So kind of a goofy question...

If you had something inclosed in an area that generated a fair amount of heat, and you wanted to try and keep this item cool, what would be the most effective, efficient fan placement...install the fan blowing ouside air into the box, or install the fan drawing hot air out of the box??

I understand their are variables...fan design, sealed, etc, so let's just go with a hypothetical.

 

So, hypothetically you want a way to keep your Flux Capacitor cool? GREAT SCOTT!! I would say having the fan pull cool air inside the box. place the inlet where it will give "the thing that generates heat" the most cooling I.E., over the heat sinks. also, this way if you need to install an air filter this will be an easy way to do.

 

Well, the spelling certainly is...

A fan pushing in is more efficient because the air pressure on the low side of the blades is higher. And it creates more turbulence inside the chamber, which means better heat transfer.

 

So it was spelled wrong .. I was waiting to see what the hell he was talking about.

 

Yea, it was supposed to say "Most" but you can't edit the title after you're done...or at least I don't know how.

Actually steve, I disagree with your logic there. Look at most radiator cooling fans. They're pullers, not pushers. Technicaly, a low pressure area would be created just behind the fan area. Low pressure means low temp. It would also tend to create a venturi effect, which has the potential to move more air. Just because you don't feel it blowing on you doesn't mean it's not working. Are we talkng about anything that amounts to anything?? Most likely not, but it is basic physics.

 

"Mowt" wasn't the ONLY splenlig error.

Radiator fans aren't arranged for peak efficiency, which is what you asked about. No, low pressure doesn't necessarily mean low temp; especially when you're talking about the MINUTELY lower pressure on the back side of a dry radiator. Nor is there any venturi, which only moves more air when the venturi pressure is HIGHER than ambient (like a blowgun on an air compressor).

If you had studied basic physics, you wouldn't have asked this question, so don't now try to teach it to us. Your radiator comparison isn't remotely similar to an enclosed heat exchanger.

 

You have 2 minutes after posting to fix it - go to the forum index and double click the open space just to the right of the title, an edit box will open up, correct it and hit Enter.

 

computer fans pull hot air out of the box.

Hot air already wants to move to cooler area, so its easier to help it along it way instead of forcing cold air into the warm area.

 

That's along the lines I was thinking. I can come up with a bunch of places a puller is used over a pusher for cooling of a compartment. But I think fan design has a larger influence over how well it works above a pusher.

Sorry about the spelling, using the phone and it throws in it's own auto-correct sometimes and I didn't catch it.

 

yah i actually added my own secondary cooling fan to my computer directly above the powersupply heat sink's fan and it pulls warmer air out then the original fan supplied does, since the heat sink fan blows right to left, and the factory fan blows front to back it was trying to turn the air 90*

but i agree fan design is just as critical as location

 

With computers, you generally want both pushing and pulling fans (or just an exhaust with natural low intake) - with slightly more power on the exhaust. It's the direction of the airflow that makes the most difference - a low intake (to pull in cool air) and a high exhaust (to pull out the hot air) - heat rises. If you have more intake than exhaust, you will build up positive pressure that will disturb proper airflow.

 

Not mine. It's only gravity's greater action on the cooler/denser air that causes convection. But in an enclosure, convection isn't significant as a mechanism of heat transfer.

And neither of those matters anyway. The question is: which way is more efficient? The answer is: pushing cooler/denser air is more efficient than pulling warmer/less-dense air. For each rev of the fan blade, you'll move more mass of cool air than of warm air, and it's the mass that absorbs the heat.

The direction you push it doesn't matter unless you're pushing it thru a LOOOOONG vertical duct with a temperature gradient between the ends. But that wasn't a condition of the original question.The tiny bit of pressure that MIGHT occur in a computer case is insignificant to the airflow within the case, but any increase in density will cause a faster heat transfer, which is good. Another benefit of a pressurized case is, if you have filters on the air inlets, you have only clean air leaking out - no dirty (dusty) air leaking in. So for both reasons, a little air pressure in the case is desirable.

 

Does that mean I will get better gas mileage with me seat heaters on?

Sorry couldnt help myself, physics makes my head hurt and stuppid comments are the only thing that relieve the pain.

 

A lot of computers have fans pushing cold air in the front and pulling hot air out the back. Power supply fans vary with most oem style atx pulling hot air out of the case through the supply. More expensive performance supplies have the fan on the inside pulling hot air from the case and pushing it through the supply.

 

.....