Phase Phase Change Material as cold thermal energy storage / Zone Phase Change Material Melting Output Variable / Freezing Enthalpy

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They were listed in the variables list (See figure above).

I know. Again, there is no such Output:Variable in Input/Output Reference although they may be selected from a drop-down list in your idf file.

And I don't even know what you expect to see from Zone Phase Change Material Melting/Freezing Enthalpy. One Output:Variable outputs only one value, but the profile of your PCM does not have clear single phase change point.

I tested the addition of PCM on the inner walls for cold thermal energy storage. Previous research showed that PCM reduces temperature fluctuations and energy consumption. However, my simulation results contradicted the published papers, showing increased fluctuations with PCM. To identify the issue, I examined the inner surface temperature and discovered it never reached the PCM temperature. Upon checking the PCM enthalpy to see if phase change accures, I found it remained at 0, indicating no phase change occurred. The PCM used had a phase change range of -18°C to -16°C (Rubitherm SP-17).

In order to examine the state inside the PCM, you should output Output:Variables such as CondFD Surface Temperature Node <x>, CondFD Surface Heat Flux Node <x> and CondFD Surface Heat Capacitance Outer Half Node <x> rather than Zone Phase Change Material Melting/Freezing Enthalpy.

Thank you very much for your comment.

I have other questions.

• Is this the good approach to model a CTES system?

• How do I set a setpoint for the refregiration system to start cooling when the internal temperature is -18°C and stop when the internal temperature reaches -22°C?

Thank you.