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Time dependent material properties

Posted 12.06.2013, 17:22 GMT-4 Low-Frequency Electromagnetics, Heat Transfer & Phase Change Version 4.3b 3 Replies

Kasper Joergensen
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Hello

I'm trying to make a simplified thermal model of a Li-Ion battery. I'm using the Joule Heating model and a time dependent study.

I want to model the State of Charge with either an integration of the current going in / out of the battery over time - or simply a piecewise function of time (since the current is constant +/- X Ampere).

I've made the piecewise function, but when I try to make the electrical conductivity a function of time it stays constant during my simulation.

Is there anyway to make a material property a function of simulation time?

Greetings
Kasper Jørgensen
3 Replies Last Post 16.06.2013, 15:23 GMT-4
Duarte Albuquerque
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Posted: 1 decade ago 12.06.2013, 20:59 GMT-4
Hi,

Did you put a "t" inside your function when defined the material properties?

for example: sigma(t)

It works with temperature "T".

Kind Regards,

Duarte Albuquerque
Hi, Did you put a "t" inside your function when defined the material properties? for example: sigma(t) It works with temperature "T". Kind Regards, Duarte Albuquerque
Kasper Joergensen
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Posted: 1 decade ago 13.06.2013, 04:23 GMT-4
Hello

Just checked to make sure and I've got a (t) after my function. I'm trying with a piecewise function that is +1 for half of the simulaion and -1 for the other half (Lets call it pw1).

Function name: pw1
Argument: t
Start End Expression
0 1/2*cycle 1
1/2*cycle cycle -1

The expression for the electrical conductivity is

sigma = 14000+pw1(t)*12000

which should make a huge difference in the terminal voltage, but is only causing a minor change.

Greetings
Kasper Jørgensen
Hello Just checked to make sure and I've got a (t) after my function. I'm trying with a piecewise function that is +1 for half of the simulaion and -1 for the other half (Lets call it pw1). Function name: pw1 Argument: t Start End Expression 0 1/2*cycle 1 1/2*cycle cycle -1 The expression for the electrical conductivity is sigma = 14000+pw1(t)*12000 which should make a huge difference in the terminal voltage, but is only causing a minor change. Greetings Kasper Jørgensen
Kasper Joergensen
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Posted: 1 decade ago 16.06.2013, 15:23 GMT-4
Hello

I've got my piecewise function to take the first piece, but it doesn't change to the next piece when the time passes into the next interval. Any idea on how to force COMSOL to do that?

Greetings
Kasper Jørgensen
Hello I've got my piecewise function to take the first piece, but it doesn't change to the next piece when the time passes into the next interval. Any idea on how to force COMSOL to do that? Greetings Kasper Jørgensen

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