EggXpert

Well, people, the third installment of my series is about a week overdue, as work and family and weddings have to take precedence over you (I know, I'm sorry).  Now that I'm back (well, back with sufficient time to get my thoughts in order), I'm going to discuss Case Airflow and Cooling, as was requested earlier.  I know many people have probably written what I have before, but my goal is to write it for everyone to understand, in an organized, intelligent fashion that can be used as a learning tool so perhaps you won't have to keep referencing my post every time you want to remember how to fix up your case all nice. :)

That was a rather long paragraph, looking at it.  Well, without further ado, here's my lesson on Case Airflow Techniques:

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This is a great reference for pre-buying builds, to help you plan out your system smarter and cooler, but can also be applied to pre-existing builds quite universally, although there may be few exceptions (as there always are with any rule).

Every case that you look at will have holes in some form or another.  Holes are good for your case.  They let air in, they let air out - but holes in-and-of themselves aren't much use to us (although they will come into play later).  What these holes need are fans. I don't care how fancy your build is, cooling starts with the fans.  If you don't have your fans organised correctly, you can really screw up your build, as heat is the number one offender when it comes to killing computers.

So, there are three (actually two) categories your case can fit into.  The one that I'm excluding here is 'balanced', which means the air your fans take out and the air your fans take in is balanced.  This is rarely achieved, and not necessarily optimal, so I will not cover it here (I might hit on it at the end...).  The other categories include 'Positive' and 'Negative' Airflow.  Well, you might ask, How do I tell which category my build falls into?  Dear and faithful reader, it is quite simple!  Let me set it up for you.

Intake - Exhaust = Airflow

But that's not all!  You can't simply add up the number of fans and try to do the math!!  No!  It might be simple, but it can't be that simple (sorry).  Each fan has a CFM (cubic feet / minute).  This specification is how much airflow the actual fan can do (optimally).  This is what you must plug in for your true Airflow number (The actual number of fans and size of fans doesn't matter - only the total CFM in, and total CFM out).

That's it!  You can either have a positive Airflow, when your intake CFM outnumbers your exhaust, or a negative Airflow, when your exhaust CFM outnumbers your intake.

So now you fall into one of two categories, positive or negative.  Which one's better?  Which one do I want to be in?

I can tell you that it's not negative.  Let me explain.  When your case fans intake less air than they push out, we get a sort of vacuum.  And vacuums suck. (Sorry, I don't know if that bad pun was avoidable or not - but, yes, I went there. :P)  If your case Airflow is negative, your exhaust fans will draw air from every slit and slot in your case possible.  This includes not only your spare, unused intake/exhaust holes, but also your 5.25" drives, any uncovered PCI/PCIe/AGP slots in the rear of your case, your 3.5" floppy (if you have one), and even unused USB and Firewire ports.  So, even if you have nice little filters on all your fans, you could still get all sorts of dust in your computer (so that's how it happens!...).  And if this extra intake is still not enough, the vacuum created can overheat your components.  No moving air - no whisked away heat from heatsinks as well as no whisked away heat from direct contact with components.  This includes your RAM, your PSU, your CPU, your GPU, and all those other 3-letter acronyms/abbreviations that geeks like to use.  Not such a good position.

On the other hand, you have different fingers.  Likewise, on the other end of the Airflow spectrum, you have Positive airflow.  Positive is good!  This means that your case is taking in more air than it can expel (forcibly, at least).  Cool air comes in, air blows out, and you get a good mix inside your case.  If any extra 'stale' air can't be pulled out by the exhaust fans, it will find its way out naturally, via spare exhaust holes, or the bad-intake list presented earlier.  It's not bad for air to go out this way, as it won't bring more dust into your case. :)

Also, recently, more and more cases are being built with air ducts on the side panel.  Though they may not look savoury (especially in clear or windowed cases), they do help immensely in providing fresh air for your processor if it needs it.  And, well, if it doesn't need it, it doesn't hurt the case at all, so it's win-win. :)

Another thing you'll have to look at is, what is in your case that can obstruct airflow.  The most common response will be - IDE cables!  These things will kill the airflow from permeating your entire case, and there are two ways to correct this problem.

   1. This way is probably the best way for upcoming builds, but might not work for older computers that are being fixed up - SATA.  Serial ATA cables are much, much smaller than Parallel ATA (IDE) cables.  Make sure your mobo and components are set up for SATA - it's actually pretty comparable in price anymore.
   2. This way is for those looking to save a handful of change, or those refurbishing older systems, etc.:  Take two of the little zip tie things.  Roll up your IDE cable as best you can, and put one zip at the top (by the device) and one zip at the bottom (by the motherboard).  This will get most of the width of the cable out of the way, and is more aerodynamic, for better airflow.

As a general rule, fans in the front should blow in (intake), fans in the back should blow out (exhaust), and air ducts and holes in the sides of the case should be left free to naturally balance the air pressure.

Check your CFM, check the dimensions of the fans to ensure they'll fit where you want them to go, and make sure you have enough power to run them all in addition to everything else you people jam in your cases. ;)  Follow these rules, and your build will last you well into the future, and make you very happy in doing so. :)

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Any other questions/comments, please post below. :)  Thanks for reading, and watch your arms and legs as you exit the ride.

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