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CarbonParticleCombustionEPSolnME525SP2011

# CarbonParticleCombustionEPSolnME525SP2011 - Carbon Particle...

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1 Carbon Particle Combustion One-Film Model Example Problem ME 525 SP2011 Consider a burning carbon particle. Analyze the process using the one-film model. The particle diameter is 20 microns (20x10 -6 m). The burning rate of the carbon particle (diagram on next page) is given by  2, 4l n 1 1 OO s Cs g g Os YY mr Y      D 2 12 , 2 42 Cm i x O s Ou s MW MW P k Y MW R T Assume that the burning process is quasi-steady and that the particle temperature is uniform. Evaluate g at the particle surface temperature, assume that 2 mix O M WM W , and use the following properties: 1900 s TK , 10 / g ms D ,   0.128 / g kW m K  , 1 20 / km s , 800   00 0 , ( ) , 2( ) , 2( ) 1900 1900 0 / , 1900 396,000 / fCs fO g fCO g h K h K kJ kmol h K kJ kmol  Assume that the surface reaction is given by () 2 ( ) 2 11 sg kg C kg O kg CO   , and that the oxidizer is air. (a) Calculate the burning rate C m . This will involve an iterative process. The first step in the process is to assume that the oxygen mass fraction at the surface is zero and then calculate C m from Eq. (1). Perform at least two complete iterative procedures to calculate values for C m and Y . (b) Calculate the mass fluxes 22 and CO O mm   at s rr , just outside the particle surface. Use an assumed value of C m if you do not complete part (a). Indicate the direction of the mass fluxes (c) Calculate the gas-phase temperature gradient at s . Consider a control volume with the inner surface at s and the outer surface at s . For full credit draw the control volume boundaries and indicate the energy transport terms into and out of this control volume. Again, use an assumed value of C m if you do not complete part (a). Assume a surface emissivity of 0.7 for the carbon particle.

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2 Solution: (a)  2 5 3 3 32 8314 260 32 : 10 0.20 260 1900 mix O g g g kg MW MW kmol J J kmol K R kg kg K kmol At the surface J Pk g m R Tm J K kg K
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CarbonParticleCombustionEPSolnME525SP2011 - Carbon Particle...

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