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July 11, 2020, 01:29 |
heat of combustion
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#1 |
New Member
mohsen
Join Date: Jul 2020
Posts: 8
Rep Power: 5 |
Hi,
i have e reaction for Propane and heat of combustion is 24.2 MJ/kg. I don't know how to set 24.2 MJ/k in CFX? Can you hlp me? Tnx |
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December 24, 2020, 23:48 |
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#2 |
Senior Member
Kira
Join Date: Nov 2020
Location: Canada
Posts: 435
Rep Power: 8 |
Hello Mohsen,
Please check out this thread, I believe it goes over what you are asking: change heat of combustion In sum, ANSYS CFX does not use the heat of combustion, or heat of fuel explicitly anywhere in the combustion model. It uses thermodynamic properties of the material. The ANSYS CFX implementation of the energy equation does not use any split of the enthalpy material definition. For these properties (and you can consult a Thermodynamics book), Sample reaction: A * Propane + B * O2 + C * N2 --> D * CO2 + E * H2O + F * N2 heat of combustion formula as a function of the enthalpies defined as: h_material = h_material_ref + Cp_material (T - T_ref) Once you work out the heat of combustion, it should be a function of the reference enthalpy of your type Propane and the adiabatic flame temperature for the value you have. |
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December 25, 2020, 12:01 |
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#3 |
Senior Member
Gerry Kan
Join Date: May 2016
Posts: 347
Rep Power: 10 |
Dear Mohsen:
The 24.2 figure you posted is some kind of heating value (as an aside for hydrocarbons it should be closer to 50 MJ/kg fuel, you should check it again). That said, you don't specify heat of reaction in a reaction. What you need are the (temperature dependent) heats of formation for each of the species involved in your reaction mechanism, as part of their thermophysical properties. The energy released will be summed up across all species according to your mechanism and local thermodynamic state. Hope that helps, Gerry. |
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