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Heat Transfer between two temperatures

  1. Feb 17, 2016 #1
    Hi,

    I'm trying to calculate energy loss between two areas. One area is -25C and another is +15. The contact area(door) is 20m^2. Is convective heat transfer formula the right way to calculate it, or what should I use? I want to find out the how many kW I need to keep cold area at -25 when the door is open.

    Thank you
     
  2. jcsd
  3. Feb 17, 2016 #2

    Nidum

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    Sounds like a lost cause from your description so far .

    If this is a cold room type problem the solution may lie more in redesigning the door system than in calculations and installation of high power cooling equipment .

    Anyway not enough information to give proper answers . Please describe the problem in more detail .
     
  4. Feb 17, 2016 #3
    I agree that the solution lies in door system, but the payback on that door system depends on how much do I lose by not doing it.
    I appreciate there might be no way how to easily calculate it.

    My problem is: I've got a site that is cooled down to -25C. I was told that opening the door(10.2m^2) to the yard(+15C) costs me 500KWh , but I've got no way of verifying that statement. Is there a way how to verify that or not?

    Thank you
     
  5. Feb 17, 2016 #4

    Nidum

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    It may be possible to come up with an answer experimentally .

    You will have a power usage meter supplied by the power company .

    Keep the door permanently closed for at least 24 hours - maybe during a holiday period . Measure the power used during this period .

    Measure the power used on a normal working day with doors opening and closing for the same period .

    See how much difference there is in power usage .

    Ideally repeat the experiment a few times .

    The above will give reasonable answers if the cold room uses most of the power coming into your site .

    You can do a very accurate assesment if you privately install a power usage meter specifically for the cold room .
     
  6. Feb 17, 2016 #5

    Nidum

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    What fraction of the time is the door open for during normal working ?
     
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