There are people who think that the more fans you have in the PC case, the better its thermal performance will be . However, the reality is quite different, and having too many fans can even be counterproductive, so below we tell you how many fans you need to have in your PC case to optimize airflow and thus maximize the internal cooling of the case.
Of course, each user will be limited in this regard with the fans that the box supports, since not all of them admit, for example, three fans on the front, and there are even those that do not even have holes to install fans in the ceiling. In any case, the important thing is to design in advance the air flow that you want your box to have, and that is where we are going to start.
Designing the airflow of the PC case
This really has more science than it may seem, and indeed we need to think about and design the airflow in the box to work optimally. We must bring in fresh air from the outside, and exhaust the hot air from the inside to the outside effectively. Since hot air tends to rise , ideally to maximize airflow, the fans that draw the hot air outside should be located above, while those that bring in the fresh air from outside should be located below.
The reason why hot air rises is because it is less dense than cold air, so by pure convection it will always be located at the top of the chassis, hence everything we are going to see below.
This is why the rear case fans are located high up, and generally in line with the processor heatsink, in order to vent the hot air out as quickly as possible. It should also be taken into account that graphics cards that are not blower-type heatsinks are the element that generates the most heat, which maximizes the importance of having a good rear fan.
In the following diagram you can see how an air flow would behave in ideal conditions in the case of a PC, with the fresh air that enters represented by blue arrows and the hot air that leaves, with red arrows.
So how many fans do you need?
The minimum number of fans you need in the case will depend on the type of heatsink you have. For example, if you have a tower-type heatsink like the one seen in the photo above, they will already be expelling hot air towards the rear grill, although it is true that the rear fan will be helping to evacuate the heat not only from the heatsink. but also from the graphics card.
Therefore, the ideal number of fans for adequate air flow is at least two: one at the front that draws cool air inside and one at the rear to draw warm air outside.
Of course, if we have more fans in front bringing in fresh air and if we add fans in the ceiling taking hot air out, we will be maximizing cooling. There is some discussion here on the inclusion in some chassis of a fan in the floor with the flow upwards. Formerly it was believed that this fan improved cooling, but the passage of tests has shown that it ends up breaking the flow of the front creating vortices, so we do not recommend it at all.
One thing you should keep in mind is that under no circumstances should you have the rear fan or the upper ones blowing air from the outside to the inside. As we discussed earlier, hot air tends to rise and this could even be counterproductive. Therefore, we recommend that the fans that blow in air should always be placed at the front and bottom of the case, while those that blow air should be placed behind and above .
