Negative or positive pressure? Does it matter?

[Shrek]

An electrostatic filter would be interesting. Does it exist? (sorry, I'm not very knowledgeable about filters)

Electrostatic filters exist, but I don't know of any for computers; they will still need periodic cleaning but I believe would not be very restrictive; the cyclone idea might be a lot simpler, but again I have not seen it used on computers.

Like many people I just blast things out now and again, but 'compressed air' is way too expensive and a blower is a better idea, but this can lead to a discussion of electrostatic dangers. I recall a story of a submarine probe that was ballasted with CO2 so it would float to the surface; the electronics were failing because the dry gas was developing electrostatic discharge as it brushed passed surfaces. That said, I have never had any problems, but have the ESD version of the Datavac which attends to these issues.

This problem of frictionally induced discharge can seem for volcanos.

 

[thesmokingman]

There's this thing called a Datavac, get one for the dusties.

 

[Deleted member 24505]

There's no frustration at all. Only a failure to comprehend why some people still keep thinking that I'm bothered by dust even though I've said multiple times that I'm not.

People! I have dust filters. I also acknowledge the fact that dust finds its way into your case regardless of your cooling setup. I don't give a rat's arse about this side of the topic. What I want is cooling and silence. Can you please, please keep this in mind before commenting, or at least not direct your comment towards trying to help me? (as giving advice about dust is clearly not helping me - it might help others, though) It would be very much appreciated.


Now that's an interesting point. My current intake fans max out at about 1200 rpm. Maybe I should look for faster ones?


Thanks for the tip. I'm trying exactly that. My current setup is fairly balanced, but clearly not powerful enough, demonstrated by the fact that I can drop a good 6-8 °C off of both the CPU and GPU by just removing the side of the case. The ideal situation would be replacing my 240 mm AIO with a 280 mm unit, and my 12 cm intake fans with 14 cm ones, but I'm afraid all these won't fit at the same time due to how close the front panel is to the rest of the case. So it's either bigger AIO with bigger fans, or just bigger intake fans at the front, but not both.

iirc a 280mm radiator has more surface area than a 360 rad, i would go for a bigger rad

 

[Shrek]

There's this thing called a Datavac, get one for the dusties.

Get the ESD version if you can afford it.

 

[thesmokingman]

iirc a 280mm radiator has more surface area than a 360 rad, i would go for a bigger rad

However the fan motors are not stronger. Unless they've actually started to size motors to the wider blade area this constant should still be true.

 

[Deleted member 24505]

Don't forget bigger 140mm fans can in theory move more air at a slower rpm, so quieter.

 

[thesmokingman]

Don't forget bigger 140mm fans can in theory move more air at a slower rpm, so quieter.

Nope, that actually makes them weaker. You want static pressure, ie more power. Years ago this was proven by Martins testing who took a AP15 on a 140mm shroud vs the a range of 140s up to deltas iirc. The AP15 killed them until the 38s.

 

[freeagent]

Get the ESD version if you can afford it.

I got the white one last Christmas

That’s why I used to push 120x38s so hard.. they are tough to beat

I failed at quoting sorry

 

[Shrek]

I got the white one last Christmas

The white one is fine (I have that one also) and I doubt will cause any issues, despite the CO2 horror story. The black one includes a ground wire and I believe the plastic parts are conductive (unlike for the white version). My only gripe is that the bearings started to chatter and it is hell to get to the lower one for oiling (I believe the same motor is used for both versions).

Seems there is also a 220V version, and I see they now have a variable speed variant.
Consumer Electronics/IT Cleaning Tools | MetroVac

 

[maxfly]

It sounds like your front fans arent pushing enough cool air into your case fast/hard enough to allow your gpu to use it before your top fans exhaust it. Try running your front fans faster and exhaust fans slower.
Or, if your feeling really really constructive, build a temporary duct out of cardboard from one front fan to your gpu.
Or get higher static pressure fans to overcome the impedance of your grills and filter in front.

 

[The red spirit]

@AusWolf Go for positive pressure. Doyll once explained that if possible, positive pressure is always better as it blows cold air onto components. Exhaust fans suck in air much weaker, than it exhausts. Since computers aren't sealed boxes, exhaust fans can't do much. They are only useful for creating flow from front bottom to top rear.

Here's the original article:

* Basic Guide to Improving Case Airflow*

How airflow works Airflow is simply displacement; for air to come into case, air must be leaving case .. or .. for air to leave the case, air must be coming into case. Think of the air around us as water and we are divers in it and a sunken van is a computer case. We can't move more water into...

hardforum.com

"But with good case intake fans we don't need exhaust fans, same as good cooler / radiator fans don't need pull fans."

But then you have sort of cubish case. I would remove front metal grille and use both stock intakes and maybe add a fan to front bottom as intake. It might not need any exhaust fans then. AIO would go to front intake and you can reuse stock fan and put it as bottom front intake. Taking side panel off more or less means that you have intake bottleneck.

 

[AusWolf]

iirc a 280mm radiator has more surface area than a 360 rad, i would go for a bigger rad

Don't forget bigger 140mm fans can in theory move more air at a slower rpm, so quieter.

@AusWolf Go for positive pressure. Doyll once explained that if possible, positive pressure is always better as it blows cold air onto components. Exhaust fans suck in air much weaker, than it exhausts. Since computers aren't sealed boxes, exhaust fans can't do much. They are only useful for creating flow from front bottom to top rear.

Here's the original article:

* Basic Guide to Improving Case Airflow*

How airflow works Airflow is simply displacement; for air to come into case, air must be leaving case .. or .. for air to leave the case, air must be coming into case. Think of the air around us as water and we are divers in it and a sunken van is a computer case. We can't move more water into...

hardforum.com

"But with good case intake fans we don't need exhaust fans, same as good cooler / radiator fans don't need pull fans."

But then you have sort of cubish case. I would remove front metal grille and use both stock intakes and maybe add a fan to front bottom as intake. It might not need any exhaust fans then. AIO would go to front intake and you can reuse stock fan and put it as bottom front intake. Taking side panel off more or less means that you have intake bottleneck.

Thanks for your insight, guys! I really appreciate it.

What you're saying basically, are two opposite things, which also makes it interesting. I wish I could have a 280 mm AIO at the top with 2x 14 cm fans as intake. It may be doable, but the space in the top front corner seems a bit tight. What I can see myself doing in the future, is getting the bigger AIO and the 14 cm fans, and experimenting with them, trying to see which config works best in real life.

Another option might be using the AIO as intake, but that wouldn't help much with GPU thermals/noise, I suppose.

 

[Solid State Soul ( SSS )]

put it simply, positive pursue means better temperatures and lower dust build up.

 

[ThrashZone]

People! I have dust filters. I also acknowledge the fact that dust finds its way into your case regardless of your cooling setup. I don't give a rat's arse about this side of the topic. What I want is cooling and silence. Can you please, please keep this in mind before commenting, or at least not direct your comment towards trying to help me? (as giving advice about dust is clearly not helping me - it might help others, though) It would be very much appreciated.

Hi,
Maybe think outside the box a little more
If current filters are not catching micro fine dust, well they are screens like most home windows use not real filters like home a/c systems use so it might be worth bettering the filters

I've used home a/c filter material little restrictive but worked very well at catrching all the micro fine dust

Currently I'm using some dark speaker cloth because it's much easier to tell when it's time to vac or blow it out and it's less restrictive

 

[AusWolf]

Hi,
Maybe think outside the box a little more
If current filters are not catching micro fine dust, well they are screens like most home windows use not real filters like home a/c systems use so it might be worth bettering the filters

I've used home a/c filter material little restrictive but worked very well at catrching all the micro fine dust

Currently I'm using some dark speaker cloth because it's much easier to tell when it's time to vac or blow it out and it's less restrictive

That's cool, but like I said, dust is not my concern. I'm interested in keeping my system as cool and quiet as possible while also keeping my dust filters on if possible. My question is related to airflow, not dust.

Edit: Everybody: Can you please read the comment you're replying to before typing anything? If someone is asking what settings they should use on their 10900K, "the 5900X is a much better CPU" is not the answer.
(crude example, but that's kind of what's happening here)

 

[Vayra86]

Dust will make it's way into the PC anyway, no matter what you do.

Sure... but I just cleaned my PC two days ago and it had a very thin, fine layer on everything and just a few small (fingertip) bundles between the heatsinks. The thing has been standing here since january 2019.

When I didn't have a filtered case I used to clean it bi monthly and found more. When I had less pronounced positive pressure but filtered case, than I do on this rig, I also had more dust in less time.

Nope, that actually makes them weaker. You want static pressure, ie more power. Years ago this was proven by Martins testing who took a AP15 on a 140mm shroud vs the a range of 140s up to deltas iirc. The AP15 killed them until the 38s.

Static pressure doesn't move air better which is what case fans are for. I've had pressure fans in the front and they had to run much faster and louder than non pressure optimized fans.

Pressure is for rads, isn't it?

 

[The red spirit]

Thanks for your insight, guys! I really appreciate it.

What you're saying basically, are two opposite things, which also makes it interesting. I wish I could have a 280 mm AIO at the top with 2x 14 cm fans as intake. It may be doable, but the space in the top front corner seems a bit tight. What I can see myself doing in the future, is getting the bigger AIO and the 14 cm fans, and experimenting with them, trying to see which config works best in real life.

Another option might be using the AIO as intake, but that wouldn't help much with GPU thermals/noise, I suppose.

I just tested theory of no exhaust fans in my case (Silencio S400) and conclusion is that exhaust fans are good. Here are temps with exhaust fans stopped and with exhaust fans working (I ran prime95 small FFTs and Unigine Tropics for 20 minutes and only care about maximum temperatures):
CPU Package 78C - 73C
CPU Core 78C - 73C
PCH 48C - 46C
VRM MOS 76C -73C
PCIe x16 48C - 46C
SSD (OS SSD) 38C - 37C
GPU Diode 67C - 65C
GPU VRM 1 64C - 62C

Exhaust fans helped to me, I guess its a good idea to use them. What we can take away from doyll's assertion is that intake fans are more valuable than exhaust fans, but you need to create some flow in case to make it cool well. Intake fans are more valuable likely because they push cold air into case and cold air is more dense and less viscous. Fans are also able to create far more pressure when they exhaust air, rather than suck it it. You have active pressure and static pressure then. In intake active pressure is lower and you rely on static pressure more. Computer fans are made to create airflow and they are either way weak at creating pressures. They are not compressors, they are not sealed and and unsurprisingly they don't produce much pressure. If I understand correctly, computer fans are able to take in air and then exhaust it at fast rate. They have just enough pressure to deal with some obstructions, static pressure fans have better ability to to deal with them, meanwhile airflow fans suffer greatly with any obstruction at all. The main point in fans is to have good air exhaust velocity and just enough static pressure to deal with obstructions, else you need more rpms and lose some velocity.

I think that my first advice was a little bit shit. But when I thought more, you need to put 2 static pressure fans on radiators. You are either way advised to use static pressure fans as intakes to beat resistance of grilles and other obstructions and you should use static pressure fans on radiator anyway, so it saves fans. You can install AIO as bottom intake (but consider that it's AIO and I have no idea if it affects longevity of it) and then use stock case fans as two top exhausts. That should create a nice air chimney effect. It should work rather well, despite GPU mounted horizontally. Here's an example of chimney airflow:

That's probably the best bet with least amount of fans used. Your main problem is that 280X doesn't have any proper rear exhaust and you only have top exhaust. So in typical built, people would use front intake and top exhaust, but air doesn't like bending 90 degrees. As for grilles, you can likely remove top grille without dust consequences as you still have glass cover for dust to land on it. Bottom intake doesn't have tall feet, so maybe filter is a good idea. If feet were tall, you could use it without filter as fans only have so much force to suck dust from floor. ANd if you have static pressure fans, they will have to spin faster to create same airflow as generic fan, so be warned. Anyway, just test out various things and see what happens, theorizing so much isn't good without putting ideas to practice

 

[TheoneandonlyMrK]

I just tested theory of no exhaust fans in my case (Silencio S400) and conclusion is that exhaust fans are good. Here are temps with exhaust fans stopped and with exhaust fans working (I ran prime95 small FFTs and Unigine Tropics for 20 minutes and only care about maximum temperatures):
CPU Package 78C - 73C
CPU Core 78C - 73C
PCH 48C - 46C
VRM MOS 76C -73C
PCIe x16 48C - 46C
SSD (OS SSD) 38C - 37C
GPU Diode 67C - 65C
GPU VRM 1 64C - 62C

Exhaust fans helped to me, I guess its a good idea to use them. What we can take away from doyll's assertion is that intake fans are more valuable than exhaust fans, but you need to create some flow in case to make it cool well. Intake fans are more valuable likely because they push cold air into case and cold air is more dense and less viscous. Fans are also able to create far more pressure when they exhaust air, rather than suck it it. You have active pressure and static pressure then. In intake active pressure is lower and you rely on static pressure more. Computer fans are made to create airflow and they are either way weak at creating pressures. They are not compressors, they are not sealed and and unsurprisingly they don't produce much pressure. If I understand correctly, computer fans are able to take in air and then exhaust it at fast rate. They have just enough pressure to deal with some obstructions, static pressure fans have better ability to to deal with them, meanwhile airflow fans suffer greatly with any obstruction at all. The main point in fans is to have good air exhaust velocity and just enough static pressure to deal with obstructions, else you need more rpms and lose some velocity.

I think that my first advice was a little bit shit. But when I thought more, you need to put 2 static pressure fans on radiators. You are either way advised to use static pressure fans as intakes to beat resistance of grilles and other obstructions and you should use static pressure fans on radiator anyway, so it saves fans. You can install AIO as bottom intake (but consider that it's AIO and I have no idea if it affects longevity of it) and then use stock case fans as two top exhausts. That should create a nice air chimney effect. It should work rather well, despite GPU mounted horizontally. Here's an example of chimney airflow:

That's probably the best bet with least amount of fans used. Your main problem is that 280X doesn't have any proper rear exhaust and you only have top exhaust. So in typical built, people would use front intake and top exhaust, but air doesn't like bending 90 degrees. As for grilles, you can likely remove top grille without dust consequences as you still have glass cover for dust to land on it. Bottom intake doesn't have tall feet, so maybe filter is a good idea. If feet were tall, you could use it without filter as fans only have so much force to suck dust from floor. ANd if you have static pressure fans, they will have to spin faster to create same airflow as generic fan, so be warned. Anyway, just test out various things and see what happens, theorizing so much isn't good without putting ideas to practice

Err Long post , ended well, theorising isn't going to get you there.
One thing though air very much likes 90° bends.
Laminar flow is usually temporarily, requires very high for a pc flow rates and also requires server level fans to have any hope of occuring.
Turbulent flow is Typical.

 

[AusWolf]

I just tested theory of no exhaust fans in my case (Silencio S400) and conclusion is that exhaust fans are good. Here are temps with exhaust fans stopped and with exhaust fans working (I ran prime95 small FFTs and Unigine Tropics for 20 minutes and only care about maximum temperatures):
CPU Package 78C - 73C
CPU Core 78C - 73C
PCH 48C - 46C
VRM MOS 76C -73C
PCIe x16 48C - 46C
SSD (OS SSD) 38C - 37C
GPU Diode 67C - 65C
GPU VRM 1 64C - 62C

Exhaust fans helped to me, I guess its a good idea to use them. What we can take away from doyll's assertion is that intake fans are more valuable than exhaust fans, but you need to create some flow in case to make it cool well. Intake fans are more valuable likely because they push cold air into case and cold air is more dense and less viscous. Fans are also able to create far more pressure when they exhaust air, rather than suck it it. You have active pressure and static pressure then. In intake active pressure is lower and you rely on static pressure more. Computer fans are made to create airflow and they are either way weak at creating pressures. They are not compressors, they are not sealed and and unsurprisingly they don't produce much pressure. If I understand correctly, computer fans are able to take in air and then exhaust it at fast rate. They have just enough pressure to deal with some obstructions, static pressure fans have better ability to to deal with them, meanwhile airflow fans suffer greatly with any obstruction at all. The main point in fans is to have good air exhaust velocity and just enough static pressure to deal with obstructions, else you need more rpms and lose some velocity.

I think that my first advice was a little bit shit. But when I thought more, you need to put 2 static pressure fans on radiators. You are either way advised to use static pressure fans as intakes to beat resistance of grilles and other obstructions and you should use static pressure fans on radiator anyway, so it saves fans. You can install AIO as bottom intake (but consider that it's AIO and I have no idea if it affects longevity of it) and then use stock case fans as two top exhausts. That should create a nice air chimney effect. It should work rather well, despite GPU mounted horizontally. Here's an example of chimney airflow:

That's probably the best bet with least amount of fans used. Your main problem is that 280X doesn't have any proper rear exhaust and you only have top exhaust. So in typical built, people would use front intake and top exhaust, but air doesn't like bending 90 degrees. As for grilles, you can likely remove top grille without dust consequences as you still have glass cover for dust to land on it. Bottom intake doesn't have tall feet, so maybe filter is a good idea. If feet were tall, you could use it without filter as fans only have so much force to suck dust from floor. ANd if you have static pressure fans, they will have to spin faster to create same airflow as generic fan, so be warned. Anyway, just test out various things and see what happens, theorizing so much isn't good without putting ideas to practice

That's an interesting test, thanks for that. I'm definitely not gonna neglect using exhaust fans, especially since my AIO is mounted as top exhaust. Which made me think... You're right that with the glass top on my case, I would probably be alright without a dust filter under it. And... if I used my AIO as front intake, I probably wouldn't need a filter there, either, as the radiator naturally filters larger dust particles (smaller ones get into your case anyway). I'm just not sure how that would affect GPU thermals. I guess this is something worth testing. The only thing I can't do is have bottom fans, as they would interfere with my motherboard's connectors (front panel, audio, SATA, etc.).

 

[freeagent]

Pressure is for rads, isn't it?

120x38s were used for cabinet cooling long before rads were a thing on the desktop.. The mills and lathes at work all use 120x38s and 140x38s for cabinet cooling as well.

 

[Deleted member 212040]

Stop caring about negative or positive pressures. Dust is an unwinnable battle. Get yourself an anti-static electric blower and dust out your PC once in a while.

 

[The red spirit]

That's an interesting test, thanks for that. I'm definitely not gonna neglect using exhaust fans, especially since my AIO is mounted as top exhaust. Which made me think... You're right that with the glass top on my case, I would probably be alright without a dust filter under it. And... if I used my AIO as front intake, I probably wouldn't need a filter there, either, as the radiator naturally filters larger dust particles (smaller ones get into your case anyway). I'm just not sure how that would affect GPU thermals. I guess this is something worth testing. The only thing I can't do is have bottom fans, as they would interfere with my motherboard's connectors (front panel, audio, SATA, etc.).

Well, the most brutish attempts to cool your PC is to use AIO as front intake, add two bottom intakes and use two top exhaust fans. I was just saying that with chimney airflow you can likely get rid of two fans without negative consequences as they will create more air blow than airflow. If you had vertical card bracket, I'm sure that chimney would work totally fine, with horizontal GPU I'm not sure if it will work well. The problem with it is that it blocks airflow and thus starves upper case of fresh air intake. front intake may be useless then as on bottom it would just blow air in and air will be blocked by GPU, on top front intake would blow air in, but it wouldn't be able to go far in case as it would get sucked in by exhaust AIO. Perhaps that's still better to ram some cold air, but it's feels so unnecessary, when vertical card bracket could solve that problem in much more effective way. That sounds nice and all, but in reality bracket on Amazon is expensive, 50 burger dollars. I really want to slap someone at Corsair for not making rear exhaust fan mount or for not including vertical GPU bracket for already overpriced case. They could have just marketed vertical mount for those RGB wankers and they would suck it up. That would have good for airflow and for bling, but as is, it's neither.

 

[AusWolf]

Well, the most brutish attempts to cool your PC is to use AIO as front intake, add two bottom intakes and use two top exhaust fans. I was just saying that with chimney airflow you can likely get rid of two fans without negative consequences as they will create more air blow than airflow. If you had vertical card bracket, I'm sure that chimney would work totally fine, with horizontal GPU I'm not sure if it will work well. The problem with it is that it blocks airflow and thus starves upper case of fresh air intake. front intake may be useless then as on bottom it would just blow air in and air will be blocked by GPU, on top front intake would blow air in, but it wouldn't be able to go far in case as it would get sucked in by exhaust AIO. Perhaps that's still better to ram some cold air, but it's feels so unnecessary, when vertical card bracket could solve that problem in much more effective way. That sounds nice and all, but in reality bracket on Amazon is expensive, 50 burger dollars. I really want to slap someone at Corsair for not making rear exhaust fan mount or for not including vertical GPU bracket for already overpriced case. They could have just marketed vertical mount for those RGB wankers and they would suck it up. That would have good for airflow and for bling, but as is, it's neither.

I think Corsair only thought about people with water-cooling with this case, as it doesn't rely so much on back exhaust as tower style air coolers do.

If I could mount fans on the bottom for a chimney style airflow, I'd definitely do that! But unfortunately, even 12 cm fans there would leave me no room to connect the front panel headers, so it's a no-go. Even the Corsair website states that the bottom fan mounts can only be used with a mini-ITX motherboard, which as I've seen, is definitely true. I'll be away from home next week, but later I'll try to test what a front mounted (intake) AIO with no dust filters do to GPU temps. If it's a feasible option, I'll consider upgrading to a 280 mm AIO and/or 14 cm case fans, and see how (if) they fit.

Stop caring about negative or positive pressures. Dust is an unwinnable battle. Get yourself an anti-static electric blower and dust out your PC once in a while.

Please read back a couple of posts.

I don't care about dust! My question is about airflow and internal case (and GPU) temperatures! Thank you.

 

[Deleted member 212040]

Then that's case dependent. Some cases are built for positive pressure, some for negative and some for balanced. On my 500DX I have four 140mm fans, two intakes & two exhausts. As it's the proper airflow configuration for this case.

 

[The red spirit]

I think Corsair only thought about people with water-cooling with this case, as it doesn't rely so much on back exhaust as tower style air coolers do.

If I could mount fans on the bottom for a chimney style airflow, I'd definitely do that! But unfortunately, even 12 cm fans there would leave me no room to connect the front panel headers, so it's a no-go. Even the Corsair website states that the bottom fan mounts can only be used with a mini-ITX motherboard, which as I've seen, is definitely true. I'll be away from home next week, but I'll try to test what a front mounted (intake) AIO with no dust filters do to GPU temps. If it's a feasible option, I'll consider upgrading to a 280 mm AIO and/or 14 cm case fans, and see how (if) they fit.

Well, that's even more fucked up then. Your only option is to have front intake and top exhaust. Two fans on each. Still, I think it's better to put AIO on front, but this needs testing. I really don't want it on top, because you are supposed to use pressure fans on intake and put obstructions on intake. Hot air is less dense, more viscous and is much harder to pressurize it, therefore using static pressure fans on hot air exhaust just looks like a bad idea and GPU almost always expels more heat than CPU, so you take it quite hot air and make it even hotter, that's probably bad for CPU temps.