Quote:
Originally posted by SysCrusher
This is the question I keep running through my mind. If there is micro-channels or any surface geometry that causes enough pressure drop, will it render the jet impingement useless? I'm leaning towards the answer of "yes".
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As a guy who somewhat surprisingly doesn't know the full theory behind it (the 90% rule here) my answer goes like this.
For a fine-channel (I say fine - because the term "micro" is open to subjective interpretation) setup given a particular channel width, I believe that there is a pretty tight range of values that specifies the "optimal" fin width and height. This implies a direct relationship between channel width and fin height.
Now given a particular range of operable pumping pressures, say 2-4PSI for the pumps that people typically use, this then (in my mind) places a lower bound on the usable channel width before the pressure drop becomes so high that the pump can't pump enough appreciable volume through the channels, and this will result in a performance loss as the water itself heats up too much because there is not enough heat mass in the liquid.
What I'm saying is that problem is self-balancing. The point at which the jet impingement would begin to suffer would also be the point at which the micro-channel implementation would begin to suffer as well, that is, it is possible to make the channel so fine and restrictive to "damage" the jet impingement action, but in doing so you will be losing performance in other places as well, so the problem as you describe is self-defeating given a correctly ratioed fin/channel width/height micro-channel system.
The question then becomes one of "what is then the smallest micro-channel dimensions that you can use effectively with a 2-4PSI pump". I already have a fair idea of the answer to that question, but it is also tempered with the need for secondary blocks in the system to not have their performance hampered in a significant fashion by a singular restrictive block in the system, so the answer suddenly takes on a new perspective.