Hello there.
I am a newbie who recently started simulating membrane reactors for CO2 methanation(CO2 + 4H2 → CH4 + 2H2O) in Fluent.
I would like to apply the chemical reaction rate to a 3D porous media surface. Below is the actual code I wrote by looking and copying from the UDF guide and the information I found online. This reaction rate equation requires using partial pressures of chemical species, but how to express partial pressures is unclear to me.<\/p>\n
#include “udf.h”<\/p>\n
#define R 8.314 \/* Gas constant *\/
#define E_a 56000 \/* Activation Energy of each constant *\/
#define E_eq 158.7
#define E_OH 89000
#define k_a0 21.7 \/* Pre-exponential of each constant *\/
#define k_OH0 6.8e+7
#define k_eq0 137 <\/p>\n
DEFINE_SR_RATE(methanation,f,t,r,mw,yi,rr)
{
Thread *t0 = THREAD_T0(t);<\/p>\n
cell_t c0 = F_C0(f,t);<\/p>\n
real y_h2o = yi[0];
real y_ch4 = yi[1]; \/* Species numbers that match order in ANSYS FLUENT dialog box *\/
real y_h2 = yi[2];
real y_co2 = yi[3];<\/p>\n
y_h2o *= 1\/mw[0];
y_ch4 *= 1\/mw[1];
y_h2 *= 1\/mw[2];
y_co2 *= 1\/mw[3];<\/p>\n
real Nsum = y_h2o + y_ch4 + y_h2 + y_co2 ;<\/p>\n
y_h2o *= 1\/Nsum;
y_ch4 *= 1\/Nsum;
y_h2 *= 1\/Nsum;
y_co2 *= 1\/Nsum;<\/p>\n
real T_w = F_T(f,t);<\/p>\n
real K_a = k_a0*exp(-E_a\/(R*T_w));
real K_OH = k_OH0*exp(-E_OH\/(R*T_w));
real K_eq = k_eq0*pow(R*T_w, -3.998)*exp(E_eq\/(R*T_w));<\/p>\n
real TP = C_P(c0,t0); \/*Mabe this is one of the causes. I want partial pressures of species *\/<\/p>\n
if (FLUID_THREAD_P(t) && THREAD_VAR(t).fluid.porous)<\/p>\n
*rr = (K_a* pow(TP*y_h2, 0.49) * pow(TP*y_co2, 0.42) \/ (1 + K_OH * TP*y_h2o * pow(TP*y_h2, -0.5))) * (1 – (TP*ch4 * pow(TP*y_h2o, 2) \/ (pow(TP*y_h2, 4) * TP*y_co2 * K_eq)));<\/p>\n
}<\/p>\n
It compiles successfully, but when I start the calculation after initialization, it crashes immediately after displaying the following error. <\/p>\n
===============================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= RANK 0 PID 2500 RUNNING AT desktop-
= EXIT STATUS: -1 (ffffffff)
===============================================<\/p>\n
===============================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= RANK 2 PID 1764 RUNNING AT desktop
= EXIT STATUS: -1 (ffffffff)
===============================================<\/p>\n
===============================================
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= RANK 3 PID 11488 RUNNING AT desktop
= EXIT STATUS: -1 (ffffffff)
===============================================<\/p>\n
I believe it is caused by the UDF, as this error disappears when I unhook the UDF. Can someone please help me? Thank you.<\/p>\n","protected":false},"template":"","class_list":["post-290957","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t