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Old 02-21-11, 12:44 PM   #9
Piwoslaw
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I've read about storing heat in phase-change materials.

One idea to keep automotive engine coolant warm was a phase change salt, see this thread over at EcoModder for more info.

Another idea, on a larger scale, is to use wax (paraffin). Basically, you need a well insulated container with lots of small tubes crisscrossing, then you fill that up with the right type of wax. Paraffin is a by-product of oil refining, I read somewhere that many refineries would be glad to get rid of their extra paraffin. Make sure you get the type with melting point around the temperature you want to keep your heat stored. Once everything is working, water flowing through the tank will be warmed up - you'll see it's exit temperature gradually decline, then flatten out for while (melting temperature of the wax), then decline again. The rate at which heat is tranfered from wax to water (or water to wax when charging) depends on how close together the tubes are, how much surface area they have, etc.

Parafin tanks work great when paired with a heat buffer.

I can't remember the exact numbers, but I think that a paraffin tank can store something like 30%-80% more heat than a water tank of the same size. If anyone is interested I can try to find more info.
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