How can one determine the total mass or volume of fluid in a Simscape Thermal Liquid model?

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Joe Sullivan 2018-9-13

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回答： Luke Halberstadt 2024-6-24

The model consists of three loops thermally associated by heat exchangers. One primary loop cools two secondary loops. I want to know total coolant mass to evaluate the model against expected characteristic behavior. For example, how long should it take for a thermal transient to travel each loop path?

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K_Anthony 2023-7-10

Any updates? I am working on a system where I need to specify the total volume of a refrigerant...

Yifeng Tang 2023-8-15

@K_Anthony the heat exchanger blocks for the two-phase domain (2P) typically log the "mass" variable in simlog. You can view that in the Simscape Result Explorer.

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Answer 1

Luke Halberstadt 2024-6-24

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The mass of liquid in a Simscape network may not closely match the mass of liquid in the real system even when the Simscape network behavior is very close to that of the real system, so be cautious if you try to calculate or set the fluid mass within the Simscape network.

Why is this? Some Simscape blocks have an internal volume and others do not. For example, the Flow Resistance (TL) and the Centrifugal Pump (TL) do not have internal volumes. Asking Simscape for the total fluid mass in the system would be likely to undershoot unless you added pipes/chambers to match the real system geometry. And these extra blocks might have undesireable effects on the overall system simulation goals.

For more information about fluid blocks internal volumes, see Modeling Isothermal Liquid Systems. The concepts here also apply to the Thermal Liquid domain.

If you really need to calculate or set the mass of liquid in your system, I would personally recommend using a MATLAB live script. The script could calculate system initial conditions based on the desired fluid mass or calculate fluid mass based on logged internal node variables as hinted at by Yifeng earlier. In the script, you could precisely control the fluid mass accounting and also include additional geometric information from data sheets or CAD models.