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Thread: Exam question

  1. #1
    Join Date
    Oct 2009
    Posts
    10

    Exam question

    Does anyone know how much BTU heat needed for 15000lbs water at 10C to turn into ice at -7.8C?

    What is the proper set temperature for Ice rink?

    Your help is appreciated!!

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    You do know the answers are in your text books, don't you.
    How many BTUs does it take to lower 1 pound of water 32F.
    How many BTUs to turn 1 pound of water to ice.

    Multiply by 15,000 and you will have the answer.
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  3. #3
    Join Date
    Oct 2009
    Location
    Ontario, Canada
    Posts
    831
    What helps me is to draw out the sensible/latent chart. Latent heat of fusion is 144 BTUs and latent heat of evaporation is 970 BTUs.

    The formula we get is Q=SH*W*TD for sensible heat. Being your Sensible heat*weight*temperature difference. Latent heat in your case would be the latent heat of fusion. So as beenthere stated multiply that (144)*15000.

    Remember SH for ice and steam is 0.5 and water is 1.


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