Trying to make sense of fan sizes and optomizations for custom case build

[Mothballs]

I'm working at a Scratch case Build, which is still very early stages, but I'm trying to make sense of fan choices and pressure/flow/noise optimization, as that will set a few solid tick boxes on the cases looks and the build approach. It's supposed to be a more classy looking gaming build.

The goal is a good, clean chassis look, so No side panel fans, in an ATX tower, and the focus is Air Cooling, most likely with Noctua products, the the final case having wood portions and the ever popular tempered glass and aluminum for the rest of the build.

Aesthetically, I want dual 200mm Fans at the front, Because that look has always been top notch in my books, With Dual top 140mm Exhausts (Low Noise Adaptors used here, most likely?), and a single rear 140mm as well. Possilby a 120 or 140mm in a lower mount to cool a drive bay under a PSU shroud.

The Issue is, as Shown with the H500P, that the lack of static pressure from the giant 200MM fans leads to issues with cooling as the exhaust fans push out more air then the front can supply, and the top fans will quickly divert air up and away from the CPU. This could be solved if there was a counter rotating 200mm fan to stack on the back of the others to boost output, but that also increases turbulence and noise.

Even assuming that the Datasheets 25% performance Advantage of the Noctua over, say, the Coolermaster RGB 200mm Fans when it comes to static pressure is true, it leaves me a long way behind a trio of 140mm Fans, though on average, the noise level should be much lower if I'm reading things correctly.

The 200mm design means I can't have any front panel obstructions other then a light mesh (non Issue), though from what I can tell CPU temp performance actually increases slightly by making a back pressure on the top exhaust with a direct obstruction (Glass panel) that would divert Air 90 degrees. So There are a few things I can figure out.

The main questions are:

• If I go down the 200mm route and build something large enough to hold E-ATX sized boards, will lowering Top fan RPM / Applying back pressure help the case pressure overall?
• Are the top fans actually more likely to hinder cooling, "stealing" cold air from the low pressure front fans overall?
• How much impact will a PSU shroud have on cooling performance? Should the shroud have a basement fan and ventilation pass through to assist the front 200mm fans /cool Drives?
• Are there any tricks to aid in a dual 200mm front fan design when it comes to getting air to proper components?
• There's probably more to ask here, but It's 2 AM and I've been staring at the screen for two hours.

[LogicalDrm]

First, please provide sketch or something. Its easier to give advice when we know how fans will be used.

 

1 hour ago, Mothballs said:

The main questions are:

• If I go down the 200mm route and build something large enough to hold E-ATX sized boards, will lowering Top fan RPM / Applying back pressure help the case pressure overall?

 

Honestly pressure isn't main thing. You want to have constant airflow from intake, through cooled parts and out of the case. You can achieve that by making higher rpm fans spin slower to compensate slower rpm fans. You can do some basic calculations with CFM ratings, though those aren't so accurate and many things effect on them.

 

1 hour ago, Mothballs said:

• Are the top fans actually more likely to hinder cooling, "stealing" cold air from the low pressure front fans overall?

 

This will depend on how fans are located with cooled parts. If you have exhaust fan located in airflows path before cooled part, ofc it will exhaust cool air before that gets into cooler.

 

1 hour ago, Mothballs said:

• How much impact will a PSU shroud have on cooling performance? Should the shroud have a basement fan and ventilation pass through to assist the front 200mm fans /cool Drives?

 

I can't answer before I see what plan is. Shrouds are there to hide PSUs (usually). If PSU intakes from outside and exhaust to outside, it doesn't have effect on general airflow.

 

1 hour ago, Mothballs said:

• Are there any tricks to aid in a dual 200mm front fan design when it comes to getting air to proper components?

 

Adding assisting fans inside to point to cooled parts.

 

In general I would recommend not going 200mm route as main intakes.