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Old   February 20, 2020, 14:38
Default Energy Storage Calculation
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Hello,


I am running a transient melting and solidfication simulation on PCM. I would like to calculate and record the total energy stored in the PCM with time. In terms of boundary conditions I have a flux on one side of the "box", and convection on the remaining three sides. Anaytically I know it would be a simple energy balance but I don't know how to translate that into Ansys. Any help would be greatly appreciated.


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Old   February 20, 2020, 15:56
Default PCM as Energy Storage
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Calculation in a CFD tool is similar to analytical energy balance. Since you are using PCM as an energy storage device, that implies it is able to provide energy as long as it is in liquid phase. Once solidified, it needs to be re-energized or recharged. So, the amount of latent heat available in the remaining liquid is the available energy. In Fluent, you can describe it using a custom-field-function or an expression as the volume Integral of the product of density, liquid fraction, and latent heat of fusion. If using CFF, create a CFF as product of three parameters and then setup a volume integral monitor over whole PCM domain using CFF as variable.
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Old   February 20, 2020, 16:58
Default PCM as Energy Storage
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Hi Vinerm,


Thanks for that very good suggestion. It makes sense and puts me in the direction. I assume the same procedure would be used to sensible energy but changing latent heat of fusion with Cp and difference in Temperature from initial temperature?


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Old   February 20, 2020, 18:53
Default Can't plot named expression
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Hello,
I followed your suggestions and made a named expression as seen in the attached picture. However, when I try to create a plot, it doesn't come up as a report definition. What am I missing here?
Thanks in advance.
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Old   February 21, 2020, 04:33
Default Expressions and CFF
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Expressions cannot be plotted directly as contours. However, you can select those as monitors during the run. Better option would be to create a CFF and then create a volume integral of the CFF.

Yes, you can define the heating and cooling part as well using the sensible heat. In that case, as you mentioned, specific heat is to be used and the reference temperature would either be the temperature of the surroundings or the temperature to which storage system need to supply the energy.
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