UDF for condensation or boiling
Hello everyone,
I am doing a project about condensation in FLUENT. There is a watervapor two phase flow passing through a cooler wall. I am searching a UDF for condensation. Does anyone have the UDF code for condensation or boiling? Thanks in advance. Yvonne 
Re: UDF for condensation or boiling
I think I saw one about mass transfer in multiphase flows based on saturation temperature on the UDF manual. DEFINE_MASS_TRANSFER, or something like that.

Re: UDF for condensation or boiling
hello edi ghirardi,
I already got them. thank you reply. Best Yvonne 
Condensation UDF
Hi Yvonne,
I was searching for a condensation UDF. I am working on condensation through microchannels. I need to give water vapor at the inlet. I was wondering if i need to use udf...Since it is condensation, as the fluid flows through the channel, there should be a phase change. I was wondering if i shud give the option of multiphase in fluent. Please help me on this. I would also appreciate if you could send me ur udf file. Best Regards Yaamunan 
Hi Guys
I have one developed part of my work. It is working nicely. However, you may need to change according to your problem. ************************************************** ** DEFINE_DPM_LAW(Boiling_sree, p, ci) { double cp_gas, vap_rate_const, latent_heat; double temp_diff,term,dia_ratio; double fv = DPM_VOLATILE_FRACTION(p); double diam_dry = 0; cphase_state_t *c = &(p>cphase); double qrad = 0.0; Material *m = p>injection>material; double min_liquid_mass = P_INIT_MASS(p)*(1.0  DPM_VOLATILE_FRACTION(p)); double liq_mass = PI*(pow(P_INIT_DIAM(p),3)/6.0)*(1.0  P_INIT_LF(p))*MATERIAL_PROP(p>injection>material,PROP_rho); law = 3; vapor_on = FALSE; boil_on = TRUE; /* Message (" ****Control is in Boiling: %16.8g, liquid mass:%16.8g, law: %i\n",liq_mass,min_liquid_mass,law); */ if (P_MASS(p) <= liq_mass) { if (ci) AddSources(p); p>current_law_index++; HeatMassUpdate(p,ci); vapor_on = FALSE; return; } if (DPM_WET_COMBUSTION(p)) { m = p>injection>evaporating_material; diam_dry = P_INIT_DIAM(p) * pow(1.P_INIT_LF(p),1./3.); } else { if (fv < 1.) diam_dry = P_INIT_DIAM(p) * pow(1.fv,1./3.); } /* Message (" ****diam dry: %16.8g, org dia:%16.8g\n",diam_dry,P_DIAM(p)); */ latent_heat = MAX(1.e20,MATERIAL_PROP(m,PROP_latent_heat)); if (ABS(latent_heat) < 1.e20) latent_heat = 1.e20; cp_gas = c>sHeat; /*Message (" ****Cp gas: %16.8g\n",cp_gas); */ if (cp_gas < DPM_SMALL) cp_gas = DPM_SMALL; temp_diff = c>tempP_T(p); if (temp_diff < 0.) temp_diff = 0.; /* Message (" ****temp_diff: %16.8g, c>temp:%16.8g\n",temp_diff,c>temp); */ if (dpm_par.radiation_p) { qrad = DPM_EMISSIVITY(p,P_MATERIAL(p))*(.25*c>G  SIGMA_SBC*pow(P_T(p),4.)); } /*Message (" ****q_rad_default: %16.8g, q_rad: %16.8g, time_step: %16.8fl \n",qrad, qrad1,p>time_step); */ if (qrad < 1.e9) { /*Message("it is true\n");*/ vap_rate_const = 8. * c>tCond / (P_RHO(p)*cp_gas)* log(1. + cp_gas*temp_diff/latent_heat); term = P_DIAM(p)*P_DIAM(p)  vap_rate_const*(1. + 0.23*sqrt(p>Re)) * p>time_step; P_DIAM(p) = (term > 0.) ? sqrt(term) : diam_dry; } else { /*Message("it is false\n");*/ real ku = 2.0 + 0.46*sqrt(p>Re); real alpha = 2.*qrad/(P_RHO(p)*latent_heat); vap_rate_const = c>tCond * temp_diff * ku; term = P_DIAM(p)  (vap_rate_const + qrad*P_DIAM(p))*alpha*p>time_step / MAX(qrad*P_DIAM(p),DPM_SMALL); P_DIAM(p) = (term > 0.) ? term : diam_dry; /*Message("term: %16.8g, diam: %16.8g\n", term, P_DIAM(p));*/ } if (DPM_WET_COMBUSTION(p)) { P_DIAM(p) = MAX(P_DIAM(p), diam_dry); P_LF(p) = MAX(0., 1.0  diam_dry*diam_dry*diam_dry /(P_DIAM(p)*P_DIAM(p)*P_DIAM(p))); P_RHO(p) = P_LF(p) * MATERIAL_PROP(p>injection>evaporating_material,PROP_rho) + (1.P_LF(p)) * MATERIAL_PROP(p>injection>material,PROP_rho); P_MASS(p) = P_RHO(p) * PI * P_DIAM(p)*P_DIAM(p)*P_DIAM(p) / 6.; } else { dia_ratio = P_DIAM(p)/P_INIT_DIAM(p); P_MASS(p) = P_INIT_MASS(p) * dia_ratio*dia_ratio*dia_ratio; } /*Message (" P_Mass:%16.8g, Liquid_fraction:%16.8g \n",P_MASS(p),P_LF(p));*/ } ************************************************* Hope this helps sree 
Hello sreerao!
I have recently started to work with UDF and can not understand what this line means : { if (ci) AddSources(p); //what exactly does that mean?? p>current_law_index++; HeatMassUpdate(p,ci); // and that too??? vapor_on = FALSE; return; } Thanks in advance. 

request for udf for condensation
where is available udf for condensation in manual???? or can specify any other resourse??

Wall condensation
Hi,
I have to model the wall condensation for water vapor. I am new to UDF writing. If you could mail me the UDF, it will a great help to start with. Thanks. Quote:

Quote:

Have a look at tutorial titled Heat and Mass Transfer with the Mixture Model
and EvaporationCondensation Model. It demonstrates usage of evaporationcondensation model. I dont think you need UDF unless something very complex is happening in your model. 
Wall Condensation
Hi,
I have to model condensation of water vapour in a vertical minichannel. I am new to fluent. Could anyone help me with it please? I am using the evaporation/condensation model. However, I am not having the condensate film on the wall.. :confused::confused: Thank you 
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