Enthalpy vs temperature curve

kr660170 · January 28, 2019, 11:01

Dear All,

I am working on the Simulation of Paraffin wax (Phase Change material). Can someone explain me how to create enthalpy vs temperature curve in Ansys Fluent? I am looking forward for your reply. Thanks in advance.

Kind Regards,
Karthikkumar

AlexanderZ · January 28, 2019, 22:29

https://www.grc.nasa.gov/www/k-12/ai.../enthalpy.html

H2 - H1 = Cp(T2- T1)

best regards

DanielMarques · June 2, 2020, 07:42

Hi,

I am not sure but maybe you will need to see something about UDFs.

Have you solved it?

Could you also help me with someting?

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. Could you help?

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January 28, 2019, 22:29		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	https://www.grc.nasa.gov/www/k-12/ai.../enthalpy.html H2 - H1 = Cp(T2- T1) best regards

June 2, 2020, 07:42		#3
DanielMarques New Member Daniel Marques Join Date: Jul 2019 Posts: 9 Rep Power: 7	Hi, I am not sure but maybe you will need to see something about UDFs. Have you solved it? Could you also help me with someting? 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. Could you help?