The centrifugal fan should keep the air inlet resistance as small as possible to convert as much work as possible into effective work, which also requires the air inlet of the centrifugal fan to be much larger than the air outlet.

Similarly, if the size of the air inlet and the air outlet are the same or even smaller than the air outlet, the effective power conversion rate of the centrifugal fan will decrease, and the static pressure of the fan outlet air will become smaller.