Fan are positive displacement pumps so, keeping the RPM costant, volume of gas moved does not change with the volumic mass of the gas itself. On the other hand will vary the power required to the engine, of any type it is.
One of the most important parameters for calculate the absorbed power of a fan
is the global efficiency, which depends on a lot of factors as the kind of construction, the RPM,
the shape of the blades etc..
Choosing the right efficiency is possible to evaluate every kind of fan, both axial and centrifugal. Results will have a lot of correspondence with real values for a lot of aim also in the industrial system field.
Select gas to be transported
Required gas flow
Total pressure required
Direct current or alternating current single-phase
Tri-phase alternating current, Y or delta link
Normally greater fan will have bigger efficiency than smaller one.
Please remember that is difficult to find engines with installed power equal
to the required power.
Depending on type of motor, will be always a certain reserve of power needed to compensate not
expected load variation.
Normally the most overestimated motors are the internal combustion type, on the contrary of the electric ones, they have better efficiency if not loaded at 100%.