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Spherical Thermos
Spherical thermos design keeps hot drinks hotter, cold drinks colder | |
The most efficient shape for an insulated vessel is a sphere, having the least surface area of any shape for a given volume. Therefore I propose a spherical thermos. It would have either flattened or weighted bottom so it would stay upright on its own, or a flat-bottomed holder. It would also have a
cover that blends in smoothely with the spherical design.
Ball-shaped Thermal Carafe
http://www.tabletoo...tton-lid-white.html
Spherical shaped vessel with convenient handle and spout. [jurist, Oct 30 2006]
wonderful thermos
http://www.consumer.../stanley_vacuum.jpg
i have the one on the left, but mine is green. [bleh, Oct 30 2006]
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Annotation:
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The spherical shape may be appealing to the eye, but I'd prefer an insulated vessel that was easy to handle and pour. Perhaps the [linked] model is the better compromise. |
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I thought these would be commonplace, but a quick search revealed otherwise. |
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I frequented a government-surplus outlet in my youth, which always had large (100 liter?) dewars for sale. I always thought it would be fun to have one, and keep liquid nitrogen around, but I never had the funds. |
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At first glance, this appears to be undisputable, but I would like to throw a complication in:
When the thermos is less than full, the liquid spreads itself over the bottom of the sphere. In that case, the surface area of the liquid is quite high, compared to its volume. I wonder if there is an optimum shape which accounts for the various states of fill? |
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//When the thermos is less than full, the liquid spreads itself over the bottom of the sphere. In that case, the surface area of the liquid is quite high, compared to its volume. I wonder if there is an optimum shape which accounts for the various states of fill?// |
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For the smaller volume of liquid, it would be best contained in a smaller sphere. However, a chain of small spheres would not be as efficient when the vessel is nearer to capacity: with 15 small spheres, for example, when filled to capacity the liquid would have nearly 2.5 times the surface area it would have had in a single sphere. |
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But how about a thermos made of several spheres of *different* sizes? A few extra stalks would help the vessel to balance at various angles. We could have a large sphere in the centre, with smaller spheres around it. |
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By choosing the position you balance the thermos, you could fill the sphere(s) which most closely match the volume of liquid you're putting in, while leaving the others empty. And the surface area when it's completely filled would be less than a chain of small spheres. |
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For example, with spheres of volume 1, 2, 4 and 8, the surface area when totally filled would be only 1.5 times that of a single sphere of volume 15, while allowing you to better optimise for smaller volumes, especially when less than half-full. |
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Or you could just have a handful of various-sized thermos spheres and pick the one that's the best size for the job. |
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But [Ian]'s thermos balloon would be coolest, in both senses of the word. |
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how long do you guys need to keep your hot things hot and cold things cold?? I have a stanley thermos that works beautifully for 12 hours. its cylindrical, and looks like an artillery shell, but does the trick. |
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Thermos be a way to optimize this. |
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/ a flattened or weighted bottom / |
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You have deviated from the purity of your original thought with this concession to practicality, [--]. Stick with the sphere. Those who dislike the rolling may purchase some ineffecient, lesser thermos. |
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Totally OT-
//practicality, [--]. Stick with // |
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I love that you abbreviated his/her name, [bungston]. |
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I like the thermos balloon. Start with two balloons made of materials with appropriate thermal and mechanical properties, and fill the outside of the inner one with styrofoam beads. Then you just have to connect the inner balloon to a valved dispensing straw, and find an easy means of filling the thing (include an integral pump?). |
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As it decreases in size, the surface area is reduced but the insulation value remains the same. |
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[Worldgineer]- Maybe I'm not getting it but wouldn't the R value decrease the bigger it got because the same amount of beads would have to cover more area thus get thinner? |
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At this point, I'd like to throw another spanner in the works:
I've been thinking about the spread of liquid over the bottom of the sphere, and since the insulation is very good, it is fair to say that the air space above the liquid is the same temperature as the liquid, but it's effective heat transfer to the vessel body is not as much, but of significance. Also, once the liquid has been poured out, the fresh air must be heated/cooled one time. The amount of air only depends on the amount of liquid removed, and not on the shape, unless Mr. Tindale's balloon is used. |
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[NSS] Of course. But I was thinking about the other direction - instead of your thermos becoming less effective as you empty it, it becomes more effective ("remains the same" was incorrect, except in an overall sense). |
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/ a flattened or weighted bottom / |
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Nah, keep the spherical thermos, but add a flat-bottomed holder. |
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The holder isn't a bad idea. I've added it to the description. |
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