Usefulness of blowhole exhaust?

[slowpogo]

I have a Praetorian case, which has an 80mm exhaust on the top (the "blowhole"). I've read many places that this doesn't do much to cool a case.

I'm wondering if anyone has an explanation for this. Hot air rises, no? For that reason alone an exhaust at the top of a case seems like a good idea. And given that the intake fans are near the bottom of the case, wouldn't this promote some good airflow, between the top fan and the rear one? any thoughts appreciated..

 

[LOUISSSSS]

in the praetorian case i wouldn't do any harm besides noise to make the 80mm top fan as an exhaust. i see no reason to make it an intake in your scenario. but hot air only rises straight up when there is barely any airflow, with decent airflow, the hot air will travel from the intake to the exhaust fans without a problem, showing you no change in CPU, GPU, HDD temperatures with the 80mm top hole in use...

 

[pkme2]

I've replaced my top 80mm on my LL with YL 120mm. Quieter and a better exhaust.

 

[HardWarrior]

Hot air rises, yes. If your PSU isn't flush with the top of your case you'll end up with a bubble of warm, and potentially warming air at the top of your case. How bad is this? I don't think it's much of a problem, but if it's an issue for you, an 80mm fan will correct the problem easily. There's no real point in re-drilling your case for a 120mm, unless of course too, which is fine.

 

[Zepper]

Unless there is no other (or there is an ineffective) exhaust fan, a blowhole won't contribute much to cooling and does provide an opportunity for you to feed your computer things like sodas and beer. Murphy's Law suggests that such opportunity given will be an opportunity taken... It may also scavenge air from your PSU.
. If it was mine, I'd block off the blowhole. However, if your computer does have pockets for hot air like above the PSU and/or above the drive stack, then maybe a very slow and quiet fan might help move those out, but the fan would almost have to be mounted on the outside of the case to do it or use one of those open-frame fans like the Arctic Cooling or with slots in the sides like the Unincom or Silverstone. Remember: Air; like water, electricity and students; take the path of least resistance...

.bh.

 

[dunkster]

Top blow holes may make sense for a case with limited rear exhaust, such as a case with a single 80mm rear vent fan. The 'convection' argument is just silly. Cases without forced ventilation are hot cases.

A case with combination of side-vents and top-vent creates a short-circuit air flow path that results in reduced front-intake air flow, resulting in 'hot' hard drive operation.

Top-vents that create low internal air pressure can result in stalled air flow through the power supply. Power supply temps rise, thermally-controlled PS fans run at high speed to attempt to compensate for high PS temps.

My experience indicates that 'traditional' front-to-back forced air flow is still the best ventilation scheme. There are a lot of cases with vents all over the case that produce 30C CPU idle temps, but with hard drive idle temps of 50C.

If you're modding your case for best ventilation, I'd suggest focus on:
- Eliminate air flow restrictions.
- Balanced intake/exhaust flow.
- Air path providing adequate air flow over all system components.

Hope this helps!