Dear researchers:
I am a newbee in the CFD simulation. Now I wish to simulate the wick structure by Fluent and the evaporation process in this region. The wick is saturated with water and being heated, the vapor escapes from its surface. But I don't know define the surface of the porous zone in Fluent.
https://www.sciencedirect.com/search?qs=wick%20structure%20in%20a%20loop%20heat%20pipe&show=25&sortBy=relevance
hello Du Sheng can you please describe the whole problem?
i am also working on the similar problem.
You can use Thermal-FSI simulation in ADINA software. I have worked on the similar problem in biomechanical project.
In my opinion, you do not have to define surface of the porous zone in Fluent if only the porous zone is defined itself. I mean, it is made “automatically”, but if only the porous zone and neighboring zones (of “pure” fluids or solids) are defined as a single part on the geometric step of preparations. You can do it in Modeler, for example, before meshing. In this case you can get conformal interface between different zones.
https://www.sharcnet.ca/Software/Ansys/17.0/en-us/help/wb_msh/msh_Conf_Mesh_Parts.html
Nagesh Dharavath Nagesh thanks for your notice, i am working on simulation of a loop heat pipe with wick. i wich to simulate the wick structure in a 2-D model with the utilization of Porous Zone. however, there is no capillary phenomenon occurred in the result. Do you know whether the Porous Zone in Fluent can solve this problem?
Miroslawa Kolodziejczyk thanks for you recommendation. this picture is the schematic of my model. the boundary of porous zone is defined as INTERIOR. If boundary of porous zone defined automatically, would it be "WALL"? I wich simulate the capillary phenomenon with the porous zone, can you give me some advice?
The process you described as: “The wick is saturated with water and being heated, the vapor escapes from its surface” is difficult to model, not only for “a newbee in the CFD simulation”.
It is not exactly my area, so I am not sure about the physics of the process, and I am, currently, cut off from Fluent, so I can’t check my answers, and, I’m warning you, I can be wrong.
To model the wick in Fluent you can use the porous media model or heat exchanger model. The porous media model is, in my opinion, the simplest way, but I barely used the heat exchanger model, I can be wrong.
The wick is to be heated, so in porous media model you should use Non-Equilibrium Thermal Model with heat sources, which have to be modelled:
https://www.sharcnet.ca/Software/Ansys/15.0.7/en-us/help/flu_ug/flu_ug_sec_bc_porous_media.html#x1-3730008.19_netm
And this model demands the heat transfer coefficient between water (or mixture of water and water vapour) and the solid matrix of the wick to be modelled.
You are trying to model the change of phase, so your problem is multiphase in fact. In Fluent you can use some of Multiphase Model. To put water in porous zone and humid air in “empty” zone, and assume the evaporation only on the interface (as the sources of water vapour) between them will be the simplest model, but I can’t check if it is possible.
The capillary effect in porous media model can be modelled by anisotropic inertial resistances (see User’s Guide).
In the picture, you've sent, the boundary between red and blu should be "interior", but the bottom on? Is it the axis or maybe the solid wall?
Miroslawa Kolodziejczyk thanks for your help, these figures are my simulation results. The Viscous Resistance and Inertial Resistance are estimated with Blake-Kozeny equation. You figured out that the capillary effect can be modelled by inertial resistances. But sadly, the liquid cannot saturate into the wick automatically. So i really doubt about the simulation of capillary effect with IR.
So, something is flowing into the porous zone. But I do not know boundary conditions and the physics of the flow in heat pipe with wick is a little bit unclear to me, but if the bottom is a heated solid wall it should not be “interior”!
Maybe this will be of some use to you:
https://www.researchgate.net/post/How_to_simulate_flow_in_porous_wick_pores_are_of_range_micrometer_due_to_capillary_action_using_FLUENT_for_modelling
Porous medium in Fluent is a fluid governed by N-S eq. Flow in porous material is usually described by Darcy’s equation, but Darcy’s equation is just a simplified form of N-S eq., so I think you can model the flow in wick using Fluent.
From what I’ve seen on Internet the porosity of wick is directed, anisotropic. I would try applying laminar flow in porous zone and maybe anisotropic porosity rather than anisotropic resistance.
The physics of the problem is difficult, so simulations are difficult and can be spoiled in many ways. Check all settings.
Du Sheng ,my work exactly matches with your one, but iam very new to the ANSYS FLUENT so far iam reading papers inorder to find the methodology and not even started simulation.But I think we can do this by VOF model ,porous media formulation ,wall adesion (to account surface tension effect),thermal equilibrium model.I will let you once i started doing simulation.If your intrested we can have conversation through email:[email protected]
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