PC fans are one of the most important elements to achieve good cooling, and also to prevent heat from building up on the components and inside the chassis of a PC .
Nowadays, there are a wide variety of fans on the market that offer different features and have different prices, and it is important to highlight that they are no longer merely a functional element but have also become something that can greatly influence the aesthetics of our equipment.
It’s very easy to understand. Manufacturers are increasingly paying more attention to the design and aesthetics of fans because they are visible in most configurations, and in many cases they integrate customizable RGB LED lighting systems that allow them to better fit the aesthetics of different assemblies.
These lighting systems can also have a certain functional value. For example, manufacturers such as Corsair allow you to set temperature alarms that will make the fans’ lighting turn red if a certain temperature threshold is exceeded, and this lighting can also be used to create effects that improve immersion in games.
How PC fans work
A PC fan works in a very simple way, it spins to move the air in a specific direction. To differentiate where the air will move, we just have to look at it and identify the front face of the fan, which in most cases is where we will only see the blades, while on the back face there are usually small plastic lines that reinforce the structure of the fan casing.
This is important because the front of the fan indicates the area where the air enters, and the back is where it leaves. If we want to bring in cold air, we will have to place the fan with the front facing outwards, and the back facing towards the inside of the unit. On the other hand, if we want to take out hot air, what we have to do is place it the other way around, that is, with the front facing inwards and the back facing outwards.
To move air, fans can rotate their blades within a certain RPM (revolutions per minute) range. The higher the speed, the greater the airflow, but also the more noise and wear. That is why most manufacturers choose to find a balance between these values instead of maximizing the rotation speed.
However, it is important to note that not all fans perform equally well at the same RPM level, and that the size of the fan makes a significant difference, as this determines the amount of air it can move per minute , a value expressed in cubic meters per minute . So, for example, a 40 mm fan will not have the same surface area as a 120 mm or a 140 mm fan, and this means that it will not be able to move the same amount of air even if it spins faster.
A 140mm fan that spins at a slower speed will be able to move more air than a smaller one that spins at a faster speed. This represents an important value in terms of noise, as the former will also be quieter than the latter, and will have a greater cooling capacity.
140mm fans move more air and are quieter , so they are the best option for installing them in the front of the chassis to bring in cold air. On the other hand, 120mm fans generate a higher static pressure, which makes them the winning option if we are going to place them on a radiator.
Installing and configuring PC fans
PC fans are attached to the chassis with the screws provided by each manufacturer . The assembly process is very simple, and their installation is not complicated either, since they use three- or four-pin power connectors that must be plugged into the corresponding connectors on the motherboard. These will be identified both on the motherboard and in the manual.
However, it is important to remember that models with RGB LED lighting also come with an additional connector to power the system. In these cases, it is advisable to use a HUB that allows us to simplify the connection process and cable management. These types of hubs are usually connected to a SATA power connector.
We can also use controllers that will allow us to adjust the speed of the fans and create custom profiles. This will prevent the fans from always moving at a fixed speed that can sometimes be too high or too low for what we really need. These types of controllers are very easy to use, as they usually have dedicated software, and it has a very user-friendly interface.
So far, so good, but it is important to keep in mind the basic rules of thermodynamics when installing PC fans, as these will influence their performance and the airflow of the computer. Hot air tends to rise , which means we should use this to our advantage to improve the cooling of our PC and make things easier for the fans.
When using fans on the top of our PC’s chassis, they should be placed with the front facing inwards. This way, they will draw hot air out, and as it tends to rise, the process will be even faster. If we place them the other way around, we will be bringing in cold air, and pushing the hot air that is trying to rise, causing it to stay inside and worsening the airflow.
Airflow and Internal Pressure Types: Why They Matter
Depending on how we configure the fans, we may find ourselves with negative pressure, neutral pressure or positive pressure inside our PC. Below we will see what each one consists of:
- Negative pressure: occurs when we have more fans taking out hot air than putting in cold air.
- Positive pressure: This is the opposite, that is, it occurs when we have more fans bringing in cold air than taking it out.
- Neutral pressure: occurs when both values, the cold air inlet and the hot air outlet, are equal.
If you are wondering which of those three options is the best, I can confirm that the ideal is neutral pressure, that is, trying to balance the inlet and outlet air flow, although achieving this can be complicated since we will need to generate cold air intake from the base and from the front of the PC, and have hot air output at the back and top.
If you cannot afford this option, don’t worry, the positive pressure system cools optimally, and you will only have to worry about cleaning the dust a little more frequently since it will enter in greater quantities.
Remember that the air that enters plays a very important role, because it is what cools elements that only have passive dissipation , such as RAM memory, radiators present in the motherboard’s VRM system and SSD units that have small passive dissipation blocks. This air heats up when it enters the computer, and it must be removed to the outside to prevent it from accumulating, which is why it is so important to balance the air inlet and outlet
However, don’t get too hung up on it, in the end, in most configurations something as simple as two fans bringing air in at the front, and one fan taking out hot air at the back, is more than enough to create a good internal airflow. If we wanted to improve this configuration, it would be very easy, just add two fans at the top taking out hot air.
What would happen if you place the fans incorrectly?
Inside a PC we have different air flows that are at different temperatures. Hot air tends to rise due to its greater density , while cold air tends to fall, something that, as I have already mentioned, we must take into account when placing the fans at the top and bottom of the chassis.
Therefore, placing fans that bring in cold air at the top of the chassis is a major mistake, and placing fans that take out hot air at the bottom is also a mistake. The ideal is to reverse positions and place the fans that take out hot air at the top, and those that take in cold air at the bottom.
With this configuration we are taking advantage of the natural behavior of air in its different temperature ranges. As hot air rises, the fans that extract hot air placed at the top will have a much easier time extracting it, and as cold air descends, the fans that draw air into the lower part of the chassis will also work optimally.
Let’s think for a moment about what would happen if we decided to purposely set up an inefficient configuration , that is, if we placed the fans at the top bringing in cold air and those at the bottom taking out hot air. In the attached image you can see a clear representation of this scenario.
We have a major problem, because the fans at the bottom are blowing out cold air instead of hot air, and the fans at the top are blowing in cold air that does nothing but push the hot air that is trying to get out from above . The red lines represent the hot air, and the blue ones the cold air.
With this placement of the fans we are reducing the presence of cold air inside and keeping a greater amount of hot air in the chassis, something that would significantly increase the temperature inside the chassis and would have a negative impact on the working temperatures of the components of our equipment.
Things would be even worse if we had the rear fan bringing in cold air instead of exhausting it, since it would be contributing to increasing the cold air pressure that prevents hot air from escaping, as you can see in the attached image. This configuration could increase the temperature inside the PC by up to 10 degrees , although this figure can go higher in countries where the climate is very hot..