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Getting inverted results on mass-fraction

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Old   March 22, 2016, 08:58
Default Getting inverted results on mass-fraction
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Hello everyone

I‘m modeling a flow inside cylindrical tube filled with the catalyst and this tube is exposed to a constant heat flux (100000 W/m2). The inlet gas is ammonia under around 600 K and 50 bar and when the gas go through the catalyst inside the tube it dissociate to nitrogen and hydrogen. The flow is turbulent, i calculate the viscosity resistance, inertial resistance, porosity and the surface to volume ratio (because i assume it’s wall surface reaction). My reaction is based on Arrhenius equation, so i thought i don’t need to write UDF function. When i applied all these conditions the reaction occur, however, the mass fraction result isn't correct. Based on the equation of my reaction 2NH3 ------ N2 + 3H2 which means the result of dissociated ammonia is very much 20 - 30 % N2 and 60 - 70 % H2 and about 10% NH3 (not dissociated). However, I'm getting exactly the opposite 60-70% N2 and 20 - 30% H2 and i don't know exactly why this is happening. Do you have any idea how can i solve this problem? Please help



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Last edited by Abdiwe; April 5, 2016 at 09:46. Reason: see "Moderator note:"
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