Simscape Thermal Model Error "Thermal Temperature must be greater than absolute zero"

I'm designing a thermal model of a battery cabin. Using Simulink, I found the heat rejection from the battery packs.

I built my model based on the featured examples of thermal systems, Modeling Heat Transfer of a Projector and an article called "Development of a multi-room building thermodynamic model using Simscape library".

For modeling the FRP cabin and battery shell structure, I used a simplified 2R-1C network (2 resistors and 1 capacitor). My model is given below.

And here is my solar radiation subsystem:

I made beginning temperature values of my thermal masses 300 K and used the ode15s as my solver. When I run the model I face with the error:

Error compiling Simscape network for model thermal_model.

Caused by:

• One or more assertions failed at compile time.
• ['thermal_model/Air inside FRP cabin']: Temperature must be greater than absolute zero In foundation.thermal.elements.mass (line 35)

Even when I run the model for 1 second I get this error. It doesn't make sense that with solar radiation and ambient temperature air temperature goes below absolute zero.

What am I doing wrong? Any help would be appreciated.

[Riccardo Monti]

Hi! I have a similar issue, did you manage to solve it?

[Can]

Hi Riccardo,

Sadly I couldn't solve this problem and didn't complete the physical model, I created a mathematical model instead.

[Joel Van Sickel]

Hello Riccardo,

make sure you aren't using a heat flow sensor incorrectly to connect your system to a thermal reference (absolute zero)

Regards,

Joel

[Fionn]

how did you create the mathematical model?

Answer 1

[Joel Van Sickel]

It is highly likely that your heat flow sensor is grounding the Air Inside FRP cabin thermall mass block. heat flow must be measured as a through variable, while temperature is an across variable. This means a temperature sensor can be connected directly to a thermal reference. However, the heat flow sensor should be between the thermal mass and the rest of the thermal network.

I realize this is too late for the original question but the updated comment kicked this back up on the list so I figured I'd answer it.

Regards,

Joel