Case airflow

Cita8

Cita8

Cita8

Associate
Joined
6 Sep 2018
Posts
155
Location
Scotland
Hi all,

I'm subscribed to the usual suspects on YouTube and they all still advocate the fans at the front bringing air into the case and fans at the back blowing the "hot air" out.

It just doesn't sit well with me and science basically.
Some great videos explaining why as well but I've forgoten them :rolleyes:

The upshot is basically that to cool a device like a CPU/GPU, the best way to do it is to blow cool air on it.
The idea of "sucking air" into a case and "heat rises" is all well and good but it isn't really viable in modern PC cases with power hungey components.
Old fashioned setups (I built a Cyric PC) with the nondescript grey case with one fan at the back and the PSU fan giving motherboard cooling are still the argument for the suck in/blow out theory.

Tests by the likes of "experts" like Steve from GN still promote this idea.
There is no such thing as sucking air into a modern PC case as that would need a fully sealed case.

So, the best we can do is to blow cooler room air at the components and the case vents will deal with it.
This negative vs positive pressure stuff is for YouTube "influencers".

Please comment, but of course, this is only my opinion.
Cheers
 
Positive and negative pressure are real, plenty of people have experienced higher dust levels when reconfiguring fans.

Airflow however is a very very analogue thing so it's not black and white, however there's a substantial difference between "sucking cool air in" via exhaust fans, and having reliable amounts of fresh air supplied to the system.

Many people focus on the idea that if you supply enough fresh air, the rest takes care of itself. I'm largely of this belief, though I will then check a case for hotspots and consider a crafty exhaust fan near them.

@doyll believes in the "bring good air in the front and let it go straight through via low air resistance at the back". That's a good model for balanced CPU and graphics card cooling.

Experimentation is key!
 
I agree with mostly what's been said. But I will caveat that cooling is not just about the performance, or the dust allowed in, but also about risk (air vs water, especially when you also factor in the importance of) and noise as well normally (unless you've lost most of your hearing, in which case, you can have a hurricane blowing through you woulnd't notice it. And that don't count ol' timers! :p I use my ears for testing, not a sound meter because you can't hear it :p)

Positive Pressure is not as great as many push it to be, I agree. The key thing being, you still get dust. Just not as much as Negative Pressure. But still dust in the case (even with filters). Unless as said you start to seal off the system, in which case things aren't a basic Positive or Negative Pressure setup anymore as there's much more (ghetto?) modding going on to further the results of the setup (Positive or Negative) you are using. So this needs to be remembered when deciding on Positive or Negative Pressure. And lets be honest, if you don't bother clean the inside of your case every so often, it doesn't matter which Pressure you use, so really you should also factor in that Negative Pressure is also often a bit cooler too from all the extra air pulled in from gaps/vents, which depending on case design, may yield better results.

With modern systems now generating tons of heat (even with plenty of airflow on it), and both GPU and CPU being in close promixity to each other, even with plenty of ventilation and extraction, typically there is a lot of heat being trapped in the upper rear of the case (because you can't get rid of it quickly enough). Here, whilst Air alone may not be ideal, using Water with Air may yield much better results, especially over noise produced. At least comparitively when factoring the risk involved (leaks, but only on the GPU which likely will just drop harmlessly down onto the) most modern setups PSU covered in a shroud, and the AIO able to be mounted to the front of the case, by moving the GPU heat source over to the front of the case where the AIO rad is, this gives the case more time at the upper rear to dissipate or be expunged without having the heat being absorbed into the case itself before the cooler air from the intakes cool it back down. Whilst also giving time for the front of the case to cool down from airflow as well that was generated from the GPU heat being transfered to the AIO rad. This should allow you to run more fans at lower speeds for reduced noise whilst the temperatures start soaring. Something that can't be done if you utilise only Air for cooling two (or more) heavy heat components in close promixity. Whilst going all Water, will yield a risk point on the CPU where leaks could damage CPU, Motherboard and possibly more. Here, just the GPU where it's further away from more critical components, is a fair bit safer.

It's just a shame that there's still so many GPU's that are non-compatible with GPU/AIO kits. (Powercolor RX580 Red Devil, I'm looking at you... :mad::mad::mad:)
 
Cita8 said:
Hi all,

I'm subscribed to the usual suspects on YouTube and they all still advocate the fans at the front bringing air into the case and fans at the back blowing the "hot air" out.

It just doesn't sit well with me and science basically.
Some great videos explaining why as well but I've forgoten them :rolleyes:

The upshot is basically that to cool a device like a CPU/GPU, the best way to do it is to blow cool air on it.
The idea of "sucking air" into a case and "heat rises" is all well and good but it isn't really viable in modern PC cases with power hungey components.
Old fashioned setups (I built a Cyric PC) with the nondescript grey case with one fan at the back and the PSU fan giving motherboard cooling are still the argument for the suck in/blow out theory.

Tests by the likes of "experts" like Steve from GN still promote this idea.
There is no such thing as sucking air into a modern PC case as that would need a fully sealed case.

So, the best we can do is to blow cooler room air at the components and the case vents will deal with it.
This negative vs positive pressure stuff is for YouTube "influencers".

Please comment, but of course, this is only my opinion.
Cheers
Click to expand...
First thing is to differentiate between airflow and air-blow. Blowing air generally creates turbulence that reduces air-flow. We want cool air flowing into case, to components, through component coolers, to exhaust vents and out of case without the heated air coming out of components mixing with the cool airflow to them. Below is link to simpe guide to case airflow and how to optimize it, including how to monitor airlfow temp into coolers vs room.
https://forums.overclockers.co.uk/t...-i-put-my-temp-sensor.18564223/#post-26159770
 
doyll said:
First thing is to differentiate between airflow and air-blow. Blowing air generally creates turbulence that reduces air-flow. We want cool air flowing into case, to components, through component coolers, to exhaust vents and out of case without the heated air coming out of components mixing with the cool airflow to them. Below is link to simpe guide to case airflow and how to optimize it, including how to monitor airlfow temp into coolers vs room.
https://forums.overclockers.co.uk/t...-i-put-my-temp-sensor.18564223/#post-26159770
Click to expand...
Thanks
 
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