In refrigeration there are certain factors that make the difference. Possibly the greatest of them is neither the number of fins, heat pipes or density and thickness of the body of the radiator or block in question, if not the fans used. Many users know the importance of them and that is why they spend many hours learning about performance and specifications, but how do you know at a glance if a fan is focused at high static pressure ?
In other articles we have precisely dealt with the data to be taken into account to assess what a high static pressure is and how many mmH2O are needed for it to be considered. Now we are going to try to discern certain values just by looking at a fan, in a more or less acceptable range of success and above all, how to avoid being haunted when buying one model or another.
Manufacturers often offer unrealistic values for high static pressure fans
We cannot trust the exact values of the manufacturers, that is the reality. Many give static pressure levels that are measured at peak, while others give sustained values and finally others give the weighted average.
As there is no way of knowing what type of measurement they are relying on, the ideal would be to have the P / Q of each one at hand, something really complicated despite the times. So we are only left with our expertise and knowledge to discern, without looking at a comparison, which fan can push more air through a restriction like a heatsink or just a dense radiator.
First of all we have to choose 12 cm fans. The reasons are simple and we will not go into them in depth, since we already discussed them in other articles:
- Perfect diameter.
- Possibility of achieving higher RPM.
- Adjusted cost in materials.
- Better engine balance.
- Blades long enough.
With this clear, we will focus on the details, since these will make the difference. From the inside out, we will have to take into account the size of the motor they include, since the diameter of the same implies a completely different blade design.
As a rule, a larger motor implies a greater number of blades, and with it a more aggressive angle of the blades, which is important in order to “push the air” and the general sound. To compare more or less on equal terms and RPM we will take the Corsair ML120 Pro and the Vardar 120 Evo as an example.
As can be seen with the naked eye and although in this specific case we have the same number of blades, the motor diameter is much larger in the Vardar than in the Corsair, mainly due to the difference in technology between them.
The motor is key to the design of the blades
This causes the Vardar to need blades with a wider turning angle, where width is gained from the central motor until it reaches the end of the frame, thus generating a vortex of greater draft in this area. The Corsair by having a smaller engine can afford wider blades from its base that will drag more air into the central area.
In addition, the angle of attack is less and the diameter of the blades in the final area next to the frame is much larger than in the Vardar. It goes without saying when looking at its specifications that the EK fan achieves 3.16 mmH2O at 2,200 RPM, while the Americans fan rotates at 2,400 RPM and theoretically achieves 4.2 mmH2O of static pressure.
Everything said so far makes sense if we look at a high-end fan, but focused on moving air and therefore nothing focused on static pressure.
The image above shows a Corsair AF120, a low noise, low RPM fan that seeks to move the maximum amount of air with little restriction. As we can see, its motor is in the middle between the two named fans, but its blades reveal its functionality: flat, low angle of attack, a lot of separation from the end of them to the edge of the frame, very little width and a lot of separation between them in terms of angle of rotation.
Height, inclination or distance, keys to understand how it works
Another key aspect will be the height and inclination of the same if we want to know the type of fan we are seeing.
Here we see perfectly how the blades come out of the lowest part of the engine and are located halfway down the engine, where the angle of attack is designed to drag the maximum amount of air and, by turning and forming the blades, introduce it perpendicularly.
Other manufacturers and models opt for a greater number of blades, more curves and with more aggressive angles of fall in their final part, where they intend to take advantage of their disadvantage in terms of engine size with greater height of the same.
This type of fan is normally very optimal in terms of pressure and sound, since the curvature achieved is more abrupt, but allows less air leakage due to the small space between blades. In addition, the distance with the frame is usually really small because they hardly deform the blades with the turn.
Looking at these details, we will be able to distinguish between fans for static pressure and to move air without having to see its specifications and even over time we will be able to intuit more or less which design is more effective.