Two-Phase Cascade Heat Exchanger

Question

ALis 2023-4-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1946878-two-phase-cascade-heat-exchanger

评论： Yifeng Tang 2023-5-16

I have been having issues in implementing a simple 2P-2P heat exchanger that exchanges heat between 2 refrigerants (R134a and R1234yf for example). My model takes >10 minutes to compile and consistently does not converge. How would I setup and initialize a simple cascade heat exchanger like that?

Error Below

An error occurred while running the simulation and the simulation was terminated

Caused by:

['untitled/Solver Configuration']: At time 1.091055e-08, one or more assertions are triggered. See causes for specific information.

Specific internal energy at port B must be less than or equal to Maximum valid specific internal energy. The assertion comes from:

Block path: untitled/Mass Flow Rate Source (2P)1

Assert location:

o In between line: 111, column: 5 and line: 111, column: 11 in file: C:\Program Files\MATLAB\R2023a\toolbox\physmod\simscape\library\m\+foundation\+two_phase_fluid\+sources\mass_flow_source.ssc

Specific internal energy at port B2 must be less than or equal to Maximum valid specific internal energy. The assertion comes from:

Block path: untitled/System-Level Heat Exchanger (2P-2P)

Assert location:

o (location information is protected)

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Answer 1

Yifeng Tang 2023-4-28

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https://ww2.mathworks.cn/matlabcentral/answers/1946878-two-phase-cascade-heat-exchanger#answer_1225554

Suggestion: check the parameters you've set for the heat exchanger, source, and reservoir blocks. Pay special attention to the cross section areas and mass flow rate. The error message suggests that the ideal mass source needs to raise the presure by a LOT to push through the required amount of liquid. If you try to push too much flow rate through too small pipes, such pressure raise can cause problem such as out of bound of valid max pressure or energy.

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ALis 2023-5-16

That was part of the answer, it also turns out that the long compile time was due to a bug with index reduction. Turning off index reduction solved the long compile time.

Yifeng Tang 2023-5-16

Thanks for the follow-up ALis. You are talking about the index reduction method in the solver configuration block, right? I've noticed the system-level heat exchanger blocks and the system-level refrigeration cycle block have this slow compilation issue, unique to R2023a I've heard. The Dev is aware. Hope it'll get fixed soon.

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