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Energy for heating the air to a specific temperature

  1. May 27, 2015 #1
    Hi all. I'm trying to find haw much energy is required to get the air heated up to one desire temperature in oven. . I guess the next issue will be haw much energy is required to keep the temperature at the setting point.
    A theoretic starting point will be useful from your side, if possible.
    Thank you.
     
  2. jcsd
  3. May 27, 2015 #2

    Svein

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    You need to find out:
    1. The specific heat of air
    2. The volume of the air you want to heat
    3. The thermal conductance of the oven
    4. The ambient temperature
    From there on, it's only plugging in numbers in formulas,
     
  4. May 28, 2015 #3
    Thank you for your advice. I will came back after measurements/calculations ( for 1-4 ) for the "data assembly" for the final scope: formulas for energy required.
     
  5. May 29, 2015 #4
    I guess, if the calculation are correct :) that we are talking about:

    The specific heat of air - 1.026 kJ/(kg K)

    The volume of the air you want to heat - 64 m3
    The thermal conductance of the oven - upload_2015-5-29_14-13-59.png
    upload_2015-5-29_14-13-31.png
    upload_2015-5-29_14-14-28.png
    The ambient temperature 40+273K

    I will appreciate your further guidance.
    Thank you.
     
  6. May 29, 2015 #5

    Svein

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    Adding in the specific mass of air ≈ 1kg/m3 gives you 64kg air to heat. Ignoring thermal leakage, this gives 64⋅1.026 kJ/°K from ambient So if you want the oven to reach 200°C, you will need 64⋅1.026⋅160 kJ = 10 506,24 kJ.

    Thermal conductance: You have calculated a specific thermal conductance, but we need the inner surface of the oven to get ahead. The thermal conductance for the oven is given in W/°K and you would usually measure it by heating the oven to a given temperature and then turning off the power and measuring the temperature in the oven vs. time.

    If your thermal conductance is 1W/°K and you want to keep the oven at 200°C (160°C over ambient), you need to supply 1W/°K⋅160°K = 160W.
     
  7. May 29, 2015 #6

    CWatters

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    The heat capacity of the oven might be needed as well as it's thermal conductance.
     
  8. Jun 3, 2015 #7
    Thank's a lot!
    I got the idea, I think I can manage from this point.
     
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