Hello all,
I am simulating a 3D model of a copper coil carrying a current placed in a vacuum. Due to current flow, there is an inductive heating in the coil. To cool it, I am using a water source. In short, two physics are used in COMSOL simulations: 1) Magnetic field, 2) Heat transfer in solid. I am interested in knowing the final temperature of water at the outlet after X number of hours.
I am facing a little problem while interpreting the results. At first, I am checking the outlet temperature of coil when there is no water flow. Normally, the coil temperature should stabilize after X number of hours. But in my simulations, the temperature of coil is different for different number of hours.
For example, the temperature stabilizes at 30 C in 3 hours for an overall time of 10 hours. But if I repeat the same simulation for 100 hours, the temperature stabilizes at 35 C in 10 hours.
I am not able to locate the problem. Can anyone help me in that?
hallo,
i think it has something to do with the time steps taken by solver. When you increase the range of the time solver more interpolation of the results take place. You could try to limit the maximum time steps in the solver takes.
If this did not help, you could provide me a copy of your model and I will take a look.
Zaid Thank you for the reply. Dont you it has to do something with the properties of the materials such as thermal conductivity, density, heat capacity etc.
As I am trying to generate a vacuum around my coils, therefore I am maintaining the thermal conductivity, heat capacity, density close to zero. And by playing with these parameters, the temperature stabilization varies. COMSOL gives an error if I used exact zero value for above mentioned parameters.
Well, in this case i would use separate the physics node to model the problem. The first physics node is the magnetic field physics with a vacuum domain having a small value of conductivity ("eps" works) and an epsilon of 1. For the heat physics, i would ignore the vacuum domain in the simulation altogether. Losses due to radiation may be ignored if the temperature is low.
Still, your question relate to the time-dependent solution having different steady-state solution at varying range. I remember running with this issue in my simulations too. This thread may clarify the issue:
https://www.comsol.com/forum/thread/39634/problem-while-changing-the-study-steps-of-a-time-dependent-model?last=2013-10-22T23:05:41Z
Therefore, I still suggest that you take a look at your time-dependent solver setting.
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