I want to cool down a lot of water with a huge ice cube. What's the best shape to maximize the rate of heat transfer?
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8$\begingroup$ Could you use the huge ice-cube making process to cool the water directly? $\endgroup$– Todd WilcoxSep 28, 2015 at 2:59
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$\begingroup$ Is this a question about the best physical shape for heat transfer then there really is no correct answer, because maximizing surface area can be done a number of different ways. But for practical cooling, Asher's right, Crushed ice is the fastest, but that's obviously not a "huge ice cube" $\endgroup$– userLTKSep 28, 2015 at 5:43
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2 Answers
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The more surface area, the more heat transfer. Ideally you'd use a single-molecule sheet, but that's impractical. Practically, using crushed ice is very simple and very effective. You could also freeze water inside drinking straws or on baking sheets to achieve high area-to-volume ratios.
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5$\begingroup$ A single-molecule Sierpinski carpet might be marginally more effective, than a single molecule sheet. But even more impractical. $\endgroup$– userLTKSep 28, 2015 at 5:49
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2$\begingroup$ If it needs to be a single contiguous piece of ice you could use old heatsinks to make molds, then make heatsink icecubes. $\endgroup$– J...Sep 28, 2015 at 11:04
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$\begingroup$ The baking sheets idea is neat (ideally use a flexible one to make it easy to break up the sheet to convenient dimensions and for ease of stirring), but getting the ice out of drinking straws would be tricky. $\endgroup$– Chris HSep 28, 2015 at 12:59
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$\begingroup$ @ChrisH If you use straight straws usually all it takes is to run water over the outside of the straw. $\endgroup$– AsherSep 28, 2015 at 15:21
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$\begingroup$ I assume you mean just to release the ice; the plastic would be a thermal barrier to cooling? $\endgroup$– Chris HSep 28, 2015 at 15:30
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The size/shape of the container holding the liquid to be cooled has some bearing on the question. A thin sheet of ice has lots of surface area, but could interfere with convection bringing warm liquid in to mix with already-cooled liquid.
Whether this is relevant at all depends on factors like whether you're cooling a lot of liquid by only a degree or two, or cooling a small amount of liquid by a lot.
That is probably related to how much of the ice will melt in the process? (If hardly any ice will be left at thermal equilibrium, it won't take up much space, and probably didn't take long to melt most of it quickly.) Relative volume of the ice at the start and liquid at the start is a function of these things, but is another way of looking at them.
Will the mechanical action of adding the ice to the liquid cause significant currents?
