General Mechanical

General Mechanical

Negative temperature

    • momidor
      Subscriber

      Good morning, 


      I did a transient thermal simple case. Having input:



      • +22 C ambient,

      • +150 C, +60 and +10 C at three parts of steel

      • 3 W/mm3 of heat flow at small part of steel 

      • radiation

      • convection


      I received silly, - 4094 C, negative temperature output as hereunder. Why ?


      Thanks in advance for tips. 


       





       

    • peteroznewman
      Subscriber

      I moved this to the Thermodynamics Category.


      Is this a multistep solution?


      Is there a step change in the loads on the model at the time when the negative spike occurs?

    • dinhan0394
      Subscriber

      can you show the mesh (mesh model and mesh quality) and boundary conditions (values as constant or variable by time)?

    • momidor
      Subscriber

      Hi, 


      The source is a pick of heat is "Internal heat generation" 3 W/mm3 which is changing from one steel item to another one by one.



    • dinhan0394
      Subscriber

      Where does your model have a negative temperature?


      Try increasing the mesh quality in the model (transitions between heat sources and surrounding bodies), using linear elements (element order = linear).

    • peteroznewman
      Subscriber

      Use smaller elements in a region around the problem area.

    • momidor
      Subscriber

      Hello, 


      Thanks for help.


      I had a wrong thermal data of the steel. Also I changed to Study-State Thermal and now is ok. 


      All the best 


      Momidor

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