It's been my observation over the years in the mechanical world and somewhat based upon things I've heard, that running a fan at high speeds versus low speeds does not equate to more cooling at a 1:1 ratio. Window air conditioners are a good example. Running them on high doesn't really enhance their cooling effect. I've found that they work just as well, if not better, at low speed and you don't have to listen to the sound of a turbo-prop mounted in your window. Years ago, RallyBob sold me a set of pulleys for my GT that slowed down the speed of my water pump. It worked great and provided a 15*-30* reduction in thermostat temp. The theory being that the slower moving water has more time to absorb heat from the engine. I have this combo on my car right now and it is one cool cat. I also have a cheapie, plastic, electric radiator fan on a thermostat to supplement the 7 blade engine fan on my 2.4. My car's thermostat never goes past 180* even in backed up traffic on a high humidity 100* day. I also have the 3-core heavy duty OGTS radiator. Highly recommended for ALL GTers.
There's a bow wave or cavitation effect(please supply the correct terminology) that happens as the speed of water or air increases as they flow over surfaces. This "effect" causes a static barrier of air or water to form at the surface which impedes the heat transfer to the air/water passing by. Having air/water linger a bit longer in the vicinity of a heat source greatly improves the heat transfer to the air/water.
When I was shopping for an electric radiator fan I saw all sorts of speed and CFM claims from various manufacturers, with commensurate higher and higher prices for said fans. Based upon my experience, I contend that expensive, super high CFM, fans are a waste of money on a street driven, non-raced, Opel GT. I contend that ANY cheap average CFM fan will get the job done just as good as expensive, cyclone-inducing, noisy, fans. I also observe that common cars with electric fans don't have fans that spin at light speed. In fact, they seem to spin at a fairly tame speed.
What do you guys think?
General discussion on this topic.