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A small insulator

  1. Sep 27, 2007 #1
    We just got assigned to make an insulted cup for holding 200cc of boiling water
    It has to be able to hold 1 liter of water though
    Also, must be minimal size and mass

    There is a competition and whoever has the warmest water after 10 minutes, w/ smallest size and mass, gets the most points, wins etc

    So I was thinking of using a vacuum insulated cup, where we suck out the air betweeen two cups, one bigger than the other,

    Would this be a good idea, and how do we do it?

    ..\\.........// Sort of like this, no air between two sides
  2. jcsd
  3. Sep 28, 2007 #2
    Well there is no point creating a vaccum between 2 cups - which is going to be rather difficult to do- if the top is going to remain open, Your idea is right though ie to creat insulation. I would suggest to fill the gap with insulating material such as cork, and use silver foil for the inside of the cup, to minimise radiation loss.

    And put a lid on it!!!!
  4. Sep 28, 2007 #3
    Thank you for your help.

    The is going to be sealed, and there will be sheet cork around the outside of the inner cup. I have designed a bike pump to act as a vacuum and it removes over 75% of the air

    Any other thoughts?
  5. Sep 29, 2007 #4
    Well great if you managed to get the air out. Just be careful the cups don't collapse due to the vaccum. Cheers!!
  6. Sep 29, 2007 #5


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    Remember to space the inner cup away from the bottom of the outer one, as well as the sides.
    If the goal is simply to have the warmest water, and it isn't specifically outlawed by the rules, you could also wrap a resistance coil around the inner cup and stash a battery in there. :devil:
  7. Sep 29, 2007 #6


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    What are the cups made of? A very good insulator can be made from alternating sheets of paper and foil.
  8. Sep 29, 2007 #7
    What are the rules?

    Danger's most excellent solution points out that we don't know the rules. Do you get to preheat the inside cup? How large can you go in diameter? How much can you spend? Can you pump on the vacuum right up till the last minute? etc. If you decide to use a vacuum, make sure you support the two cups in the space between them; small blocks of styrofoam glued to the outer cup, and occupying maybe 10% of the volume, should work OK. Be sure to cover the edge between the lid and the cup(s). That small leak will drain heat like crazy.
  9. Sep 29, 2007 #8
    We cannot use foam or fiberglass, the hard part is to make it small and light. So what can I do, in conjunction with the vacuum to maintain high temp?
  10. Sep 29, 2007 #9


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    Back to electrical heating, since it apparently isn't forbidden.
  11. Sep 30, 2007 #10
    Could you explain how to do the electric heating?
  12. Oct 1, 2007 #11

    so I found out that I cannot use the resistance coils. I was reading that rubber has low thermal conductivity and what if I connect a balloon to a larger cup, the vacuum the air out from between them so the balloon inflates from within. Also does anyone know if the fact that not all of the air is vacuumed then will it affect the insulation and by how much?
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