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Fan to fight static pressure

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Captain Random Senior Evil
Nov 8, 2001
I'm making an experimental AC unit, and I need a fan that can really blast air thru a narrow pipe. I can make adapters no problem. The pipe is only 7/8 inch diameter. I don't need a lot of air volume, but the more the merrier. I'm considering dismantiling a vaccuum cleaner... and I'm testing out an 8 inch room fan right now. I saw a brand of room fans, Vornando, that looked like the design could do pretty well against high pressure. I don't think case fans will qualify for this job. Any suggestions? Preferably something cheap. I'd like to use 2 matched fans, one on each end of the pipe, if one can't do the job alone.
I think your in need of a blower, not a fan. They're capable of much more static pressure than any bladed fan ever thought of.

You can check out www.mcmaster.com , that's where I got my 105 cfm blower from. I'd recommend a 115 volt one though, the 12 volt I have takes 4.4 amps and has claimed the life of one of my better psu's for accessories.
McMaster.com won't allow direct links because of jave scripting, so you'll have to hunt through their menu's. The part number on my blower isn't mcmaster's part number.

Oh, and it's $40

Happy hunting!
Necking down a centrifugal blower hurts the cfm but there are many form factor blowers available. Look here

The less you have to neck it down the better. There are many blowers in the 1 to 2 inch outlet range, but small outlets usually equate to small wheels and small cfm. Somewhere on that page is a good compromise between how much you have to neck down.


Thanx for the response guys.... I knew I was going to need something heavy duty. I'm still shopping around for some parts... I'm trying to spend less than $100 on this project.

Although really, its just an excuse to get some gear for watercooling, and a chance to expand my list of expensive hobbies.

If you're interested in the AC design I'm tinkering with....

Ambient air will get blown thru a 7/8 copper coil. The coil will be submerged in icey water, a 5 gallon hexagonal fishtank. The copper tube's terminal end will blow right into my cpu fan duct. I'll use pipe insulation on the part of the copper coil that's above water. I think condensation on the inside of the coil will be a problem after a while, so I'll drill a hole in it for a plug, so that I can drain it now and then.

The second stage involves a pump(Maxijet 1200) and a second reservoir kept in the icebox of a minifridge. This will chill the water in the fishtank, and help keep the ice from melting so fast. This whole apparatus will exist outside of my pc's case and will be independent of my pc's psu.

I also plan on dyeing the water with the insides of a few highlighters so it will glow in blacklight.

I don't know if it will work at all... But if I can move air thru the submerged copper coil, it should get cooler than ambient. The fishtank will be right next to my pc, so the air won't have much of a chance to heat back up. I'll put a basin under the fishtank since it'll probably sweat onto my desk if I don't. I think having an ice-cold aquarium next to my pc will probably reduce the ambient temps slightly anyway.

Any comments are welcome...

The original thread where I posted and revised the design is Titled "Ice Water Bong for Air Cooling". Now I refer to it as the Cheapo-chill fishtank AC.
That tubing is going to dehumidify the air passing through it big time. The moisture in the air will condense in the tube as you suspect and it'll probably be enough water to choke the tube off in a matter of hours. Then if you have enough blower power the water may blow out of the tubing onto your CPU and the surrounding area. You have designed a small scale dehumidifier.


Yep, I haven't started this project except in theory, but I was going to make the coil into a double spiral. I want to bend a trap into the end of it. Maybe a small hole or three drilled into the trap will allow that condensed water to drain out without compromising the pressure of the system too much. I'll also probably use a foam filter to catch any stray droplets. Once it is built, I'll use it very cautiously... maybe only for short periods, and only when I'm sitting at the pc. It should sound like a bong when it starts to choke ;)

Another note, it's pretty dry here in the summer.

Its for fun, ya know. And I'll probably canabalize the parts or rebuild it into an H20 setup eventually.

I appreciate your input very much.
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I'm not too sure on this, but it sounds to me like you are not going to get a lot of air flow through that tube (even when its not full of water :))

As an option, have you considered pumping cold water through the tube from the tank to the duct, and then blowing air over the coil (or maybe a small rad) into the duct?

Actually if I get a small radiator I might try that. I might not even need a fan if I stuck it in front of my cpu's side panel duct, or I could use a small room fan. The fans in my side panel would suck the coolness from the radiator... if indeed it could transfer enough coolness into the air.
Highlighters sound a little messy, other sources of flourescent dye, might be tracer dye, used for tracing underground streams and stuff, and sources of pollution, don't know where to get it though really. That's flourescent.

Also there's flourescent marker dye for using in the sea or water when you're shipwrecked, should be able to get that from boating stores.

I guess those professional graphic arts highlighters with liquid ink reservoirs wouldn't be so bad though.

Road Warrior
UV dyes

Good suggestions... if I ever get back into pollution testing thru school, I'll try to get a hold of some UV dyes. I could ask my old high school chem teacher tool.