Fluids

Fluids

Building a Solar Radiation Model

    • patrickm7995
      Subscriber

      I am attempting to make a model with a cone and a flat bottom plate, like this:

      The bottom plate is set as a wall that is opaque with an absorptivity of 1 (absorbing all radiation from the sun and anything that reflects or emits off the walls). The cone is set as a wall that is opaque with various mixtures of absorptivity and reflectivity. The walls are set to zero conductivity. The top boundary is set as an velocity-inlet that is opaque with a transmissivity of 1.

      The air is also set to a near vacuum (1e-5) and near zero conductibvity (1e-5) because it is attempting to model space, and it is initialized to 2.7K (ambient temperature in space). I have Monte Carlo radiation turned on to re-radiate any solar radiation that is absorbed by the walls.

      Running this, I find temperatures that are vastly too high for what is expected in this scenario, and some areas max out at 5000K. Is there anything I am already doing wrong in the setup, or anything I may want to check?

      Thank you,

      Patrick

    • Swathi V. V.
      Ansys Employee

      Hi,

      Are you getting this high temperature at the initial iteration? If yes, you can neglect it because as solution gets stable the correct temperature profile will be established.

      Please make sure the mesh quality is good and also the material properties are correctly defined.

      Can you elaborate on how you are setting the transmissivity to 1 at inlet for opaque surface? what is the temperature of fluid entering the inlet? Is the fluid flowing out?

       

      • patrickm7995
        Subscriber

        Hello,

        The high temperatures goes down to 1 to 5 faces that are limited to over 5000K after multiple iterations.

        The mesh quality passes the quality test in the general section. 

        And under the boundary conditions tab, for the inlet condition, I am setting the radiation to look like this:

        I am setting the inlet temperature to 2.7K as well as fixing the air temperature to 2.7K under the cell zone conditions tab. I don't have the fluid flowing out anywhere because the bottom of the cone is closed; this bottom face is where I need to measure the temperature.

        I would to heat up, but still be relatively low in temperature, close to this 2.7K, but they are well above that, in the 1000s K.

        Thank you.

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