Blower Wheel Relative to -Blower Output-

[mobiledynamics]

The fall blower is a gasser Echo

For quick cleanups , or 95% drying the cars weekly (yes, I wash them that often)......I use my Dewalt 40V
New Milwaukee Dual Battery unit came in....which was on my radar, but I might as well ask.
On paper, I believer it is more powerful than the Dewalt 40V

But the blower wheel on this is *half* the size of the Dewalt....


Whaddya say boys. The larger the blower wheel, the more volume...
Or now, it's more about the how the air flows from what-ever design is the design....

 

[Mooky]

Flow, pressure and power are governed by the “Fan affinity laws” Other variables include speed, inlet and outlet geometries.

For the same speed, impeller and volute designs, the flow varies by the cube of impeller diameter ratio. Second graph and equations above, show the relation of diameter to the flow/pressure/power:

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This assumes the same speed and impeller/volute design. Different manufacturers almost certainly use different geometries for their impellers & volute.

 

[timgunn1962]

Should that be "flow varies by the cube ROOT of the impeller diameter", assuming all else is equal? I tend to think in terms of changing the speed of existing fans, rather than changing impeller diameters, and it's giving me a headache.

Fans are fairly complex things to try to compare. You can have a large volume of air, moving very slowly, for very little power, or you can have a smaller volume, moving faster for the same power.

Doubling the volume of air at the same speed takes double the power (direct relationship). Doubling the speed of a given volume of air takes 4 times the power, and/or 4 times the pressure, (square relationship). Doubling both the speed and the volume takes 8 times the power (cube relationship).

For centrifugal fans, the peripheral speed of the impeller is important. Half the diameter, but running at double the speed will give a similar pressure rise, which in turn will give similar air speed. That's assuming all else is equal, which it won't be because there are so many variables for the designer to play with.

It's not quite rocket-science, but it's far enough out of the normal experience of most people that you are usually best off just leaving the design to the designers and making any judgement based on how well it does the job you need it to do. It does mean you may need to read reviews or actually try the blower before making a purchasing decision, which is a bit of a nuisance.