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Energy and calculating vaporization of water

  1. Jan 11, 2007 #1
    1. The problem statement, all variables and given/known data

    I have a certain amount of water, which is heated by a 12V battery, which has an electric current of 13A. I need to work out the time taken to reach boiling temp, where the specific heat of water is given as 4200 J kg -1 C -1? Also need to know how to calculate the time taken to vaporize all the water using the standard latent heat of vaporization?

    2. Relevant equations

    I = Q/T for the first part in working out the time taken to boil the water, but not sure???

    The second part working out vaporization and the time to vaporize water, really no idea? Please help or offer some guidance.


    3. The attempt at a solution

    As Above... Sorry its all a bit vague...
     
  2. jcsd
  3. Jan 11, 2007 #2

    Hootenanny

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    Welcome to the Forums,

    Okay, do you know any expressions for electrical power?
     
  4. Jan 11, 2007 #3
    a few, mostly this one:

    P = /\Ee
    ____
    t = I/\V

    this is the equation I think electrical energy to convert into other forms of energy, but not sure where time and vaporization come in???
     
  5. Jan 11, 2007 #4

    Hootenanny

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    Okay, the expression I'm looking for is P=iV, which we can re-write as Q = iVt. This means the amount of heat energy (Q) that the circuit supplies to the water in a time t is Q = iVt. Does that help?
     
  6. Jan 11, 2007 #5
    Its something for me to look at, I'll do a load more reading tonight. Thanks for the insight, anything helps at the moment, all the equations seem to roll into one!!!
     
  7. Jan 12, 2007 #6
    Just do a Process modell using ODE'S

    Input-output=accumulation.

    Do it a component balance so only use energy & temp
     
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