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Air inside closed domain the pressure does not raise respecting to the temperature

    • Muhamad Eldebawy
      Subscriber
      Hello,nI am wondering when I add heat to air inside a closed tank the pressure did not raisenI put the air density constant 1.225 and I need the pressure to rise respecting to the temperature nThanks n
    • Rob
      Ansys Employee
      If the density is constant how would the pressure increase? n
    • Muhamad Eldebawy
      Subscriber
      Hi Rob,nthanks for your answer.nI mean in real life if I heated air inside a closed tank the pressure will increase and the total density of air should be constant. So how can I get the same behaviour by simulation ?nEven if I used incompressible ideal gas I can not get increase in pressure.nthanks a lot n
    • Rob
      Ansys Employee
      Pressure should rise as the gas expands, however as it's sealed you need ideal gas as the total mass is constant. With incompressible the gas expands but density can't alter through pressure so the solver may throw away excess volume. n
    • Muhamad Eldebawy
      Subscriber
      using the ideal gas does not give me a raise in pressure. it satisfies the equation of state (ideal gas law) but the density changed respect to temperature. if I heated air inside tank to 400k the pressure inside should raise to 1.4 bar. What I got when I put the air as ideal gas and the boundary condition at constant temperature 400k. the density changes and I can not get the real life behaviour. Can you tell me please who can I make the density constant and get only increase in pressure respecting to temperature ?nthanks a lot n
    • DrAmine
      Ansys Employee
      Real life behavior is what Rob said. Ideal Gas plus buyoancy effects. Moreover think about using transient solver to track pressure build-up n
    • Muhamad Eldebawy
      Subscriber
      Hi DrAminenThank you for your reply.nI did a very simple simulation just a cube all sides are walls type and isolated except one side has a constant temperature 400k.nmaterial of cube is air (ideal gas)nsimulation is pressure-based and transient nthe results were as follow:ndensity decreasedntemperature increased until reached to 400 knthe pressure is calculated from ideal gas lawnI am just wondering if this behaviour is a real life behaviour if I heated air sealed in a tank to 400k ?nwhy the density decreased and it should be constant no mass in or out ?!nthanks a lotn
    • Rob
      Ansys Employee
      What conditions did you initialise at? That determines the mass of gas in the domain (ideal gas determines density & domain gives the volume) and is then heated up. If you used hybrid (default) I have no idea what the solver did without setting up & repeating the step. n
    • DrAmine
      Ansys Employee
      The only thing which remains constant and should be ideally constant is the mass of the air in the cube. All other things can vary!n
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