[Sorabh]

DEFINE_PROPERTY(cell_Density,c,t) //density defined
{
	real density;
	real temp = C_T(c,t);
	if (temp < 273)
		density = 921;
	else
		density = 999;

	return density;
}

 DEFINE_SPECIFIC_HEAT(my_user_cp, T, Tref, h, yi) //specific heat defined
 {
   real cp;
   if (T<265)
	   cp = 1800;
   else if (T >= 265 && T < 270)
	   cp = 1800 + 102.856*(T-265);
   else if (T>=270 && T <= 272)
	   cp = 3600 + 642.8*(T-272);
   else
	   cp = 3600;
   *h = cp*(T-Tref);
   return cp;
 }

DEFINE_SOURCE(perfusion_2,c,t,dS,eqn) //need to extract the value of the above macros for this
{
	real physical_dt,temp_old,temp_now,temp_older,T_derivative,source; //source_1
	real T_derivative_now,T_derivative_old,T_derivative_2;
	physical_dt = RP_Get_Real("physical-time-step");
	temp_older = C_T_M2(c,t);
	temp_old= C_T_M1(c,t);
	temp_now=C_T(c,t);
	T_derivative_now=(temp_now-temp_old)/physical_dt;	
	T_derivative_old = (temp_old-temp_older)/physical_dt;

	T_derivative_2 = (T_derivative_now-T_derivative_old)/physical_dt;
	
	real rho = (real)cell_Density; //trying to get the values
	real c = (real)my_user_cp;

	source = tq*rho*c*T_derivative_2;
	dS[eqn]=0;

	return source;
}

I intend to use the property off the 2 DEFINE_PROPERTY macros, and use it in the DEFINE_SOURCE macro. How should I do it?

In the above code, I tried typecasting, but I am clearly missing something.

Any help would be appreciated

[AlexanderZ]

problem is here

	real rho = (real)cell_Density; //trying to get the values
	real c = (real)my_user_cp;

you've defined macros for density and specific heat so you should use macros to get that values

	real rho = C_R(c,t); //trying to get the values
	real c = C_CP(c,t);

for more information look into Ansys Fluent Customization manual

best regards