Blowhole or Suckhole

[wedge22]

I currently have a SK83G with an 80mm blowhole, would it work better as a Suckhole?

[specofdust]

Try it and see, simple as that.

[Gordy]

Depends where it is in relation to the other air flows.

As a rule you want to have the same amount of air going in via fans as going out via fans or your fans have to work harder to suck air through vent holes and gaps.

I have two front blowholes on my shuttle drawing air into the chassis. With the rear fan and psu fan sucking air out the back.

[StormPC]

Gordy, you blow out and suck in.

You're right about the fans working harder if there are fans sucking and blowing in the same case, but as long as there is roughly the same amout coming in as going out it is of little concern. As a matter of fact, you really need more blowing than sucking, because if you don't the vents become useless. You want cool air coming into the vents. If you have exactly the same going in fans as coming out fans there is zero case pressure and no air comes into the vents. You want negative case pressure which is created by more air being blown out than sucked in. This causes air to be sucked in through the vents.

My SN25P has 3 fans in the rear all blowing air out. The CPU area is isolated from the rest of the computer pretty much, and it blows the heat out the left side. There are two fans on the CPU in a push-pull arrangement, but the fan doing the pushing is not mounted on the case, it's a few inches from the right vent. It's a pretty efficient design.

In general, since heat rises it is best to have a hole in the top of the case blowing. If it is sucking it will blow the heat back down into the case. The goal of moving air is to get the cold air in and the hot air out. Fans which are in the bottom half of the case should suck, and the ones in the top should blow.

I hope this helps.

[wedge22]

I tried it and although it seemed the cpu was cooler my mobo got upto 65c so it was not good.
I have now removed my floppy drive and I am trying to work out if i can fit a fan into the space left there so i can have something sucking air in from the front.

[stud]

Fitting a fan in the floppy drive won't be effective. Are you sure you're getting temps in the 60s? - seems way too high. What temps does Speedfan show? How hot is your hard drive?

[wanga]

.... I am trying to work out if i can fit a fan into the space left there so i can have something sucking air in from the front.

the best method is to add exhaust fans where ever you can (will obviously depend on your case/chassis design). one solution is to attach the fan to the outside of the case. the objective should be to "suck" air from the inside and "blow" it out, thereby increasing negative pressure in the case. that way more air is sucked in via the vents to cool the internal components.

[DanceswithUnix]

Seems odd to me that everyone is saying you should suck air out of a case.

I was once told that you should always blow air into a box, as you can only get so much vacuum, but you can pressurise as much as you like

[autopilot]

It's not about sucking or blowing, it's about having an even as possible flow of air going in and out. If you have a too much air going in, it will just sit there are heat up. To much out and a slight vacuum effect will mean that there is not enough air in the case moving around for the heat to convect (transfer) with. Just have an even amount of fans blowing and sucking, preferably at opposite end of the case.

[DanceswithUnix]

Quite agree on even air flow, my home PC has a big front fan blowing in and exhausts extracting out at the back to snake air through the whole case.

Most people don't have that though, they either have just the PSU fan or one fan + PSU (like in the Shuttles) and rely on a bunch of holes to provide the rest of the flow.

Now. I'm sure any given case will work best in the way the case designer intended it, but it does seem odd to me that everything seems so suck biased when a vacuum is not a good heat conductor. Perhaps it all comes down to dust collection or the fact that you can't be sure as a designer how hot the air is that you are blowing in.

[wanga]

it does seem odd to me that everything seems so suck biased when a vacuum is not a good heat conductor.

the purpose of the vacuum is not to conduct heat, but to create negative pressure within the case in order to induce higher levels of air flow across the components within the case... so long as there are vents placed in appropriate places (not judging the actual vent design effectiveness).

certainly we can install a "blow" fan - say at the front of the case - to create a push-pull effect, but the problem here is that the push/blow fan will invariably cancel out some of the localised negative pressure created by the "suck"/exhaust fans. consequently the flow pattern within the case may be disrupted, which may be suboptimal.

of course it all depends on the case/chassis design so each solution will be unique. IMO "suck"/exhaust fans will be most effective given that the case is well ventilated/designed.