Radiator airflow using negative pressure

The alternative to direct air cooling

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Radiator airflow using negative pressure

Post by johan851 » Wed Jan 06, 2010 5:14 pm

I've been thinking about changing my case for a while (and possibly ditching watercooling). Right now I have a SLK3000B with an MG Metro (car) radiator bolted to the side. There are three low speed Yate Loons at about 7v on the radiator and another two inside the case. The (extremely loud) hard drives became less annoying when I soft mounted them, but the case is still a little loud. The biggest hassle is trying to move the thing around - it's very heavy and awkward, and all of the exposed radiator fins are a bit fragile.

I was thinking of moving to mATX and going to air, but I also liked the looks of the Antec 300, which has almost exactly the same dimensions as the case I have. I hesitate going to air cooling because I like my overclocking, and it's hard to resist the urge to tweak. And I know watercooling can be quieter.

I figured a 2x120mm radiator might fit in the front of the Antec 300, and I found a person who has done this rather nicely: http://www.techpowerup.com/gallery/details.php?id=2124

The problem with radiators is always the pressure needed to push air through them as well as the fan hubs and other dead spots. The real question of this post is this: do you think an Antec 300 with a quiet 120mm and 140mm fan at the top rear would provide enough negative pressure to pull air through a radiator at the front, assuming the rest of the case is sealed? Would that be a quiet setup?
[size=75]Asus P5K|Intel E2160|4GB DDR2|HD 4670|3x 7200.10|Seasonic S12 600w|SLK3000B[/size]

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Post by 1398342003 » Sun Feb 07, 2010 9:07 pm

Fan dead zone has an effect, but not an extremely large one. You could consider having the fans blow out the front instead of in, and use the side panel 120mm fan hole as the intake vent.

The Thermochill 120.2 is designed to run very well with low speed/pressure fans, I'd recommend it.

Assuming that you have the 120.2 and all other holes sealed (difficult but possible) then you may succeed. No guarantees.

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Post by jonj678 » Mon Mar 08, 2010 10:33 pm

The OP is suggesting a sealed case, where the fans are mounted at the top, rear corner of the case and the radiator is some distance away. As such you mentioning dead spots it completely irrelevant. Were he mounting fans directly onto the radiators, the performance improvement from using shrouds is considerable, and again, you'd be incorrect.

Your suggested setup would be very quiet. Effective cooling would be heavily dependent on successfully sealing the case, if you're using a normal psu then this exhausting is good and useful. If it's a passive one then you need to keep a close eye on how hot it's running for a while. Internal air temperatures will be quite high as you're blowing all the waste heat through the case before you remove it.

What are you cooling, and what temperatures do you want to maintain? I'm not aware of any relevant test data but in terms of establishing uniform airflow through the radiator you couldn't do it any better, performance should be pretty close to what the radiator would produce with two 1600rpm fans attached on the basis that the fans are further away, so more effective, one's a 140mm, and it's probably supplemented by the psu. So I'd guess performance would be 0.04C/W, but there's a fairly big error margin on that. Interested to see your results.

The antec 300 is a nasty, flimsy thing. Prone to resonance and full of holes. Are you sure this is the one you want?

I believe you will see very good results from this arrangement in terms of noise, as long as you can keep the case sealed. Overclocking will take a hit as the motherboard is now bathed in warm air. Overclocking and silence are always somewhat at odds to each other though, so I doubt that surprises you.

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Post by 1398342003 » Tue Mar 09, 2010 12:42 am

I realize what the OP is saying, I just wanted to clarify it a bit for him. My point being that the dead spots, even when the are an issue, are not a large issue.

I don't agree that the setup has very good potential. It does have some ability, but the combination of all of the exhaust heat being pulled into the case and the need for complete sealing are it's failings. The PSU fan will spin faster than necessary and sealing any case is a nightmare alone.

I thought my previous post was larger and more detialed. Hmm... anyways, another solution is to get a case with a rear 120mm fan and top 120mm fan, and attach single fan PA120.1 radiators on the inside of the case where the fans would normally go. Then place the fans (with shrouds if you want) sucking air through the radiators.

A simiar plan will work on a case with a pair of 120mm mounts on the top, but there you could use a PA120.2.

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Post by Bat » Sun Mar 14, 2010 4:51 am

How about trying it with your existing case and radiator, to start with?
Take the fans off the radiator and use case exhaust fans to suck air through the radiator into the case.

Or you could turn the fans round: positive pressure would give similar water temperatures with cooler in-case air temperatures.

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