PSU fan CFMs seem inefficient

[xbassman]

I am modding my Truepower430 power supply. Sleeving it and installing one of those UV covers.
I was looking at the fan arrangement and noticed something that looked a bit odd.

I checked the specs on the stock fans and the intake is a Top Motor DF1209BA 92x25 mm. It produces 57.1 CFMs @ 35.8dBA. The exhaust is a Top Motor DF1208BA 80x25 mm. And it produces 39.0 CFMs @ 34 dBA.

If both fans are running @ 12V the that would create positive pressure causing heat to escape from PSU vents back into the case. (TP430 has vent slots on both sides and front)

So I figured that I would go ahead and change out the fans while I have this puppy cracked open.
I am replacing the exhaust with a Panaflo H1A. (I have plenty lying around) The specs are the same as the Top Motor, but I am sure it will be quieter. As for the 92mm intake I ordered this.
It produces 48.11 CFMs @ 34.5 dBA.

It will be interesting to see the difference after installation.
Also the UV cover omits the side vents so if positive pressure is causing heat to escape it will only be through the cracks and front vents. I am going to go ahead and attach them to the same connectors as the stock fans so they will be thermally controlled, that is, unless either fan doesn't spin up under the voltage given.

Anyway I have excellent airflow in my case (it runs cooler closed up, than with the door off)

I am interested to hear any opinions or suggestions

 

[0roo0roo]

those cfm numbers are in a free air situation. the inside of a psu is very cluttered, dropping the real output of the fans quite a bit.

 

[xbassman]

Originally posted by: 0roo0roo
those cfm numbers are in a free air situation. the inside of a psu is very cluttered, dropping the real output of the fans quite a bit.

Yeah...I realize that, I am really looking at the relative numbers between the two fans.
Seems to me that it would be more efficient if they created negative pressure like the older style power supplies with only one fan, or removed all the other vents using positive pressure like the FSP power supplies that have the 120mm fan underneath. That way heat wouldn't be escaping into the case.

I have even debated possibly installing a Panaflo U1A for exhaust which would almost equal the output of the 92mm intake I ordered, but if it ever runs @ 12v it would probably be too loud. I already have one of those on my CPU.

 

[iwantanewcomputer]

i'm with you on the negative pressure dealie. my psu has a 120 fan on the bottom with a honeycomb grill for the back and a few small slits on the front. I'm considering covering these slits. Aynbody think this will help?

 

[xbassman]

Originally posted by: iwantanewcomputer
i'm with you on the negative pressure dealie. my psu has a 120 fan on the bottom with a honeycomb grill for the back and a few small slits on the front. I'm considering covering these slits. Aynbody think this will help?

As long as there is no fan drawing air in through those slits I can't really see that they have a purpose. I only have one power supply similar. It's a Fortron 350 watt and it has no vents except for the perferations on the back.