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Problem with DEFINE_DPM_PROPERTY

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Old   September 28, 2010, 13:47
Question Problem with DEFINE_DPM_PROPERTY
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Henry
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Hi all,

I wrote a simple UDF to incorporate vapour pressure data of urea water solution (UWS) into a urea spray simulation. Problem is I do not know if the DPM evaporation law is actually taking my vapor pressure reading into account as I could not see the changes I expected from the addition of UWS vapour pressure data during post-processing.

Note: After I interpreted the UDF, I simply replaced water's vapor pressure in the MATERIAL/PROPERTY section.

Could anyone please let me know if I am on the right track? The UDF is as follows:


/************************************************** *
UDF that defines Adblue vapour pressure
************************************************** **/

#include "udf.h"
#define MWurea = 60.06;
#define MWh2o = 18.02;

DEFINE_DPM_PROPERTY(Adblue_Vap_Pressure,c,t,p)

{

real Tp = P_T(p);
real LF_h2o = P_LF(p); /*liquid fraction of water in Adblue*/
/*First obtain real water vapor pressure based on particle temperature*/
real vp_h2o = 0.0;

real n_urea = 0.0;
real n_h2o = 0.0;
real n_N = 0.0;
real rho_h2o = P_RHO(p);
real rho_urea;
real V1 = 0.0;
real V2 = 0.0;
real a = 0.0;
real vp_adblue;

rho_urea = 1.32;

if ((Tp >= 300.0) && (Tp <= 333.0)) {
vp_h2o = 776468.0 - 5319.5 * Tp + 9.145 * Tp * Tp;
}
else
{
vp_h2o = -11585500.0 + 108092.0 * Tp -337.58 * Tp * Tp + 0.3533* Tp * Tp * Tp;
}

/*Vapor Pressure for water due to urea concentration*/

V1 = 18.02 / rho_h2o;
V2 = 60.06 / rho_urea;

n_h2o = LF_h2o / V1;
n_urea = (1.0 - LF_h2o) / V2;
n_N = n_urea / n_h2o;

a = n_N/3.3;
vp_adblue = vp_h2o / pow(10.0, a);

/*printf("LF = %f P_ablue = %f", LF_h2o, vp_adblue);*/
return vp_adblue;

}


Thanks for your help in advance!

Best regards,
Henry
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