Cpu cooler exhaust cfm question

[Qu9ke]

I'm looking to build a positive pressure case, but I was wondering something. Do I take into account the exhaust cfm from the cpu cooler, in this case being the Noctua NH-D15, when adding the exhaust cfm together? I was originally thinking of going with an AiO cooler, but I want to stay away from risks of leaks, however minimal they may be.

My intake: 148.7+64.4+64.4=277.5 cfm
My exhaust (excluding cpu cooler): 82.1+64.4+64.4=210.9 cfm
Noctua NH-D15 cfm: 82.5

So do I add 82.5 to 210.9 to get my total exhaust cfm? Is that how it works? If so it looks like at maximum speeds, my case would be negative pressure.

 

[coozie7]

No, it will make very, very little difference.

 

[TJ Hooker]

No, because your CPU cooler just blows air within the case; it doesn't exhaust it.

 

[Qu9ke]

No, because your CPU cooler just blows air within the case; it doesn't exhaust it.

That's all I needed to know. Thank you. Thanks to you too coozie just in case you see this.

 

[Paperdoc]

Let me add a note. I applaud your paying attention to air flow balance, and share your preference for a slightly positive pressure in the case. However, I find it impossible to be sure that calculations based on specs of maximum air flow from fans can predict net balance. In fact, I don't know any reliable way.

Instead, I try to do the best estimating job I can. Then AFTER the system is assembled and running, you can TEST for the real result. How? You need some source of a visible tracer like smoke. An incense stick or cigarette will do. Move the smoke source around the outside of the case NOT near fan grilles but close to small holes like drive slots. Observe which way the smoke flows. If it goes into the case, you have a negative pressure in there and can suck dust into those openings. If it blows away from the case, it has positive pressure.

 

[Qu9ke]

Let me add a note. I applaud your paying attention to air flow balance, and share your preference for a slightly positive pressure in the case. However, I find it impossible to be sure that calculations based on specs of maximum air flow from fans can predict net balance. In fact, I don't know any reliable way.

Instead, I try to do the best estimating job I can. Then AFTER the system is assembled and running, you can TEST for the real result. How? You need some source of a visible tracer like smoke. An incense stick or cigarette will do. Move the smoke source around the outside of the case NOT near fan grilles but close to small holes like drive slots. Observe which way the smoke flows. If it goes into the case, you have a negative pressure in there and can suck dust into those openings. If it blows away from the case, it has positive pressure.

Funny you bring that up because that is exactly what I was thinking about doing. I thought about using some incense. I appreciate the input though.