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Now that's a very interesting dataset. It appears that once you're at roughly 40mph or more that the post-cooler can get to and stay in the range of 102 plus or minus a couple degrees. So 15 degrees warmer than the presumably ambient pre-cooler air.

Except that presuming the pre-cooler air is ambient is probably a mistake, what with all the warm air coming off the radiator and flowing right up the windshield into the scoop.

xtn
 

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The most efficient use of an external mister would be to get the smallest droplet size, and get the mist spread out over the largest possible surface area of the IC, and get those millions of tiny droplets to vaporize during contact with that surface.

Some of you seem to have a bit of a misconception about cooling the air first, and then having the cooling air flow through the IC. Spraying the perfect mist, by itself, does not cool the air. Put your hand in the flow a couple inches down-stream from the nozzle and you will feel cooler air. By the time the air reaches your hand, you will feel a bit of cooling due to evaporation, but the bulk of the cool effect you feel is just the fact that a cool mist is being sprayed on you. The real (most effective) cooling comes from the evaporation. The exact point of evaporation is what pulls the largest hunk of heat energy out of the surroundings. Having the liquid water flash over into steam while it's in contact with the IC will pull a lot more heat out of it than just flowing cooler air over it will.

So you want a fine mist, located just far enough up-stream to spread out and reach the whole width of the IC, but not so far up-stream that a lot of it has evaporated by the time it gets to the IC. So yes, you want the liquid water (albeit in tiny mist droplet form; a single squirt-gun stream aimed at the middle won't be nearly as effective) to reach the IC in the liquid state. Ideally the front of the IC fins would be slightly wet, and as the airflow pushed the droplets across the fins to the exit side, the water would evaporate, and the very back edge of the IC fins would be dry. This would indicate you are pulling out about as much heat as is possible with such a system. In an ideal world your mister system would have sensors to determine this condition, and increase or decrease the mister flow as the IC heated up and cooled down to maintain this ideal condition.

Since nobody is likely to develop that sort of thing any time soon, we set the flow to establish that condition during hot track usage. At other times, if the IC is not hot enough to turn it all into steam, then use less water, or just accept liquid blow-by if there is a means to prevent it puddling up after the IC. Not like you should complain about it. "Awww my IC is too cool to vaporize all the mist," is kind of a silly complaint, don't you think?

xtn
 

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Hmm.... as long as the droplets evaporate completely, I'm not sure whether it matters whether that happens first in the air going through the IC, or on the surface of the IC itself. The latent heat of evaporation still has to be carried away by the air flowing through the IC.
Assume an appropriate mist level that will not waste any liquid water out the back of the IC...

The results will be better getting the water droplets to pull heat out of the IC fins directly than pulling the heat out of the air first. The cold air passing over the fins does not have nearly the heat transfer rate, per unit of surface area, that water has. Liquid water has much better heat conducting characteristics than air. With your method, you'll get cooler air out the back of the IC, having wasted some potential energy absorbtion, than if you had let the water absorb the heat energy at the IC itself.

Are you cooled down more on a hot summer day by an evaporative cooler that is blowing cool, humid air on you (water already evaporated) or by having a mist blown directly on you while you stand in front of a regular fan and letting the water evaporate directly off your skin?

EDIT: Also, spraying directly on the IC would only get mist on the first few mm's of surface area from the front of the IC... theoretically you'd want the entire surface area of the IC to be more efficient (true evaporative chillers are designed to get a maximum surface area wet), and it seems the best way to do that would be to cool the air, which is going to contact the entire surface area.
If the water is completely evaporating within the first few mm of fins as the airflow passes through, then you could turn up the volume of water being supplied. Assuming a small enough droplet size, it will all be passing through the IC, coating whatever fins it touches. The only reason it would be coating only the first few mm is if it's evaporating faster than new droplets are coating the fins. If that's the case, you need more water for maximum cooling capacity.

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I nominate this thread as Most Valuable Thread Ever.

xtn (who doesn't even have forced induction, but recognizes the value anyway)
 
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