Fluids

Fluids

Pressure Loading during Paraffin Wax (PCM) Melting

    • Johnkim4865
      Subscriber

      Hello,


      I am trying to simulate regarding paraffin wax melting with pressure application on top small region area to observe how paraffin wax behaves with particular load.



      Above image is about non-pressure paraffin wax with heating boundaries on both sides (left) and 2 psi pressure application on small region of top of paraffin wax with all same conditions as left picture.


      I am just wondering if this simulation is right approach to see the behavior of paraffin wax with loading condition.


       


      Many Thanks,


      Bohyung Kim

    • Rob
      Ansys Employee

      What are you expecting to see with the "pressure application", and what do you mean by it?  Depending on the set up the blue (paraffin) looks reasonable if the walls are heated, but very difficult to judge with limited information. 

    • Johnkim4865
      Subscriber

      The setup I processed for above case are


      : Transient with gravity - Activation of Energy, k-omega SST model with activation of non-Newtonian, and Melting/Solidification


      : In material properties of paraffin wax, I set up bosinnesq for density.


      : Boundary Conditions - Both left and right sides are heat applied by 100 degree Celsius (Convection was neglected)


      : Rest of the other setups are performed as default values and time step size was 0.001 with 45 iteration in total of 30 seconds with convergences. 


       


      So the crux of this simulation was to observe by pressuring on top of paraffin wax compared to non-pressuring application, how much liquid fraction and total temperature is relatively deducted. Not sure about the way I simulated is valid way to observe a melting behavior of phase change material without flow under pressure.


      Thanks for the quick reply rwoolhou!


       

    • Rob
      Ansys Employee

      Unless you have properties that are pressure dependent it'll not make any difference. Everything you've shown is temperature dependent only so changing pressure shouldn't do anything. 

    • Johnkim4865
      Subscriber

       


      I understand what you meant by pressure dependent properties.There was a material property called coefficient of thermal expansion.


      Do you think that property is not involved in pressure change?


      If not, would you be able to suggest some tips or ways to set up pressure dependent properties for the above case?


      Many thanks for your help.

    • Rob
      Ansys Employee

      It depends on the pressure. If the pressure change (not value) is small then you just need to set the properties for that pressure.  Thermal expansion coefficient is used in the Bousinesq approximation: check the maths as it doesn't actually change the material density. 


      In your case you've increased the domain pressure from something to something+2psi   (I assume you're American as everyone else uses SI now....). This may affect the solidus & liquidus temperatures but that's about it: liquids aren't overly compressible. 

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