Optimal Fan Placement and Direction for Air-Cooling a Computer


My current computer has always run unusually hot no matter what steps I have taken such as: lots of fans—including four 120mms; thermal grease—both generic and Arctic Silver V; placement of the system—ie on top of a desk hutch in open air; etc.

My case came with an 80mm fan hole in the center of the side panel. I tried putting a fan there both blowing in and blowing out, but neither had much effect. I tried putting a 120mm fan just over the CPU, but again little effect. I even tried putting four 120mm fans on the side of the case with no effect (other than lots of noise). I also tried using a new PSU with a 120mm fan built in right over the CPU; again little effect. I cut a 120mm hole in the top of the case and put a fan blowing out there and that seems to have had the most effect of everything that I have tried. So now I am looking for information on fan placement and direction.

Unfortunately I am having trouble finding information on optimizing the actual placement and direction of fans in a computer case. Where can I find practical information on what fans (eg size) to put on what parts of the case, and in which direction to have them blowing. That is, not-too-technical thermodynamic/aerodynamic/fluid-dynamic tips for air-cooling a computer.

Thanks a lot.

Edit – To address some questions:

  1. The CPU used to run between 45-60°C (I actually had to set the BIOS CPU throttling to 70°C in the summer).

  2. I am aware of the whole airflow concept for computers (in one side, out the other). However, none of the configurations I had tried had given good results; I have even tried taking all of the panels off of the case and leaving the motherboard in free, open air without success. Which is why I asked for specific help.

  3. I do clean out the dust and oil the fans now and then.

  4. My case is the main problem since it has specific fan holes built in, which reduces the places that I can put fans (at least without cutting it up). For example, the rear has a metal panel that has an 80mm and a 60mm fan hole, that’s all. There is a double-80mm fan hole at the front-bottom of the metal panel of the case, but it is covered by the plastic bezel with the power and reset buttons, so it is completely blocked off.

  5. I have already maximized the space inside the case by using rounded cables, running wires along the edges, and putting my expansion cards and drives in a configuration that leaves as much central space as possible.

Best Answer

This is a rather interesting article on the subject.

It was our assumption that the tests with ALL the fans in operation would produce the best results but it didn’t. Time to idle represents how effectively the configuration removes heat from the PC case. The shorter the time the better. CPU peak and idle as well as System peak and idle are easy to interpret. We would like to think that System temperature represents an average of how cool every component in a PC is.

  • The top and rear exhaust produced the best CPU and System results but nearly placed last for time to idle. We tested three times for this result as we didn’t believe the first two.
  • A single rear exhaust fan produces the best results overall. This flushes the theory of more is better right out the door.
  • A top only or top and front combination places in the middle of the pack for CPU and System peak cooling BUT does whisk away the heat in a very short amount of time.
  • Even with no cooling fans besides the heatink…heatsink size and type of fan can deliver good results.

So there you have it. A few theories dashed upon the rock perhaps. At least for this type of PC case and components. What should be taken away from this? Quite simply that more may not necessarily be better but, for us enthusiasts, more may be cool…for looks.

Related Question