What if I did not define convection

Jerome Teoh

Hi. 

What if I do not define the convection surface of my object adjacent with the air.

Is it gonna be a isolate region, mean that there will not be heat transfer relationship in between.

Or it will auto assume heat conduction?

 

Thanks.

Jerome.

 

Alexandru-Ionel Constantin

Jerome Teoh said:

Thanks Alexandru,

 

This is helpful.

I have a couple follow-up questions.

• What if the adjacent region is air? I'm wondering as to how Flux defines air. Will it be treated as conduction to the air if I didn't assume convection? Please bear with me (this is a silly question).

• For Steady State AC Magnetic coupled with Transient Thermal 3D application, if I have regions that is made of ceramics, rubber. What can I define for the magetic property? Should I just assume relative permeability with value of 1, then checking the magnetic definition as 'magnetic non conducting region (or dielectric)' in the volume region, or I should not need to define magnetic property, and putting inactive region?

Thanks,

Jerome.

Hi Jerome,

 

If the adjacent region is the air, you can have two options:

 - to impose a fixed value of air temperature;

 - to specify the value of the h - convection coefficient(in W/(m^2*K) and the air temperature at an infinite distance from the object.

 

For Steady State AC Magnetic coupled with Transient Thermal 3D application, if you have volume regions that are made of ceramics, rubber(insulators), you can define them as air or vacuum regions in the magnetic definition, because the lines of the magnetic field will close through them, so you need them to be active regions. If you have surface regions you can define them as inactive in the magnetic definition.

 

You can see the Altair Flux™ 3D >Open example>Tehnical tutorials> Magneto Thermal Application - Bridle > Induction heating at high frequency.

 

Best regards,

Alexandru

Alexandru-Ionel Constantin

Hi jerome,

 

If you do not define the convection/radiation surface for your object adjacent to the air, it will be an isolated region(Adiabatic region).

 

Heat conduction will be assumed between adjacent regions with a defined values for thermal conductivity, for steady-state thermal study and for a transient thermal study you will also need the values for the volumetric heat capacity.

 

Best regards,

Alexandru

Jerome Teoh

Thanks Alexandru,

 

This is helpful.

I have a couple follow-up questions.

• What if the adjacent region is air? I'm wondering as to how Flux defines air. Will it be treated as conduction to the air if I didn't assume convection? Please bear with me (this is a silly question).

• For Steady State AC Magnetic coupled with Transient Thermal 3D application, if I have regions that is made of ceramics, rubber. What can I define for the magetic property? Should I just assume relative permeability with value of 1, then checking the magnetic definition as 'magnetic non conducting region (or dielectric)' in the volume region, or I should not need to define magnetic property, and putting inactive region?

Thanks,

Jerome.

Alexandru-Ionel Constantin

Jerome Teoh said:

Thanks Alexandru,

 

This is helpful.

I have a couple follow-up questions.

• What if the adjacent region is air? I'm wondering as to how Flux defines air. Will it be treated as conduction to the air if I didn't assume convection? Please bear with me (this is a silly question).

• For Steady State AC Magnetic coupled with Transient Thermal 3D application, if I have regions that is made of ceramics, rubber. What can I define for the magetic property? Should I just assume relative permeability with value of 1, then checking the magnetic definition as 'magnetic non conducting region (or dielectric)' in the volume region, or I should not need to define magnetic property, and putting inactive region?

Thanks,

Jerome.

Hi Jerome,

 

If the adjacent region is the air, you can have two options:

 - to impose a fixed value of air temperature;

 - to specify the value of the h - convection coefficient(in W/(m^2*K) and the air temperature at an infinite distance from the object.

 

For Steady State AC Magnetic coupled with Transient Thermal 3D application, if you have volume regions that are made of ceramics, rubber(insulators), you can define them as air or vacuum regions in the magnetic definition, because the lines of the magnetic field will close through them, so you need them to be active regions. If you have surface regions you can define them as inactive in the magnetic definition.

 

You can see the Altair Flux™ 3D >Open example>Tehnical tutorials> Magneto Thermal Application - Bridle > Induction heating at high frequency.

 

Best regards,

Alexandru

Jerome Teoh

Thanks!

Jerome Teoh

However, I go ahead in doing to define air or vacuum regions.

I got some error like this.

Best,

Jerome.

Alexandru-Ionel Constantin

Jerome Teoh said:

However, I go ahead in doing to define air or vacuum regions.

I got some error like this.

Best,

Jerome.

Hi Jerome,

 

In your case, you need to define it as solid conductor region, in the magnetic definition. For the material you need to define the magnetic property(B(H)), chose linear isotropic and set the value of relative permeability to 1, then define the electrical property(J(E)), chose isotropic resistivity and set the value of the material resistivity, in addition to the thermal properties, thermal conductivity and volumetric heat capacity.

 

Best regards,

Alexandru