Modeling cold energy storage with phase change materials

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  • Last Post 02 June 2020
DanielMarques posted this 02 June 2020

Hi

I am simulating the use of a phase change material with low temperature melting point. The idea is to place a slab of pcm around a pipe of an heat exchanger so i did a 2D model with a circle inside a rectangular shape of PCM.

For the PCM i used piecewise-linear properties at density, thermal conductivity and specific heat. For the liquidus and solidus temperature i inserted a 0.5 tolerance from the real point. For example 251.5 and 252.5 Kelvin for a melting point of -21 degrees.

On boundary conditions I used adiabatic walls at top and bottom of the rectangle. At the outside wall I placed temperature fixed at 298K since the material is polyurethane and I added a thickness of 0.09m. At the inside wall of the rectangle I used convection BC with 255 Kelvin, an h value of 5 and a very small thickness of aluminium. The pipe of the heat exchanger BC was coupled.

When simulating for a time step of 1s I have sometimes the problem of floating point exception. And the simulation is already taking a lot of time.
I also tried adaptative time step using 0.01 of tolerance with fmin=0.9 and fmax=1.5 but the simulation is taking too long...always using time-steps around 10-3. I will need months for a single simulation without beeing certain if the floating pointe exception error will happen again or not.

I tried to use a refined enough mesh and the levels of skewness on the metrics are good i guess since the max value is 0.6 and the average is very low.

Many times this model is reaching a situation of floating point exception. Can anybody help?

abenhadj posted this 02 June 2020

I ran this kind of cases meltingpf ice block due to convective external air flow with NITA do might be worth testing it

Best regards, Amine

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