General Mechanical

General Mechanical

Convection settings in Mechanical

    • laureano.gonzalez
      Subscriber
      Hi SM community,
      I am running a transient thermal analysis in Mechanical, where I have a tank with sand at the bottom and water on top. In the face between the two elements, I added a convection load (not sure if this is required).
      In the convection definition, I would like this face to initiate the simulation with the initial temperature (24 C  in water, sand and air). Then, I would like ANSYS to determine the temperature at the water-sediment interface, so I can compare simulated temperatures with the observed data; then, adjust the model until I get a match. I tried by assigning the initial temperature to the "Ambient Temperature" tab (constant, tabular and function options) (attached image), but it seems that the interface tends to keep the initial temperature even though the sand temperature and temperature outside the tank (input air temperature) are changing throughout the simulation period. 
       
      I am attaching an image of the tank temperature distribution, where the dark blue colour corresponds to the temperature (around 24C) at the water-sand interface (where I defined the convection load).
      Could you please guide me on what I am doing wrong? Thanks in advance.
       
      Laureano Gonzalez uploaded a photo
       
      As additional information, I have declared a convection load boundary condition at the interface between the tank and the air. This is the temperature vs time input I am giving to ANSYS, apart from the known heat rate I am inducing to the heater. Below is a snapshot of the boundary conditions I have included in my model.
       
      Laureano Gonzalez uploaded a photo
       
       
       
    • peternewmancsh
      Subscriber

      In Mechanical, a Convection boundary condtion is applied to an exterior face of the model, not an interface between two bodies. The reason is convection assumes an infinite supply of Ambient or bulk fluid whereas you have a finite tank of water so the equation would not apply.

      Use Fluent to define one body with the thermal properties of solid sand and the other body to have the thermal and fluid properties of water. You can put a Convection boundary condtion on the top face of the water to have convective heat transfer to the air. Fluent will compute the fluid motion of the water, which will carry heat to/from the sand. You need to turn on Gravity and have temperature dependent density of water to allow natural convection to occur.

    • laureano.gonzalez
      Subscriber

      Hi Peter,

      Thanks a lot. I'll try your suggestion in Fluent.

       

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