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Unread 03-28-2003, 12:57 PM   #57
Graystar
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Join Date: Mar 2003
Location: Brooklyn, NY
Posts: 112
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Quote:
Originally posted by JFettig
If you dont mind, I think Ill make you a base too, how wide is the channel area in there? I think Ill make it with a 1/8inch end mill and leave a fin in the center, how does that sound?

how thick is the thickest peice you can use with that clip? this would end up being 1/4inch+ your top.

I would make the channels 1/8inch deep and leave a 1/8inch base, then probably leave it up to you to lap it
Sure thing! That would be cool.

If you don't mind, lets talk in decimal, since my copper is .043".

I've got three layers of copper, and I add another 2 layers for clip pressure. I can go to three additional layers I think. So that's .258" max thickness of the entire block. That gives you .172" as the max base thickness. Since 1/4" is .25, it won't work unless I get a different clip. However, since you are cutting your channels into the block, I think my middle layer would be unnecesary. So that would give you another .043, giving you .215 max. Hmmm.... .25 would be almost like adding another layer. I don't know if I can clip it with a block that high.

So you'll have to make the base, 1 1/4" by 5/8" x .215". The tubing is 3/8" OD. Each tube is positioned 1/8" from the three closes edges. This should tell you where you need to start and end your channels.

I'm assuming that you mean channels running from one outlet to the other. Personally, I think channels are not all they're cracked up to be. What follows are my own thoughts by just sitting and thinking...I don't have any actual experience with a channelled design.

The idea of the channel is to increase the surface area. However, there are two problems introduced when you increase surface area with a channel. First, the area that you added is above, not at the same level as, the base. So heat has travel further to get to where it can be transferred to water. This reduces efficiency. So the gain from channels is a balance between increase surface area and lost efficiency, not simply an absolute increase due to surface area. Second, when you have channels, you create drag, which slows down the water. Slower water doesn't cool as well, so again, you've reduced performance.

So the gain from an increase in surface area must overcome the losses from decreases in efficiency caused by greater conduction and slower flow. Also, you have to consider design very carefully with fins. You must insure that every water molecule has a definite path in and out of the channels, and the pressure to move it. Otherwise, you'll end up with water sitting in the channel. That is why I suggested getting rid of my middle layer if you are going to cut channels. All the water would move through my wider top channel, because there's less resistance, and water would just sit in the lower channels.

I think with 1/8" deep channels you're going to have a similar problem *unless* the entry point of the water is at the base of the channel. That will put pressure where it needs to be to move the water. If you add such a base to my design, you'll only move the water at the top of the channels.

So in addition to cutting channels, you will also need to drill 3/8" blind holes at each end of the channel to accept my tubing. Otherwise, I'm pretty sure we're just going to get hotspots from bad flow.
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