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September 27, 2011, 10:35 |
UDF for pellets
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#1 |
New Member
Zsolt Vaszi
Join Date: Jul 2010
Posts: 8
Rep Power: 15 |
Hi everyone,
I want to simulate with eulerian multiphase model one gasifier. The gasifier is just a cylinder in whitch I have 3 phases. The first is the air need to gasification, wood pellets and ash. In this case I want to know just I the air is flows around the pellets. But I need an UDF for changeing the pellets to ash in time. I wrote this UDF. If some can please correct it: #include "udf.h" #define OMEGA 7.26E-3 #define K_F0 0.0257 #define K_S0 1.0 #define d_b 0.00683 /* mean diameter of bulk material */ real rho_b = 2250.; /* particle density */ real cp_b = 835.; /* specific heat capacity */ real A_V_sphere = 6.0/d_b; /* area-to-volume ratio of a sphere*/ real A_b_V; /* area-to-volume ratio */ real k_solid(real e_gas) { real k_sol; real a = K_S0/K_F0; real b = 1.25*pow((1.-e_gas)/e_gas, 10./9.); real t1 = (a-1.)/pow((1.-b/a),2.0)*(b/a)*log(a/b); real t2 = -((b-1.)/(1.-b/a))-0.5*(b+1.); real gm = (2./(1.-b/a))*(t1+t2); real k_bs = K_F0*(OMEGA*a + (1.-OMEGA)*gm); k_sol = k_bs/sqrt(1.-e_gas); return (k_sol); } DEFINE_PROPERTY(conduct_gas,cell,thread) { real k_bf, k_gas; k_bf = K_F0*(1.-sqrt(1.-C_VOF(cell,thread))); k_gas = k_bf/C_VOF(cell, thread); return (k_gas); } DEFINE_PROPERTY(conduct_solid,cell,thread) { real vol; /* cell volume */ real vol_m1; /* cell volume time step minus 1 */ real fac; /* factor in time derivative */ real fac_m1; /* factor at time step minus 1 */ real eps_b = 1.0 - C_POR(c,t); /*solid volume fraction*/ /* d(fac*V*phi)/dt = fac*V/dt*phi - fac_m1*V/dt*phi_m1 = apu * phi - su */ vol = C_VOLUME(c,t); vol_m1 = vol; fac = rho_b*cp_b*eps_b; fac_m1 = fac; *apu = -fac*vol / delta_t; *su = fac_m1*vol_m1*C_UDSI_M1(c,t,i)/delta_t; } |
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