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This is under home:water, but could be in various other places.
Make a object whose Y-axis projection resembles the complementary shape to a Sierpinski gasket and which is fractal in transverse section because it consists of wiggly vertical elements of different heights in a self-similar sort of way,
out of a high-temperature superconductor. Bathe it in liquid nitrogen, causing it to become superconductive, and pass a current through it, then replace the nitrogen with a warmer fluid such as air, water or petrol. The element will start to resist the current, heat up suddenly and expand, causing it to de-crinkle but not break. The heat will then be imparted to the replacement fluid over a very large surface area, causing it to heat very suddenly.
Most of the energy input is in the cooling rather than the heating, which is why i think a high temperature superconductor would be better. There would be rapid thermal expansion, but that's dealt with by the concertina-y nature of the shape. The superconductor concerned would also have to be coated with something inert or be itself quite unreactive, and have a high melting point for this to work.
This has various applications. It can be used as a convector heater, domestic water heater, kettle, soup saucepan and internal combustion piston heater. In the last case, a fuel-air mixture enters the chamber and is ignited using the heating element as well as compression and the cylinder heat doesn't reach the end of the piston.
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Annotation:
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Also, "Make a object whose Y-axis projection resembles the complementary shape to a Sierpinski gasket" borders on magic. |
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There is a minimum resolution at which things can be produced. For aluminum extrusion, the minimum is going to be about .1-.5mm. This can already be done with convoluted fins without the need for an exesively complex shape. Maching can get much finer, but base cost is higher, and increases with the level of detail. |
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Not to mention that fluid flow is going to be non-existant with to fine and complex a shape, there's a reason why heating elements have a certain spacing. |
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It clearly is impossible to have a genuine fractal of that kind due to the limits matter itself has on resolution (though atomic matter itself is sort of self-similar). It wouldn't be made of aluminium because that doesn't superconduct. I agree that there may not be a suitable substance which does this, but that's not because of the resolution issue. I would imagine something like vapour being deposited on a surface could do this - for example, snowflakes don't need to be moulded. |
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I don't understand why fluid flow is necessary for something which heats up that quickly and closely. There doesn't need to be convection within the structure itself because all parts of the fluid would be very close to the surface of the element. Transfer of heat to the rest of the fluid can occur after it's left the vicinity of the element, though there could be a problem with adhesion in the case of liquids. |
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[Bigsleep], i couldn't swear to this right now, but the heating from resistance wouldn't occur while the substance is superconductive, but from the point where it ceases to be. At that point, specific heat capacity would be a factor. The energy from the former current can't just disappear when it warms up, so i presume it would become heat. Superconductors do conduct in the sense of carrying a current, don't they? At the point where they develop resistance, the kinetic energy of the electrons would have to go somewhere. Am i missing something? |
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If the channels get to small, the liquid will not flow through even when pumped or drained out for use. |
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I suppose it might be possible to grow triangular crystals to infill a sierpinski triangle, but the best current technology at even a moderate level of resolution produces component with lengths of milli- or even nano- meters, not the decimeters you would need for a heating element. |
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Thanks, [bigsleep]; doing it now. |
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[MechE], i have a tendency to think that if a three-dimensional shape can be imagined, it can be made, but how would be another question. Concerning viscosity, OK but that wouldn't influence gases so much, would it? |
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//Am i missing something?// |
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Yes. I'm not sure what you're missing exactly, but I think I can smell a fish... |
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From a thermodynamic point of view it seems that you take a super-cold item that has a running current and then place it into a relatively hot environment. As the element heats up - i.e. takes energy from the surrounding environment - it loses it's super conducting quality. As it loses it's superconductivity, the resistance of electric flow kicks in and may contribute to increased heat effect (but is still very, very cold). The fractal nature of the material contributes to a large surface area - adding to the conduction of heat from the environment into the material. |
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I can't see how this system can impart heat energy... at least no better than a regular element. (Unless I am the one missing something) |
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Viscosity is viscosity, gasses are much lower, but still non-zero. Also, since gasses are compressible, the source pump or blower will reach it's static pressure much more quickly than a fluid pump will. |
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[Jinbish], i don't think the problem is thermodynamic as such. The negative entropy is the temperature difference created by liquefying the nitrogen in the first place. There may be another problem but it isn't clear to me what it is. Energy is also imparted to the system through the initial current. This is not in any way free energy, just quick energy. |
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As an aside, i'm now wondering what physical characteristics apply to plasmas, e.g. viscosity? Surface tension? |
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I fail to see how using a very cold super conductor can be used to heat anything with any sort of efficiency. |
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wouldn't it be easier to forgo all the complexity of super conduction and just design a heating element with a large surface area? sounds like you're describing a resistive heating element that switches from super conducting to resistive. but why is it super conducting in the first place? as that doesn't help it store or transmit any energy as heat? |
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The reason for the superconductivity, and of course i may well be wrong, is that i expect heating to be more rapid and pronounced. The temperature difference is not much of a problem, since you're only talking about a hundred Kelvin, not liquid helium temperatures. So far as i can tell, putting a current through steel wool raises its temperature from about three hundred to eighteen hundred in a fraction of a second. If there's no resistance, this could surely happen even more quickly. |
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I'm aware that i'm just making assertions here and need to know more about superconductivity, but your annotation deserves a reply. I'll come back when i'm less susceptible to talking bollocks unwittingly. |
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It's interesting on a couple of levels. |
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It sounded initially as though the initial cold, superconductor state was as a closed system - which when bathed in some other material would switch to a resistive one, dumping the cycling energy into the material. But I don't know if a current, once established in a superconductive circuit keeps "going round" - if there was no resistance, and the circuit were long enough, maybe it would be possible to set up a self-sustaining wavefront that orbited the superconducting material without any outside help (after the initial kick-off) |
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And, if you could do that, and had a current moving, could you also use induction and other electro-magnetic properties to induce or otherwise perpetuate other energetic movements within other semi-conducting units. |
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So that's the first interesting bit - the next is to do with constructing the perfect surface for heat transmission. Is the goal to process as much cubic footage in as short a time as possible? Or to raise the temperature for a given amount of gas/fluid to as high a temperature in as efficient a way as possible? (Subtly not the same thing) To continually refresh the energy-temperature conversion, you'd need a flow-route for your electricity/coolant to go from a point of low potential to a point of high potential - and fith a big fractal it's tricky to get your carrier into all the nooks and crannies (think human circulation and how it can go wrong at the extremities) only you've got that problem with your carrier, and also, inversely in your dumping material too. i.e. If you put a sponge in the middle of a pipe - it would slow down the flow of fluid in the pipe (the dumping material) and there would probably be mini flows through the sponge where most of the pipe material went through, and other areas of the sponge where the flow was pretty stagnant. |
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I'm currently trying to get my head round superconductors so i'm not quite ready to read what you've written. Even so, i'd like it to clarify that i am in no way proposing anything like a perpetual motion machine. This would involve a lot of energy input. |
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