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UDF unit and FLUENT output

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Old   September 14, 2010, 22:52
Default UDF unit and FLUENT output
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ALAM
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Hello,
I am using UDF for particle reaction rate. But the difficulty is the consistence of unit. In my UDF(given below) equation the unit is per second. But the FLUENT gives the unit kgmol/m2-s after convergence. Could you please tell how can I get the same unit in FLUENT solution. Is it possile to plot rate of reaction versus time?

/* UDF of specifying the surface reaction rate of a particle */
#include "udf.h"
#define A3 1.36e6
#define E3 1.38e8
#define n3 0.68
#define shi 2.0

DEFINE_PR_RATE(user_pr_rate,c,t,r,mw,pp,p,sf,dif_i ,cat_i,rr)
{
real ash_mass = P_INIT_MASS(p)*(1.-DPM_CHAR_FRACTION(p)-DPM_VOLATILE_FRACTION(p));
real one_minus_conv = MAX(0.,(P_MASS(p) -ash_mass) / P_INIT_MASS(p)/ DPM_CHAR_FRACTION(p));
if (!strcmp(r->name, "reaction-3"))
{
real kp3 = A3*exp(-E3/UNIVERSAL_GAS_CONSTANT/P_T(p));
real kd3 = 2.303*log(one_minus_conv);
real ke3 = sqrt(1-shi*kd3);
*rr=-kp3*one_minus_conv*ke3;
}
}


With thanks,
Alam

Last edited by saifulraju; September 22, 2010 at 06:58.
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Old   September 15, 2010, 02:31
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Byron Smith R J
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hai
The rate of surface reaction should be fed in kmol/m2 s only. whatever you give through ur udf will be computed and expressed by fluent in its unit only. so convert the unit kg/s into kmol/m2 s in hte udf and try the solution
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Old   September 15, 2010, 11:52
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Hi,
Thank you. But if the rate of reaction has the unit (per second), it is not possible to convert in kgmol/m2-s.
So what will I do in this case?
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Old   September 16, 2010, 00:35
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Byron Smith R J
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hai
you can manupulate the unit 1/s by multiplying the rate obtained by density, divide by surface area per unit volume and molecular weight (1/s x kg/m3 xm3/m2 x kmol/kg = kmol/m2 s. hope this helps
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Old   September 21, 2010, 22:22
Default time vs rate of reaction
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Dear Byron Smith R J,
Thanks. I got the point.
Could you please tell me how can I get the numerical data for plotting time versus rate of reaction.
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