With 'Flux' it is equal to: -a * Temp.x(x,t) which may be a function of t AND x With 'Cond. aux limites': Phi_h_S(t)-Phi_h_P(t), which is a function of t, not of x.
If I define:
I can:
Then the solve block becomes:
So you have two different constraints for Phi_d(x,t), but you could also state:
Which leaves Phi_d.x(x,t) undefined, and that might explain why I get an 'undefined variable or function' error message.
If you could set initial conditions for Phi_d(x,t), you might be able to solve for Temp and Phi_d simultaneously.
In order not to confuse and not to waste time in the interpretation of your file, you should provide us with the text and the equations to be used in Mathcad, including the initial and boundary conditions.
I am very interested in all yours responses. Thank you very much for spending time helping me for this problem. The data being confidential, I had simplified the functions, which could have made the subject less comprehensible to you. The thermal exchange and boundary condition functions are described with very severe transients. now I will put in practice your precious advice.
