[MarouaO]

HI , I'm not too familiar with UDF ,i'm a begginer. I searched a lot and i didn't understand from where the equations dependent to temperature come ??(conductivity,viscosity,Cp,Density of base fluid)- i mentionned the equations with bold please help me.

Here an exemple:

Brinkman model

#include "udf.h"
#define fi 0.02
#define ro_s 3950
/*#define cp_f 1845*/
DEFINE_PROPERTY(cell_density, cell, thread)
{
real ro_nf;
real ro_f;
real tt= C_T(cell, thread);
ro_f=1000*(1-((tt+15.7917)*((tt-277.1363)*(tt-277.1363)/(508929.2*(tt-205.0204)))));
ro_nf=(((1-fi)*(ro_f))+(fi*(ro_s)));
return ro_nf;
}
DEFINE_SPECIFIC_HEAT(cell_specific_heat, T, Tref, h, yi)
{
real cp;
real cp_f;
real cp_s;
real ro_f;
cp_s= 765;
cp_f=9616.873445-48.73648329*T+0.1444662*((pow((T) ,2)))-0.000141414*((pow((T) ,3)));
ro_f=1000*(1-((T+15.7917)*((T-277.1363)*(T-277.1363)/(508929.2*(T-205.0204)))));
cp=((1-fi)*(ro_f*(cp_f))+(fi*(ro_s*(cp_s))))/(((1-fi)*ro_f)+fi*ro_s);
*h = cp*(T-Tref);
return cp;
}
DEFINE_PROPERTY(thermal_conductivity, cell, thread)
{
real tt= C_T(cell, thread);
real mu_f;
real ro_f;
real k_eff;
real ks;
real kf;
real Re;
real Pr;
real cp_f;
cp_f =9616.873445-48.73648329*tt+0.1444662*((pow((tt) ,2)))-0.000141414*((pow((tt)
,3)));
kf=-1.1245+0.009734*tt-0.000013158*tt*tt;
ks=35;
mu_f=0.02165-0.0001208*tt+(1.7184e-7)*tt*tt;
ro_f=1000*(1-((tt+15.7917)*((tt-277.1363)*(tt-277.1363)/(508929.2*(tt-205.0204)))));
Re= (2*ro_f*tt*1.3806488e-23)/((22/7)*25e-9*(mu_f*mu_f));
Pr= (mu_f*cp_f)/(kf);
k_eff=kf*(1+(4.4*(pow((Re) ,0.4)))*(pow((Pr) ,0.66))*(pow((tt/273.15)
,10))*(pow((ks/kf) ,0.03))*(pow((fi) ,0.66)));
return k_eff;
}
DEFINE_PROPERTY(viscosity, cell, thread)
{
real mu_f;
real mu_eff;
real tt= C_T(cell, thread);
mu_f=0.02165-0.0001208*tt+(1.7184e-7)*tt*tt;
mu_eff =mu_f/(pow((1-fi) ,2.5));
return mu_eff;
}