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help,why the negative energy source does'nt make the temperature decrease, thank you!

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Old   November 6, 2009, 04:04
Default help,why the negative energy source does'nt make the temperature decrease, thank you!
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patrick
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I am simulating the over-heated liquid evaporation. but the temperature did not decrease. Actually it should because some liquid evaporate into gas and the latent heat is from the liquid. I have done this for over months, but little progress is obtained. who can help me? I would appreciate your help. the model is as below:
liquid saturation temperature:3.7K
liquid initial-state temperature:4.2K
the liquid is in the state of over-heated. It should be evaporate by absorbing the energy of partion of liquid.
the model is vof. udf is as below:
DEFINE_ADJUST(m_dot_adjust, domain)
{cell_t cell;
Thread *mix_th,*pri_th ,*sec_th;
Domain *d;
d=Get_Domain(1);
thread_loop_c(mix_th,d)
{pri_th= THREAD_SUB_THREAD(mix_th, 0);
sec_th= THREAD_SUB_THREAD(mix_th, 1);
begin_c_loop(cell,mix_th)
{

if(C_T(cell, mix_th)>=T_SAT)
{
m_dot_l=0.1*C_VOF(cell,pri_th)*C_R(cell,pri_th)*(( C_T(cell,mix_th)/T_SAT)-1);
C_UDMI(cell,pri_th,3)=m_dot_l;
m_dot_l_m=0.1*C_R(cell,pri_th)*fabs(C_T(cell,mix_t h)-T_SAT)/T_SAT;
C_UDMI(cell,pri_th,4)=m_dot_l_m;
m_dot_l_eng=0.1*C_VOF(cell,pri_th)*C_R(cell,mix_th )/T_SAT;
C_UDMI(cell,pri_th,5)=m_dot_l_eng;
}
else
{
m_dot_v=0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)*(( C_T(cell,mix_th)/T_SAT)-1);
C_UDMI(cell,sec_th,9)=m_dot_v;
m_dot_v_m=0.1*C_R(cell,sec_th)*(-(C_T(cell,mix_th)/T_SAT)+1);
C_UDMI(cell,sec_th,10)=m_dot_v_m;
m_dot_v_eng=-0.1*C_VOF(cell,sec_th)*C_R(cell,sec_th)/T_SAT;
C_UDMI(cell,sec_th,11)=m_dot_v_eng;
}
}end_c_loop(cell,pri_th)
}
}
DEFINE_SOURCE(liq_src, cell, pri_th, dS, eqn)
{
Thread *mix_th,*sec_th;
mix_th = THREAD_SUPER_THREAD(pri_th);
sec_th = THREAD_SUB_THREAD(mix_th, 1);
if(C_T(cell, mix_th)>=T_SAT)
{source0=-C_UDMI(cell,pri_th,3);
dS[eqn]= -C_UDMI(cell,pri_th,4);}
else
{source0=C_UDMI(cell,sec_th,9);
dS[eqn]=0;}
C_UDMI(cell,pri_th,12)=source0;
return (source0);
}

DEFINE_SOURCE(gas_src, cell, sec_th, dS, eqn)
{
Thread *mix_th,*pri_th;
mix_th = THREAD_SUPER_THREAD(sec_th);
pri_th = THREAD_SUB_THREAD(mix_th, 0);
if(C_T(cell, mix_th)>=T_SAT)
{source1=C_UDMI(cell,pri_th,3);
dS[eqn]= 0;}
else
{source1=-C_UDMI(cell,sec_th,9);
dS[eqn]=-C_UDMI(cell,sec_th,10);}
C_UDMI(cell,sec_th,13)=source1;
return (source1);
}

DEFINE_SOURCE(mixture_eng_src, cell, mix_th, dS, eqn)
{ Thread * sec_th,*pri_th;
pri_th= THREAD_SUB_THREAD(mix_th, 0);
sec_th= THREAD_SUB_THREAD(mix_th, 1);
if(C_T(cell, mix_th)>=T_SAT)
{source3=-20800*C_UDMI(cell,pri_th,3);
dS[eqn]= -20800*C_UDMI(cell,pri_th,5);}
else
{source3=20800*C_UDMI(cell,sec_th,9);
dS[eqn]=20800*C_UDMI(cell,sec_th,11);}
C_UDMI(cell,mix_th,14)=source3;
return (source3);}
the evaprated liquid is monitored. the source0 is negative and the source1 is positive. the source3 is negative. therefore, the source3 is added into the energy equation, the temperature should decrease, why it increase? who can help me, it drives me crazy.
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Old   November 6, 2009, 04:07
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patrick
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my email address is bj-luo@hotmail.com, welcome everyone to communicate with me, thank you very much!
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Old   November 6, 2009, 05:04
Default help,why the negative energy source does'nt make the temperature decrease, thank you!
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Shane
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Try to check the value of C_UDMI(cell,sec_th,(3,4,5,9,11) and source1(2,3).

Try to check these two steps.

1) Are they are geeting properly assigned.

2)Also I believe real value are getting truncated.


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Old   November 6, 2009, 11:08
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patrick
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hello sircorp,

thank you for your help. the C_UDMI(cell,sec_th,(3,4,5,9,11) and source1(2,3) are correct. source0=-1.79,sour1=1.79,source3=-1.79*20800;
I have spent lots of time on it. it is very strange. the energy source is negative, but the temperature is increasing. begging for help!!!
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Old   November 8, 2009, 08:25
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maybe the problem is from the enthalpy. I assigned both the gas' and the liquid's standard state enthalpy is 0 with a 4.2K reference. but now I found the enthalpy is -1058514j/kg for liquid and -2147306j/kg for gas at 4.2K. I feel confused "is not it 0"? why? who can give me some words, thank you
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Old   November 8, 2009, 11:54
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is there someone who give me some words about re-defined the enthalpy? h=cp*t? is it possible?
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Old   May 12, 2010, 17:39
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Wei Shao
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Have you solved your problem? I have the same problem
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