SimScape Thermal Variable Convection

Hi,

I am attempting to create a SimScape custom block that is based upon the "Convective Heat Transfer" block available in the base thermal foundation library in SimScape. The problem I am trying to solve requires the parameters to vary, both the heat transfer coefficient and the heat transfer area.

Essentially what I am attempting to do is modify the basic Convective Heat Transfer block such that the Area and Heat Transfer Coefficient are classified as "Inputs" rather than "Parameters" so that I can connect to them.

To begin understanding this, I was able to find a pre-written block which accomplishes what I want partially with the Heat Transfer Coefficient here: File Exchange. Using this block and the documentation for block creation in SimScape, I was able to replicate this block exactly as a learning experience. However I am having issues in utilizing this with the coefficient actually being allowed to vary.

For example, if I create a basic thermal circuit with the base model Convective Heat Transfer and run it the model will work as expected. If I then replace that block with my custom made one and specify the heat transfer coefficient as a constant using the Physical Systems constant, it will produce exactly the same result. However, once I attempt to apply any time-variable signal to the input created on the custom block, I get results that do not make any sense. Rather than producing a temperature history from the initial temperature to the source temperature at steady state, any time varying signal will cause a temperature history that is constant and equal to the source temperature. In my mind, this means for some reason the heat transfer coefficient is being set to zero and therefore zero heat transfer. And the only way this is possible is if the object temperature is equal to the source temperature.

Am I missing something here? Is it not possible to do what I am attempting? I would expect it to be possible based on the Electrical library's implementation of the variable resistor.

Any help is appreciated.

Thanks,

Chris McNamara