Feeding experimental data (temperature) in to Ansys to get conductivity

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Last Post 12 February 2018

mami826 posted this 11 January 2018

Hi All,

my aim is to find the thermal conductivity of litz wire and also convection coefficient of litz wire and air.

So, I am running experimental analysis (10A current into litz wire) and capturing the temperature of litz wire. So, I have temperature profile versus time for litz wire. Would you please help me how I can feed the results (temperature profile) into ansys maxwell (reverse engineering) to define unknown thermal conductivity or in thermal analysis convection coefficient?

Is it possible?

Thanks Regards

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peteroznewman posted this 09 February 2018 - Last edited 09 February 2018

This is possible. ANSYS has a Design Exploration toolbox that makes the process of searching for a thermal conductivity or convection coefficient to match experimental data easier.

While the electromagnetic field the wire generates may be its primary function, you are asking about a thermal problem, so this model may be built in a Transient Thermal or a Steady State Thermal model instead of Maxwell. A Fluent model may be appropriate to help calculate the convection coefficient.

If you want to get started on this, please reply with more details on the experimental setup for measuring the temperature profile of the wire.

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mami826 posted this 12 February 2018

Thank you so much peteroznewman,

I would say I run the experimental test to measure the coil temperature using the thermal camera (please have a look at the pics-attached file). So, I have a temperature versus time profile from experimentation.

Moreover, I modeled coil in Maxwell and apply 20 A and create coupling with transient.

But in transient, i have to apply convention coefficient as a temperature function.

As I said in my previous post, I would like to define convection film in transient based on experimental results.

Thank you so much again.

Regards

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peteroznewman posted this 12 February 2018 - Last edited 14 February 2018

Please tell me more about the wire material and the coil as a whole.

What is the total length of wire in the coil?

What is the diameter of the wire?

How many turns are in the coil?

Are all the coils planar (in one layer) or are the coils in multiple layers, and if so, how many?

What is the total resistance of the coil in Ohms?

How does the resistance change when the temperature goes up?

What is the voltage across the coil?

Is the circuit constant voltage or constant current?

Transient Thermal Optimization Example Model

I created a very simple model that you can play with to learn some of the capabilities of ANSYS Design Optimization. It is just a circular wire with a parameter for the diameter, the wire body has an internal heat generation parameter and a heat transfer film coefficient parameter. It solves in 4 seconds and I can plot the time history of the surface temperature.

When you add parameters to an ANSYS model, you get a Parameter Set block in the Project Schematic.

That lets you easily type in values and solve that model in a table format. Below are 16 trials where I just typed in the values I was interested in and clicked Update.

You provided some experimentally measured values.

If I take the temperature at 150 s = 46 C, 300 s = 54 C and 600 s = 62 C as target values, I can try to adjust the available parameters to match those targets.

An observation was that the Internal Heat Generation was a good parameter to adjust to get T600 to hit a target value of 62 C. I can do that by trial and error (or manually apply a bisection algorithm), or I can add a Direct Optimization block to the system.

Then I can tell ANSYS to search for the value of Internal Heat Generation that satisfies the objective that T600 = 62 C and it automatically searches, solving the problem 16 times to arrive at the value.

While that value satisfies T=600 target of 62 C, the T=150 value is 45.2 C so does not satisfy the target of 42 C, and that is where a two parameter optimization can be employed to vary the diameter and the internal heat to satisfy two objectives.

With two objectives, it has brought the T150 temperature on target, though the T600 has drifted off somewhat.

I hope these examples give you a taste for what is possible. There are many other tools in the Design Exploration toolbox, so I hope you try these out on your project.