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Posted for Ernest Christley <echristley@nc.rr.com>:
"Ed Anderson" <eanderson@carolina.rr.com> wrote:
So unless my math is way off (always possible), Rusty, I would recommend saving your money for something like a custom radiator. FWIW
Ed Anderson
I wouldn't say the math is off, but I would question your assumptions Ed. The implied assumption is that a 3.5" thick fin has the same thermal properties as a flat plate. I see them as being very different.
In a radiator, the water runs through a tube, transfering heat to the tube wall as it passes. Only coolant that is in actual contact with the wall transfers heat, and in a round tube the volume to surface area ratio isn't extremely high. The tube wall then transfers that heat to a metal fin. Cool air comes along and passes between a couple of fins. It first begins to accept heat from the fin as it passes the leading edge of the fin. The amount of heat tranfer is proportional to the difference in temperature of two objects. As the air is approaching the trailing edge of the fin, it is almost the same temperature. The problem is only made worse by the fact that there is another fin right next to it doing the same thing. Unless there is a large air volume, there is very little heat tranfer going on at the trailing edge of that fin (may be that not all of your fins go all the way through because they weren't doing anything).
Now, consider what Rusty has done. He takes the coolant and spreads it in a thin layer, all of which is in direct contact with the 'tube' wall. His flat 'tube' has a much higher surface area to volume ratio, allowing the heat to transfer to the tube wall more efficiently. Instead of transfering the heat to a fin for the air to pick up, the tube itself is it's own fin. The heat only has to cross from the inside to the outside of the tube wall. Once the heat is on the outside, there is no interaction with an adjacent fin, and it can be arranged such that the entire surface area of the tube is exposed to cool air at once.
Now, unfortunately, OpenOffice will not read the doc file that Rusty sent, so I do no know how he tested. The air volume would be very important for the comparison. Rusty, would you mind posting the data you have in rtf format.
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