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[POLL]Radiator Fans: Push or Pull? - Page 2

Poll Results: Is it better for fans to push or pull air through a radiator?

 
  • 63% (109)
    Push
  • 36% (63)
    Pull
172 Total Votes  
post #11 of 22
Quote:
Originally Posted by Sethy666 View Post
Sir, your logic is irrefutable...

Ive never seen it explained quiet that way before.
That made no sense whatsoever.
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post #12 of 22
Quote:
Originally Posted by b-roca View Post
ok here is the easiest way to explain this

go get a shopping trolley full it with a whole lot of crap then round around the shopping center pushing it then try the same thing but this time pulling it you should be able to see a difference just try not to let the shopping trolley hit you in the back of the ankles it hurts
Very interesting comparison!

Let me give another one, probably not as entertaining.

A computer fan is a very simplified version of a plane propeller. In real life, things are not as simple but basically the Bernoulli equation (and Newton's Laws) describes the behaviour.

When a propeller spins up, you want the intake end to be free of obstruction. Picture this: most of the planes with propeller(s) have them in the front of the plane (and wings). Rear propeller planes do exist but they are of a small percentage. This minority should give us another hint. You can almost think of the plane (its wings) as the radiator as both act as a 'resistance' and both benefit from the air flow over them. Front incoming air has a lower velocity but higher pressure (due to curvature of fan blades and Angle of Attack...etc) while rear outgoing air has a higher velocity but lower pressure.
post #13 of 22
Quote:
Originally Posted by TheWolfe View Post
That made no sense whatsoever.
b-roca's explaination or my reply?
post #14 of 22
An airplane can't be used in comparison, unless your fans are capable of moving your case because it is no longer a static situation. Imagine this, a blowing computer fan has dead spot in its center, which reduces air flow thru the fins (less surface area cooled). A pulling computer fan will pull evenly to reach its optimal flow. Also, blowing & sucking your hand is not the same. Try putting a fan in your front door blowing in & you won't notice much of anything. Now turn on an attic fan that pulls air from the house & you will hear air flow at the front door.
post #15 of 22
Quote:
Originally Posted by windfire View Post
Very interesting comparison!

Let me give another one, probably not as entertaining.

A computer fan is a very simplified version of a plane propeller. In real life, things are not as simple but basically the Bernoulli equation (and Newton's Laws) describes the behaviour.

When a propeller spins up, you want the intake end to be free of obstruction. Picture this: most of the planes with propeller(s) have them in the front of the plane (and wings). Rear propeller planes do exist but they are of a small percentage. This minority should give us another hint. You can almost think of the plane (its wings) as the radiator as both act as a 'resistance' and both benefit from the air flow over them. Front incoming air has a lower velocity but higher pressure (due to curvature of fan blades and Angle of Attack...etc) while rear outgoing air has a higher velocity but lower pressure.
You can't use the airplane as an example for computer fans.
The airplane moves quite fast, "ripping" the air of it's direction.
Your computer case does not move, or is this COMPUTER

/edit: Ops didn't see pig69's reply, same thought.
Edited by zefs - 5/28/10 at 2:20am
    
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post #16 of 22
Quote:
Originally Posted by zefs View Post
You can't use the airplane as an example for computer fans.
The airplane moves quite fast, "ripping" the air of it's direction.
Your computer case does not move, or is this COMPUTER

/edit: Ops didn't see pig69's reply, same thought.
Sure, if you wish, try not to focus that much on the moving plane then (vs stationary computer case).

Try to focus more at the (relative) movement of air molecules with respect to the blades. Think Bernoulli.

PS Funny video
post #17 of 22
man you guys have to over complicate s***. According to b-roca's law it is hard to pull s*** than push it and if you guys couldn't figure out the last explanation I will give you another one. This one has to do with cars, so since when have we ever had a front wheel drive car? answer - we haven't all the fast cars are rear wheel drive because the car is pushing no pulling but then we see that all the really fast cars are four wheel drive because they have way more traction which is like push and pull
post #18 of 22
How much of a temp difference is it anyway? I hear push is louder, for someone who is after silence would the temp increase justify placing the fan in pull?
    
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post #19 of 22
I'm not sure "better" is the right thing to ask. In point of fact, for almost all (there are some exceptions) fan designs, you'll get just a little bit more air flow in a push configuration, but using a pull configuration isn't that much different and makes vacuuming dust significantly easier. In a normal dust environment, the obstruction from dust if not vacuumed every month or so will make up the difference.
post #20 of 22
Quote:
Originally Posted by B-roca View Post

man you guys have to over complicate s***. According to b-roca's law it is hard to pull s*** than push it and if you guys couldn't figure out the last explanation I will give you another one. This one has to do with cars, so since when have we ever had a front wheel drive car? answer - we haven't all the fast cars are rear wheel drive because the car is pushing no pulling but then we see that all the really fast cars are four wheel drive because they have way more traction which is like push and pull

That analogy sounds a bit familiar to me wink.gif

And obviously, I completely agree with you. If you look at the physics of automobiles, front-wheel drive is inherently limited to around 265-270hp before it becomes too difficult, or impossible, to drive safely. Rear wheel drive can take over 1500bhp and still be streetable. All-Wheel Drive is good for the same as rear wheel drive, it's simply easier to drive (less talent) and can launch much more easily. That makes it sound like AWD is King, but it does add at least 250-350lbs to a car, greatly increase parasitic losses, and the chances of snapping an axle are significant.

And, no matter if you use push or pull, there is going to be a dead spot.
With pull, however, you are not able to overcome the boundary layer, while with push the higher pressure causes turbulence which disrupts the boundary layer and allows for more efficient heat transfer.


Push-Pull is still the best, especially if you have shrouds for the push side.
   
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