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Flame Temperature of an Acetylene Cutting Torch

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Flame Temperature of an Acetylene Cutting Torch

Introduction

 

A cutting torch is powered by acetylene burned in 100% theoretical air. The combustion reaction is

 

C2H2 + 2.5 O2 + 9.4 N2 → 2 CO2 + H2O + 9.4 N2

 

This application will calculate the adiabatic flame temperature by equating the enthalpy of the reactants and products; this heat balance is solved numerically with fsolve .


Thermodynamic data are extracted from the ThermophysicalData:-Chemicals  package.

 

restart:
with(ThermophysicalData:-Chemicals):

Heat of Formation

 

h_f_C2H2 := Property("HeatOfFormation", "C2H2,acetylene", useunits);
h_f_CO2  := Property("HeatOfFormation", "CO2",            useunits);
h_f_H2O  := Property("HeatOfFormation", "H2O",            useunits);
h_f_N2   := Property("HeatOfFormation", "N2",             useunits);

228200.000*Units:-Unit(J/mol)

 

-393510.000*Units:-Unit(J/mol)

 

-241826.000*Units:-Unit(J/mol)

 

0.

(2.1)

Enthalpies

 

h_C2H2 := Property("Hmolar", "C2H2,acetylene", "temperature" = T):
h_CO2  := Property("Hmolar", "CO2",            "temperature" = T):
h_H2O  := Property("Hmolar", "H2O",            "temperature" = T):
h_N2   := Property("Hmolar", "N2",             "temperature" = T):

 

Reference Enthalpies

h_r_C2H2 := eval(h_C2H2, T = 298 * Unit(K));
h_r_N2   := eval(h_N2,   T = 298 * Unit(K));
h_r_CO2  := eval(h_CO2,  T = 298 * Unit(K));
h_r_H2O  := eval(h_H2O,  T = 298 * Unit(K))

228193.4012*Units:-Unit(J/mol)

 

-4.36864*Units:-Unit(J/mol)

 

-393515.5699*Units:-Unit(J/mol)

 

-241831.0385*Units:-Unit(J/mol)

(3.1)

Heat Balance

 

Heat of reaction

H_reactants := 1 * Unit(mol) * h_f_C2H2

228200.000*Units:-Unit(mol)*Units:-Unit(J/mol)

(4.1)

Heat of products

H_products :=
  2 * Unit(mol)   * (h_f_CO2 + h_CO2 - h_r_CO2)
+ 1 * Unit(mol)   * (h_f_H2O + h_H2O - h_r_H2O)
+ 9.4 * Unit(mol) * (h_f_N2  + h_N2  - h_r_N2):

 

Hence the adiabatic flame temperature of the cutting torch is

fsolve(H_reactants = H_products, T = 1000 * Unit(K))

2909.571423*Units:-Unit(K)

(4.2)

 

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