Temp increases after making a side hole?

Here is my current setup:

Lian Li PC-V1000B case. Scythe SFF21F fans all controlled by Sunbeam fan controller. Two 120mm fans in the front of the case as intakes, one in stock position and one in a 3 bay Lian Li device. 120mm fans at the back in stock location as exhaust.

I'd previously added a 120mm "blow hole" up top to help with temps after I installed an ATI cablecard tuner and a 2nd GTX 285. That helped ALOT.

Well today I was playing with an extra blank side panel I have and decided to add another fan just opposite the video cards. I made another 120mm hole and added a fan. Basically mimicing what Lian Li did on the Plus II model...

1st as intake and then tried it as exhaust. In either configuration I noticed the video card temps actually went up!

I have an engineering background and have taken some Thermodynamics and Fluid Flow classes so I know its very complicated, but how can this be?

Should I change how my fan RPM are set to better take advantage of this by creating more case pressure or something? Right now, I either have all the fans at 100% or around 70% to keep the noise down.

Thanks, Shawn

Here's a much older pic of the case...

is your ambient really high ? if so when your pulling in air into the case, your shooting hot air in...not cool air

How much do the temps go up? Is it just the video card how about the cpu?

you need to add a fan to the top hole to move air out.
Having just an open hole up top causes the air inside to stagnate since there is no positive pressure created.

I forgot to mention that I do have a 120mm SFF21F on the blowhole as an exhaust.

Ambient temps are around 68 F.

SLI setup temps at idle are around 55 C or so and CPU core (i7 920) around 48 C.

When I added the side fan all the temps went up 2-3 degrees. I expected the opposite to happen!

I've read about this happening, and unless we run a simulation, I suppose we won't know what's going on... but we can take an educated guess:

- You have a dominant front-to-back airflow pattern
- When you introduce airflow from the side, perhaps you are disrupting that pattern
- Perhaps some of the air is then recycled for a bit longer, and/or is diverted to less useful areas, and then simply exhausted out without first absorbing much heat.

- Maybe try decreasing the RPM of the side-intake fan. Introducing more ambient air is usually a good thing, and maybe you can do it w/o disrupting the flow.

- Because you are exhausting out the top and back, I suppose the logical intakes would then be front and bottom. But I think if you overwhelmed the flow pattern with positive pressure from the side (say... 4x120mm fans) then it wouldn't matter as much.

Any of that sound reasonable?

Thats should very reasonable. I might actually try taking the rear fan and making that an intake and then the side panel and top the only exhausts and see how that works. That way all the air would be flowing in (from both ends) and the only exhausts would be near eachother. I'd also turn my CPU heatsink 90 degrees and have the fan below pushing air through and upward....

Sounds interesting, wish we had an Infrared thermal cam & CFD to see the hot/cold spots & turbulent flows

Archmage sounds right, with the 'recycle'-d air thought. Car / powertrain cooling systems require well placed seals & baffles near the lower front bumper. It prevents "Hot-Air Recirculation", which would cause a car's A/C to give-up pretty quickly in the summer.

A routed path, either from dryer tubing, plastic housings, or other controlled airpaths would probably solve this. Could be turbulent air impacting from multiple directions creating a 'stagnant flow' effect.

The fan RPM change is a good idea.. what were you thinking - set the front Intake low to initiate flow, and the Exhaust high to pull the heat out?

sounds about right. airflow is supposed to flow front to back/top in this case. when you introduce side intake (or exhaust for that matter) that far back im betting you're disrupting the airflow.