The Thermal Design and Fan Choices

Before going into the fan choices, there are a number of design issues to be considered, but these depend on the components to be used. Several things are sure, even at this moment in the build. CPU and a third party CPU cooler, whether that is a Noctua cooler or another brand, a nVidia GTX 68x video card, which is a 2.5 or even 3 slot card, and an Areca raid controller card. For audio the on-board capabilities will be used, so no extra sound card. In my workflow and with my material there is no need for an AJA, Black Magic or Matrox card, especially with the four monitor support on the Kepler cards. So this means quite simply only a video card and a raid controller in the system.

This is very important to know, because with the video card blowing out the hot air at the back and a number of open PCIe slots at the back as well, it simply means you need to have at least a balanced air pressure or a positive air pressure, but never a negative air pressure. You may wonder what I mean by that. A balanced air pressure is an airflow where the amount of incoming air into the case is about equal to the amount of air blown out of the case. A negative air pressure means there is more air being blown out of the case than the intake fans deliver and reversely a positive air pressure is where the intake fans suck in more air than the exhaust fans blow out of the case.

With only two PCIe cards installed in the system it is necessary to use at least balanced air pressure or better positive air pressure, because then the cooling of the video card is not hampered by the air coming in through the open slots in the case of negative air pressure.

Water cooling is quiet and the lower the noise from the PC the better. Well, I'm not going to dispute that, it is a sound(less) idea, but there are some drawbacks about water cooling and the major drawback, often overlooked by many is that the radiators need fans to dissipate the heat and the fans are the noise creators in the first place. A second thing often overlooked is that the radiators operate in the same ambient temperature as air-cooled systems, so they have no advantage there. Let's try to put the pro's and con's of watercooling versus air in perspective:

Pro's of water cooling:

  • It saves the sound of at least one fan on the CPU cooler, possibly two in a push-pull configuration.
  • It saves the sound of the video card fan, if there is a cooling block available for the video card in use.

Con's of water cooling:

  • It is far more expensive than air cooling and not much better.
  • It still requires fans for the radiator(s), negating the advantage of no CPU or video fan.
  • It adds the sound of the pump.
  • It is a difficult and time consuming job to install and requires more maintenance than air cooling.
  • It requires a large chassis, or external housing and the clutter that brings.

The major noisemakers in a system are the mechanical parts, fans and conventional disks. With increasing numbers of disks the benefits of water cooling diminish, because the disks all make noise and there does not exist a cooling block for disks, so fans are still required there.

With a closed video card that outputs hot air at the back and a number of empty PCIe slots, I want at least balanced air pressure, but prefer positive air pressure. So that means I have to calculate the amount of cool air going into the case (measured in CFM, cubic feet per minute) and the amount the exhaust fans can displace and take into consideration the intake filters that will prevent dust and debris to accumulate on the fans and thus reduce the intake air flow.

The exhaust airflow on the mobo side is 3 x 46.9 = 140.7 CFM out the front from the Chenbro disk cages and the exhaust airflow from the video card (don't know yet how much that is) which is estimated at another 40 to 45 CFM, so in total there is an airflow being sucked out of the case of around 180 to 185 CFM. But we need to add to that the airflow from the CPU cooler, the Noctua NH-D14 Special Edition in push-pull configuration, and the exhaust fan on the back of the case, so we need to add about 75 CFM, bringing the total up to around 260 CFM.

Looking at these requirements and fans available, I ended up with 5 fans on the motherboard side of the case, 4 for intake at 75 CFM each, giving a total of 300 CFM pushed into the case, and one exhaust fan on the back of the case in addition to the ones mentioned already. That gives a nice positive air pressure on this side of the case. I again had to change my initial selection and have opted for the Zalman ZM-F3BL fans, because of the high CFM rating and the low noise level. I will not use the LEDs, but that is what they come with. I hate a badly designed Christmas tree under my desk.

Things are of course a lot easier with the Magnum TH10 case in comparison to a standard case, because of the divided case, a mobo side that contains only mobo, CPU, cards and disks and on the other side the PSU, that only contains the PSU and disks, so the heat sources are nicely distributed.

For the PSU side I opted for 4 intake Noctua NF-P12 fans and 2 exhaust fans, giving me 4 x 54 = 216 CFM intake and 108 CFM exhaust air flow, plus the airflow from the PSU, so again a positive air pressure. The reason is simply to keep the noise level down, so the Noctua felt the best option.

Keep in mind that you will need to filter all intake fans and clean those filters regularly. If fans get dirty, they have to work harder, the bearings will suffer, create more noise and the cooling performance goes down. That is the reason I'm looking into Demciflex filters for all the intake fans. However the Magnum case is not magnetic, so I have to request the custom models with the Xtra Magnet.

Here the Zalman fans are installed. From an aesthetic point of view, black silicon pins would have been nicer than these white silicon pins, but a black marker can do miracles and now at least I know there is no noise from vibrations. Keep in mind that the fan frame, the four supports that keep the fan together are always on the exhaust side of the fan.

Another way to find the correct intake or exhaust direction of a fan is to look for the air-flow direction arrows on the fan housing.

A nice thing to notice in this case is that the position of the fan mount can be adjusted very easily. You can place it higher or lower in increments of 12mm to exactly cool where you need it most. There is a margin of around 84mm available to position it higher or lower, otherwise the mesh opening in the hinged door will obstruct the airflow.

DemciFlex has been asked to make custom intake filters for these side mounted fans. I just sent them the exact dimensions and the same for the front intake filter, which is a bit more complicated because of the panel in the middle. Meanwhile the Noctua fans have arrived and have been installed.

Here are the drawings DemciFilter made for me for the custom filters for both the side-intake filters and the front filters. When I receive them I will add pictures of them.

The DemciFlex custom made filters have arrived. This is what it looks like on the front side, from the inside of the front cover. It is very fine mesh, easy to remove from the magnetic fastener for cleaning.

For the front fans I put the dust filter on the inside of the front cover, because the fans are in fixed positions, but for the side fans I put the dust filter right over the fans, to allow for placing the fans in a different position and still keeping the air filter in front of the intake fans.

The choice of the CPU cooler is most likely the Noctua NH-D14 SE2011. To mount this cooler on the CPU, I have opted for cooling paste from Coollaboratory, Liquid Ultra. There is one caveat with this cooling paste, it corrodes aluminium, so you better make sure that the flat surface of the cooler is completely copper. The cooling capabilities of this specific paste are extraordinary and way better than for instance OCZ Freeze Extreme.

Warning: If you are considering a much better affordable system, based on the Ivy Bridge processor, be warned that the cooling paste Intel uses on the Ivy Bridge is no good, especially when overclocking. At stock speed the i7-3770K runs 11 degrees hotter than with Liquid Ultra cooling paste and at 4.6GHz even 20 degrees centigrade. However if you change the cooling paste, you also void the warranty.