h a l f b a k e r yPoint of hors d'oevre
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Indoor waterfall features are nothing new. They usually
have a pump that moves water to the top where it flows
down over a back plate. This creates a pleasant trickling
sound and a little bit of a random visual effect due to
unpredictable turbulence in the water flow.
To make this a bit more
interesting, we can make the back
plate of the waterfall more dynamic. To do this, the
backing should consist of a grid of metal tiles separated by
thin insulation. Behind each tile, a thermoelectric
cooler/Peltier device is bonded, complete with an
associated heatsink. When a voltage is applied, the
individual tile begins to cool. Ultimately this will cause a
layer of ice to build up. If activated long enough, this ice
will form a protrusion and the waterfall will flow pleasingly
around it.
Tiles can be activated individually or in groups to make a
constantly changing ice layer over which the water is
flowing. Of course, the interaction will have additional
complexities. Water will cut channels leading to dead
zones and accelerated melting. Occasionally, ice will
destabilize and detach, possibly in large sections, maybe
high up leading to the unfortunate crushing of the resident
pianist. Art always costs.
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Annotation:
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In humid environments, you might not even need to add the
water! |
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Hmm. Are Peltiers really up to generating ice in a flowing
stream of water? |
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Yes, if you stack them. But other heatpump technologies are available. |
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//Yes, if you stack them.// I don't believe that to be true.
Stacked Peltiers can achieve greater temperature differentials
(though not as great as you might hope), but I don't think the
flux increases much. |
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I think this would only work if the flowing water were kept at
very close to 0°C. |
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//Are Peltiers really up to generating ice in a flowing stream
of water?// |
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A lot depends on how efficiently you remove heat from the
hotside. I recommend ice water as an excellent candidate
for this. Don't ask where that's coming from. |
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Where's that coming from? |
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The Thwaites Glacier, probably. |
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One figure picked out is that with the most powerful 135W peltier, the difference would be only 8.44e-4 C. |
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What if they were recursively stacked in insulated layers? The cool of one, is dropped by 0.0008.44 by next until the ice happens. Only a horn of 13,000 odd tiles. |
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It would be a heavy sculpture in body and energy. |
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On second thoughts, a good ice maker with a pinscreen conductive interface would work, especially if the water was precooled. |
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[+] Ok, if a society has enough spare solar energy to make public space ice sculptures then i'm all for it. |
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// What if they were recursively stacked in insulated
layers? The cool of one, is dropped by 0.0008.44 by next
until the ice happens. Only a horn of 13,000 odd tiles. // |
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Peltier coolers are not 100% efficient. (I've heard they're
usually around 5% efficient, but one company claims they
should be, IIRC, somewhere around 80–90%.) Therefore,
each one in the stack must pump not only the heat from
the thing being cooled but also the waste heat of every
Peltier cooler below it in the stack. This is why I have
never heard of anyone making a stack of more than two. |
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^ Would not a tiled cone stack be sensible, heat output on the outside and the temperature stepdown starting from a ring of tiles around the largest volume? |
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In cold climates it could be a bismuth 'waterfall'. The melting pount of Bismuth is 271.4 degs C. The bismuthfall could therefore double as a local area heater. |
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It would not be a problem to cool the flowing bismuth so that it forms crystals dynamically. It should be straightforward to prevent the bismuth from crystallising locally by means of using randomly sequenced electrical heaters. Bismuth crystals are also rather attractive. |
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There may be a problem with longer-term operation arising from formation of oxides. In this event, the bismuthfall would need to be either protected by a blanket of inert gas, or submerged in hot oil to reduce oxidation. |
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Oxidation will be a huge problem. The USSR had endless difficulties with their lead-bismuth cooled submarine reactors and eventually gave up on the technology. You would have to put your device in an enclosure filled with dry Argon. |
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Instead of Peltiers, perhaps a system of valves that can
squirt liquid nitrogen or something on demand? |
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Why not just have a liquid nitrogen fall then ? That would be cool (literally) and would coincidentally permit the inclusion in the display of other fascinating physical phenomena like the Meissner effect. |
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Have a collecting trough for the LN, below which is a powerful magnet, and on it place a number of "pebbles" of superconducting material. The pebbles are subject to the Meissner effect and therefore float above the liquid until they heat above their critical temperature. Then they splash back in, cool down, and repeat the cycle. |
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//and repeat the cycle// Why would they repeat? When they
fall into the LN2, they will cool and become superconducting.
But then they will be locked in place by the Meissner effect.
What lifts them up again? |
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