http://rog.asus.com/222442013/graphics-cards-2/video-cooltech-fan-dual-bladed-tech-demo/
of course, if you think of a normal say case fan, as a fan in a square holder. That holder acts to direct the air from going everywhere in the first place so the air has to go down.
It's a very interesting fan when you can't put a fan in a normal holder, however on these heatsinks, there is very little reason you can't do that. It's why your average prolimatech style heatsink always works better, better airflow from proper fans.
The biggest heatsink with rubbish airflow will be destroyed by even a fairly small heatsink with somewhat decent airflow.
The only reason to use a fan without a case that also acts to channel the air, is if the heatsink is designed around that very concept. Think of a Zalman flower cooler, where it had an "open" fan, because it had fins below and to the side.
When you don't have heatsink surrounding the fan, there is no reason at all to not have the fan in a holder to direct the airflow into the heatsink. Would the cooltech style fan work better in a normal case fan..... would it provide higher cfm, or higher pressure, don't know, possibly, it might be worse, it could be the same.
When I first saw it with crap pictures I thought it might be trying to direct air underneath the center of the fan body, because you usually get a deadzone in a heatsink under the middle of any fan(something those TMD? fans tried to fix with a tiny middle and the magnets around the outside of the fan).
