Center for the Built Environment

Ceiling fans have been widely used for a long time as an effective cooling equipment to create sustainable indoor environment. However, it is rather difficult for the current measuring techniques to capture such a complicated airflow field in a whole-room scale. In this study, a novel large-scale airflow measurement technology, quad-view colour sequence particle streak velocimetry (CSPSV), is developed and applied to measure the airflow induced by a ceiling fan in a 4 m × 2.5 m × 3 m chamber. Four cameras were used in the new method, two at the higher position measuring airflow near the ceiling while the other two at the lower position measuring airflow near the floor, to capture the room-scale flow field. After reconstructing the vectors from each camera pair, the airflow vectors are merged to fill the blind zone near the ceiling and floor. Based on the three-dimensional three-component vector field measurement data, the averaged velocity vector, turbulence intensity, and vorticity were calculated and the airflow patterns were analyzed. The results indicate that the quad-view CSPSV method provides a more comprehensive measurement in room-size complex air movements such as ceiling fan airflow. Six pattern zones can be identified for a typical ceiling-fan-induced airflow. The flow under ceiling fan swirls along its path with the same rotation direction of fan blades with the core shrinking gradually and becoming diluted by the surrounding air. This study provides a new velocimetry method for room-sized complex airflow and a better understanding of ceiling fan airflow pattern, which is helpful to the new concept of integrating ceiling fan with air conditioning system.