Questions about positive and negative air pressure within a case.

[ProtoflareX]

As of late, I have been doing a lot of research on air flow within a case, and the aspect of case air flow that I'm looking into currently is air pressure. After learning about the differences between positive and negative air pressure, I believe that I want my case to err on the side of negative air pressure so that the chance of heat pockets forming within the case is reduced, even if I have to deal with more dust as a result. As far as I can tell, it is pretty simple to figure out whether your case leans more toward positive or negative pressure by analyzing just the case fans, but I would like to know how other fans within the case, such as the PSU fan, GPU fans and CPU heatsink fans affect air pressure as well. Do those fans need to be taken into consideration too, or is air pressure established solely by the case fans?

[mwomp]

IMO, air pressure is not solely measured by the case fans, sometimes the GPU (depending on it's exhaust style, ie Blower) and the PSU play some role. RPM and fan-size matter also, not just the number of fans (which I'm sure you know). Passive exhaust plays a role as well, whether or not most of the case is air-tight or has machined holes. Cable-management also can affect air-flow.

 

I was just reading last night about how depending on passive ventilation/card style you might be recycling warm air into the GPU, which was pretty interesting. Unfortunately I can't find the article with the GPU consideration.

Jay had a video where he used incense smoke to visualize what the air inside his PC was doing depending on how he arranged his fan setup. It really helped to see how big an impact his passive vents had.

[ProtoflareX]

19 minutes ago, mwomp said:

IMO, air pressure is not solely measured by the case fans, sometimes the GPU (depending on it's exhaust style, ie Blower) and the PSU play some role. RPM and fan-size matter also, not just the number of fans (which I'm sure you know). Passive exhaust plays a role as well, whether or not most of the case is air-tight or has machined holes. Cable-management also can affect air-flow.

 

I was just reading last night about how depending on passive ventilation/card style you might be recycling warm air into the GPU, which was pretty interesting. Unfortunately I can't find the article with the GPU consideration.

Jay had a video where he used incense smoke to visualize what the air inside his PC was doing depending on how he arranged his fan setup. It really helped to see how big an impact his passive vents had.

I wasn't aware that GPUs had different exhaust styles. Would you be willing to link me some pictures of the different styles? I want to figure out what style the GPU I'm planning on buying in the future is.

[mwomp]

15 minutes ago, ProtoflareX said:

I wasn't aware that GPUs had different exhaust styles. Would you be willing to link me some pictures of the different styles? I want to figure out what style the GPU I'm planning on buying in the future is.

Blowers are loud but exhaust heat from the case over the heatsink, directly out the back. They also tend to run much hotter. These are suggested if you have restricted space inside the case- good for small builds.
Internal exhaust doesn't direct heat out the back, it forces the air from inside the case over the heatsink, but doesn't direct the air out the back, it just gets "recycled" in the case.
Single fans are louder and run hotter than double fans. Most of the cards available will be the internal exhaust, that seems to be the current trend.

[WoodenMarker]

15 minutes ago, ProtoflareX said:

I wasn't aware that GPUs had different exhaust styles. Would you be willing to link me some pictures of the different styles? I want to figure out what style the GPU I'm planning on buying in the future is.

Spoiler

Depending on whether the fins are vertical or horizontal, more or less of the air might exhaust out of the rear.

Every fan affects the air pressure and there are localized zones of higher or lower pressure.

That being said, air pressure in and of itself isn't particularly helpful in regards to cooling. I recommend just running fans at as high rpm as possible while keeping noise low enough that it doesn't bother you and finding acoustic sweets spots when it comes to setting fan curves for optimal cooling. 

[ProtoflareX]

22 minutes ago, WoodenMarker said:

That being said, air pressure in and of itself isn't particularly helpful in regards to cooling. I recommend just running fans at as high rpm as possible while keeping noise low enough that it doesn't bother you and finding acoustic sweets spots when it comes to setting fan curves for optimal cooling. 

Oh, well that simplifies things considerably. I thought it was something that I needed to take into consideration given that I am looking to build an enthusiast level rig. If it's not worth prioritizing over RPM, CFM and noise levels, then I won't bother trying to "optimize" the air pressure.