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How can I verify calculated heat loss?

  1. Jan 5, 2012 #1
    Hi all,

    I have calculated the expected heat loss (fabric not ventilation) of a room in a house using Q=Ʃ(UAΔT) for each building element (window, door, wall, ceiling etc) making the room. The units are Watts.

    How can I measure the actual observed heat loss of the room? I am currently monitoring the internal room air temerature and the external air temerature. Shouldn't I be able to calculate the heat loss after switching the heating off and observing the rate of temerature decrease? Obviously I need the figure in Watts to compare against the calculated heat loss.

    Thanks in advance...
     
  2. jcsd
  3. Jan 5, 2012 #2

    Simon Bridge

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    Yep - Pretty much how you'd do any heat loss experiment.
     
  4. Jan 5, 2012 #3
    Thanks for the reply but I was hoping for an equation to plug my temperature readings into...
     
  5. Jan 5, 2012 #4

    Simon Bridge

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    You don't have a model for heat loss?

    The rate of heat loss depends on the current temperature, so it's actually an exponential.
    You heat loss calculations assume a constant internal temperature - so they would correspond to the initial heat loss ... which involve curve-fitting.

    You can relate a change in temperature to a change in energy right?
    Ideally you want to determine this experimentally ... use a heating element of known power to heat air in a well insulated box and measure the temperature - plot Temp vs time. OR you can use one of the many theoretical models for air ... PV=(5/2)NkT (diatomic ideal gas) to get an approximate figure (you should apply such models to your theoretical heat-loss to turn it into a change in temperature).

    Of course you could verify directly - since the calculation you did was for equilibrium at a particular operating temp, you can directly measure the energy pumped into the air from the heaters. This should match the heat loss.
     
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