zone directly, the temperature of supply air it provides is normally higher than in a MV system, so the ability to remove cooling load is limited with the same amount of air. On the other hand, passive chilled beam (PCB) systems have been shown to be able to remove a large cooling load while saving energy. Therefore, this research studied a coupled configuration that combined DV and PCB, and examined its thermal and ventilation performances through the measurements of airflow velocity, temperature, and contaminant (simulated by sulfur hexafluoride, or SF6) concentration at various locations. Measurement results were compared with those in the same room but with only DV system. A third set of measurements was also conducted to test how sensitive the results were to room layout and ratio of heat removed by PCB. Experimental results showed that PCB increased the overall air flow velocity in occupied zone, although the maximum airflow velocity was still observed at floor level, which was similar as in a DV only system. When both PCB and DV systems were used, temperature gradient was observed in most locations of the room. Meanwhile, contaminant concentration stratification was seen to be destroyed by PCB in this experiment. Similar trend was observed in the third set of measurement which had a different room layout and a lower ratio of heat removed by PCB.