[hanswoerd]

I am using a DEFINE_HEAT_MASS UDF to calculate source terms for my discrete phase. This discrete solid phase reacts with oxygen and at some point the sum of species source terms in the cell exceeds the total amount of oxygen present in that cell. To solve this I would like to define a upper limit of the source term like so:

real m_o2_cell = C_R(c,t)*C_VOLUME(c,t)*y_O2; /* mass of oxygen in cell [kg]*/
real m_DPM_cell = C_DPMS_CONCENTRATION(c,t)*C_VOLUME(c,t); /* mass of discrete phase in cell [kg]*/
real m_o2_max = m_o2_cell * TP_MASS(tp) / m_DPM_cell; /* distribute the present oxygen evenly over all DPM mass in the cell and scale with particle mass [kg]*/
real dmdt = MIN(dmdt_kin, m_o2_max/CURRENT_TIMESTEP); /* calculate corrected dmdt [kg/s]*/
dzdt->species[ind_O2] -= dmdt; /* change in gas phase species mass [kg/s]*/

Obviously, non-specified variables are defined earlier in the UDF.
However, the macro C_DPMS_CONCENTRATION(c,t) just gives back a value of 0 each time the UDF is called. In Fluent I can access this DPM concentration as well under discrete phase variables//DPM concentration, which gives values larger than 0.
Am I using the macro incorrectly or do I need to add some command to access this data?