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-   -   dpm-DEFINE_DPM_LAW (http://www.cfd-online.com/Forums/fluent-udf/92322-dpm-define_dpm_law.html)

tomas September 9, 2011 21:52

dpm-DEFINE_DPM_LAW
 
hi,
I would like to simulate particle heating in the plasma torch,The total
heat flux on the particle surface in the plasma Q is described using the heat transfer attributable to the plasma flow and the radiation loss as
Q=\pi*(dp)^2*h*(T-TP)-\epsilon\sigma((TP)^4-(Ta)^4)
h is the heat transfer coefficient T is plasma temperature ,TP is particle temperature,epsilonis the emissivity,sigma is Stefan–Boltzmann con-
stant,Ta is the ambient temperature.dp is particle diameter
Q can also be written for the particle temperature change and the phase changes such as melting
Q=\pi/6*(\rho*cp*(dp)^3*dTP/dt(tp<Tm,Tm<TP<Tb)................................ .........(1)
cp is specific heat,Tm is melting point ,Tb is boiling point

Q=\pi/6*(\rho*Hm*(dp)^3*dx/dt(tp=Tm)......................................... ....................(2)
Hm is the latent heat,rho is particle mass
Once the particle is completely molten (x = 1), its temperature is allowed to follow again Eq 1
My question is: I'm using UDFs to define the the heat of fusion during the transition,if I use DPM in fluent ,how can i use DEFINE_DPM_LAW Macro
to discribe this Eq ,
Thx

tomas September 12, 2011 07:28

UDF that uses DEFINE_DPM_SWITCH to
switch between DPM laws using a criterion. The UDF switches to DPM_LAW_USER_1 which refers to condenshumidlaw since only one user law has
been defined.if i have two ,Any suggestions of how to tackle this issue?
tomas

tomas September 13, 2011 06:46

nobody help me!!!!!!!!!:mad:

tomas October 5, 2011 11:31

#include "udf.h"
#include "dpm.h"
#include "mem.h"
#define Ta 300
#define Em 0.8
#define Tm 1983
#define sgb 0.0000000567
#define Tb 2500
#define Cpp 800
#define Hm 369000
#define Hv 12480000
DEFINE_DPM_LAW(HeatLaw,p,ci)
{
real area, rel_vel, Re, Pr, HTC, delta_temp,delta_x,delta_p;
float x = 0;
cphase_state_t *c = &(p->cphase);
area = 4.0 * M_PI * pow(P_DIAM(p),2.0);
Pr = c->sHeat * c->mu / c->tCond;/* Prandtl number */
HTC =c->tCond * (2.0 + 0.6*pow(p->Re,0.5)*pow(Pr,1./3.))/ P_DIAM(p);
if (P_T(p) < Tm)
{
delta_temp = P_DT(p) * (area * HTC * (c->temp-P_T(p))-area*Em*sgb*(pow(P_T(p),4.0)-pow(Ta,4.0))) /(P_MASS(p)*Cpp);
P_T(p) = P_T(p) + delta_temp;
}
else if (P_T(p) = Tm && x>O&& 1>x )
{
delta_x=P_DT(p) *6* (area * HTC * (c->temp-P_T(p))-area*Em*sgb*(pow(P_T(p),4.0)-pow(Ta,4.0)))/(P_RHO(p)*Hm);
x=x + delta_x;
}

else if((P_T(p) < Tb )&&(P_T(p) >Tm ))
{
delta_temp = P_DT(p) * (area * HTC * (c->temp-P_T(p))-area*Em*sgb*(pow(P_T(p),4.0)-pow(Ta,4.0))) /(P_MASS(p)*Cpp);
P_T(p) = P_T(p) + delta_temp;
x=1;
}
else
{
P_T(p)=Tb;
delta_p=-P_DT(p) *2* (area * HTC * (c->temp-P_T(p))-area*Em*sgb*(pow(P_T(p),4.0)-pow(Ta,4.0)))/(P_RHO(p)*Hv);

P_DIAM(p)= P_DIAM(p)+delta_p;


}

}

tomas October 5, 2011 11:39

why it showed no change in melting process (Tp=tm )

tomas November 21, 2011 09:11

.................

ghost82 November 21, 2011 09:47

Sorry I can't help you but can you check this?

else if (P_T(p) = Tm && x>O&& 1>x )

tomas November 25, 2011 20:49

hank you very much ghost82. I do apprecaite your concern. All the best,

Tomas

ian.maes August 29, 2013 05:20

DPM in combination with plasma
 
Hej Tomas!

This thread is already more than 2 years old and unfortunately I cannot help you with your problem (if that would still be necessary...), but I am trying to model plasma gasification using the DPM model.

I read that you also combine a plasma flow with the DPM model, so I was hoping you could help me with something.

I have written several UDFs to calculate the high-temperature thermodynamic and transport properties of the plasma flow, but now I find that this results in a conflict with using the DPM model...
As far as I know, it's not possible to use a UDF for density, but only the ideal-gas-law when using combusting paricles.

Did you manage to solve this problem in some way?

Thank you in advance!

Ian


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