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the electric potential dependent on temperature

Posted Mar 1, 2013, 5:40 p.m. EST Low-Frequency Electromagnetics Version 4.0, Version 4.2 4 Replies

Basant Badwy
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hello,
please help me

i am trying to make a model of an electrode in a cylinder of biological tissue, i want to make the electric potential on the electrode dependent on the temperature of the tissue, where if the temperature of the tissue become 90 deg C for example the electric potential on the electrode become zero.

i don't know how can i make that.

basant
4 Replies Last Post Jul 1, 2015, 9:20 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 2, 2013, 3:09 a.m. EST
Hi

how do you define your volatge V ? by a constant value 90[V] it remains like that, but you could write V0+DV*(T0-T) and define V,DV,DT as parameters this would give yyour V value a slop of DV[V/K] from V0 for values above T=T0

--
Good luck
Ivar
Hi how do you define your volatge V ? by a constant value 90[V] it remains like that, but you could write V0+DV*(T0-T) and define V,DV,DT as parameters this would give yyour V value a slop of DV[V/K] from V0 for values above T=T0 -- Good luck Ivar
Basant Badwy
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Posted: 1 decade ago Mar 18, 2013, 3:22 p.m. EDT
hi Ivar,
thanks for your response

i want to make the electric potential dependent on temperature, To control the temperature so it does not exceed 90 degC, where

V=V0 if T<90 degC

and V=0 if T>90 degC

and i set the temperature initial value to 37 degC

i tried to set the electric potential to V0*(310<T<363), but that doesn't control the temperature and it reached to 240 degC, i don't know what is the right expression for electric potential to achieve this condition .

thanks
basant
hi Ivar, thanks for your response i want to make the electric potential dependent on temperature, To control the temperature so it does not exceed 90 degC, where V=V0 if T90 degC and i set the temperature initial value to 37 degC i tried to set the electric potential to V0*(310
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 18, 2013, 3:58 p.m. EDT
Hi

there used to be a model library example on temperature control, as your case with "if" statements is rather what one calls a "bang-bang" controller and is known for it's instabilities and overshoots. If you define your temperature measure as the average over a small or larger domain, and then use the T-Tref as driver for a global dependent variable Vinput it should work in stationary mode. OIn time mode you need to set some definition or limits on the derivative of V, try to use "smooth ramp or step functions, rather than "if"'s

--
Good luck
Ivar
Hi there used to be a model library example on temperature control, as your case with "if" statements is rather what one calls a "bang-bang" controller and is known for it's instabilities and overshoots. If you define your temperature measure as the average over a small or larger domain, and then use the T-Tref as driver for a global dependent variable Vinput it should work in stationary mode. OIn time mode you need to set some definition or limits on the derivative of V, try to use "smooth ramp or step functions, rather than "if"'s -- Good luck Ivar
Cleber Pinheiro
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Posted: 9 years ago Jul 1, 2015, 9:20 a.m. EDT
Dear colleague,
I desire to implement a temperature control in my 3D MODEL. It consists the physics coupling between heat transfer and electric currents. The electric potential V is controlled such as the maximum temperature is below 100ºC. I tried to use the maxop1 operator with the sintax 14*(maxop1(T2)<100[degC]), where 14 is electrical potencial (14V) and T2 is temperature variable, but it not is working: the temperature grows without control. I use the time-dependent solver relative tolerance equal to 1e-4 (to properly resolve the switching conditions).
I'm using COMSOL MULTIPHYSICS 4.0
I await help.
Best regards

Cleber da Silva Pinheiro
Dear colleague, I desire to implement a temperature control in my 3D MODEL. It consists the physics coupling between heat transfer and electric currents. The electric potential V is controlled such as the maximum temperature is below 100ºC. I tried to use the maxop1 operator with the sintax 14*(maxop1(T2)

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