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Thermodynamics - Burning Butane in an Oven

  1. Jan 24, 2013 #1
    You have a butane torch and an oven.

    Two scenarios:

    1. Butane is burning in an oven heated to 200 C, does the burning point of the butane change at all?

    2. Butane is burning in an oven heated to 2000 C, does the butane have a cooling effect on the oven?

    The burning point of butane is 1950 C in air.

    In the first situation, the ambient temperature is sure to increase, and I assume that the burning temperature of the butane will increase, simply because the surrounding air will not have as much of an effect on the butane.

    In the second scenario, I haven't the slightest clue.
     
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  3. Jan 24, 2013 #2

    rollingstein

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    Shouldn't this depend on what temp. the butane came in at?

    Whether the heat of combustion at 2000 C is less or more than the heat capacity of the gas?
     
  4. Jan 24, 2013 #3
    Burning the butane is exothermic and will never have a cooling effect. It will simply make the oven hotter. The burning temperature given is only valid for standard atmospheric conditions. http://en.wikipedia.org/wiki/Gas_burner

    I suppose burning in a hotter environment will make the flame hotter.
     
  5. Jan 24, 2013 #4

    rollingstein

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    Aren't you neglecting the cooling effect of specific heat? Cold butane into a hot oven cools.

    Is the exothermicity large enough to compensate?
     
  6. Jan 25, 2013 #5
    The combustion energy is 2.89 MJ/mol.

    specific heat of Butane is 98.5 J/(K mol), so heating it by 1725 K takes 0.170 MJ/mol.
     
  7. Jan 25, 2013 #6

    rollingstein

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    Thanks! Clearly, no cooling effect.
     
  8. Jan 26, 2013 #7
    The process is reactants ==> burning == products.
    As stated the the adiabatic flame temperature and heat of combustion cna be stated for a standard atmosphere.
    If the environment temperature increases, not all of the products will be formed ie perhaps CO instead of C02 will continue to be one of the species if the oven temperature is great enough. This will affect the flame temperature and and how much heat can be obtained from the reaction. It is not a linear relationship with temperature.
    A certain oven temperature can be reached where the reactants will break apart into their constituent parts and no products are formed but continue to persist as a plasma.
     
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