Positive pressure advice

[VWood]

Hello, this is my first time on this forum and I have a question concerning a build that I am doing.

The last time I did a full build was when DDR3 RAM was the fancy high speed RAM no one needed and only belonged on high speed GPU’s, and there was hardly any talk about things like case pressure.

 

I have two questions:

1.       Would static pressure intake fans better help to regulate the pressure of the case? I know that fan RPM is the best way to ensure positive pressure, however, it makes sense to me that, since air has a hard time escaping back through a static pressure fan, that it would make it easier to ensure a positive pressure envelope if you used static pressure fans on all intakes. If you have experimented with varying setups extensively what is your experience, especially when fan speeds increase?

2.       This may seem a little silly, but, do you ever plug any holes in order to facilitate air flow and pressure? Like closing some of the unused slots at the back of the case or half the top vent if there is only one fan on a two fan vent and only leaving specific openings where you want the air to flow through? For example leaving the slot or two just beneath the GPU open to ensure faster airflow past it but closing the others.

 

I would appreciate any advice,

Thank you.

[LukaH]

static pressure fans are always a good option to use. because you always have some obstruction in front or behind the fan. They are optimized to push or pull air through obstacles. Generally you achieve positive pressure with just more intake fans, or if you have more outtake fans you can regulate with rpm but this would requires some testing.

 

i'd only close off holes if i had negative pressure because of dust. I had some experience with closing off holes with sound dampening foam but the result was a hotter pc (positive pressure). It is better to have more ventilation unless noise is a concern.

[Mira Yurizaki]

Just now, VWood said:

I have two questions:

 

1.       Would static pressure intake fans better help to regulate the pressure of the case? I know that fan RPM is the best way to ensure positive pressure, however, it makes sense to me that, since air has a hard time escaping back through a static pressure fan, that it would make it easier to ensure a positive pressure envelope if you used static pressure fans on all intakes. If you have experimented with varying setups extensively what is your experience, especially when fan speeds increase?

CFM in vs. CFM out would be a better way to ensure positive case pressure, not RPM, since CFM changes with fan size for the same RPM. As far as using high static pressure fans, they're useful if you're trying to shove air through something that has restricted airflow like through a heat sink or a drive cage. I'm not under the impression they work any better than a high AF fan if it's blowing away from the obstruction since air will just get sucked into the fan anyway.

 

Just now, VWood said:

2.       This may seem a little silly, but, do you ever plug any holes in order to facilitate air flow and pressure? Like closing some of the unused slots at the back of the case or half the top vent if there is only one fan on a two fan vent and only leaving specific openings where you want the air to flow through? For example leaving the slot or two just beneath the GPU open to ensure faster airflow past it but closing the others.

No. This is bad for positive pressure systems because you want those gaps for air to escape. It's only useful in negative pressure systems.

[Alexzz_]

What i did to achieve positive pressure was use 2 intake fans and 1 exhaust. simple as that, no need to closely monitor rpm cfm or such as long as they perform about the same. I would not recommend plugging holes since it only obstructs airflow. However if your case has a Mesh with holes in it on top (like my s340) and you decide not to use that fan slot you can always cover it to prevent dust from falling in. What i did was put carbon fiber wrap on top of it.

[LogicalDrm]

1. Doesn't matter.
2. Wouldn't make much difference.

[HisEvilness]

Static pressure is there to help air in the case and in the area of the hardware fans to scoop it up and use it.
RPM would increase static pressure, yes but the blade design will dictate if the fan is built for that purpose.
The closing of a hole would make sense for noise will help little but even less with air since it almost impossible to get an air tight sealing.

But i use this for my own builds to calc some stats and get an idea who the pressure will be: Case Cooling CFM, Static Pressure and Watt Calculator (1).ods