# Water vapor condensation

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 September 14, 2011, 15:32 Water vapor condensation #1 New Member   Enrico Bezzi Join Date: Aug 2011 Posts: 9 Rep Power: 8 I'm trying to simulate the condensation of water vapor of moist air as a mass transfer. I have a multiphase fluid: phase 1 is a mixture of air and water vapor, and phase 2 is water liquid. I wrote a UDF where I used a macro called "define_mass_transfer" and compiled it in Fluent. But when I try to initialize the calculation, I receive a "segmentation violation error". Does anyone know why? Or can anyone tell me another way to simulate condensation? The UDF I wrote is this: #include "udf.h" real H2O_Saturation_Pressure(real T) { real esp; esp=7.5*(T-273.15)/(237.7+T-273.15); return (611*pow(10,esp)); } DEFINE_MASS_TRANSFER(vap_condensation,c,t,from_pha se_index,from_species_index,to_phase_index,to_spec ies_index) { real m_lg; real x_h2o, x_sat, w_sat; /* w=mv/ma; x=mv/(ma+mv) */ #define p 101325 x_h2o = C_YI(c,t,from_species_index); w_sat = 0.622*H2O_Saturation_Pressure(C_T(c,t))/(p-H2O_Saturation_Pressure(C_T(c,t))); x_sat = w_sat/(1+w_sat); m_lg = 0.; if (x_h2o > x_sat) { m_lg = (x_h2o-x_sat)*C_R(c,t); } return (m_lg); }

 July 27, 2012, 12:40 #2 New Member   Mike Join Date: Jun 2012 Location: Wooster, OH Posts: 5 Rep Power: 7 Enrico, Did you figure out how to model your condensation successfully? I am interested in modelling condensation myself and would like to know how others have tried implementing it. Thanks. -Mike

 July 28, 2012, 06:39 #3 Member     Join Date: Mar 2011 Posts: 64 Rep Power: 8 Condensation is like evaporation. It can be modeled using phase interaction of the VOF models. __________________ Saeed Sadeghi Ansys Fluent CFD Consultant

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