Clarification on "adiabatic" vs "isothermal" assumption in Local Restriction (IL) block

In the documentation for the Local Restriction (IL) block under the Isothermal Liquid library, it's stated that:

“The restriction is adiabatic. It does not exchange heat with the environment.”

This seems to contradict the isothermal assumption. Adiabatic conditions imply no heat exchange, which could lead to temperature changes due to internal energy changes. However, isothermal conditions require constant temperature, which would necessitate heat exchange with the surroundings.

My Question:

How can the restriction be modeled as adiabatic while still ensuring that the entire liquid network remains isothermal? Shouldn't there be heat exchange modeled to preserve temperature consistency in light of pressure losses?

I look forward to any better insights for this! Thank you.

Answer 1

[Jakub]

Hi Vibha,

All isothermal liquid block does not implement of any thermal transfer equations. However, same local restriction blocks are reproduced in other libraries:

https://www.mathworks.com/help/releases/R2024b/simscape/ref/localrestrictiontl.html

https://www.mathworks.com/help/releases/R2024b/simscape/ref/localrestrictiong.html

https://www.mathworks.com/help/releases/R2024b/simscape/ref/localrestrictionma.html

To clarify: the block has not implemented any thermal effect. If you want to indicate the thermal effect due to friction losses you may see the following example:

https://www.mathworks.com/help/simscape/ug/hydraulic-fluid-warming-due-to-losses.html

But in case of isothermal liquid, Local Restriction (IL), the phrase "The restriction is adiabatic" may not clearly indicate it.

[Vibha]

Got it. To account for the heat transfer, we need to use dedicated blocks. Thank you for clarifying.