Energy constraints encourage the use of energy-effective electrical appliances such as ceiling fans to achieve indoor thermal comfort, especially in developing countries (e.g., China and India) and regions with mild and warm climates. Ceiling fans accounted for approximately 6% of residential electricity consumption in India in 2000, which might increase to 9% in 2020.
To better guide indoor airflow design with ceiling fans, this study systematically investigates the air movement distribution in an unoccupied office room installed with a ceiling fan, as influenced by (1) fan rotational speed, (2) fan blade geometry, (3) ceiling-to-fan depth, and (4) ceiling height.
From the study, we found:
- Increasing rotational speed of a ceiling fan enhances average air speeds in the occupied zone, especially in the region below the fan blades. Furthermore, velocity profile self-similarity exists for different rotational speeds in the main jet zone below a ceiling fan.
- Through validation against experimental data, the ceiling fan-driven flow pattern is well predicted by the Standard k-ε turbulence model when incorporated with the Multiple Reference Frame (MRF) fan model.
- Both the blade geometry and insufficient distance from fan to ceiling may have significant effect on the velocity distribution in the cylindrical zone below the fan blades. However, the average air speed in the cylindrical zone is only slightly affected, suggesting that the blade geometry is not practically critical in influencing the thermal comfort of occupants. Moreover, similarities of air speed profiles were identified for fans with additional blade shapes and different numbers of blades.
- For the examined configurations, the rotational speed and ceiling height have a greater effect on the velocity distribution and average air speed in the occupied zone than do the blade geometry and the distance between fan and ceiling.
More details in the paper:
Chen, Wenhua, Shichao Liu, Yunfei Gao, Hui Zhang, Edward Arens, Lei Zhao, and Junjie Liu. “Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan.” Building and Environment 130 (2018): 14-26.
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