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Setting temperature as a variable

Posted 24 juil. 2014, 04:44 UTC−4 Heat Transfer & Phase Change 11 Replies

York Busche
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Hello everyone, I am currently modelling a HV cable in a steady state analysis. I managed to calculate the losses in the cable but I am having a problem defining the exact parameters of the temperature since the heat losses are temperature dependent.

My question is, if it is possible to set the temperature in an area as a variable if the heat source is dependent on the temperature.

As an example I have heat loss in conductor, insulation and sheath. Each of them are temperature dependent. If I let a certain current through the conductor a certain temperature set in each area of the cable. Is there any way to select those temperatures and set as a variable?

Regards
11 Replies Last Post 11 sept. 2014, 11:20 UTC−4
Kramer
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Posted: 10 years ago 24 juil. 2014, 13:55 UTC−4
Dear Yorke,

Of corse you can.

You have to define the function, in which temperature appears, as an heat source.

Try to set it as:

Thermal conductivity (W/m*K) * Temperature (K) / Area (1/m^2)

Dear Yorke, Of corse you can. You have to define the function, in which temperature appears, as an heat source. Try to set it as: Thermal conductivity (W/m*K) * Temperature (K) / Area (1/m^2)
York Busche
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Posted: 10 years ago 25 juil. 2014, 05:17 UTC−4
Thank you for your answer, but I mean how can I set the temperature as a variable so it is has the temperature is will be having when it is in steady state.
Thank you for your answer, but I mean how can I set the temperature as a variable so it is has the temperature is will be having when it is in steady state.
Pieter Westerik
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Posted: 10 years ago 28 juil. 2014, 08:17 UTC−4
You need two physics nodes: 'heat transfer in solids' and 'electric currents'. For both physics you set all boundaries as appropriate for your problem. To heat transfer in solids you add a node 'heat source'. You make this a general heat source and change Q from 'user defined' to 'total power dissipation density' to make the resistance losses the heat source.
If you click the heat transfer in solids node, at the bottom of the settings of this node there will be a setting 'dependent variables', which should by default say 'Temperature: T'. So 'T' will give you the temperature at every location in your geometry. Now in the electric currents physics, 'current conservation' node you can set the temperature to 'temperature (ht)' instead of 'user defined', and under electrical conductivity you can use 'T' in your expression for the conductivity.

Please tell me if something is not clear in the above explanation.
You need two physics nodes: 'heat transfer in solids' and 'electric currents'. For both physics you set all boundaries as appropriate for your problem. To heat transfer in solids you add a node 'heat source'. You make this a general heat source and change Q from 'user defined' to 'total power dissipation density' to make the resistance losses the heat source. If you click the heat transfer in solids node, at the bottom of the settings of this node there will be a setting 'dependent variables', which should by default say 'Temperature: T'. So 'T' will give you the temperature at every location in your geometry. Now in the electric currents physics, 'current conservation' node you can set the temperature to 'temperature (ht)' instead of 'user defined', and under electrical conductivity you can use 'T' in your expression for the conductivity. Please tell me if something is not clear in the above explanation.
Hei Hadi
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Posted: 10 years ago 11 sept. 2014, 06:20 UTC−4

You need two physics nodes: 'heat transfer in solids' and 'electric currents'. For both physics you set all boundaries as appropriate for your problem. To heat transfer in solids you add a node 'heat source'. You make this a general heat source and change Q from 'user defined' to 'total power dissipation density' to make the resistance losses the heat source.
If you click the heat transfer in solids node, at the bottom of the settings of this node there will be a setting 'dependent variables', which should by default say 'Temperature: T'. So 'T' will give you the temperature at every location in your geometry. Now in the electric currents physics, 'current conservation' node you can set the temperature to 'temperature (ht)' instead of 'user defined', and under electrical conductivity you can use 'T' in your expression for the conductivity.

Please tell me if something is not clear in the above explanation.


Dear Pieter,

Thanks for your nice explanation. I would like to simulate the temperature effects on a magnetic sensor. I have done your top instructions! but i have problem in the last sentence, where you say: "under electrical conductivity you can use 'T' in your expression for the conductivity."
I couldn't find this electrical conductivity! Just there is electrical conductivity in "conduction current" tab, so i dont know i have to put on user defined or other options?

I appreciate if you could help me?
Thanks
[QUOTE] You need two physics nodes: 'heat transfer in solids' and 'electric currents'. For both physics you set all boundaries as appropriate for your problem. To heat transfer in solids you add a node 'heat source'. You make this a general heat source and change Q from 'user defined' to 'total power dissipation density' to make the resistance losses the heat source. If you click the heat transfer in solids node, at the bottom of the settings of this node there will be a setting 'dependent variables', which should by default say 'Temperature: T'. So 'T' will give you the temperature at every location in your geometry. Now in the electric currents physics, 'current conservation' node you can set the temperature to 'temperature (ht)' instead of 'user defined', and under electrical conductivity you can use 'T' in your expression for the conductivity. Please tell me if something is not clear in the above explanation. [/QUOTE] Dear Pieter, Thanks for your nice explanation. I would like to simulate the temperature effects on a magnetic sensor. I have done your top instructions! but i have problem in the last sentence, where you say: "under electrical conductivity you can use 'T' in your expression for the conductivity." I couldn't find this electrical conductivity! Just there is electrical conductivity in "conduction current" tab, so i dont know i have to put on user defined or other options? I appreciate if you could help me? Thanks
Pieter Westerik
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Posted: 10 years ago 11 sept. 2014, 06:58 UTC−4
Are you using 'electric currents' physics?
Are you using 'electric currents' physics?
Hei Hadi
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Posted: 10 years ago 11 sept. 2014, 07:31 UTC−4
Yes, i am using electrical currents physics to simulate effects of magnetic field on Hall sensor.
I wanted to see what is the effects of temperature changes on my simulation!
Yes, i am using electrical currents physics to simulate effects of magnetic field on Hall sensor. I wanted to see what is the effects of temperature changes on my simulation!
Pieter Westerik
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Posted: 10 years ago 11 sept. 2014, 10:39 UTC−4
If you put user defined you can put your own expression dependent on T. If you choose 'from material' then the conductivity as defined in the material will be used, but I am not sure if the temperature dependence is defined for your material, I think if it has the 'linearized resistivity' parameters defined it should also work.
If you put user defined you can put your own expression dependent on T. If you choose 'from material' then the conductivity as defined in the material will be used, but I am not sure if the temperature dependence is defined for your material, I think if it has the 'linearized resistivity' parameters defined it should also work.
Hei Hadi
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Posted: 10 years ago 11 sept. 2014, 10:54 UTC−4
Dear Pieter,

Thank you for your kind help. My big problem is when i use Silicon as material for my sensor, i don't have "Temperature" tap in "current conservation" in "Electric Currents" physics!!! So i can't put any value for Silicon temperature.

do you have any suggestion for changing the Silicon temperature?
Dear Pieter, Thank you for your kind help. My big problem is when i use Silicon as material for my sensor, i don't have "Temperature" tap in "current conservation" in "Electric Currents" physics!!! So i can't put any value for Silicon temperature. do you have any suggestion for changing the Silicon temperature?
Pieter Westerik
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Posted: 10 years ago 11 sept. 2014, 11:14 UTC−4
Not 'temperature' tab, you need the 'model inputs' tab, which has settings for the temperature.
Not 'temperature' tab, you need the 'model inputs' tab, which has settings for the temperature.
Hei Hadi
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Posted: 10 years ago 11 sept. 2014, 11:18 UTC−4
I have "Model Input" tab! But there is no setting for temperature when i use Silicon as material !!!!
I have "Model Input" tab! But there is no setting for temperature when i use Silicon as material !!!!
Pieter Westerik
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Posted: 10 years ago 11 sept. 2014, 11:20 UTC−4
Can you maybe upload your model?
Can you maybe upload your model?

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