Center for the Built Environment

In a warm environment air movement with elevated velocity is a well-known cooling strategy. The local air movement is typically generated by cooling fans (e.g. ceiling fan, table fans, etc.). Appearance, power input and price are the main parameters considered today when purchasing cooling fans, while their cooling capacity and efficiency of energy use are unknown. A new index is introduced, named “cooling fan efficiency index” defined as the ratio between the cooling effect (measured with a thermal manikin) generated by the device and its power consumption.

The index was determined for a ceiling fan, a desk fan, a standing fan and a tower fan in a real office at three room air temperatures and at different fan speed levels. The results revealed that the index is sensitive enough to identify differences in the performance of the cooling devices. A standard method(s) for testing fan cooling effect and index(s) for determination of their efficiency, such as the proposed in this study cooling fan efficiency index, need to be developed.

The cooling fans generate a non-uniform velocity field around occupants which cannot be described with a single air velocity value. Therefore it is not clear how to apply in practice the recommended in the present standards eleveted velocity in a warm environment. The standards need to be revised.