This article is the second instalment of the airflow guide, giving more in-depth considerations for achieving optimal airflow. It covers the correct choice of fans, other components, the number of fans and more information on case pressure.
Picking the right (number of) fans
To select suitable fans, the following questions should be asked:
- Does my chassis have either a mesh panel, or a completely open front?
- Does my chassis have relatively open dust filters with low airflow resistance?
- Does my chassis have fan slots opposite to each other (front-back or bottom-top) to aid in maintaining a continuous stream of air through the entire chassis?
If you answered one or more question with “no”, that suggests that airflow might be restricted. This applies in closed, “silent” or “soundproofed” chassis, or ones with tight dust filters etc., you might want to consider using more fans, fan models from the higher end of the performance spectrum, and/or running your fans at a higher rotational speed.
The ingredients for good airflow
Several factors influence the airflow within a chassis.
Firstly, the space that your other components, mainly the GPU, claim, should be considered. If you are using a larger (over 300mm in length and/or 3+ slots in thickness) GPU model, like some of the NVIDIA 40 series cards, you might have a harder time cooling it in some, especially smaller chassis. In this case, a chassis which allows intake fans to be mounted at the bottom of the chassis supplying fresh air to the graphic's card, and a mesh side panel, or even fans on the side, can benefit the GPU greatly.
Considering fans and their setup, two key factors should be addressed: selecting an appropriate number of fans and placing them optimally within the chassis.
As mentioned previously, the right number of fans depends entirely on the chassis you are using. Furthermore, the budget you allocate for fans plays a critical role. If you are working with a more sensitive budget, our redux line of fans is a great choice. Furthermore, this means taking an even more delicate approach to placement, since the number of fans might be smaller.
From here on out, we will be using the Fractal Design North as an example, since it offers a great combination of sufficient fan slots, types of dust filters, and a mesh panel on the top (or side). The principles applied in our choice can, of course, be extrapolated to other cases. Using the following checklist, you can make sure that your case is well suited to support good airflow:
- A (generally) open front panel (e.g. a coarse mesh without dust filters or with minimally restrictive ones). Even though glass or closed front panels might be aesthetically appealing, these are immensely restrictive and are the main contributors to high case temperatures.
- When examining the dust filters more closely, the density of those, as well as the distance to potential fans, is important. Even though a tight mesh can stop dust from entering the case, it can clog a lot easier, and, following that, provide much more resistance to air entering the case. You can test the dust filters' resistance by blowing through them and feeling the difference in the air moved with and without the dust filter.
- The number of fan slots is important as well. We generally recommend a total of at least five 120mm fan slots in a standard mid-tower case. This does not mean that all of them must be populated, but the presence of a fan slot means two things: Firstly, it gives you the opportunity to add more fans in the future if necessary. Secondly, a fan slot means an additional space that air can freely move through.
When working with a small number, for example, three fans, the placement is very straightforward. Two in the front (top and middle) as intake and one in the back as exhaust will be sufficient for hardware that does not produce large amounts of heat.
With an additional fan, four in total, the possible combinations of fans, and whether to use them as intake or exhaust, become more, but not more complicated. Basically, two possibilities are favourable here. Either three in the front as intake, populating all three fan slots, and one in the rear as exhaust. Alternatively, you could place two in the top two fan slots in the front as intake, one in the top rear spot as exhaust, and one in the back as exhaust. The second option is more focussed on CPU cooling, as the front fans direct air more directly to the CPU heat sink, and the exhaust fans pull air directly away from it.
If you want to use five fans, there are multiple different ways to install them, depending on your preferences regarding CPU and GPU cooling. We concluded in our testing of this particular chassis, that the lowest average temperature between the CPU, GPU, and chassis can be achieved by doing the following: three in the front as intake, one in the top as intake combined with an NA-IS1-12 inlet spacer, and one in the back as exhaust. This once again supplies a large amount of fresh air to the CPU heat sink, especially with the top fan pushing air directly to the front CPU heat sink fan and exhausting the hot air instantly through the back. Moreover, the GPU benefits from this configuration, as the bottom front fan is constantly directing air to it.
At last, six fans are the optimum in this chassis. This configuration may seem unconventional for some, as it disregards one of the rules mentioned in the first part of this guide (namely that you shouldn’t mix intake and exhaust fans on one face of the case), but in our testing, the setup that performed best uses two differently oriented fans on the top, the front one as intake with an NA-IS1-12 inlet spacer and the back one as exhaust. All other fans (front and rear) can be adopted from the five-fan configuration.
Influencing pressure in the chassis
The primary way, chassis modding aside, to control case pressure is the ratio of intake to exhaust fans. Generally speaking, a difference of one or two fans between intake and exhaust is enough to influence the pressure inside the chassis. So, to use our example chassis, the preceding configurations show the positive pressure configuration that we deemed to be advantageous.
Another, or the next, step that can be taken is to adjust the fan speed. In an extreme scenario, this can be the determining factor whether a chassis displays the behaviour of a positive or negative pressure situation. For example, if there are two intake fans and two exhaust fans present in the chassis, you can adjust the fan speeds to either create positive (intake faster than exhaust) or negative (exhaust faster than intake) pressure.