SP Fan CFM vs AF Fan CFM

[jejaka_h]

which one is better? the sp have 62 cfm and the af have 63 cfm

 

[synphul]

Cfm is a unit of measure, just like mm or inches. There's no one that's better than the other. Cfm stands for cubic feet of air per minute. Sp is an abbreviation for static pressure, usually measured in mm/h2o. The higher the static pressure the more 'force', it doesn't necessarily mean more air. It means when the air flow is restricted either by objects like blowing air past hard drives, through a dense finned radiator or cooler, pulling air through a filter etc it will be able to continue moving more air than a fan with lower pressure or 'strength'.

An example would be an air filter on an intake fan. If two fans are both moving 63cfm of air, that's what they're rated at in an open air environment, no restrictions. The introduction of a restriction such as a filter, the fan with higher static pressure may move 60cfm while the lower static pressure of an 'airflow' fan may only be able to move 50cfm of air. These aren't factual numbers, just a way to explain the difference.

The fact that a company labels one fan 'sp' vs 'af', those are loose descriptions they've come up with. 2 fans may have a static pressure of .8 mm/h2o and the other static pressure of 1.2 mm/h2o. Both may be called 'airflow' fans while an 'sp' or 'static pressure' optimized fan may be capable of 2.4 mm/h2o. What the real performance of the fan is in terms of ratings on measurable scales means more than whether it's called 'airflow' or 'sp'. It just means the 'airflow' fan produces less static pressure than that company's other fans or those they designate as 'sp' optimized. Sometimes airflow fans can be quieter but not always. It again depends on the specs and its noise rating.

Since both fans you're comparing (no idea which they are) are rated to the same cfm, the next thing I would look at is the noise level rating. If you want a quieter fan, pick the quieter one. If they're both capable of 62-63cfm (hardly any difference) and they're both around the same noise level, maybe 20dba and 22 or 23dba, then I'd probably choose the static pressure optimized.