Discussion Forum

Hi,

In a rectangle (XY plane) heat is flowing in from one side which contacts an isothermal surface and flowing out from the opposite side under a temparature difference 10[K]. I need to find the total heat gained by the material of the rectangle till the difference in these two heat flow rates is below a given value. I do not want to use the heat capacity values of the material but instead would like to find the heat stored inside it from the difference of heat coming in and going out and integrating this over the time till the difference of these two flow rates is below a certain value. (The entire process actually simulates the working of an instrument which I want to study theoretically using computer simulation). The algorithm for the calculation is perhaps like this:

q=integrate(from t=0 to t=tc): (q_in(t) - q_out(t))dt
where tc is defined as the time when q_in(tc)-q_out(tc)<q_c.
q_c has a value typically about 10% of steady state value of (q_in+q_out)/2

Assuming, for example, the four corners of the rectangle at (0,0;x,0;x,y;0,y) and x=1cm, y=1mm, it is important to note that q_in is average heat flow derived over the top side (0,y;x,y) whereas q_out is average heat flow derived over bottom side (0,0;x,0) of the solid rectangle in 2D geometry and the study has to be transient one and the physics in this case could be the conductive heat transfer.

My questions are:
1. Can Comsol handle the calculations according to the apparently simple algorithm described above?
2. Can a derived value (say, average normal conductive heat flux, measured over one side of the rectangle) be called in another expression along with another derived value (say, average normal conductive heat flux, measured over a different side of the rectangle)? If yes, how?
3. Can Comsol let conditional iterations be done as required by the above algorithm (q_in(tc)-q_out(tc)<q_c)?

Thanks in advance,
KB