Thanks for the info and replies. When I asked the question I had no idea it would spark conversation about heat management. This is an interesting subject for sure. Computer heat management is something I like to work on. I bought an Antec Nine Hundred case earlier this year because my older case was not heat efficient. This was an issue because several video cards I've had recently have generated a lot of heat.
One of the replies here pointed me to a review on Newegg that covered the concepts of heat being produced and contained. Well, as much as I appreciate the Physics 101 review my thoughts were more around the question of dissipating heat after the power is cut. So, is it necessary to move heat off of a processor after the fan has shut off? According to everything I've read here, the answer is no. But I'm still not convinced...
While it is true that if power is cut to a processor, for instance, the processor no longer produces heat. It is also true that it contains heat and probably lots of it. And, assuming the processor has a good heatsink/fan, when power is cut the fan will stop but the heatsink will continue to absorb heat. Or, will the heatsink help maintain heat - like an insulator? At any rate, heat dissipation efficiency drops dramatically when the fan stops.
Ok, so, if I take all the comments at face value, there is no point in continuing cooling after something has been shut off. It is, as the commentor on Newegg would lead me to believe, only for the thermodynamically challenged. Given all of that, I'm wondering about projector bulbs for example. Most projectors have, at least in my experience, a feature that keeps a cooling fan going after the light shuts off. In fact, there is a warning in the manual the you must maintain power to the unit to keep the fan going even after the bulb has been shut off in order to avoid damage to the bulb. So why? Why do that if the bulb is no longer receiving power and is no longer producing heat? Is the answer the glass bulb does not have some sort of heatsink? Even so, wouldn't it be better to let the glass bulb cool more slowly than more quickly?
Oh well, in the end I may buy one of these gadgets just for laughs and giggles. It may not extend the life of my video card but it may help keep things from being so hot when I reach in there to work on stuff five minutes after the machine has been shut off.
Oh, and by the way, I have had at least two (maybe more) cars in which the fan continued to run after the car was shut off. I'm not so sure they were a result of flukes of wiring. The fan continuing to run after the car was shut off only happened when the cars were running hot. In one case, a new thermostat did the trick. After the thermostat change the car starting running at its normal temperature range and the fan running after shutdown stopped. Sounds to me like it was designed that way. These were small cars with sideways-mounted engines with electric cooling fans. I have had to replace fans like these on several occasions (mostly dirt in the motor, etc). I guess the on-running fans on cars went the way of the power supplies that did the same thing. Oh well, maybe they'll make a comeback someday...