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

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Can on 7 Nov 2021
Commented: Joel Van Sickel on 19 May 2022
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:
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.
  3 Comments
Joel Van Sickel
Joel Van Sickel on 19 May 2022
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

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Answers (1)

Joel Van Sickel
Joel Van Sickel on 19 May 2022
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

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