Why does better efficiency not always mean better performance? | What The Tech?!

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.
Do you know of any other applications where efficiency isn't everything?
Leave us your opinion in the comments.
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