Need help with airflow through PC.

[RatedZOfficial]

I've just ordered some new fans to lower my temps on the PC.

The main fan is a 230mm BitFenix Fan; along with two 120mm arctic cooler fans.
My case is a BitFenix Phenom MiniITX.

These are the two ideas I currently have. (This pic isn't mine but has the same layout obviously apart from the missing GPU on here)

So anybody?

 

[USAFRet]

In the front/bottom, out the top/back.
Heat rises.

 

[Chayan4400]

The top diagram is the best solution, but the top right fan should be intake.

Intake is slightly greater than Exhaust, to maintain positive pressure in the case and so stop dust from collecting.

 

[RatedZOfficial]

The top diagram is the best solution, but the top right fan should be intake.

Intake is slightly greater than Exhaust, to maintain positive pressure in the case and so stop dust from collecting.

Positive pressure? Can you explain a bit more? And the bottom right fan (big one) is 156.3 cfm so is there really need for anymore air coming in? The two top 120s are 74 CFM and the 140 is 86.7 cfm.

 

[Chayan4400]

The top diagram is the best solution, but the top right fan should be intake.

Intake is slightly greater than Exhaust, to maintain positive pressure in the case and so stop dust from collecting.

Positive pressure? Can you explain a bit more? And the bottom right fan (big one) is 156.3 cfm so is there really need for anymore air coming in? The two top 120s are 74 CFM and the 140 is 86.7 cfm.

Positive pressure simply means that the air pressure inside the PC is greater than the air pressure outside. Thus, since air moves from ares of high pressure to lower pressure areas, it will blow air out of the many small holes in the case which decreases dust build up.

Negative pressure is the complete opposite, and thus as air is drawn in through the small holes dust builds up.

The easiest way to see what is inside your PC is to calculate total CFM of intake and exhaust fans.

If total CFM of intake > exhaust, pressure is positive.
If total CFM of intake < exhaust, pressure is negative.

In your diagram, using values you stated above:

Intake = 156.3 CFM
Exhaust = 74+74+86.7 = 234.7 CFM

Pressure = Negative by a long shot!

If you turn the top right fan around:

Intake = 156.3=74 = 320.3 CFM
Exhaust = 74+86.7 = 160.7 CFM

Pressure = Positive

Thus, it would be best if you did turn that top right fan around.

 

[RatedZOfficial]

The top diagram is the best solution, but the top right fan should be intake.

Intake is slightly greater than Exhaust, to maintain positive pressure in the case and so stop dust from collecting.

Positive pressure? Can you explain a bit more? And the bottom right fan (big one) is 156.3 cfm so is there really need for anymore air coming in? The two top 120s are 74 CFM and the 140 is 86.7 cfm.

Positive pressure simply means that the air pressure inside the PC is greater than the air pressure outside. Thus, since air moves from ares of high pressure to lower pressure areas, it will blow air out of the many small holes in the case which decreases dust build up.

Negative pressure is the complete opposite, and thus as air is drawn in through the small holes dust builds up.

The easiest way to see what is inside your PC is to calculate total CFM of intake and exhaust fans.

If total CFM of intake > exhaust, pressure is positive.
If total CFM of intake < exhaust, pressure is negative.

In your diagram, using values you stated above:

Intake = 156.3 CFM
Exhaust = 74+74+86.7 = 234.7 CFM

Pressure = Negative by a long shot!

If you turn the top right fan around:

Intake = 156.3=74 = 320.3 CFM
Exhaust = 74+86.7 = 160.7 CFM

Pressure = Positive

Thus, it would be best if you did turn that top right fan around.

You Sir are a genius! Thank you.

 

[Chayan4400]

Yikes! Just noticed your top 2 fans are on a radiator. That certainly changes things!

On a radiator, you should have both fans in the same direction. Also, they should be sucking in cooler air from the outside in order to maximize cooling, so they must be used as intakes.

Now we can't have the two others as exhaust, as that would lead to negative pressure and anyway would completely disrupt the air channels inside the PC. Making the back fan the only exhaust won't work either, as that would lead to extreme positive pressure, which is also not ideal (We are looking to get SLIGHT positive pressure, along with a uniform air channel).

Thus, the best setup really is the SECOND picture, as it maintains a good flow of air inside the PC, has the fans on the radiators in the right direction and also manages to keep the pressure inside slightly positive.

I'm EXTREMELY sorry for this oversight!!

 

[RatedZOfficial]

No sorry I didn't specify clearly enough the picture isn't mine, and I do not have water cooling therefore the two top fans are separate fans without a radiator