Three-Dimensional Membrane Imaging with X-ray Ptychography: Determination of Membrane Transport Properties for Membrane Distillation

Membrane distillation (MD) is a desalination technique that uses a membrane to thermally separate potable water from sea or brackish water. The mass transport processes through the membrane are commonly described by the dusty gas model. These processes are modeled assuming uniform, ideally cylindric...

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Bibliographic Details
Published in:Transport in porous media 2021-06, Vol.138 (2), p.265-284
Main Authors: Cramer, Kerstin, Prasianakis, Nikolaos I., Niceno, Bojan, Ihli, Johannes, Holler, Mirko, Leyer, Stephan
Format: Article
Language:English
Subjects:
Brackish water
Capillaries
Civil Engineering
Classical and Continuum Physics
Computational fluid dynamics
Computed tomography
Desalination
Direct numerical simulation
Distillation
Drinking water
Earth and Environmental Science
Earth Sciences
Flow coefficients
Geotechnical Engineering & Applied Earth Sciences
Hydrogeology
Hydrology/Water Resources
Industrial Chemistry/Chemical Engineering
Mass transport
Mathematical models
Membrane structures
Membranes
Permeability
Porosity
Three dimensional flow
Three dimensional models
Tortuosity
Transport properties
Viscous flow
X ray imagery
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Summary:Membrane distillation (MD) is a desalination technique that uses a membrane to thermally separate potable water from sea or brackish water. The mass transport processes through the membrane are commonly described by the dusty gas model. These processes are modeled assuming uniform, ideally cylindrical capillaries and are adjusted for the membrane geometry by including porosity and tortuosity. The tortuosity is usually set to 2 or is used as an adjusting parameter to fit theoretical models to experimentally measured data. In this work, ptychographic X-ray computed tomography is employed to map the three-dimensional (3D) structure of three commercial state-of-the-art PTFE membranes in MD. The porosity, tortuosity and permeability (viscous flow coefficient) of the samples are computed using the lattice Boltzmann method. The intrinsic permeability is compared to the dusty gas model and an apparent permeability is proposed which is corrected for Knudsen slip effects at the membrane structure. Article Highlights 3D structure of membranes for distillation measured at full height at an unprecedented detail using X-ray ptychography for the first time. Comparison of the dusty gas model to 3D direct numerical simulation: permeability and Knudsen effects. Membrane characterization and calculation of the hydraulic tortuosity factor from 3D flow field simulations.
ISSN:0169-3913
1573-1634
DOI:10.1007/s11242-021-01603-4