[newbie2]

hi!
im using ansys 12.1 and i had to introduce a source term for my problem.i wrote the following udf for that.
#include "udf.h"
DEFINE_SOURCE(first,c,t,dS,eqn)
{
real source;
source=-0.00892;
dS[eqn]=0;
return source;
}
its a packed column which is separating two gases through adsorption.i interpreted the udf without any errors and introduced it in the mass accumulation term and the accumulation term for one of the gases. the results dnt show any change in the concentration of the exiting gas mixture throughout the column.
is there something wrong with the approach or the udf?