Static Pressure and Airflow Specs
- Thread starter Astravius
- Start date
Solution
synphul
Champion
- Mar 11, 2011
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Usually it says in the name, like corsair mentions sp120 or af120 (sp for static pressure and af for airflow). There aren't really two clear cut difference in fans, fans come in a variety of designs and all ranges of airflow and static pressure. Some have higher airflow than others and some have higher static pressure than others.
The larger the fan, typically the faster it has to spin to achieve the same static pressure. As the surface area increases, pressure tends to decrease. It's also due to rpm's, much of the reason for larger fans (say a 140mm vs 120mm) is to move the same amount of air at a lower speed. To achieve 70cfm the 120mm fan may have to move at 1600rpm while the 140mm may only have to spin at 1200rpm to also move 70cfm of air. Bigger blades moving slower, moving same amount of air but the blades spinning slower results in less pressure due to lower speed and larger size.
You can somewhat tell by looking at the fan blade design though it's best to check specs of the exact fan you're looking at to determine how much static pressure it offers. Fans designed with many slim blades with wider gaps between the blades are capable of moving plenty of air but without much pressure. Wider fewer blades closer together and that have a steeper angle tend to offer more pressure.
This is a really varied example but it shows different fan blade designs. The left would be more airflow designed, the right photo static pressure (notice it's also on a radiator where static pressure is preferred.)
The larger the fan, typically the faster it has to spin to achieve the same static pressure. As the surface area increases, pressure tends to decrease. It's also due to rpm's, much of the reason for larger fans (say a 140mm vs 120mm) is to move the same amount of air at a lower speed. To achieve 70cfm the 120mm fan may have to move at 1600rpm while the 140mm may only have to spin at 1200rpm to also move 70cfm of air. Bigger blades moving slower, moving same amount of air but the blades spinning slower results in less pressure due to lower speed and larger size.
You can somewhat tell by looking at the fan blade design though it's best to check specs of the exact fan you're looking at to determine how much static pressure it offers. Fans designed with many slim blades with wider gaps between the blades are capable of moving plenty of air but without much pressure. Wider fewer blades closer together and that have a steeper angle tend to offer more pressure.
This is a really varied example but it shows different fan blade designs. The left would be more airflow designed, the right photo static pressure (notice it's also on a radiator where static pressure is preferred.)
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