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Transport of Concentrated species & Laminar flow

Posted 18 nov 2025, 21:44 GMT-5 Computational Fluid Dynamics (CFD), Chemical Reaction Engineering 0 Replies

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Hello,

I am a Nuclear science and technology doctoral student and I wish to simulate hydrogen & Helium mixture separation by palladium membrane. (Tube shaped) Here is the question.

Case Overview: This study involves helium-hydrogen mixture transport through a pipeline lined with a palladium (Pd) membrane. Hydrogen is able to permeate through the membrane walls, while helium remains confined and flows only within the pipeline.

Boundary Conditions: Constant inlet mass flow rate, Constant outlet pressure, Uniform temperature along the entire pipeline

Model Setup: A coupled model: using the Transport of Concentrated Speciesand Laminar Flow interfaces. Strong coupling between mass transfer and fluid flow is achieved via the Reaction Engineering functionality.

However, the simulation yields unphysical results, as described below. Observed Anomaly: As the He–H₂ mixture flows through the pipeline, hydrogen permeates outward through the Pd membrane. The total mass flow rate of the mixture is expected to decrease along the flow path, and the mass flow rate of helium should remain constant across any cross-section of the pipeline. However, the current model shows a constant flow velocity along the pipeline, while the mass flow rate of helium increases toward the outlet. This results in a higher helium mass flow at the outlet than at the inlet—indicating a clear violation of mass conservation. Visually, it appears that the model artificially compensates for the loss of hydrogen by increasing the helium content.

Objective: Identify the root cause of the mass non-conservation and adjust the model such that the flow velocity decreases gradually along the pipeline, consistent with physical expectations.

It would be of a great help if anybody could guide me on these.

Thanks, Leopold Jiang

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