Source term linearization and its boundary
 

Hi there,
It's been a while since I logged in for the last time,
I'm dealing with a combustion of household refuse,and I just try to couple the temperature of the air injected to burn it and that of the refuse
I've got trouble with linearizing the source term.Here is the equation:
S = A*(pow(Tp,4)-pow(T,4));
A is a constant,Tp is equal to 1273 K (constant)
I've read some book and come out with this way of linearizing this equation:
S = S*+d/dT(S)*x(T*-T);
then we can break it into Sc and Sp (S = Sc+Sp*T)
the problem is that it seems like the values of T are unrealistic!!!
Since we need to underrelax(0.01 recommended for that case) the source term I should create a field;and I dont know if I didnt do well with boundary of the source that's why I came out with bad results
Can somebody give me a hand please?I'm stuck!
Best Regards