Curious as to "fan logic".
I notice that in, say, kitchen hoods, central A/C air handlers, squirrel cage blowers are almost always used. btw, does "blower" imply the squirrel cage config? I will use "SC blower" visavis traditional blade-type "fan".
The SC blowers in A/C seem to be most often single large squirrel cages, whilst the sc blowers in kitchen hoods seem to be smaller dual cages, on either side of a double-shaft motor.
SC blowers seem to be super-efficient air movers. I scavenged two good-sized ones from a Lennox system, the cage about 1 foot long by 1 foot dia, and just turning it gently by *hand* delivers quite a forceful breeze -- which surprises even the mechanically savvy I demonstrate this to.
Otoh, blade-type fans are used in "boosters" in hvac duct, window/minisplit A/C's, central A/C condensers, roof mushrooms/wholehouse fans.
What governs the choice, and why? Ito of raw cfm's per $ or per "unit size" (in cu in), is one style inherently superior to another?
The, uh, thrust of my Q is that I'm cobbling together a kitchen, and am dizzied by prices of venting hoods that I like (*easily* $2,000-4,000 and not super-fancy -- holy shit!!!), and am not particularly impressed with the few I'm able to turn on, noise-wise, flow-wise. Cosmetically, tho, they are super.
HD has a couple of decent-looking ones in the $400-500 range, but they are a little bulky.
In particular, the fact that the dual sc blowers are located *in* the hood-proper bulks many of the units up considerably, which in this application creates visual line-of-sight issues, due to proximity to an entrance door.
So, I could locate the sc blower right up at the exit vent near the ceiling, or, even better from a visual pov, use an in-line booster type fan. And then I would be able to use the old hood etc from the original set up, which everyone kind of likes anyway.
With an inline fan, I realize the motor itself serves as a flow obstacle, which in a 6" or so duct could be a considerable proportion -- which is not the case in say an outside A/C condenser, where the blades are easily 3 feet diameter..
Not to mention the grease/temp issues in a hood, but which I think could be made manageable by the right motor, filters, and periodic maintenance. I figger if I will occasionally have to clean the squirrel cage in a blower, cleaining the fan blades AND the motor in an in-line ditty isn't such a big deal.
But then, being up at the ceiling, line-of-sight issues would be minimal, so mebbe a sc blower as traditionally used in this type of venting would be better. I would lean toward a single cage like in A/C blowers, to totally get the motor out of the ductwork.
More along shop lines, I had scavenged one of these double-squirrel cage hood-type motors, and kluged it into the exhaust for my welding table. Wow, orders of magnitudes better than the inline-fan ditty I kluged earlier, super-quick fume clearance. But, the previous in-line fan could have been just shitty anyway, so I don't know if apples were compared to apples.
But other in-line fan apps have gone well: The shit motor in my mushroom eventually went, so I scavenged a window A/C 3-speed fan unit, thermostat and all, and this works great -- infinitely superior quality to the original mushroom innards, altho a bit of a pita to install.
If I get lucky, I'll find a small 3 ph motor, and put a VFD on it, for infinite speed control -- small VFD's are not that expensive. I'm hoping to luck out with a system that's quieter than some of the expensive noiseboxes I've seen. I'm surprised that with $4,000 price tags, they don't offer something like this.
Opinions, suggestions for the kitchen?