Air flow/general cooling questions

[FailPr00f]

Hi,

 

I work at a small tech store and a customer brought in his pc for troubleshooting. Still resolving the issues it’s having but noticed his air flow setup and had some questions just for my own learning. So I’m hoping someone here can answer my questions/provide some insight.

 

Attached is an unedited and edited image of the inside of the pc. The edited image illustrates the airflow as I understand it.
 

My first question is do the fans (3) taking in air from the front (right of picture) and blowing it over the radiator have their cooling for the overall case diminished by blowing over the radiator to cool the water? Not saying there is a better configuration for the setup necessarily just wondering if that does affect their cooling of the rest of the case.

 

My second question is about fans possibly canceling out airflow. Specifically here I’m referencing the top right case fan (exhaust) cancelling out the top right and maybe I’m even middle right intakes. Is this the case that the exhaust being there cancels out the airflow before it has a chance to go over the whole board so that it might be better in this case to not even have that fan installed?

 

Last note: I’m not necessarily trying to see if there is a better air flow setup for the fans (I think his cooling is fine and temps look fine under load). I just want to learn about the ideas of these things that might apply in other builds/cases.

 

Thank you in advance for any and all responses to my questions

[YoungBlade]

Fluid dynamics is an insanely complex subject. I am not an expert in this field, so take this with a grain of salt. But I'm also a fan of trying to learn whenever possible, even if it a difficult subject.

 

Basically, from my understanding, yes, to both of your questions.

 

The intake fans will pull less air into the case because they have to push it through a radiator and that air entering the case will be warmed up by the water cooling the CPU.

 

And the front exhaust fan on the top might be preventing air from making it across the board to the rear exhaust.

 

That said, the top exhaust isn't totally useless there, as it is aiding in the cooling of the CPU. The air was already warmed by the radiator, and reducing the pressure in the case with the additional exhaust fan will help the intake fans to push air through the radiator more easily.

[FailPr00f]

2 minutes ago, YoungBlade said:

Fluid dynamics is an insanely complex subject. I am not an expert in this field, so take this with a grain of salt. But I'm also a fan of trying to learn whenever possible, even if it a difficult subject.

 

Basically, from my understanding, yes, to both of your questions.

 

The intake fans will pull less air into the case because they have to push it through a radiator and that air entering the case will be warmed up by the water cooling the CPU.

 

And the front exhaust fan on the top might be preventing air from making it across the board to the rear exhaust.

 

That said, the top exhaust isn't totally useless there, as it is aiding in the cooling of the CPU. The air was already warmed by the radiator, and reducing the pressure in the case with the additional exhaust fan will help the intake fans to push air through the radiator more easily.

Thanks for the quick reply! Yeah I’m on the same page cooling is super complex so I’m taking everything with a grain of salt like you said. Still this is super informative and the tip about of the top right exhaust still removing warmed air and reducing pressure is smart.

[thrasher_565]

3 hours ago, FailPr00f said:

Thanks for the quick reply! Yeah I’m on the same page cooling is super complex so I’m taking everything with a grain of salt like you said. Still this is super informative and the tip about of the top right exhaust still removing warmed air and reducing pressure is smart.

best thing is to test it. do different combinations.  fan speed and so on. but at best it portly only like 1-2 degrees difference. is it worth the time testing well up to you.

[Dogzilla07]

Just wanted to elaborate on the good previous posts, pressure itself ,specifically more positive pressure (with a few caveats of course), is done to combat dust. Having negative (more fans and/or at bigger speed exhausting outside the case instead of intaking), can provide a little lower temps (depending how the case is designed), at the cost of more dust (as dust is being pulled into the case through every single unfiltered opening the case has as it's running).

 

When u have positive pressure while the case is working, that creates a forcefield that pushes dust out (but with certain designs, taping of ventilated area around the intakes becomes required for maximum effect).

 

Second people wrongly assume if you don't have fan than that area is neutral, doesn't participate as exhaust/intake which is inaccurate. Even without fans, ventilated panels, mesh,filters are exhaust area, same like a fan is an exhaust area, less effective, but it still makes a difference, especially if the holes are large, and there's not much material (like the back of Fractal Torrent for instance combined with its great static pressure intake fans).

 

That's because air is a fluid, in a case it behaves like water going through an aquarium, or water going through a garden hose with holes.

 

For the build above there isn't much changing that's gonna bring huge benefits. The 3 exhaust fans are not good from a noise-perspective, and removing one will lower the noise and lower dust inside the case, but at the cost of aesthetics. You can also force out dust by setting up the exhaust fans to spin slower than intake through radiator, but again minor things.

 

 

[Jeppes]

9 minutes ago, Dogzilla07 said:

For the build above there isn't much changing that's gonna bring huge benefits. The 3 exhaust fans are not good from a noise-perspective, and removing one will lower the noise and lower dust inside the case, but at the cost of aesthetics.

 

Its not that simple with closed cases like 4000X. You might even want to have more negative pressure so that the gpu gets more fresh air in from the pcie slots below it.

[Dogzilla07]

1 hour ago, Jeppes said:

Its not that simple with closed cases like 4000X. You might even want to have more negative pressure so that the gpu gets more fresh air in from the pcie slots below it.

Yes, I specified there are caveats, and that's exactly why i mentioned there isn't much changing that'll bring benefits (closed-off front cases, and impossible to mount radiator top). You can still have negative pressure with 2 exhaust fans, just by adjusting the fan speeds in the opposite direction. And the end result is less noise (but ruined symmetry). 

 

I did however not end my previous post with the "at the cost of some performance if the front is closed". With cases with closed off-front it's really hard to balance Noise/Dust/Temperature/Performance.

[FailPr00f]

14 hours ago, Dogzilla07 said:

Yes, I specified there are caveats, and that's exactly why i mentioned there isn't much changing that'll bring benefits (closed-off front cases, and impossible to mount radiator top). You can still have negative pressure with 2 exhaust fans, just by adjusting the fan speeds in the opposite direction. And the end result is less noise (but ruined symmetry). 

 

I did however not end my previous post with the "at the cost of some performance if the front is closed". With cases with closed off-front it's really hard to balance Noise/Dust/Temperature/Performance.

Thank you for the information!