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  1. #1
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    Homework Question..please help

    I really don’t understand how to do this ..please help

    How many BTU need to be added to change 5 lb of ice at 30F to steam at 215F?

  2. #2
    Join Date
    Dec 2014
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    Clues for you

    What did the instructor tell you the latent heat of fusion of water is?
    And the latent heat of evaporation?

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  3. #3
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    I'm tempted to tell you to figure it out yourself, but our site strictly forbids giving DIY advice, so I'm conflicted on what to tell you.

    Besides, I think it might be a trick question because I don't think steam can ever be hotter than 212F at atmospheric pressure. If you are talking about some ice that's inside of a pipe, then we would also need to know what pressure you are going for.

    I'm pretty sure I'd go with "D", "None of the above".
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  4. #4
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    Haha...215 gotta be a typo no?

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  5. #5
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    I think the 30 degree ice and the 215 steam are both incorrect numbers for that question. Probably tried to type the question from memory.

    OP, are you sure it isn't 32 degree ice and 212 degree steam.

    Also, in your book/books, you will find the amount of latent heat in ice, and in steam. And should be easily able to do the math to get the answer yourself.

    Giving you the answer, or telling you how to figure it out would not violate the DIY rules. But most employers would want someone to be able to figure things out on their own. And this is a very simple question to find the values for it.
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  6. #6
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    I recall in hvac school having questions like that. I think the 30 is correct, altho it would be better maybe to have a number like 20f ice. (Might be eadier to imagine)
    Then 20-32 ice btus and 32ice to 212 water and .........well cant put it all in here.....but that should surely get you going.




    There! Plug it into your equation

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  7. #7
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    Apparently this is for one of those combination ice rink/steam room that is coming out.

  8. #8
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    May 2016
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    Well it's a two part problem, first you need to turn the ice to water, that's your first equation. Second you need to turn the water to steam. Icy78 has basically solved your problem.

  9. #9
    Join Date
    May 2014
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    The ice in my freezer is 0*F.

    To the OP, not a trick question, you need to add up the latent and sensible heats.
    If you were a real tech, you'd solder a relay on that board and call it good to go.

    I do a triple evac with nitro to remove non condensables.

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