What The Tech: Higher effi­ciency = better perfor­mance?

It makes more sense to install a fan if its effi­ciency is funda­men­tally better. Right? Wrong!

Fans are complex flow machines and they respond to every change. As a rule, both centrifugal and axial fans can be used in venti­lation units. With axial fans, the air primarily flows out parallel to the axis. This enables them to deliver a high air flow – in other words, they can shift a lot of air at once. This then means that fresh and above all clean air can be drawn inward, for example. And this is also where the optimum effi­ciency of axial fans lies. However, this optimum degree of effi­ciency is close to the unstable oper­ating range. This can lead to stalling.

Due to their very focused outflow char­ac­ter­is­tics, axial fans are well suited to direct outflow into a duct network, for example. However, in conjunc­tion with a down­stream filter or heat exchanger, this becomes a disad­van­tage. Centrifugal fans are there­fore usually the choice for venti­lation units in prac­tice. In centrifugal fans, the air mainly flows from the center point outward, i.e. radi­ally. Because of this, they generate a higher pres­sure increase. By opti­mizing indi­vidual compo­nents – such as the impeller, motor, control elec­tronics, housing, or adapting the instal­la­tion situ­a­tion of the device – the effi­ciency can be further increased, thereby maxi­mizing energy effi­ciency. This can all be achieved with the lowest possible noise emis­sions.

The effi­ciency of a fan is there­fore a ques­tion of the rela­tion­ship between air perfor­mance and elec­trical power consump­tion. Ulti­mately, effi­ciency always depends on the use-case and instal­la­tion site, however.