Fan orientation?

[ThaJengo]

Dear forum,

 

Just put together a Lian Li O11 mini, but had a thought with the fans.

Currently the setup is as follows: See image, blue = intake, red = exhaust.

 

I was wondering, my front fan in the top (image: Red, far right, top), is an exhaust fan, but all it does is sucks cold air out, from the side intake.

Would it make sense to make this an intake, to try and get more fresh air in for the cpu (Noctua NHD 15 cooling the R9 5900x)?

Anyone have experience with running fans side by side in opposite flow directions? Does this cause any turbulence noise, or other problems?

 

Thanks a ton in advance :)

[GuiltySpark_]

2 minutes ago, ThaJengo said:

 

Anyone have experience with running fans side by side in opposite flow directions? Does this cause any turbulence noise, or other problems?

 

 

 

Don't do that, you'll just be ruining both fans ability to do their jobs.

 

Your setup right now is how 95% of people with that case set it up, myself included. It works fine. 

[Sprawlie]

yo want the fan path to effectively be a "wind tunnel"

 

air in one side, out the other side. with a constant stream of cool air coming in and passing over the components.

 

if you just suck in cold air from all vents, you end up creating a positive pressure situation and heated air cannot escape efficiently. This results in the inside of the case becoming really hot and your components over heating.

 

Ideally, you want neutral airflow (same in as out) but if you cannot achieve that, you are much better off creating a negative pressure inside the case with more exhaust than intake, This will result in cool air being sucked in through any opening/gap that isn't an exhaust.

 

[ThaJengo]

2 minutes ago, rickeo said:

Your setup right now is how 95% of people with that case set it up, myself included. It works fine. 

That is what I figured, was just wondering if anyone had tried something along those lines.

[leclod]

6 minutes ago, Sprawlie said:

yo want the fan path to effectively be a "wind tunnel"

 

air in one side, out the other side. with a constant stream of cool air coming in and passing over the components.

 

if you just suck in cold air from all vents, you end up creating a positive pressure situation and heated air cannot escape efficiently. This results in the inside of the case becoming really hot and your components over heating.

 

Ideally, you want neutral airflow (same in as out) but if you cannot achieve that, you are much better off creating a negative pressure inside the case with more exhaust than intake, This will result in cool air being sucked in through any opening/gap that isn't an exhaust.

 

I wonder how you can be so sure, seems like a very unprecise science to me (not yours, in general).

 

A lot of fans, more than enough I believe. How fast are they spinning at idle/full load ?

If I were you I'd just try a few scenarios (eventhough you don't need to)

[ThaJengo]

3 minutes ago, Sprawlie said:

yo want the fan path to effectively be a "wind tunnel"

 

air in one side, out the other side. with a constant stream of cool air coming in and passing over the components.

 

if you just suck in cold air from all vents, you end up creating a positive pressure situation and heated air cannot escape efficiently. This results in the inside of the case becoming really hot and your components over heating.

 

Ideally, you want neutral airflow (same in as out) but if you cannot achieve that, you are much better off creating a negative pressure inside the case with more exhaust than intake, This will result in cool air being sucked in through any opening/gap that isn't an exhaust.

 

Okay, I take it you don't know, is the answer?

I agree, in = out is best, though I disagree, and would much rather go positive pressure, as this means you filter the air in, and the escaping air can then go out where it pleases. Anyway, that was not the point.

 

Thanks for the feedback, maybe I will just have to test this. Can't seem to find anything on the net about it. Might even try reversing the airflow over the cpu cooler, and making the side an exhaust, this could give fresh air to both gpu and cpu... but leaves hot air in the case for longer... Yeah, I think it may need actually testing at home this one.

But again, thanks for the feedback, much appreciated

[Sprawlie]

Just now, leclod said:

I wonder how you can be so sure, seems like a very unprecise science to me (not yours, in general).

 

A lot of fans, more than enough I believe. How fast are they spinning at idle/full load ?

If I were you I'd just try a few scenarios (eventhough you don't need to)

heat dissipation isn't a "guessing game"... it's physics based science.

[Sprawlie]

1 hour ago, ThaJengo said:

I agree, in = out is best, though I disagree, and would much rather go positive pressure, as this means you filter the air in, and the escaping air can then go out where it pleases. Anyway, that was not the point.

 

positive pressure is the worst of the 3 options. Especially if there's insufficient airflow to get the air out of the case.

 

with this case, as it's likely you have the bottom 3 fans on intake. the two side fans on intake. if you made the top 3 fans also intake, air is giong to have a hard time finding a way out.

 

You do NOT WANT your internal case temps to go up. there are other components that may suffer if they aren't getting cool air. Your motherboard chipset or even your GPU's VRAM (especially if just passively cooled)

 

  

< removed by moderation >

 

Edited August 24, 2021 by LogicalDrm

[ThaJengo]

It is of course an exact science, flow simulations exist. But, fans a turbulent, and this is just a bit of fun, anyway, I am sure you know this already.

What I go with is:

Keep the cool and hot air separated,

Try to have an equal mass flow across fans in and out. Though a lot, myself included, often go with a slight higher intake flow, as it is filtered.

 

That was a bit off topic, sorry.

Any experience with fans side by side in opposite orientations?

[ThaJengo]

9 minutes ago, Sprawlie said:

 

positive pressure is the worst of the 3 options. Especially if there's insufficient airflow to get the air out of the case.

 

with this case, as it's likely you have the bottom 3 fans on intake. the two side fans on intake. if you made the top 3 fans also intake, air is giong to have a hard time finding a way out.

 

You do NOT WANT your internal case temps to go up. there are other components that may suffer if they aren't getting cool air. Your motherboard chipset or even your GPU's VRAM (especially if just passively cooled)

 

  

Just because you don't like the answer because it didn't already give you the answer you were looking for doesn't mean i didn't answer. Don't insult/attack someone trying to help

 

-Why is positive the worst? Linus, says: (youtube.com/watch?v=g8EN3K-eaVA)

 

 

1: =

2: + (assuming air is filtered)

3: -

 

Gamers Nexus I believe says the same. The video is a bit old, but I can't imagine anything has changed?

 

-Case temps in theory don't matter, as long as this air is 100% separated from the cold air (ducting in servers). In this case it is not, so maybe, depends on flow rate.

As long as you have good flow, and get the VRM on the cool side, then it does not matter.

 

I stated in the post, one of the top fans, I understand flipping all the fans on the top will most likely make the thing a bit warm, but maybe, all the hot air will just go out the back of the case, it is full of holes anyway?

 

My question was: "Anyone have experience with running fans side by side in opposite flow directions?"

As you did not answer the actual question, I can only assume you don't know?

 

 

 

 

 

[leclod]

2 minutes ago, ThaJengo said:

I see, guess I will give it a shot sometime and see how it does.

Me, I'd like some feedback (although I might miss it)

[ThaJengo]

1 minute ago, leclod said:

Me, I'd like some feedback (although I might miss it)

I'll try to remember to get a message in your direction. Whenever I get it done  Can't imagine it will be the immediate future.

[Kid.Lazer]

1 hour ago, rickeo said:

Don't do that, you'll just be ruining both fans ability to do their jobs.

This.

 

Remember, the fans will create a pocket of low pressure on one side of the fan and high pressure on the other. If you invert 2 fans that are adjacent to each other, that pressure differential will try to equalize as soon as possible, creating an air loop through the fans. This would be the worst way to orient your fans.

 

The best way to fix the potential issue you describe at the top right corner (although not very pretty), would be to add an air deflector to keep the airflow from short-cutting directly from one fan to the other. In practice though, it should be largely unnecessary.

[ThaJengo]

2 minutes ago, Kid.Lazer said:

This.

 

Remember, the fans will create a pocket of low pressure on one side of the fan and high pressure on the other. If you invert 2 fans that are adjacent to each other, that pressure differential will try to equalize as soon as possible, creating an air loop through the fans. This would be the worst way to orient your fans.

I agree, but that is already happening, side and top. So what is worse, 90° or 180°. I would imagine 90° so flipping the fan may help?

 

Anyway, seems there are mixed opinions. Should have guessed I suppose  I will give it a go in the future and see what happens.

[LogicalDrm]

*** Thread cleaned ***

 

Please be civil. Unless you can provide articles, even of your own testing, to prove your claims, they are just personal experience and opinions.

***

 

Though as somewhat cooling guy myself, I would like to point out that saying "positive pressure makes your case hot" is not accurate. Case is not sealed box. It has always holes for air to escape through. Plus, you are bringing constant cool air in, so logic of case becoming hot when there's hot air escaping passively and cool going in, isn't very strong. On the other side, all fans out doesn't add as much cool air into mix. It does remove hot air, but passive intake with cool not being there, thats more likely to get your case hot.

Edited August 24, 2021 by LogicalDrm

[Sprawlie]

55 minutes ago, LogicalDrm said:

*** Thread cleaned ***

 

Please be civil. Unless you can provide articles, even of your own testing, to prove your claims, they are just personal experience and opinions.

***

 

Though as somewhat cooling guy myself, I would like to point out that saying "positive pressure makes your case hot" is not accurate. Case is not sealed box. It has always holes for air to escape through. Plus, you are bringing constant cool air in, so logic of case becoming hot when there's hot air escaping passively and cool going in, isn't very strong. On the other side, all fans out doesn't add as much cool air into mix. It does remove hot air, but passive intake with cool not being there, thats more likely to get your case hot.

 

this is also not entirely true either.

 

the case is going to be the deciding factor on whether positive pressure will even work at all.

 

A case that contains a complete seal on all sides, except for the fan openings, will suffer horrendously from possitive pressure situation due to a lack of efficient openings to exhaust. 

 

I have tested this thoroughly on multiple cases. Not so much an issue if you're getting an "airflow' case that has lots of openings and is effectively just a mesh case around your computer.

 

However, Something like NZXT cases that are completely sealed except for the fan locations will suffer tremendously in a positive pressure situation. I can tell you from absolute testing and experience, that if you allow the inside of your case to become a heat sync and cannot exhaust hot air efficiently, other components will suffer. I was able to attribute a 15% decline in GPU performance due to the backside of a a GPU getting too hot due to a poor positive pressure setup that didn't allow for efficient exhaust of hot air. And in this case , the O11 dynamic in question is a completely sealed case with only fan openings. The rear "mesh" would be completely insufficient for air exhausting if all the fans are set to intake. 

 

< removed by moderation >

 

 

Edited August 24, 2021 by LogicalDrm

[LogicalDrm]

41 minutes ago, Sprawlie said:

A case that contains a complete seal on all sides, except for the fan openings, will suffer horrendously from possitive pressure situation due to a lack of efficient openings to exhaust. 

Like I said, this just isn't true. Not even with most bad airflow cases, they have other openings than just fans holes.

 

As for your redacted part, if you want to discuss about how moderation is handled here, we can continue in PMs. Continuing what has already been removed will not move the main question of this thread, nor any argument over how airflow work, to either direction.

[Sprawlie]

14 minutes ago, LogicalDrm said:

Like I said, this just isn't true. Not even with most bad airflow cases, they have other openings than just fans holes.

 

again: you are wrong:

 

Many Cases absolutely do not have sufficient openings for a proper "positive pressure" setup. the O11 dynamic and NZXT 510 are examples of cases I KNOW and have tested that will absolutely cause an internal heat sink resulting in dropped performance.

 

Even on water.

 

There is insufficient airflow openings in these cases when all fans are fitted for proper positive pressure setup. Again. I HAVE TESTED THIS.

 

I'm on my 3rd case. Going ot switch to an airflow case that isn't completely sealed like these cases and see if any different. 

 

The problem is there really isn't sufficient airflow allowed. In fact, the NZXT is one of the worst cases for this in my testing. The front intake air vents themselves are too small and too restrictive, even with a proper neutral fan setup, can still have restricted airflow.

 

Not all cases are created equal.

 

 

Therre are benefits to Positive Pressure, For example, Dust collection is worse under negative pressure since you can't control where the air comes in. Positive pressure helps with this as it prevents air coming in. 

 

Here's one specific to the 011 Dynamic in which positive pressure setups resulted in higher temps.

 

Here's the chart in it: i've highlighted the fan setups that would result in positive pressure in the 011 dynamic. All of these positive pressure setups in this specific case resulted in warmer temps with higher fan speeds in order to adjust for it.

 

 

[ThaJengo]

9 minutes ago, Sprawlie said:

again: you are wrong:

 

Many Cases absolutely do not have sufficient openings for a proper "positive pressure" setup. the O11 dynamic and NZXT 510 are examples of cases I KNOW and have tested that will absolutely cause an internal heat sink resulting in dropped performance.

 

Even on water.

 

There is insufficient airflow openings in these cases when all fans are fitted for proper positive pressure setup. Again. I HAVE TESTED THIS.

 

I'm on my 3rd case. Going ot switch to an airflow case that isn't completely sealed like these cases and see if any different. 

 

The problem is there really isn't sufficient airflow allowed. In fact, the NZXT is one of the worst cases for this in my testing. The front intake air vents themselves are too small and too restrictive, even with a proper neutral fan setup, can still have restricted airflow.

 

Not all cases are created equal.

 

 

Therre are benefits to Positive Pressure, For example, Dust collection is worse under negative pressure since you can't control where the air comes in. Positive pressure helps with this as it prevents air coming in. 

 

Here's one specific to the 011 Dynamic in which positive pressure setups resulted in higher temps.

 

Here's the chart in it: i've highlighted the fan setups that would result in positive pressure in the 011 dynamic. All of these positive pressure setups in this specific case resulted in warmer temps with higher fan speeds in order to adjust for it.

 

 

Vid 1:

 

Where is the heatsink, and the fan? This will take the supplied air and move it to the back, the fans never change orientation, maybe reverse the whole thing. I can't give data, but my friend has a bitfenix nova mid, and reversing the airflow in this case (top rear to front) gives the best temps all round).

I find that video a bit silly, and the test at the end with the stacked fans is a joke. You can stack fans, and in fact this is done many places:

 

Big drones for instance, however this only works when the props/fans are counter rotating.

"coaxial rotor to possess a distinct advantage over the conventional system—a reduction in power of about 8%"

https://strathprints.strath.ac.uk/27336/1/Brown_RE_-_strathprints_-_A_comparison_of_coaxial_and_conventional_rotor_performance_Jan_2010.pdf

 

So that makes me doubt the quality of the testing in that video.

*https://hdairstudio.com/product/sonda-x8-multipurpose-multirotor/

 

Vid 2 + table:

But this only contains one test with the air cooler?

Of course using the AIO as an intake will increase case temps, and opposite you will get higher cpu temps with the AIO being an exhaust, as it will get warm air from the GPU...

 

[LogicalDrm]

22 minutes ago, Sprawlie said:

again: you are wrong:

I'm not arguing against what you say there. Just against your point that case is sealed box. It's not.

 

In fact, I agree with most of what you are saying. You are, in my opinion, overreacting a bit with the claim that positive "pressure" (its still not sealed box and fans are not powerful enough to make it pressurised to any direction) would be cause of overheating. You are also mixing in bad airflow which does have effects, but not in so direct ways.

[Sprawlie]

4 minutes ago, LogicalDrm said:

I'm not arguing against what you say there. Just against your point that case is sealed box. It's not.

 

In fact, I agree with most of what you are saying. You are, in my opinion, overreacting a bit with the claim that positive "pressure" (its still not sealed box and fans are not powerful enough to make it pressurised to any direction) would be cause of overheating. You are also mixing in bad airflow which does have effects, but not in so direct ways.

Sure

 

But i never said it was a "sealed box".

 

I said that with mostly sealed sides, the sides that are opened, or cases that are primarily only fan openigns that have fans in them, are not sufficient airflow

 

it was the people who decided to respond in mockery who implied that i was calling it a "sealed box"

 

no shit it's not sealed. there are gaps. None of these cases are hermetically sealed, nor did I say that at any point. That was the counter they tried to use to discount what I said.hence my frustration with you doubling down on it.

 

These cases that I have outlined have poor airflow openings for positive pressure to sufficiently provide enough openings for the hot air to exhaust. Completely different in a case that is mesh sided or with giant airflow openings around it. Cases like the O11, NZZT 510 are examples I've given where the majority of the case is "sealed" in that it's not a mesh case, nor does the sides that are "sealed" intend to provide airflow.

 

The ONLY poster who ever actually used the term "sealed box" was you.

 

 

 

[LogicalDrm]

33 minutes ago, Sprawlie said:

Sure

 

But i never said it was a "sealed box".

 

I said that with mostly sealed sides, the sides that are opened, or cases that are primarily only fan openigns that have fans in them, are not sufficient airflow

 

it was the people who decided to respond in mockery who implied that i was calling it a "sealed box"

 

no shit it's not sealed. there are gaps. None of these cases are hermetically sealed, nor did I say that at any point. That was the counter they tried to use to discount what I said.hence my frustration with you doubling down on it.

 

These cases that I have outlined have poor airflow openings for positive pressure to sufficiently provide enough openings for the hot air to exhaust. Completely different in a case that is mesh sided or with giant airflow openings around it. Cases like the O11, NZZT 510 are examples I've given where the majority of the case is "sealed" in that it's not a mesh case, nor does the sides that are "sealed" intend to provide airflow.

 

The ONLY poster who ever actually used the term "sealed box" was you.

 

 

 

Take it easy. We are having mature discussion here.

 

Yes, I'm the one calling it sealed box. After you claimed falsely that bringing cool air constantly in would eventually cause case to heat up. Claiming the reason to be "pressure". But I think we have gone over that argument enough.
It's not the core thing for this thread.

 

To OPs question. I don't think changing direction of the front most top fan would provide any meaningful improvement to your overall cooling performance. The air cooler itself becomes bottleneck first. With AIO you have more body to sank heat into. With custom loop even more than that.

 

As I think you have filled this case with fans more for the looks than actual performance, I would say that turning power on that front most top fan to minimum is the best solution. Keep it looking nice while affecting least to end results.

[ThaJengo]

12 minutes ago, LogicalDrm said:

To OPs question. I don't think changing direction of the front most top fan would provide any meaningful improvement to your overall cooling performance. The air cooler itself becomes bottleneck first. With AIO you have more body to sank heat into. With custom loop even more than that.

 

As I think you have filled this case with fans more for the looks than actual performance, I would say that turning power on that front most top fan to minimum is the best solution. Keep it looking nice while affecting least to end results.

You hit the nail on the head with that one. Looks has been a big part of the reason for all the fans.

But, I also want to get all I can out of them.

 

Reducing the RPM on that fan makes sense, maybe I should try that first.

 

Seems there are more opinions here than transistors in my cpu... I'll go with the good old trial and error.

Maybe one day I will go custom loop, but the price was too high, and I don't like AIO. (AIO - personal opinion, no logic to this)

 

Thanks for your input  

[Kid.Lazer]

3 hours ago, ThaJengo said:

I agree, but that is already happening, side and top. So what is worse, 90° or 180°. I would imagine 90° so flipping the fan may help?

 

Anyway, seems there are mixed opinions. Should have guessed I suppose  I will give it a go in the future and see what happens.

You are right that it is already occurring, which I why I suggested a device to redirect airflow as a best-case scenario. But again, in practice, it isn't needed unless you are trying to get the the absolute BEST airflow pattern physically possible in that space.

 

Trying different options certainly won't hurt, other than your wasted time if you choose to view it that way. But it's also a good learning experience.

 

I would agree with @LogicalDrm that if it's really a concern, reducing the top exhaust fan to minimum speed will keep your aesthetics while also limiting the wasted airflow from your front intake.

 

My experience in wind tunnels has taught me this: no matter how much you think you know about air dynamics, it's not proven until you actually blow it, and when you do, you'll probably find your idea was wrong. :shrug:

[ThaJengo]

1 minute ago, Kid.Lazer said:

You are right that it is already occurring, which I why I suggested a device to redirect airflow as a best-case scenario. But again, in practice, it isn't needed unless you are trying to get the the absolute BEST airflow pattern physically possible in that space.

 

Trying different options certainly won't hurt, other than your wasted time if you choose to view it that way. But it's also a good learning experience.

 

I would agree with @LogicalDrm that if it's really a concern, reducing the top exhaust fan to minimum speed will keep your aesthetics while also limiting the wasted airflow from your front intake.

 

My experience in wind tunnels has taught me this: no matter how much you think you know about air dynamics, it's not proven until you actually blow it, and when you do, you'll probably find your idea was wrong. :shrug:

I think you are right, maybe I am chasing phantoms.

 

I'll have a play with it some time in the future when I am bored, hopefully I can learn a thing or two.

 

Wind tunnels, interesting, I have worked a fair bit with CFD and small scale flow setups, but never a full scale tunnel, played with a small one at uni once...

Yeah, you are probably right, seems to go that way a lot of the time

- Thanks for the input, take care