GPU Cooling: Blower Style vs Dual Fan

What are the benefits/disadvantages of each? Why does EVGA use blower style coolers for a lot of their high end cards, and other companies such as ASUS use dual fan coolers?

Blower type coolers are louder by design, but they have the advantage that they exhaust the hot air directly outside the case. They are also less dependant on fresh air being directed towards the graphics card. Blower type coolers are not all the same, some use vapor chamber technology or a smart heatpipe arrangement to maximise cooling performance. They have the ability to suck air in with much greater force because they create a lot of underpressure, so they are ideal for small cases or limited airflow cases. They work through the venturi-effect, which greatly enhances the speed of the airflow for a wind-chill effect, but this effect also reduces the airflow pressure (create a lot of underpressure as aformentioned), which means that they suck in more dust and that in extreme circumstances, the airflow might stall in the radiator when it contains a bit of dust, which causes a typical rhythmic noise of the airflow coming to a halt, thereby the pressure is maximised, which causes the airflow to restart, which causes the pressure to drop, which halts the airflow, etc... and because of the construction the heatsinks and fans are not that easy to clean.

Single fan coolers are not very efficient at all, and only suitable for cards up to 7750/650 in my opinion, and only if there is enough fresh air supply to the graphics card in the case. There are exceptions, for instance the aftermarket Zalman GPU coolers which used to be very popular are just great single fan coolers, but they require VRAM-heatsinks.

Dual fan coolers are the best performing solution if there is plenty fresh air supply to the graphics card. Typically, the heatsinks are larger and are cooled with more fresh air, and because of the downward blowing fans, the heat exchange is optimised over a larger surface, so that heatpipe or vapor chamber arrangements are more freely configurable. Dual GPU fans don't have to spin up that much, so they are a lot quieter, and the airflow is less constrained, so there is definitely less "woosh" noise.

My computer used to have a HD 3850 HIS IceQ3 which had a blower type fan. It stayed in parameters although it was audible and it had a factory defect (artifacts most of the time, had to solve them with a bit of underclock). I had to replace it with something better and working, and found a HD 4870 Palit Sonic, which is a dual fan (one is smaller than the other, and the heatsink is rather low profile). This thing is great for what I need and was worth every pennny (70$ last year). The only drawback now is that, compared to the 3850, it is always idling at 60c, rarely under (winter) and never goes past 69-72 tops. Which is fine, I think the 3850 had the same max, but ran cooler in idle. This card was designed to be hot, and I can only undervolt and underclock the idle settings to cool off 5-10 degrees c. It works fine though and can only hear the fan wind up after gaming, hardly audible though.
In conclusion, the blower fan was noisier, had collected quite a lot of chunks of dust, but was more efficient with cooling in my case (pun?). The dual fan cooler is quieter, BUT in a tight place it will increase case temps by ~5c. My case has a plastic tube which separates cpu/memory/northbridge heatsinks and fans for their separate airflow, which works great, but my new HD 4870 increased cpu temps by a little (between 2-5c).

Also, the bigger the fan is the quieter it is. There's nothing worse than a FX 5900 with a single tinny fan screeching your ears. There probably will be worse to come when those 3-slot occupying cards become mainstream (7970 is a jet engine, at least for refference cooling)

Thanks guys, great info!

I myself was a skeptic of the "Dual Fan" option. This was maily because of the lack of exhaust that comes with this option.

Last year I was using two XFX Radeon 5770's that had the refferance "Blower Design" It seemed affective, and didn't to get laud at all. It kept my case nice and cool and and I really enjoyed the sleek aesthetic.

This was untill I purchest a new Radeon 7970. GOD DAMN it was LOUD. As stated above it has been refferenced to a jet engine. No kidding. I used it for around a month until I dropped 70 bucks on a ARCTIC Accelero Xtreme 7970. One of the best things I have done.

In case you didn't know, the ARCTIC Accelero Xtreme 7970 is a "Tripple Fan" solution.  My 7970 is now silent, and runs 30 - 40 degree's cooler.  The average temps in my case have gone up around 3 degree's but it hasn't been noticeable at all.

In my opintion, the "Dual Fan" option is the way to go. It seems to me that the refferance cards are sticking to the "Blower Style" because a mix of the sleek look, and how it costs less to produce.

 

I have a HD3850 AGP and it came with a a blower fan that got jammed over a relatively short period of time (1 year). i took it out along with the plastic casing and installed 3 fans. 2 on the top and in at the back of the card blowing air at the back side of the PCB. check it out : http://www.benshardwareblog.com/pc-hardware/hd3850-triple-fan-solution