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All intake and no "dedicated" exhaust?!

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post #11 of 37 (permalink) Old 01-01-2012, 10:41 AM
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The key thing about my situation is the rear exhaust was intaking air about a two inches away from my Vemous X which had air being pushed over it. So the two fans were working directly against each other. I think other fans can be interchangeable but IMHO the read should always be an exhaust if your pulling air in the front. I might even switch the top fan on my HAF 932 round so it intakes and see if that helps my temps a degree.

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post #12 of 37 (permalink) Old 01-01-2012, 10:58 AM
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ehume has wriitten some good stuff about the question in the OP
"So, we want to be able to put air into the case. If we do it right our "positive pressure" will be just enough to move air in the case. We will want to bring in air from many directions to avoid spots of stagnant air that will heat up and warm our case contents.

We want to avoid negative pressure, since that turns our case into a vacuum cleaner with no bag and lots of little unfiltered places the air goes in. We end up with unending dust."
https://www.overclock.net/t/1041926/how-to-decide-on-a-case-for-air-cooling-warning-pics
he recommends only intake fans and free exhaust, which is the layout i have opted for as well

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post #13 of 37 (permalink) Old 01-01-2012, 11:07 AM
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You'll want a balance of intake and exhaust. Since you're going for positive pressure, I'd say run the side and bottom fans running a little faster than your exhausts. The exhausts should be at the top mostly, and one at the top rear, and the intakes at the bottom. If you have access to a smoking machine, use it to check the edges and holes of your case. the smoke should waft away slightly.

but if you don't have access to a smoke machine, a q-tip and a lighter will do in a pinch.
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post #14 of 37 (permalink) Old 01-01-2012, 12:38 PM
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I regularly run intake-only and it's fine, but you can't just turn fans around and magically have an effective positive pressure case. The cooling layout and case architecture needs to be orchestrated with some thought. The aforementioned guide/discussion with ehume is a good place to get some info.

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post #15 of 37 (permalink) Old 01-01-2012, 04:09 PM
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Actually fans pushing inward can deadhead if there isn't proper extraction of the air in the case. The fans have limited pressure capabilities. The case doesn't "ballon", the inlet fans simply stop forcing air properly into the case, which can cause over heating. That's why it's called deadheading.

There is a lot of false or misleading information online about positive and negative case pressures. You can have both postive and negative pressures and zero airflow. It's far better to pull the hot air out than to hope it finds it's way out by positive pressure only.

What a case needs is proper airflow to bring cool air in and evacuate the hot air. More fans does NOT equal better airflow. More fans may equal more turbulence and less heat removal from the case.

Even the use of smoke machines is often done improperly leading to false conclusions as I have observed with some online videos. This ain't rocket science people and some self-appointed experts even at the HSF companies get it wrong. Actual testing will tell you what works best for your specific PC case, hardware and environment.
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post #16 of 37 (permalink) Old 01-01-2012, 05:55 PM - Thread Starter
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Well im pretty sure my case is going to be hotter than your standard consumer case, the space for airflow just isn't there. Not only that but il but pulling air through a 360 rad meaning it will be heated as it enters the case anyways. This is where the idea of using the two 120mm fans up top as intake fans came in. There is a large 140mm grill on the side of the case that allows the sideways mounted psu to vent. I figure that if I force enough air in the case I can get it to force the air out. But I can see where you are coming from, Chances are I will just go back to my previous setup with the three rad fans as intake and the two top mounted fans as exhaust. The fans I have are rated for like 110cfm or something like that il probably run them a little slower on the rad tho so I dont saturate the case with warm air.

If you can imagine how much (or little) airflow my case will have as its only 17.5"h x 6.25"d x 15"l and its made of 1/8 3003 aluminum sheet, so the internal dims are a little smaller and its going to be packed pretty full with a full atx board, 2gpus, 360rad, pump, resi, and tubes.

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post #17 of 37 (permalink) Old 01-01-2012, 08:17 PM
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Quote:
Originally Posted by AMD4ME View Post

Actually fans pushing inward can deadhead if there isn't proper extraction of the air in the case. The fans have limited pressure capabilities. The case doesn't "ballon", the inlet fans simply stop forcing air properly into the case, which can cause over heating. That's why it's called deadheading.
There is a lot of false or misleading information online about positive and negative case pressures. You can have both postive and negative pressures and zero airflow. It's far better to pull the hot air out than to hope it finds it's way out by positive pressure only.
What a case needs is proper airflow to bring cool air in and evacuate the hot air. More fans does NOT equal better airflow. More fans may equal more turbulence and less heat removal from the case.
Even the use of smoke machines is often done improperly leading to false conclusions as I have observed with some online videos. This ain't rocket science people and some self-appointed experts even at the HSF companies get it wrong. Actual testing will tell you what works best for your specific PC case, hardware and environment.

no

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post #18 of 37 (permalink) Old 01-01-2012, 08:24 PM
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Quote:
Originally Posted by ihatelolcats View Post

no

People who have never studied gas flow or actually measured airflow like to argue even when their POV is proven to conflict with reality.

One scientific test is of more value than 1000 meritless opinions. That's why I recommend those who want to learn factual information regarding PC case airflow, perform tests on their specific hardware to see exactly what works for them and ignore the pointless debates by those who prefer to argue even when they have no technical understanding of the subject matter.
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post #19 of 37 (permalink) Old 01-01-2012, 08:34 PM
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Quote:
Originally Posted by AMD4ME View Post

Actually fans pushing inward can deadhead if there isn't proper extraction of the air in the case. The fans have limited pressure capabilities. The case doesn't "ballon", the inlet fans simply stop forcing air properly into the case, which can cause over heating. That's why it's called deadheading.
There is a lot of false or misleading information online about positive and negative case pressures. You can have both postive and negative pressures and zero airflow. It's far better to pull the hot air out than to hope it finds it's way out by positive pressure only.
What a case needs is proper airflow to bring cool air in and evacuate the hot air. More fans does NOT equal better airflow. More fans may equal more turbulence and less heat removal from the case.
Even the use of smoke machines is often done improperly leading to false conclusions as I have observed with some online videos. This ain't rocket science people and some self-appointed experts even at the HSF companies get it wrong. Actual testing will tell you what works best for your specific PC case, hardware and environment.

yes, if the case was entirely closed. modern case design has soooo many holes cut/drilled into the case where deadheading is extremely unlikely. especially considering most people neglect to compensate for the exhaust CFM demands of modern higher end GPU's. people often forget GPU's not only has HIGH static pressure, it also demand HIGH CFM when pushing hard. that amount of CFM demand can easily overwhelm typical stock case fans. although nowhere near the demand of GPU's, PSU exhaust fan is also another exhaust point people often overlook in their case pressure calculation. so as you can see, "deadheading" a modern case actually takes quite abit of CFM's before it even becomes a concern.
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post #20 of 37 (permalink) Old 01-01-2012, 08:46 PM
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Having holes in a case or a PSU exhaust fan does not prevent other fans from deadheading. Deadheading can occur for any number of reasons including excessive turbulence in the case from too many fans blowing inward - which is precisely my point why you need positive evacuation of the heat instead of just blowing hot air around inside the case and hoping that it finds a way out in a timely manner before it's temp increase reduces it's ability to continue to effectively cool the CPU/GPU. Without positive displacment air pumps, we are at the mercy of the fans static pressure capabilities vs. airflow resistance, not just case airflow potential.

As the OP found out you can also starve or cavitate a fan with two fans too close to each other. There are many considerations and each situation is unique. That is precisely why testing is required if you want factual data for your specific PC.
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