Z-Diffusivity?

Energy2D Forum Forums Energy2D Questions Z-Diffusivity?

This topic contains 2 replies, has 2 voices, and was last updated by  schultzf 1 year, 5 months ago.

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  • #121

    schultzf
    Participant

    I am trying to model multiple cylinders in a fluid (wood utility poles in hot treating oil) and I feel that I am getting better simulations if i turn on the z-diffusivity and check Fluid Only box. But, I am not sure what this value actually is tied to. Is it the diffusivity of the liquid medium? Also, why does this matter if I have this on?

    Related to this, I would like to add a power source for heating of the oil medium, I have a specification of a heat exchanger that works at 1.3E9 J/hr for a large tank. Can I assume a 1 m “z-direction” for the simulation as far as how much energy is delivered to the system?

    And, one more question, how is the Biot number obtained for your calculations? I have a wood and hot oil system, what heat transfer coefficient gets utilized? Can this be modified in the system parameters? Thanks!

    #122

    Charles Xie
    Keymaster

    Energy2D is only a 2D simulation tool. In order to simulate some 3D effects, the 2D plane can be coupled with an imaginary thermal source in the z dimension. You can imagine it as a thin slab that can exchange energy in the perpendicular direction. The z-diffusivity is a parameter to control that. Once it is on, the fluid simulation tends to be more stable and excessive energy can “escape” through the z-direction (as it does in reality).

    You can assume a 1 m z-direction when converting the parameters from 3D to 2D.

    With regard to the Biot number, I think it is not a fundamental property as the thermal pattern can be simulated using more fundamental properties such as the physical properties of the solid and the fluid, if I understand correctly (see this: http://www.thermopedia.com/content/585/).

    #128

    schultzf
    Participant

    Thanks Charles, this is helpful! As for the Biot Number, I see it is not fundamental, however the Heat Transfer Coefficient is something that I feel needs to be a part of the calculation if I am trying to model a solid warming in a hot liquid.

    See below:

    http://www.thermopedia.com/content/975/

    http://www.thermopedia.com/content/841/

    Am I missing something here?

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