Flow properties of an intact MPL from nano-tomography and pore network modelling

Research output: Contribution to journalArticlepeer-review

Standard

Flow properties of an intact MPL from nano-tomography and pore network modelling. / Ma, Jingsheng; Zhang, Xiaoxian; Jiang, Zeyung; Ostadi, Hossein; Jiang, Kyle; Chen, Rui.

In: Fuel, Vol. 136, 15.11.2014, p. 307-315.

Research output: Contribution to journalArticlepeer-review

Harvard

APA

Vancouver

Author

Ma, Jingsheng ; Zhang, Xiaoxian ; Jiang, Zeyung ; Ostadi, Hossein ; Jiang, Kyle ; Chen, Rui. / Flow properties of an intact MPL from nano-tomography and pore network modelling. In: Fuel. 2014 ; Vol. 136. pp. 307-315.

Bibtex

@article{6280eac5a1944859b7002eaadfa3ae11,
title = "Flow properties of an intact MPL from nano-tomography and pore network modelling",
abstract = "Adding a hydrophobic micro-porous layer (MPL) between a gas diffusion layer (GDL) and a catalyst layer (CL) at the cathode of a PEM fuel cell was found capable of improving cell performance. However, how an MPL does this is not well-understood because current techniques are limited in measuring, observing and simulating multiphase pore fluid flow across the full range of pores that vary to a great extent in geometry, topology, surface morphology. In this work, we focused our investigation on estimating flow properties of an MPL volume to assess the limiting effect of strongly hydrophobic sub-micron pores on water transports. We adopted a nano-tomography and pore network flow modelling approach. A pore-structure model, purposely reconstructed from an intact MPL sample using Focused Ion Beam milling and Scanning Electron Microscope (FIB/SEM) previously, was used to extract a realistic pore network. A two-phase pore network flow model, developed recently for simulating the flow of gas, liquid or their mixture in both micrometre and nanometre pores, was applied to the pore network. We firstly tested the validity of the constructed pore network, and then calculated the properties: permeability for both water and selected gases, water entry pressure, and relative permeability. Knudsen diffusion was taken into consideration in calculations when appropriate. Our calculations showed that the water permeability was three orders of magnitude smaller than experimentally measured results reported in the literature, and when the water contact angle increased from 95° to 150°, the water-entry pressure increased from 2.5 MPa to 28 MPa. Thus our results revealed that for a strongly hydrophobic MPL that contains nanometre pores only it would behave like a buffer to water, and therefore the structural preferential paths in an MPL, such as cracks, are likely to be responsible for significant liquid water transport from the CL to the GDL that has been observed experimentally recently. We highlighted the needs for multi-scale modelling of the interplays of liquid water and gas transfer in MPLs that contain variable pores.",
keywords = "FIB/SEM tomography, Liquid water flow, Micro-porous layer, PEM fuel cells, Pore network flow modelling",
author = "Jingsheng Ma and Xiaoxian Zhang and Zeyung Jiang and Hossein Ostadi and Kyle Jiang and Rui Chen",
year = "2014",
month = nov,
day = "15",
doi = "10.1016/j.fuel.2014.07.040",
language = "English",
volume = "136",
pages = "307--315",
journal = "Fuel",
issn = "0016-2361",
publisher = "Elsevier Korea",

}

RIS

TY - JOUR

T1 - Flow properties of an intact MPL from nano-tomography and pore network modelling

AU - Ma, Jingsheng

AU - Zhang, Xiaoxian

AU - Jiang, Zeyung

AU - Ostadi, Hossein

AU - Jiang, Kyle

AU - Chen, Rui

PY - 2014/11/15

Y1 - 2014/11/15

N2 - Adding a hydrophobic micro-porous layer (MPL) between a gas diffusion layer (GDL) and a catalyst layer (CL) at the cathode of a PEM fuel cell was found capable of improving cell performance. However, how an MPL does this is not well-understood because current techniques are limited in measuring, observing and simulating multiphase pore fluid flow across the full range of pores that vary to a great extent in geometry, topology, surface morphology. In this work, we focused our investigation on estimating flow properties of an MPL volume to assess the limiting effect of strongly hydrophobic sub-micron pores on water transports. We adopted a nano-tomography and pore network flow modelling approach. A pore-structure model, purposely reconstructed from an intact MPL sample using Focused Ion Beam milling and Scanning Electron Microscope (FIB/SEM) previously, was used to extract a realistic pore network. A two-phase pore network flow model, developed recently for simulating the flow of gas, liquid or their mixture in both micrometre and nanometre pores, was applied to the pore network. We firstly tested the validity of the constructed pore network, and then calculated the properties: permeability for both water and selected gases, water entry pressure, and relative permeability. Knudsen diffusion was taken into consideration in calculations when appropriate. Our calculations showed that the water permeability was three orders of magnitude smaller than experimentally measured results reported in the literature, and when the water contact angle increased from 95° to 150°, the water-entry pressure increased from 2.5 MPa to 28 MPa. Thus our results revealed that for a strongly hydrophobic MPL that contains nanometre pores only it would behave like a buffer to water, and therefore the structural preferential paths in an MPL, such as cracks, are likely to be responsible for significant liquid water transport from the CL to the GDL that has been observed experimentally recently. We highlighted the needs for multi-scale modelling of the interplays of liquid water and gas transfer in MPLs that contain variable pores.

AB - Adding a hydrophobic micro-porous layer (MPL) between a gas diffusion layer (GDL) and a catalyst layer (CL) at the cathode of a PEM fuel cell was found capable of improving cell performance. However, how an MPL does this is not well-understood because current techniques are limited in measuring, observing and simulating multiphase pore fluid flow across the full range of pores that vary to a great extent in geometry, topology, surface morphology. In this work, we focused our investigation on estimating flow properties of an MPL volume to assess the limiting effect of strongly hydrophobic sub-micron pores on water transports. We adopted a nano-tomography and pore network flow modelling approach. A pore-structure model, purposely reconstructed from an intact MPL sample using Focused Ion Beam milling and Scanning Electron Microscope (FIB/SEM) previously, was used to extract a realistic pore network. A two-phase pore network flow model, developed recently for simulating the flow of gas, liquid or their mixture in both micrometre and nanometre pores, was applied to the pore network. We firstly tested the validity of the constructed pore network, and then calculated the properties: permeability for both water and selected gases, water entry pressure, and relative permeability. Knudsen diffusion was taken into consideration in calculations when appropriate. Our calculations showed that the water permeability was three orders of magnitude smaller than experimentally measured results reported in the literature, and when the water contact angle increased from 95° to 150°, the water-entry pressure increased from 2.5 MPa to 28 MPa. Thus our results revealed that for a strongly hydrophobic MPL that contains nanometre pores only it would behave like a buffer to water, and therefore the structural preferential paths in an MPL, such as cracks, are likely to be responsible for significant liquid water transport from the CL to the GDL that has been observed experimentally recently. We highlighted the needs for multi-scale modelling of the interplays of liquid water and gas transfer in MPLs that contain variable pores.

KW - FIB/SEM tomography

KW - Liquid water flow

KW - Micro-porous layer

KW - PEM fuel cells

KW - Pore network flow modelling

UR - http://www.scopus.com/inward/record.url?scp=84905827769&partnerID=8YFLogxK

U2 - 10.1016/j.fuel.2014.07.040

DO - 10.1016/j.fuel.2014.07.040

M3 - Article

AN - SCOPUS:84905827769

VL - 136

SP - 307

EP - 315

JO - Fuel

JF - Fuel

SN - 0016-2361

ER -