[SOLVED] Does airflow really work the way I think it does in this case?

ProtoflareX

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I have a question about the fan setup portrayed in this picture. I don't know if I'm crazy, or if airflow actually works this way, but isn't the air being drawn into the case by the uppermost front intake fan being immediately sucked out of the case by the first top exhaust fan before it has a chance to cool anything? I also have a second question about the rear mounted exhaust fan and the top exhaust fan that is furthest back. Since those fans are in such close proximity to each other, aren't they kind of "fighting" with each other for air?
 

Barty1884

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In theory.... Kind of.

The airflow of the top intake (200mm?) will be greater than the top exhaust (120-140mm) and the air would need to turn 90' to truly go straight out of the top.
Similarly, the rear & top exhaust would "fight" for air to some degree but, given they're both removing warm air, there's not really a winner or loser - it's two fans working together to do the same job.

As DLoT mentioned, in a custom loop like that, the fans are mostly only there to move air through the radiators. They will also provide some airflow across the VRMs, and will look good.


In an air cooled setup, you have to consider that hot air rises. So, if you had 2x 200mm fans pulling air in from the front, the rear 120-140mm exhaust can't handle all of that. Hot air will rise and naturally escape via the top - the fans simply assist with that.
 
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ProtoflareX

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Most of that water cooled setup fan wise , is for looks. To highlight the water cooling setup.
I'm still curious about how air moves through the case though. Let's assume that I am using a heatsink instead of liquid cooling. It would be important for air from the front intake fans to reach the heatsink, right? Wouldn't the first top exhaust fan interfere with that?
 

Barty1884

Titan
Moderator
In theory.... Kind of.

The airflow of the top intake (200mm?) will be greater than the top exhaust (120-140mm) and the air would need to turn 90' to truly go straight out of the top.
Similarly, the rear & top exhaust would "fight" for air to some degree but, given they're both removing warm air, there's not really a winner or loser - it's two fans working together to do the same job.

As DLoT mentioned, in a custom loop like that, the fans are mostly only there to move air through the radiators. They will also provide some airflow across the VRMs, and will look good.


In an air cooled setup, you have to consider that hot air rises. So, if you had 2x 200mm fans pulling air in from the front, the rear 120-140mm exhaust can't handle all of that. Hot air will rise and naturally escape via the top - the fans simply assist with that.
 
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ProtoflareX

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Jan 3, 2014
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In theory.... Kind of.

The airflow of the top intake (200mm?) will be greater than the top exhaust (120-140mm) and the air would need to turn 90' to truly go straight out of the top.
Similarly, the rear & top exhaust would "fight" for air to some degree but, given they're both removing warm air, there's not really a winner or loser - it's two fans working together to do the same job.

As DLoT mentioned, in a custom loop like that, the fans are mostly only there to move air through the radiators. They will also provide some airflow across the VRMs, and will look good.


In an air cooled setup, you have to consider that hot air rises. So, if you had 2x 200mm fans pulling air in from the front, the rear 120-140mm exhaust can't handle all of that. Hot air will rise and naturally escape via the top - the fans simply assist with that.
Thanks for the informative reply. I'm going to be building an air cooled rig in a few months and am trying to figure out how I can maximize airflow within that case. Perhaps you can help me? The case portrayed in that picture is the Cooler Master H500M, which I plan to purchase. The front intakes, as you surmised, are 200mm fans, and both the rear and top exhaust fans are 120mm fans. I know I'm probably way overthinking this, but there are a few questions I've had about this case and airflow that have been bugging me for some time now.

1. The top of the case features an acrylic glass panel. I think the gallery section of the product page has images that show it. I could be mistaken, but doesn't that glass panel kind of interfere with hot air leaving the case? I know there are some small vents below the glass panel, but wouldn't air be able to leave the case more easily, if that glass panel wasn't there at all like with this case here?

2. In regard to top exhaust fans, the case accommodates three 120mm fans, two 140mm fans or two 200mm fans. I would like to use either two 140mm fans, or one 200mm fan instead of three 120mm fans. If I use two 140mm fans, would I create the same problem I see in the picture involving one of the fans removing air from the case before it reaches my heatsink? Would it be better to use one 200mm fan and place it in the slot closer to the rear exhaust fan then the one closer to the top front intake fan?
 
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Barty1884

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To give you an idea - just because a case "can" support X number of fans, does not mean you need to populate all slots, nor does it mean airflow will be most optimal when all are populated.
Sometimes you need some trial & error, while monitoring temps to know what the optimal setup is. Each build is different, and there's no definitive answer that applies to all.

  1. Yes, the panel will restrict airflow - in this instance, hot air escaping. It will still find it's way out, but case trends favor closed off aesthetics. Quite typical these days to see fairly closed off front panels, limiting the ability to bring air in in the first place.
  2. Potentially, yes. You're not going to remove all of the air, but you would likely be interfering to some degree.
I would suggest starting with the stock configuration (2x 200mm intake at the front, 1x 140mm exhaust at rear) and go from there. For most users, the stock configuration should be more than sufficient.
 
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ProtoflareX

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To give you an idea - just because a case "can" support X number of fans, does not mean you need to populate all slots, nor does it mean airflow will be most optimal when all are populated.
Sometimes you need some trial & error, while monitoring temps to know what the optimal setup is. Each build is different, and there's no definitive answer that applies to all.

  1. Yes, the panel will restrict airflow - in this instance, hot air escaping. It will still find it's way out, but case trends favor closed off aesthetics. Quite typical these days to see fairly closed off front panels, limiting the ability to bring air in in the first place.
  2. Potentially, yes. You're not going to remove all of the air, but you would likely be interfering to some degree.
I would suggest starting with the stock configuration (2x 200mm intake at the front, 1x 140mm exhaust at rear) and go from there. For most users, the stock configuration should be more than sufficient.
If that's the case, forget the H500M. I'm not paying that price to have air flow restricted when that's what I'm trying to optimize the most with this build. If you don't mind, I'd like to ask you a final question about a substitute case I will be buying instead, the Cooler Master H500. Unlike the H500M, the H500 has a pure mesh top panel with nothing covering it at all except for a magnetic dust filter. However, instead of a 140mm rear exhaust fan, the H500 only supports a 120mm rear exhaust fan. If I understand the significance of fan sizes and everything you've told me correctly, then the H500 will exhaust less air from the rear due to the smaller fan size, but more from the top due to not having anything restricting the escape of heated air there?
 

Barty1884

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Moderator
While yes, all else being equal a 140mm will exhaust more air than a 120mm..... All else is rarely equal. RPM of the fan etc can play a part.
Given the descriptions though yes, I would expect the mesh panel will allow more air to escape naturally and the 120mm would be fine.

Given the sheer size of the H500, there might be better options out there for you unless you want/need to size afforded by the H500....
 

ProtoflareX

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While yes, all else being equal a 140mm will exhaust more air than a 120mm..... All else is rarely equal. RPM of the fan etc can play a part.
Given the descriptions though yes, I would expect the mesh panel will allow more air to escape naturally and the 120mm would be fine.

Given the sheer size of the H500, there might be better options out there for you unless you want/need to size afforded by the H500....
When you're eyeing the Thermalright Le Grand Macho RT as your CPU cooler, the size of the H500 becomes a pro rather than a con very quickly. Anyway, thank you for taking the time to answer me questions. Your responses were extremely informative and helpful. I knew I wasn't crazy when my intuition told me there was something wrong with that fan setup.
 

Barty1884

Titan
Moderator
The Grand Macho isn't actually that big. It's wide, but height wise (so thickness of the chassis) isn't too much of a concern. It's more of a pain to plug in headers, or attach the fan, and more room doesn't make that aspect much easier - you're still bound by the cooler to MB spacing.

I have the Noctua NH-D15, and have Chromax additions. Increases the height to ~168mm.... And I have it in a Meshify-C... A compact Mid Tower :ROFLMAO: It's a pain to install, but opting for a bigger tower would not have helped at all.
Anyway, just my $0.02

No, you're not crazy. Typically maxing out fan mounts makes no sense. Some people do get caught up on it though, and think maxing it out = better performance. It can, in certain specific situations, but those are rare.
You can actually negatively impact your cooling ability opposed to improve it in a lot of instances.

You're welcome. Glad to help.
 
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