Hello,
I would like to know how to simulate water diffusion through a porous region using Ansys Fluent. Specifically, I am interested in simulating the following problem:
There is a pipe with insulation covering exposed to atmospheric conditions. Due to the condensation of water vapour at the outer surface of the insulation, water is deposited there. The water then diffuses through the porous insulation layer and reaches the outside of the pipe (inside the insulation). A constant temperature is applied inside the pipe. I would like to know the water content present at the outer surface (inside the insulation) of the pipe.
I am also interested in knowing what kind of inlet boundary needs to be applied.
I understand that this type of simulation is possible with WUFI software, but I believe it is limited to 2D geometry. Therefore, I am interested in how to solve this problem using Ansys Fluent software.
Thank you.
Dear Arun Mathew, the case can be solved by having a 2D axisymmetric boundary so that fluent can solve that in polar coordinates.
After creating the geometry of the inner pipe, the outer porous layer is to be generated as a plane as a FROZEN material so that it will be created as a separate body. Hence it can be defined as a porous media in FLUENT.
In FLUENT,
- Since condensation is a dynamic process, the analysis should be transient
- Enable the energy equation to provide temperature boundaries,
- Import water liquid and water vapour from the fluent library [materials]
- Enable the multiphase model to simulate the mass transfer by condensation [specify the saturation temperature & surface tension in the evaporation and condensation model from the interactions tab].
- Define Water liquid and Water Vapour as two phases in the VOF model
- If there is no forced flow and the flow is driven only by gravity, then you can specify the atmospheric interfaces with the fluid as pressure outlets.
- After initializing, patch the body as water liquid where it is completely water at the 0th timestep.
- Define the required results using the reports tab and run the calculation for the required number of timesteps with the smallest possible timestep size.
I have provided my response to your question. If it has been helpful, please let me know. If you have any further doubts or if my explanation was not clear enough, please do not hesitate to let me know. I am happy to assist you further.
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