UDF of evaporation
 

#include "udf.h" //包括常规宏
#include "sg_mphase.h" // 包括体积分数宏CVOF(C,T)
#define T_SAT 373 //定义蒸发温度100℃
#define LAT_HT 1.e3 //定义蒸发潜热J/Kg
DEFINE_SOURCE(liq_src, cell, pri_th, dS, eqn) //液相质量源项UDF
{
Thread *mix_th, *sec_th; //定义计算区线指针
real m_dot_l; //定义液相质量转移 kg/(m2.s)
mix_th = THREAD_SUPER_THREAD(pri_th); //指向混合区的主相即液相的指针
sec_th = THREAD_SUB_THREAD(mix_th, 1); //指向单相控制区的气相的指针，气相为第二相
if(C_T(cell, mix_th)>=T_SAT) //如果液相单元的温度高于蒸发温度，液相向气
相的质量质量转移
{
m_dot_l = -0.1*C_VOF(cell, pri_th)*C_R(cell, pri_th)* fabs(C_T(cell, mix_th) - T_SAT)/T_SAT;
dS[eqn] = -0.1*C_R(cell, pri_th)*fabs(C_T(cell, mix_th) - T_SAT)/T_SAT; //定义源项对质量转移
偏导
}
else
{
m_dot_l = 0.1*C_VOF(cell, sec_th)*C_R(cell, sec_th)* fabs(T_SAT-C_T(cell,mix_th))/T_SAT; //
如果指向混合区液相的单元温度小于蒸发温度，气相向液相的质量转移，液相得
dS[eqn] = 0.;//由于是气相向液相转移，所以液相的质量源项对质量转移的偏导为零
}
return m_dot_l;
}
what's the meaning of the number0.1 in the equation.Many other code of phase transformation has the similar constant.I wonder the physical significance.I'v been puzzled by the constant for a long time. Looking forward your answer.Thanks!

co ask
 

thanks thanks thanks

I have read that this 0.1 acts is a constant for mass transfer model and also as a relaxation factor for the source term...

In this paper

S.C.K. De Schepper, G.J. Heynderickx, G.B. Marin, Modeling the evaporation of a hydrocarbon feedstock in the convection section of a steam cracker, Computers & Chemical Engineering 33 (2009) 122e132.

you can find the basis of the model (I haven't read it because I don't have acces to it, if you have please share)

I have a question...

Did you only coded the UDF for evaporation??

Can you share the UDF for the energy equation?

Best regards....

can u plz explain the above code? and write it in english? dont understand chinese language.