5
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Computer Airflow
I have a standard Meshify 2 that has a lot of space in it. Its pretty much only got my GPU (3080) and a few drives. Anyway, it idles around 40C in my office, which is fine.
Here's my question --- I've got five 140mm fans, not including the normal exhaust on the back. Here's the setup I did today.
- Front (top to bottom): two intake
- Top (front to back): optional intake (comes on at 50C), two exhaust
The top exhausts run around 50rpm slower than the two intakes. I read that I should build negative pressure. This case is covered in filters, too, so dust hasn't been an issue.
Under load (GTAV) the system maxes out around 60C.
Is that top optional intake a waste of time?
Apologies for the terrible tagging...
Are you okay with the noice it makes under load? More fans and more airflow can, somewhat unintuitively, reduce noise. I recently sold my desktop, but I had built it for absolute minimum noise. I had one of the largest cases you could buy (RIP CaseLabs) and packed it to the gills with as many noctua fans as I could buy. Noctua fans specifically because they can be run at extremely low speed. I haven’t shopped for them in a long time, but when I bought mine, the fans rated the fastest, iPPC 3000 rpm, were able to much slower than the rest of their lineup. I couldn’t afford those exclusively, but they were able to run down to, I think, 200 rpm. They were dead silent and still moved quite a bit of air. When I had my fan curves dialed, I couldn’t get that computer to be noisy even with a full benchmark going. When I dabbled in water cooling, the loudest thing was always the pump, even with a relatively quiet pump running quite slow (that is why I went back to air cooling).
Anyway, if you are happy with the noise level, then don’t worry about it. If you are not, your best purchase is probably to replace your fans with high quality fans (I can absolutely recommend Noctua). If you still aren’t happy, throw some fans in those extra slots.
ok! so I switched things around so I have two 140mm up top, two on the front, and then I replaced the 140mm rear one with a pwm one. I am very much in the 'I need this to be silent' side of things. If I can dial it in like yours, I'll be over the moon. It never gets loud or anything, but every bit counts.
The only concern I've heard of in set-ups like that is that having an intake right next to an exhaust might cause it to pull some of the warm air being blown out back into the case. However, that always felt like one of those things you only have to worry about in very specific circumstances and it sounds like your thermals are fine
I think the top intake's benefit would likely be minimal, since a significant fraction of it is likely the exhaust from the adjacent fan. It seems easy enough to test though; just remove or unplug the top intake fan and see where your temperatures land.
Generally speaking shouldn't top area be an exhaust fan rather than intake since hot air rises? Naturally moves the hot air up and out, and could have intake at the bottom.
Either way if under load it's only a 60c you are doing quite well. Pretty sure most don't start throttling until they get to like 78-80c.
You do not want any of your top fans to be intakes, that will have a negative effect on the airflow as air will circulate in that area without actually reaching any components.
You want the front fans to blow cool air into the case, then top and back fans to pull it out. All air moving in the same direction (from the front to the back) is far better than having it go in circles.
You generally don't want to have any top fans further forward than your CPU cooler either, as that will just pull air out directly from the front fans before it reaches your components as well.
Having intake next to exhaust will kinda negate them. Each will source part of their supply from the others output.
For the most part, the difference between positive and negative pressure setups is negligible. I like positive pressure for less dust in the case (IMO having to do a full pc clean less often is better than having to clean more frequently to maintain a marginal gain).
Intuitively, if we assume the fans move the same amount of air in either orientation, then the mass flow should be the same for positive pressure vs negative pressure. The only real difference then is from the case pressure. You'd expect that that higher pressure would aid in heat transfer, and parts would be cooler.
They did some extended tests here: https://www.youtube.com/watch?v=RsD355lWows&t=864
And you'll note that the GPU temp is better under positive pressure, while the CPU temp is not. Why? Well, we aren't cooling the independently of each other, and the orientation of most GPU exhausts is towards the CPU/CPU cooler. So better cooling of the GPU means hotter exhaust which usually means worse cooling of the CPU.
Which brings be back to the original point, it doesn't really matter, it'll be a trade off (dust vs less dust, cooler CPU warmer GPU or vice versa), and as far as temps go, it'll be a difference of a couple of degrees which can be tuned away with fan curves. I really like Fan Control for dialing in fan curves
Edit: better clarity
this all makes sense. I was surprised the guy had 2x 140mm for intake and 1x 120mm for exhaust. I've got all of this running in Fan Control, which is the best thing ever.
Thanks for this!