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At higher temperature.. cant solve the equaitons

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Hi,

I am applying Joule heating in a time-dependent model, I input a constant current to a terminal and grounded the other. I set the initial value of temperature of 1673K for the whole body. When I am running the simulation, it is showing no progress.
But if I take the initial temperature to be aroung 1273K, , its giving me result.
Why is it showing problem at higher temperatures???

(PS: i set the time of 100sec with a jump of 0.1 second
and input all the properties of the material as a function of temperature---> so is it because at the high temperature some properties showing negative values, which were not supposed to be negative??????????)

Thanks in advance :) :)

2 Replies Last Post 2012年7月4日 GMT-4 08:56
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2012年7月4日 GMT-4 01:42
Hi

check your material properties too, to be shure they are defined for these large T values, the curves might saturated or interpolated strangely

--
Good luck
Ivar
Hi check your material properties too, to be shure they are defined for these large T values, the curves might saturated or interpolated strangely -- Good luck Ivar

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Posted: 1 decade ago 2012年7月4日 GMT-4 08:56
HI Ivar,

Thanks for your reply. I was thinking the same about abnormal behavior of properties at higher temp. and I tried too various combination of time and temperatures, and I find out that for higher value of either time, or temperature or both, but the comsol stuck at 79%.

However results are seen when
1) i use for 75 sec but not for 100 sec.
2) initial temperature below 1273K
3) and with both t and T high. (obviously not)

Could you please help me.... where is the problem? What i gonna do, i cant find anything to work out?
(PS: A Day before it was working, at 1273K and for 100 sec, until I changed one value of resistivity)

Pleaaaaaaaseeeeee help!!!
and thanks in advance!! :) :)

HI Ivar, Thanks for your reply. I was thinking the same about abnormal behavior of properties at higher temp. and I tried too various combination of time and temperatures, and I find out that for higher value of either time, or temperature or both, but the comsol stuck at 79%. However results are seen when 1) i use for 75 sec but not for 100 sec. 2) initial temperature below 1273K 3) and with both t and T high. (obviously not) Could you please help me.... where is the problem? What i gonna do, i cant find anything to work out? (PS: A Day before it was working, at 1273K and for 100 sec, until I changed one value of resistivity) Pleaaaaaaaseeeeee help!!! and thanks in advance!! :) :)

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