[CFDJonas]

Hello everyone,

I finally managed to get my reaction system going with the DEFINE_CHEM_STEP macro (see below). Although the mass fractions of the species are correct, I no longer see a generation of heat. The temperature profile of a converged simulation states a constant temperature of e.g. 500 K. Although my mixture has indeed different enthalpys set for the species (which are produced/consumed). Where/How do I handle reaction enthalpies when dealing with DEFINE_CHEM_STEP?

I'm using Fluent 19.2 with some other custom udf (viscosity, heat capacity, thermal conductivity and density of the mixture, although these are throughly tested).

DEFINE_CHEM_STEP(chem_steps, c, t, p, num_p, n_spe, dt, pres, temp, yk)
{
	real ck[N_COMP];
	real rates[N_COMP];
	real pres_bar = *pres / 1e5; // bar
	real rho = C_R(c, t);

	// Get concentrations from mass fractions
	for (i = 0; i < N_COMP; i++)
	{
		ck[i] = rho * yk[i] / M_i[i];
	}
	
	// Calculate the rates
	rates[i_example_species] = -k_exp * ck[i_example_species];
        // etc.

	for (i = 0; i < N_COMP; i++)
	{
		ck[i] += rates[i] * *dt;
		yk[i] = ck[i] * M_i[i] / rho;
		// Message("\n Specie %d = %f \t TimeStep = %e", i, yk[i], *dt);
	}
}

Thanks in advance!

[chengdi]

Did you enabled the energy equation?

[study_CFD]

I also encountered the same problem. Have you solved it？