I have a SanAce 109P1412H101 that I originally wanted to use on heatsink, but it wouldn't fit on either of my heatsinks because of DIMM interference. I ended up using it as a top back wall exhaust fan -- which is a disappointing use for such a good fan. Does static pressure make any difference for an exhaust fan? Or is CFM the only really important spec.? Would exhaust fans be the ideal use for the strange 3-bladed fans that some manufacturers make?
Exhaust fans: is CFM more important than static pressure?
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I have a SanAce 109P1412H101 that I originally wanted to use on heatsink, but it wouldn't fit on either of my heatsinks because of DIMM interference. I ended up using it as a top back wall exhaust fan -- which is a disappointing use for such a good fan. Does static pressure make any difference for an exhaust fan? Or is CFM the only really important spec.? Would exhaust fans be the ideal use for the strange 3-bladed fans that some manufacturers make?
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The amount of air a fan will move depends on:
Rated air flow
Rated static pressure
Air flow resistance.
You can't separate out any one of those when choosing a use for a fan. They all contribute their own part to how much air gets moved.
Perhaps this will help:
Fan P-Q Curve
Rated air flow
Rated static pressure
Air flow resistance.
You can't separate out any one of those when choosing a use for a fan. They all contribute their own part to how much air gets moved.
Perhaps this will help:
Fan P-Q Curve
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What billbartuska said.
I'll add that the P/Q curve is a way better way to see a fans performance, but sadly almost all are only done with fan at full speed. If you are like me and many others I rarely use my fans at full speed. I use them at about 25%, 50% and 70% .. so knowing how they perform at these lower speeds is way more important to me than full speed.
Also, I find static pressure rating to be way more important then airflow rating.
Let us look at fan A rated 40cfm & 5mm H2O versus fan B rated 80cfm & 1mm H2O.
Keep in mind static pressure is the amount of pressure the fan can push into a sealed container .. the point there is no airflow, only pressure.
So if there is a resistance of 1mm H2O,
fan A will be flowing about 35cfm,
fan B will be flowing 0cfm.. because the resistance is at pressure rating
Static = still, not moving.
I'll add that the P/Q curve is a way better way to see a fans performance, but sadly almost all are only done with fan at full speed. If you are like me and many others I rarely use my fans at full speed. I use them at about 25%, 50% and 70% .. so knowing how they perform at these lower speeds is way more important to me than full speed.
Also, I find static pressure rating to be way more important then airflow rating.
Let us look at fan A rated 40cfm & 5mm H2O versus fan B rated 80cfm & 1mm H2O.
Keep in mind static pressure is the amount of pressure the fan can push into a sealed container .. the point there is no airflow, only pressure.
So if there is a resistance of 1mm H2O,
fan A will be flowing about 35cfm,
fan B will be flowing 0cfm.. because the resistance is at pressure rating
Static = still, not moving.
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I think he's asking what's more important for an exhaust fan. High CFM or high static pressure fans. if the case it's in has a wire grill and not a thick mesh blocking much of the airflow the whole backpressure reducing CFM is nearly null.
In that instance the answer is CFM to remove hot air from inside the case outside.
In that instance the answer is CFM to remove hot air from inside the case outside.
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Quote:
In a case, we cannot have exhaust airflow without intake airflow. Case will only flow equal amounts enter and exit air. Fans are the tool we use to move the air. Maybe this basic guide to airflow and optimizing case airflow will help:
http://www.overclock.net/t/1491876/ways-to-better-cooling-airflow-cooler-fan-data/0_20#post_22319249
Quote:
![wink.gif]( "wink.gif")
Sorry, but it's not that simple. Think of it as a glider. What is most important part of aglider to maintain controlled flight; the wings, the horizontal stabilizers or the vertical stabilizer? We could add many other things without the above 3 things listed aglider can't sustain controlled flight..Originally Posted by mmonnin
I think he's asking what's more important for an exhaust fan. High CFM or high static pressure fans. if the case it's in has a wire grill and not a thick mesh blocking much of the airflow the whole backpressure reducing CFM is nearly null.
In that instance the answer is CFM to remove hot air from inside the case outside.
In a case, we cannot have exhaust airflow without intake airflow. Case will only flow equal amounts enter and exit air. Fans are the tool we use to move the air. Maybe this basic guide to airflow and optimizing case airflow will help:
http://www.overclock.net/t/1491876/ways-to-better-cooling-airflow-cooler-fan-data/0_20#post_22319249
Quote:
Yes, it is not really a case fan I would choose to use, but if kept at lower rpm it might work well. It's a 158cfm 9.6mm H2O fan rated 46dB .. which will be much louder when mounted and pulling /pushing air through a grill and filter if used as intake. With fan like that as intake no exhuast fan would be needed.Originally Posted by czin125
But isn't that particular 120x38 both higher CFM and higher pressure than other 120x25 fans at equal rpm?
Even at 1700rpm it should be equivalent to a 120x25 at 2000rpm, right? Lower rpm might be more pleasant sounding even if the dba was equal?
Since that company happens to have a 120x38 at 2600 rpm 39dba 99 CFM 0.283 inch and a 120x25 at 2850 rpm 40dba 88 CFM 0.257 inch
Since that company happens to have a 120x38 at 2600 rpm 39dba 99 CFM 0.283 inch and a 120x25 at 2850 rpm 40dba 88 CFM 0.257 inch
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You can't judge a fans performance by just one of it's parameters nor just it's thickness. Fans are a "system" of components that all work together.
But yes:
Quieter fans tend to move less air at lower pressures.
Thicker fans tend to move more air at higher pressures.
But yes:
Quieter fans tend to move less air at lower pressures.
Thicker fans tend to move more air at higher pressures.
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Quote:
Thicker fans can usually supply more air especially when dealing with resistance like fancy grill with fine mesh and filters. Thicker fans usually have higher pressure ratings than thinner fans.Originally Posted by czin125
Even at 1700rpm it should be equivalent to a 120x25 at 2000rpm, right? Lower rpm might be more pleasant sounding even if the dba was equal?
Since that company happens to have a 120x38 at 2600 rpm 39dba 99 CFM 0.283 inch and a 120x25 at 2850 rpm 40dba 88 CFM 0.257 inch
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