Which way do fans blow???

[Wisecracker]

Yeah . . .I kinda worry about the pci bus . . I convince myself that the front fan blows a little air in that direction. I try to keep the case as tight as I can to keep the bad stuff out . .

I'd be a little more concerned with dead air if I had the same number of intakes/exhausts thereby creating the type of *equalization* I think you're talking about. By pulling air in three places and exhausting at one I figure I'm at least moving air around . . . even if it's like the hot air floating around here sometimes . .. 😛

Be interesting for THG to do *case air flow* dynamics investigation . . .

 

[ajfink]

by all means try the cpu fan sucking air up, If you can keep the pc up and running and disable any heat protection youll likely damage the cpu. Air must be forced down onto the metal surface to dissapate the heat by cooling the surface of the metal. Having it in reverse would dilute the force of air against the metal and cause overheating.

Without the air forced onto the base the fins would have to disperse most of the heat as air is sucked up, making the base warmer.

Nah I've switched them before for shits and giggles, it still works, just not as well. As long as there's a decent amount of air being moved over the heatsink most processors won't overheat.

did you load your cpu with orthos or prime to see how well it didnt work?

Nope, but the temps (while folding) only changed a few degrees.

On a related note, I have to keep my P4 folding rig's side open to keep the temps below 50C. It's a Northwood, can't imagine what a Prescott would be like. It's a really old case that came with a 466 Celeron system, so cooling wasn't a big deal when it was put together. One 60mm intake and one 80mm exhaust.

 

[orangegator]

When it comes to heatsinks, it a matter of simple physics for having the fans blowing air onto them. The air blows onto the heatsink, across the fins absorbing the heat, and continues to move away from the heatsink. Air is the medium that absorbs heat and carries it away. If the fan was blowing away from a heatsink, especially stock ones with vertical fins, it would create a low pressure area over the heatsink. This results in less air contacting the heatsink to remove heat. Yes, some air would be "sucked" through the fins and out the fan. But the reisitance of the air having to be sucked through the fins and from air being sucked into the fan that has not passed through the heatsink first would result in less air coming in contact with the fins. This would result in far less cooling.

 

[ajfink]

I have (a different) P4 folding rig, 2.6C in a Gateway rig. It's one of the ones that is designed for single-fan cooling. It's always opened up because the proprietary PSU went bad and it's running off of a standard, really cheap ATX PSU at the moment (like $15 from Newegg). Anyway, I just took off the fan and flipped it on end (so it was blowing down on the CPU) and the temp went from 53C to 49C. The heatsink is tiny and sucks, but the mounting bracket (and the screws that hold the bracket on) are, of course, also proprietary, otherwise I'd have a better HSF on it.

So, even even systems designed to have air sucked over the HSF don't always work the best that way. The heatsink is very small, thus allowing for the most amount of air contacting the base of the heatsink, but even that doesn't remove the deficit.

 

[riodio]

With the exception of some OEM cases that are designed to have one fan cooling the whole system, and thus suck air up and blow it out of the case, nearly all CPU fans blow down on the CPU. Take off the fan after it's been running for a few months, you'll find dust all in the fins and on the heatsink.

Please don't pretend to offer misinformation as qualified advice. A CPU fan is an exhaust fan - in other words it is designed to evacuate heat. The air inside a case is warm to hot, so the idea of blowing hot air onto a CPU can be equated to a convection oven which would act to melt your CPU. For the case exhaust fan to effectively evacuate hot air from the case, adequate ventilation (i.e. air flow drawn across the case) is ideal and is accomplished by installing a blower fan opposite the exhaust fan to draw air into the case.

 

[hunter315]

This topic has been closed by Hunter315