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Negative or positive pressure? Does it matter?

@claes
I have a question for you.
Let's say i have 3 top fans exhaust ( push) and then i add another 3 and make it 6 push-pull, are those top fans still counted as 3 exhaust or 6 exhaust?
 
Fixed that for you.
Lol, mtcn is throwing you under the bus, defending an argument that you are disagreeing with, and now you’re just hurling insults because they disagree with me, even though we both think you’re wrong… this is too rich.

@claes
I have a question for you.
Let's say i have 3 top fans exhaust ( push) and then i add another 3 and make it 6 push-pull, are those top fans still counted as 3 exhaust or 6 exhaust?
It depends! Even if we assume they are all the same fans, running at the same speeds, there is still a PQ curve to account for, in addition to any obstructions (radiator, chassis air-hole machining, filters).

I would say no, which is why I joked about the “8 - 5 = 3, therefore positive pressure” math before (no offense, we’re all learning (maybe not the know-it-all’s, but hopefully!)). In the abstract, sure, if we’re accounting for a singular set of obstructions, but most fan specs are measured without resistance/obstructions and don’t scale linearly (thus the PQ curves, which are typically measured in free air and will of course change in the face of resistance).

Edit: what we can say is that there are really diminishing returns for push-pull in a chassis, to the tune of 1-4 degrees. I’m sure someone else can speak to why things don’t scale too well, so I’ll leave it to them. I’d say that there’s so much resistance (due to radiator fins, chassis holes, and filters), that there’s only so much our sweet little fans can do, but I feel like I read that the same happens in ducts and other more optimal conditions.
 
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@claes
I have a question for you.
Let's say i have 3 top fans exhaust ( push) and then i add another 3 and make it 6 push-pull, are those top fans still counted as 3 exhaust or 6 exhaust?
Now let's clarify. What you are saying is having 3 fans blowing air out of the system and then you add 3 more fans stacked with/behind them blowing air out of the system?

If this is what you're saying, then no. You added static pressure to the existing 3 fans, but not added any extra speed or extra airflow. Put another way, you have made the airflow through those vents stronger but not faster. The downside is that you added extra noise because the fan blade arrays being in such close proximity to each other will create additional turbulence that was not there before. So the additional power in the airflow is not 1+1=2. It's more like 1+1=1.4. You're not increasing the CFPM of air being moved, only increasing the force being applied to it's movement.

Does that make sense?
 
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Lol, mtcn is throwing you under the bus, defending an argument that you are disagreeing with, and now you’re just hurling insults because they disagree with me, even though we both think you’re wrong… this is too rich.


It depends! Even if we assume they are all the same fans, running at the same speeds, there is still a PQ curve to account for, in addition to any obstructions (radiator, chassis air-hole machining, filters).

I would say no, which is why I joked about the “8 - 5 = 3, therefore positive pressure” math before (no offense, we’re all learning (maybe not the know-it-all’s, but hopefully!)). In the abstract, sure, if we’re accounting for a singular set of obstructions, but most fan specs are measured without resistance/obstructions and don’t scale linearly (thus the PQ curves, which are typically measured in free air and will of course change in the face of resistance).

Edit: what we can say is that there are really diminishing returns for push-pull in a chassis, to the tune of 1-4 degrees. I’m sure someone else can speak to why things don’t scale too well, so I’ll leave it to them. I’d say that there’s so much resistance (due to radiator fins, chassis holes, and filters), that there’s only so much our sweet little fans can do, but I feel like I read that the same happens in ducts and other more optimal conditions.

The 8x front fans + the 2x exhaust are 120mm 43.25 CFM, the 3x top are 140mm 51.5 CFM, sure they don't run at the same speed because the 120mm increase/decrease speed depending CPU temps and the 140mm depending GPU temp.

Now let's clarify. What you are saying is having 3 fans blowing air out of the system and then you add 3 more fans stacked with/behind them blowing air out of the system?
Exactly.
 
Just wanted to make sure I understood your thought. My advise is not to stack your fans. If you need more airflow, buy a fan with higher RPM ratings. Stacking fans does little and makes for a very, needlessly, noisy setup.
 
Just wanted to make sure I understood your thought. My advise is not to stack your fans. If you need more airflow, buy a fan with higher RPM ratings. Stacking fans does little and makes for a very, needlessly, noisy setup.
Wait, there is a misunderstanding.
It's not stacking one fan to the other it's adding 3 more fans to the rad which makes it 6 fans ( push-pull ) so it helps to move the air through the rad.
 
Like what?
It's fan - rad -fan - dust filter.
Then the effect is the same. You are only adding force to the airflow, not speed and with the extra fans you are adding a lot of noise. Want you want to do instead is buy faster fans with stronger motors. This will improve airflow while not more than doubling the the noise being generated.

Just an FYI, having your dust filter behind the fans does nothing to reduce dust in your system, it only reduces airflow of exhaust air. Remove that filter and air will flow much more freely out of the system. Air filters should only ever be in front of intake air vents on a PC case, never behind a fan in the exhaust vents.
 
I don't like filters as a rule, imo they are restrictive. I don't bother with them, and just clean regularly. I'm not sure how much positive/negative mine is, but there does not seem to be much dust in it. This is after about 3 weeks
 

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Want you want to do instead is buy faster fans with stronger motors. This will improve airflow while not more than doubling the noise being generated.
I would have done that maybe 3 years ago when for me fans noise wasn't a problem but with my last build i went for silent fans, then adding 13 fans to be controlled by the Motherboard isn't a great idea because i hate the way they ramp up when there's some load, it's annoying, another thing is that i prefer that the GPU and CPU fans work separately depending on their temp and not on CPU load.
Just an FYI, having your dust filter behind the fans does nothing to reduce dust in your system, it only reduces airflow of exhaust air. Remove that filter and air will flow much more freely out of the system. Air filters should only ever be in front of intake air vents on a PC case, never behind a fan in the exhaust vents.
That's the point.
My problem is how to remove the dust from the top when it's time to clean it.

Top filter, never had been cleaned.
20211014_112458.jpg


I don't like filters as a rule, imo they are restrictive. I don't bother with them, and just clean regularly. I'm not sure how much positive/negative mine is, but there does not seem to be much dust in it. This is after about 3 weeks
How many rads you have, and can you remove the front Panel?
 
Yes front panel comes off
Then it's easy for you to clean it and you can do without filter, for me it's not the same.

Front panel cant be removed

20211014_120822.jpg
 
Be nice to each other, I was banned from this thread, and it can happen to you too!

:)
 
I think what has been hard to get the message across is quantity does not make up for quality. We can have all the airflow in the world, but that would make the particular case circulation be turbulent which is not what we want with "positive air pressure".
There can only be a finite amount of air volume per case cross section. We don't want to violate that and cause noise & dust build up.

Don't mix up the two.

We can only accelerate air so much until flow separations start making noise at the fan blade inlet & outlet. This being the limiting factor, then it becomes a question of how far the forced convection 'air fan' is from the actively cooled component(head a.k.a pressure vs. distance). It makes the solution very much a parametric one. You can choose a larger case, or find a smaller one with directed air channels to the components. Either way, your performance will be fine from the get go.
 
@claes
I have a question for you.
Let's say i have 3 top fans exhaust ( push) and then i add another 3 and make it 6 push-pull, are those top fans still counted as 3 exhaust or 6 exhaust?
3, it's the same airflow you're just increasing the pressure
 
My problem is how to remove the dust from the top when it's time to clean it.
Don't use a filter on your top exhaust vents, then you will not need to worry about cleaning it and you won't have any air flow resistance out the top..

Be nice to each other, I was banned from this thread, and it can happen to you too!

:)
Wait, did I miss something? I'm not seeing any hostilities going on.
Nevermind, had to click "show ignored content"..

Then it's easy for you to clean it and you can do without filter, for me it's not the same.

Front panel cant be removed

View attachment 220812
That glass panel can't be removed? Odd design..
 
That glass panel can't be removed?..
Not the traditional way.

Hard way - min 3:10 ( i am not willing to do that every 2 months :laugh: )


Don't use a filter on your top exhaust vents, then you will not need to worry about cleaning it
I wasn't talking about cleaning the top filter but cleaning the inside top glass of the case, it cant be removed
 
Not the traditional way.

Hard way - min 3:10 ( i am not willing to do that every 2 months :laugh: )



I wasn't talking about cleaning the top filter but cleaning the inside top glass of the case, it cant be removed
That is how we do it. You take pliers and crimp the inserts.
 
Although dust can be an issue where I live and the fact I have almost 20 dogs the living room my pc stays is dog free and cleaned regularly so my thinking with ambient temps being so high dust filters and possitive pressure wasn't a good idea.

But I have the greatest enemy to electronics here... House geckos!!! They have destroyed 2 air conditioners a refrigerator and a TV in the 6 years I've lived here so when my pc isn't running it's covered over this also stops dust settling while no fans are running.
 
I took a shot in the dark and bought this.
Very impressed how well it works, and I have way less dust getting on my PC
On sale it was $140. I can't believe I waited so long. I thought it would get hung up on stuff
but it doesn't. A couple of small changes I had to make but really happy with it.

p1kalmig2k.jpg
 
Noticed that Lenovo C30 does need to be closed, in order to function properly. Otherwise the CPU overheats, as no stream of air is coming through it. :confused:
 
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