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Heating Christmas puddings!

  1. Nov 18, 2006 #1

    X=7

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    Hello everyone, new member here:smile:.

    My sister asked me this today - real-life physics at work!

    She's making Christmas pud & the instructions say it takes 8 hours to cook. However, her bowls are too small, so she's made two little ones instead, and she asked how long to allow to cook them (you're not meant to disturb/ examine them while they're cooking). I guessed six hours.

    I don't need any complicated formulae, just the ratio of cooking times; is it proportional to the volume, or the surface area:confused:? I have a degree in pure maths:surprised, but was always rubbish at physics. I remember there are different types of heat transfer, but please just keep it simple. You can pretend the puds are spherical.

    Thanks

    X=7
     
  2. jcsd
  3. Nov 18, 2006 #2

    Danger

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    This isn't definitive, but you might want to experiment with it a bit. The type of frozen dinners that the wife bought last time come 2/box. Cooking 1 in the microwave takes 2 minutes, and cooking 2 takes 3 1/2 minutes. The same ratio might apply in your situation (ie: a little one takes about 60% as long as a big one).
    On the other hand, a conventional oven (which I assume that she's using) might suffer the same effect as a nuker, wherein the available energy must be equally distributed among 2 items. If that's the case, then 2 little ones in the oven at the same time might take just as long as one big one.
    Why don't you try melting various sizes of ice blocks or something similar and record the results? That might give you a handle on it.
    Sorry that I can't be more helpful.
     
  4. Nov 18, 2006 #3

    NoTime

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    It's not complicated.
    Go out quick and buy your sister a bigger bowl :smile:
    After all there is pudding at stake :!!)
     
  5. Nov 18, 2006 #4

    X=7

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    Thanks for the fast replies, Danger and NoTime:smile:. Danger, yes, I reckon you're about right but I probably won't have time to try the ice thing; I came on this physics forum in case these are well-known results. Ditto to NoTime, I'd worked that one out for myself:biggrin:!

    Thanks anyway & further contributions welcome.

    X=7
     
  6. Nov 18, 2006 #5

    Danger

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    There might be a formula that's applicable, but I'm not aware of one. The time should be based upon volume and surface area combined in some way. There are only so many calories available to heat the volume, but how close most of it is to the surface should determine how long it actually takes. When I get home, I'll try to work something out.
    Anyhow, even if we don't manage to nail this one down for you, please hang around the site now that you've discovered it. You won't regret it.
     
  7. Nov 18, 2006 #6

    X=7

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    That is what my instinct is telling me, but happy to be proved wrong:tongue:.

    Thanks for the friendly introduction, will do!:smile:

    X=7
     
  8. Nov 18, 2006 #7

    NoTime

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    There's a lot of factors.
    Transfer time is important.
    A big thick roast takes more time to cook due to the distance to the center, but you also want to adjust the temp somewhat so the outside doesn't get overdone while the center is still raw.

    If you're cooking two small bowls of pudding, instead of one big one, then the oven temp may need to be raised to get the same thermal gradient as well as shortening the time.

    Two pies in the oven cook much the same as one.
    A regular oven won't get loaded down like a microwave.
    Ovens have a big thermal mass.

    OTOH, I have never succesfully doubled a pie crust recipe. Comes out bad! So if I want more than one pie, I have to make seperate batches for the crust.
     
  9. Nov 18, 2006 #8

    Danger

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    You cook?! And all this time, I only loved you for your mind. :!!)

    Hey! Wait a minute here... aren't you a guy? :grumpy:

    Crap! Now I'm going to have to buy W cooking lessons... :grumpy: :grumpy:
     
  10. Nov 19, 2006 #9

    NoTime

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    Having a couple kids qualifies as the mother of invention. :smile:
    Gave it up when they moved out and got places of their own.
    Somthing about liking what I cooked and having no competition for the results resulted in an extra 40lbs. :grumpy: :grumpy:

    :rofl: Now there is the proverbial spanner in the works. :rofl:
    I do have being female as a minimum partner requirement :biggrin:

    Cooking is dangerous, count your blessings :wink:
     
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