Opposing PA160s - Fans and Airflow

Celoth · Post by **Celoth** » Sun Oct 21, 2007 10:26 am

In the rig I am planning, I am thinking of using two PA160s. I would have loved to get by with one, but I think it'd run too hot unless I turn the fan up to a noisy RPM.

So, I came up with the design shown below. Basically I'd be mounting the PA160s so the radiators will stick outside the sides of the case, without actually being attached to them. This has the benefit of increasing heat dissipation outside the case, and gives more room inside.

As is obvious from the drawing, there's a downside to this setup as well, and that is how the fans are sitting opposite eachother, each trying to push the air out. The air will be sucked in from the hole I cut in the bottom of the case (Lian Li V2100B Plus II on wheels).

My questions are now:

How badly will this affect the airflow given 5-6 cm or 2-2.5" between the fans? Would I need to attach a 3rd low rpm fan to help move cool air in between the two fans? I'd rather not have to for noise reasons obviously.
Would a thin divider (aluminum sheet or cardboard or similar) between the 2 opposing fans help? That way they won't be competing directly against eachother at least, and the airflow might be smoother coming from the bottom.
What fan should I look for here? A silent one obviously, but should I just grab any recommended Nexus / Scythe / Noiseblocker, or do I need to look for one designed for a more restrictive airflow?

ddrueding1 · Post by **ddrueding1** » Sun Oct 21, 2007 11:08 am

My first thought is to have the air coming in through one of them and out through the other. This way they will help each other. The air feeding the second will be a bit warmer, but that should be more than compensated for by the increased airflow. If you plan on using them in series as part of a larger system, it makes even more sense.

Celoth · Post by **Celoth** » Sun Oct 21, 2007 11:33 am

ddrueding1 wrote:My first thought is to have the air coming in through one of them and out through the other. This way they will help each other. The air feeding the second will be a bit warmer, but that should be more than compensated for by the increased airflow. If you plan on using them in series as part of a larger system, it makes even more sense.

I did think of that, but it is my understanding that at low RPMs the air will heat up more on the way through the 1st radiator, so the 2nd radiator will get fairly hot air through it. Once it's all mounted it's easy enough to test both setups I suppose, by reversing one fan and maybe even add a duct between them.

EDIT: If you look here, you can see that air temp goes up by 8Â°C from 23.5Â°C to 31.5Â°C just by passing through one PA160, with a liquid temperature of 37.4Â°C in and 36Â°C out. Those numbers speak against using the fans in serial mode IMO.

ddrueding1 · Post by **ddrueding1** » Sun Oct 21, 2007 5:05 pm

Do you plan on using them in series, or as two different circuits? If you use them in series, the water can flow opposite the air. This means the water would go through the warmer radiator first, then the cooler one.

The other thought would be to have both radiators on the same side, one above the other, so they don't compete.

mumford · Post by **mumford** » Sun Oct 21, 2007 5:14 pm

I think the setup as posted is fine. Wire both radiators in parallel.

Celoth · Post by **Celoth** » Sun Oct 21, 2007 11:43 pm

Based on some feedback on ocforums.com, I will probably be making a duct for each fan like this:

The picture above shows a pull config, but the same duct should be equally good for a push config. Not sure which of the two would be the better choice though.

I might try a Noiseblocker fan on them.

jaganath · Post by **jaganath** » Mon Oct 22, 2007 1:21 am

I'm not sure I have understood the diagram correctly, but are you blowing the hot air down in the ducted version?

StApostol · Post by **StApostol** » Mon Oct 22, 2007 5:42 am

Yeah, it will probably work better if you blow the hot air up, rather than down.