Could decasing a fan make it work better?

mathias · Post by **mathias** » Fri Nov 19, 2004 7:00 pm

How would a fan push air if it was modified similarly to a fan used with a CNPS7000, except maybe keeping two corners for mounting? I'd expect that if it's blowing air both forward and to the sides, it would pull air more. Of course this wouldn't work for exhaust case fans, unless mounted outside the case.

Trip · Post by **Trip** » Fri Nov 19, 2004 8:19 pm

I imagine an external fan sucking through an air hole would pull more air than an internal fan blowing through the air hole.

mathias · Post by **mathias** » Sat Nov 20, 2004 8:22 pm

I'm told it won't work, but I think I'll go ahead and try something like this with a ZMF1 I won't need when I get an antec 3700AMB.

For a CPU fan, I think I'll cut out two sides, the ones facing the case fan and PSU, and the corner between them, so that it blows some air in those directions.

mathias · Post by **mathias** » Sat Dec 04, 2004 12:58 pm

I've tried it, and it doesn't seem to work. I removed one side of a crappy thermaltake adjustable fan, and I could hardly feel any airflow there. Putting a strip of paper there seems to indicate that it was actually pulling air in from that direction a bit.

inet · Post by **inet** » Sat Dec 04, 2004 4:56 pm

I was actually thinking of exactly the same thing this morning when I couldnt sleep. Actually it was for a CPU fan, but I've decided anything that spins even remotely close to 1000 times per min probably has a frame for a reason.

So that it doesnt fly off and blind someone for example

lenny · Post by **lenny** » Sat Dec 04, 2004 9:48 pm

Just guessing here - maybe the frame helps guide the air out the exhaust end of the fan, otherwise air would exhaust along the sides as well?

The Zalman CNPS7000 fan does not have a frame. And seems to cool very well.

Another reason for the frame - so that you can mount it

mathias · Post by **mathias** » Sat Dec 04, 2004 9:58 pm

lenny wrote:Just guessing here - maybe the frame helps guide the air out the exhaust end of the fan, otherwise air would exhaust along the sides as well?

That's what I asumed, that was the point of this, but it seems to take air in from there.

I'm assuming a fan that exhausts to the sides also would require differently shaped fins, an intermediate design between a regular fan and the kind on vga/nv/ati silencers.

powergyoza · Post by **powergyoza** » Mon Dec 06, 2004 4:42 am

I tried it before and it did not work at all. Terrible cooling performance for conventional heatsinks like my old AX-7. I nearly fried my CPUs.

Trip · Post by **Trip** » Mon Dec 06, 2004 8:08 pm

oh, duh, i misunderstood the first post somehow...

ONEshot · Post by **ONEshot** » Mon Dec 06, 2004 8:27 pm

I believe the new Arctic Silencer Heatsinks do that. I guess they must have a reason to do that.

mathias · Post by **mathias** » Mon Dec 06, 2004 8:52 pm

ONEshot wrote:I believe the new Arctic Silencer Heatsinks do that. I guess they must have a reason to do that.

You mean the "freezer" heatpipe towers? I think the blades on those or maybe some of the regular arctic cooling heatsinks seemed oddly shaped, I guess to work better without the frame, and they all have 5 blades only.

lenny · Post by **lenny** » Mon Dec 06, 2004 9:28 pm

powergyoza wrote:I tried it before and it did not work at all. Terrible cooling performance for conventional heatsinks like my old AX-7. I nearly fried my CPUs.

Guessing that you tried it in blow mode. Maybe it'll work better in suck mode vs. the same fan in a case in suck mode?

Actually, now that I thought about it a little more, that may not be true. In a regular fan in suck mode, the exhaust (hot) air will be blown away from the HSF. In a decased fan, the hot air might get recirculated more easily.

cpemma · Post by **cpemma** » Sun Dec 12, 2004 12:52 pm

The venturi profile of the surrounding tube will increase the pressure of the fan, so remove some of the tube and you'll need a very free-flow case for cfm not to drop off IMO.