Converting watt into temperature (celcius)

Discussion in 'General Electronics Chat' started by rajat1684, Aug 28, 2013.

  1. rajat1684

    Thread Starter New Member

    Aug 26, 2013
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    Thanks you all.

    Intersting..I think I can understand now why more power (watt) means more heat (KJ).

    Converting watt into temperature (celcius)

    Say 70% of 50 watt of Halogen Bulbs converts into heat (hypothetically)
    i.e. = 0.7*50 = 35 watt of heat

    Bulb is on for 5 minutes = 60*5 = 300 sec

    1 watt = 1 joule/ sec, thus 35*300 = 10500 joules = 105 KJ
    Specific Heat of Dry Air (Cv) = 0.716 KJ/kg.K
    Thus,
    105KJ/0.716KJ/kg.K = 146 Kg.K
    Density of Air = 1.3 Kg/m3

    Thus 146 (Kg.K)/1.3 (Kg/m3) = 112.3 K-m3

    This means temperature rise will be 112.3 K per m3 of dry air.

    Converting Kelvin to Celsius

    Celsius = Kelvin- 273
    Celcius = 112.3-273 = -160.7 (taking mode = 160 degree celcius)

    Is this correct that temperature rise will be 160 degree celcius?
     
  2. rajat1684

    Thread Starter New Member

    Aug 26, 2013
    13
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    Sorry because I'm not an electrical engineer any advice would be good for me
     
  3. wayneh

    Expert

    Sep 9, 2010
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    A degree kelvin is the same size as a degree celsius, so no need to go any farther once you have °K.

    Your calculation is reasonable although I haven't checked every detail. One problem, though, is that both the density and the heat capacity are not constant, but are functions of temperature themselves. So the precise answer requires integral calculus.

    Depending on what happens to the light, it might end up heating the air as well.
     
  4. rajat1684

    Thread Starter New Member

    Aug 26, 2013
    13
    0
    Thanks wayneh :)
     
  5. rajat1684

    Thread Starter New Member

    Aug 26, 2013
    13
    0
    It just seems lot of rise in temp so just thought to share it in forum
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,085
    3,024
    Oh, hey, you slipped a decimal in converting to kJ.
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,979
    3,690
    Here...with errors corrected.

     
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