[Guide] Air Flow & Pressures

Positive or Negative?

  • Positive

    Votes: 7 100.0%
  • Negative

    Votes: 0 0.0%

  • Total voters
    7

Wraith

Bettyswollocks
Introduction.
Welcome to the OC3D Case Air flow & Fan setup Guide, the idea with this guide is to enlighten you in the correct ways to setup the cooling system within your case environment to achieve the optimal running conditions for your hardware, within this guide we’ll be taking a look at selecting your fans and educating you in the types of air pressure that have different profound effects on cooling performance and throwing in some build advice for good measure.

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Fans.
We’ll kick this off with fans, the obvious place to get started really as they are the only way you’ll be moving air through your case. When choosing your fans you have a multitude of boxes to tick, size, style, colour, RPM (rotations per minute), CFM (cubic feet per minute), noise, voltages. We won’t be focusing on the aesthetics of fans in this guide just the functionality as that is all we’re really interested in, namely the size, rpm and cfm, these are the only important factors when providing the cooling for our cases.

Sizes, PC case fans vary in size a lot but I’ll stick with the 4 main sizes which include, 80mm, 120mm, 140, and 200mm, the latter 200mm fans luckily are not seen that often and tend to be somewhat a novelty item which come factory fitted in some cases, as far as cooling efficiency goes these are pretty lacking in the performance department and generally most enthusiasts swap them out for either 120mm or 140mm fans, on the other hand we have the 80mm fan, you don’t see many these days but they are still used for instance in small ITX builds and and rack mount servers, they were quite popular in the 90s and early 2000 as not many consumer cases back then had 120/140mm fan mounting options especially for rear exhausts, for their size though they do move quite a good amount of air but they are quite noisy. Moving onto the most popular fans for case cooling we have the 120 and 140mm fans, over the last decade we have seen quite the advancement in performance and effectiveness of fans also with this the ever increasing popularity of AIO (all in one) water cooling solutions and custom loops, which born a new breed of fan, the static pressure fan specifically used for the cooling of radiators.

RPM, in lamens terms it’s the speed at which the fan rotates (rotations per minute) the slower the fan the less air is moved and also they remain quieter, adversely the faster a fan spins the louder it will become, what you will find amongst enthusiasts is that they will trial many different fans before settling on a certain setup, now what they are looking for is a fine balance between air flow, acceptable noise levels and temperatures whilst still maintaining their optimal case air pressure. I won’t be going into every possible combination of case and fan setup but the rest of the guys within the community will give their opinion and even show you how they do it, just ask they don’t bite ?.

CFM, The cubic feet per minute of a fan is the amount of air that a fan can move in 60 seconds, for example a 44CFM fan will at full speed move 44 cubic feet of air in 60 seconds. Quite simple eh? Yes it is but we don’t like simple so here we’ll throw a spanner in the works, chances are that your fans are making you deaf running at full speed so you’ll want to turn them down.. You can do this a number of ways, either with a dedicated controller, inline resistors or via the bios or 3rd party software controlled fan curve, but that inherently adds another problem.. your airflow is going to take a hit, so pay attention and do a little simple maths to roughly calculate what you have going into your case and what you have exiting.

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Dust & Air Quality.
Now this is where we get down right dirty, and I mean dirty… it matters not how much you clean and hoover around, dust is dust, it’s simply everywhere and unfortunately unavoidable over the space of a week you will notice it, just glance at a sun shaft blazing through your window and you’ll see it invading your precious air just ready to infect and pollute your pristine rig, so with this in mind you should consider upgrading or adding extra dust filters to your system as well as maintaining your usual cleaning routines, your rig will thank you for it and ensure you have good clean air passing through your PC. ;)


Pressures.
This is where we get to the nitty gritty of our subject, which is best? and how do I achieve a set pressure type, firstly we need to open your imagination a little, think of your case as an air tight box with holes cut out for your fans.. got it? Good!. Right, in this air tight box we have all your precious components generating heat and need to be cooled so firstly we need a source of nice cool clean air "Intake" and after that somewhere for the air to escape from or "Exhaust", now that we have that little mental image lets talk pressures.

Positive Air Pressure.
Positive air pressure is simply thought of as More air in than going out or a resistive push flow, now this can be achieved by either having more fans as intakes or higher effective CFM than the exhausts have. This is widely thought of as the one to aim for, but as with everything there are small drawbacks i.e over time cooling performance may drop slightly, this could be due in part to stagnant air build up as your not exhausting all the air your pushing in. On the other hand it is the more dust friendly option as your intakes are filtered (or should be).

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Negative Air Pressure.
Negative air pressure is simply thought of as More air out than going in, or a pulled flow. This option is the polar opposite to positive pressure in the fact your exhausting more air than the intakes can deliver, again by way of either more exhaust fans or higher exhaust CFM. Now remember our imaginary air tight box? Now look at your PC, notice the fault in this?, that's right your case is not air tight and has panel gaps, mesh and those little nooks and crannies open to the elements, now with negative pressure setups this is how the dirty dust gets in, it is essentially sucked in through those gaps and delivered right to your hardware this being the main drawback of this configuration.

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Conclusion.

In conclusion well there is no real conclusion it is all down to you and what you and your hardware prefer, I will say that while this explains the differing air cooling configurations, there are one or two other things to take on board that have been missed and that is PSU placement, GPU cooling and the ever questionable side panel fans, with the PSU, which way round you place it is up to you either way will exhaust just fine although it will add to your pressure situation should you have it fan facing upwards. GPUs are a pain again when it comes to cooling, the vast majority of reference models will exhaust their own heat out the case (blower style) and non reference cards will simply radiate heat throughout your rig and thus you'll rely on your case fans to do the heat extraction.

Now the question regarding side panel fans, these to me serve no real purpose and are generally a hindrance especially to the normal direct flow of air through your case, but that said during those hot summer months I have on occasion used one to help extract warm air from the GPU area as that is generally and roughly were they are positioned.

So to wrap this up, positive or negative the choice is yours... but now you know. ;)

Any questions? throw them at the thread hell even show us your setup.

~Wraithguard~​
 
Well if you have two high airflow fans as front intake and 2 high pressure fans as an out-take on the roof (on a rad) or two/three HP fans on the cpu cooler tower shouldn't that balance things out. The psu shouldn't be a factor since most quality ones have a zero rpm mode and rarely suck that much air, and there's always (almost) the option to have them suck air from the bottom, which for some people isn't the best thing aesthetics wise.
 
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