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!
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/).
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.