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Which is better for exhaust: High airflow or static pressure? - Page 2

post #11 of 18
Quote:
Originally Posted by ciarlatano View Post

In addition to the fact that "static pressure" and "airflow" labels really don't mean anything in actual usage.....and that suction capabilities and static pressure are once again being confused.....
Not that it matters, but how high and low pressure systems effect weather and weather forecasting is basically the same way airflow works in case cooling .. or maybe it does matter more than I want to admit. tongue.gif
post #12 of 18
Lets say we have a fan thats 100CMF and has 10Air pressure.
Its getting 50CMF with the current aplication

But with a fan that has 70CMF and has 15air pressure
Its getting the rated 70CMF in the application.

Therefore you would want to look for the fan that has 15 air perssure or more.
Every certain application has its own air resitance.
We need enough air pressure to be able to get max ratings.

having 99999CMF and 10 airpressure means your only going to get 50CMF in the application
Same performance as the 100CMF can
post #13 of 18
Quote:
Originally Posted by Iwamotto Tetsuz View Post

Lets say we have a fan thats 100CMF and has 10Air pressure.
Its getting 50CMF with the current aplication

But with a fan that has 70CMF and has 15air pressure
Its getting the rated 70CMF in the application.

Therefore you would want to look for the fan that has 15 air perssure or more.
Every certain application has its own air resitance.
We need enough air pressure to be able to get max ratings.

having 99999CMF and 10 airpressure means your only going to get 50CMF in the application
Same performance as the 100CMF can

Exactly.

Unless the marketing material says "optimized for (static pressure or airflow)" and there are unregulated tests done to arrive at the specs on the box. In that case the fan has enough power to blow the Corsair sailboat across the Atlantic in complete silence, while having enough suction capability to take the state of Virginia with it. rolleyes.gif
post #14 of 18
Quote:
Originally Posted by ciarlatano View Post

Exactly.

Unless the marketing material says "optimized for (static pressure or airflow)" and there are unregulated tests done to arrive at the specs on the box. In that case the fan has enough power to blow the Corsair sailboat across the Atlantic in complete silence, while having enough suction capability to take the state of Virginia with it. rolleyes.gif
Just leave Virginia where it is, but sink the sailboats. Won't take much of a leak in the hull to overpower their noisy bilge pump. biggrin.gif
post #15 of 18
High Air-flow will be better than High Static Pressire fans where there is no resistance to the air moving through the case.

In almost every situation however there is always a lot of resistance to air flow. Even if you don't have filters (which is just stupid) grills / components and wires get in the way - (also I bet your case isn't a tunnel, with intake at one end and exhaust at the other) any time the air has to change direction, that causes turbulance, which is also a restriction.

Consequently in almost every case, SP fans will give a better performance / noise ratio.

Identify SP fans by looking at the surface area of the fan blades. If you can poke your finger straight through the gaps in the blades, that's bad.
post #16 of 18
Thread Starter 
So I'm wondering as well, if there is a way I can hookup tubes in a way that the fans can help move stuff through them...

Its generalized and broad because there is no actual system... yet... still need to find the right parts, moving oats and whatnot.

Also yes, I didn't realise static pressure didn't help with suction, thats probably the most important aspect of the fans that I need, The size of fan could be 120mm or 140mm

All the air is blowing from bottom to top.
post #17 of 18
Quote:
Originally Posted by SaintsEnd View Post

So I'm wondering as well, if there is a way I can hookup tubes in a way that the fans can help move stuff through them...

Its generalized and broad because there is no actual system... yet... still need to find the right parts, moving oats and whatnot.

Also yes, I didn't realise static pressure didn't help with suction, thats probably the most important aspect of the fans that I need, The size of fan could be 120mm or 140mm

All the air is blowing from bottom to top.

ok... not sure if you are understanding what we are saying and still not sure what type of contraption you are trying to build so we are going back to the basics smile.gif

CFM = cubic feet per minute. it's the rating of how much air is moved at the given rate. a 100 CFM fan will move 100 cubic feet volume of air (at STP or standard temperature and pressure) per minute with no airflow resistance. CFM rating is affect by the amount airflow resistance so the more airflow resistance it encounters (air filters, obstructions, etc) the lower the actual CFM becomes. however, the counter to air flow resistance is static pressure. if the air that is being moved is pushed by a high static pressure then the amount of reduction due to airflow resistance is minimized. so with high static pressure, the airflow resistance may only diminish the airflow by a small percentage instead of a large percentage.

static pressure is the amount of force the fan exert upon the air that is in the system. it is also the vacuum force applied on the intake side of the fan. static pressure is generally measured in pascal or PSI(pounds per square inch) or other measurements such as mm/h2o(millimeters of water) which is a variation of barometric pressure measurement that is measured in mm/hg or millimeters of mercury. computer fans generally use mm/h2o when giving static pressure information but occasionally you will be given other units of measure which you have to use google to convert the units.

so given that, if you have high static pressure, you will have a higher percentage of the rated CFM pass through the system. lets say you have a given airflow resistance (air filter) with a low static pressure fan, only 40% of the rated CFM has enough energy to overcome the airflow resistance of the air filter. however with a very high static pressure, the fan may generate enough pressure to push 90% of the rated CFM pass the same air filter. this is only a very basic illustration of why we need to know what kind of conditions and components we are working with so we can give you a best guess of what you may need. however if the project must remain undisclosed, we can only give you the information you need to make your own judgement of what needs to be done in your situation.
post #18 of 18
To add some additional info to what psyclum said.

Static pressure is the maximum pressure the fan and push. In simple words this is the point the pressure stops the airflow. No air is flowing. None at all. Static is stopped, still, no movement. A totally worthless measurement.

CFM is almost as worthless. it is testing the fan as if we are going to use it to circulate air in a room Any time a fan is used in a computer there is resistance .. a grill, a filter, HDD cage, cables, fins, etc. The airflow to pressure curve (P-Q curve) gives us a much better representation of how a fan really flows air. Here is a link to some graphs and how they can be interpreted.
http://www.overclock.net/t/1491876/ways-to-better-cooling-airflow-cooler-fan-data/0_20#post_22644574
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