Positive Pressure Math

[HerEscutcheon]

So I'm trying to figure out the math involved for creating positive pressure within a case. The NZXT H440, to be exact. I know it already comes with 4 decent fans (3 intake, 1 exhaust) and using that setup will indeed create positive pressure, but I'd eventually like to upgrade the cooling and sound (and appearance) with Scythe Gentle Typhoons and maintain that positive pressure. Here's the specs for the different rpm models...

 

Scythe Gentle Typhoon 120mm Fans

800 rpm    ---  28 cfm  ---  9 dba

1150 rpm  ---  37 cfm  ---  16 dba

1450 rpm  ---  50 cfm  ---  21 dba

1850 rpm  ---  58 cfm  ---  28 dba

 

I figured that if I have 3 intake fans at 1450 rpm, that would create a total of 150 cfm. If I then also have 4 exhaust fans at 800 rpm, that would create a total of 112 cfm. The total intake (150 cfm) would be higher than the total exhaust (112 cfm), meaning I'd have positive preasure (+38 cfm). Now, did I do this right? Or am I missing something?

 

Alsø, does the CPU cooler affect any of this? It will eventually have 2 Gentle Typhoons at either 1450 or 1850 rpm, and will blow towards the rear exhaust fan. I want to make sure that if the fans ramp up to full, the case will still have positive pressure.

 

Alsø alsø, I know that many case fans are kinda overkill, but it'll look really cool. B) Especially if NZXT decides to make a black on black / grey on black version of the case.

[Freaky_spider]

you did the 'math' right but there will always be dust build up in your system.

[HerEscutcheon]

you did the 'math' right but there will always be dust build up in your system.

I know I can never prevent all dust, but I'd just like to have less than more.

[dragosudeki]

If you want less just get dust filters. I wrap your entire case in dust filters >.<

[ijKs Snow]

Try all different kind of fan orientation when you get your system.

 

Since you are using an air cooler for your CPU, yes it will effect temps depending on fan orientation. For example, if you put a fan in the rear of the case, then you should always have the air flow going the same way as the cooler. If you put it going opposite ways or into each other, it will cause turbulance which can cause extra noise and higher temperatures.

 

The whole computer air flow pressure is slightly flawed. It seems like whoever wrote the original theory in the PC community seemed to have ripped the idea off of car radiator air flow concepts.

 

There are many arguments in the hardcore PC community on why the balanced air flow doesn't always provide the best cooling capabilities in the computer chassis.

 

The reason being is that computer cases aren't air tight. There are cracks between panels, air holes, etc.

 

I have all my fans as intakes on my ITX build, and it provides ~3-4 degree cooler performance then if I had a balanced air flow. Also it pushes air from inside the case to outside between all the cracks and holes in the case providing better dust filtration. Try out multiple different types of fan orientation and pick the one that provides the best temps.

[HerEscutcheon]

Try all different kind of fan orientation when you get your system.

 

Since you are using an air cooler for your CPU, yes it will effect temps depending on fan orientation. For example, if you put a fan in the rear of the case, then you should always have the air flow going the same way as the cooler. If you put it going opposite ways or into each other, it will cause turbulance which can cause extra noise and higher temperatures.

 

The whole computer air flow pressure is slightly flawed. It seems like whoever wrote the original theory in the PC community seemed to have ripped the idea off of car radiator air flow concepts.

 

There are many arguments in the hardcore PC community on why the balanced air flow doesn't always provide the best cooling capabilities in the computer chassis.

 

The reason being is that computer cases aren't air tight. There are cracks between panels, air holes, etc.

 

I have all my fans as intakes on my ITX build, and it provides ~3-4 degree cooler performance then if I had a balanced air flow. Also it pushes air from inside the case to outside between all the cracks and holes in the case providing better dust filtration. Try out multiple different types of fan orientation and pick the one that provides the best temps.

Thank you for all that info! I'll keep it in mind when I'm fiddling around with the case.

[airdeano]

So I'm trying to figure out the math involved for creating positive pressure within a case. The NZXT H440, to be exact. I know it already comes with 4 decent fans (3 intake, 1 exhaust) and using that setup will indeed create positive pressure, but I'd eventually like to upgrade the cooling and sound (and appearance) with Scythe Gentle Typhoons and maintain that positive pressure. Here's the specs for the different rpm models...

 

Scythe Gentle Typhoon 120mm Fans

800 rpm    ---  28 cfm  ---  9 dba

1150 rpm  ---  37 cfm  ---  16 dba

1450 rpm  ---  50 cfm  ---  21 dba

1850 rpm  ---  58 cfm  ---  28 dba

 

I figured that if I have 3 intake fans at 1450 rpm, that would create a total of 150 cfm. If I then also have 4 exhaust fans at 800 rpm, that would create a total of 112 cfm. The total intake (150 cfm) would be higher than the total exhaust (112 cfm), meaning I'd have positive preasure (+38 cfm). Now, did I do this right? Or am I missing something?

 

Alsø, does the CPU cooler affect any of this? It will eventually have 2 Gentle Typhoons at either 1450 or 1850 rpm, and will blow towards the rear exhaust fan. I want to make sure that if the fans ramp up to full, the case will still have positive pressure.

 

Alsø alsø, I know that many case fans are kinda overkill, but it'll look really cool. B) Especially if NZXT decides to make a black on black / grey on black version of the case.

 

the math is good, but the variables are not pulled into the equation.

 

relying on the manufacturer published specifications being truthful are basically open

or under no-load conditions.

 

when installing these fans, sorts of variables come into play. mainly on the intake side

of the arithmetic. when air is pull from the outside, presumably, it will be filtered. the

filter can easily reduce (40-60%) the amount of air drawn into the system.

so your intake at 150cfm, through a filter at 40% would be 90cfm filter corrected.

 

also relying on no obstructed exhaust discharge of that fan of 35-60mm. when the

exhaust is restricted, it causes a disturbance (reversion) in the air-flow. so again not

accounting for variables will flaw the math and lead to false results.