4.6 Article

Mass transfer in fibrous media with varying anisotropy for flow battery electrodes: Direct numerical simulations with 3D X-ray computed tomography

Journal

CHEMICAL ENGINEERING SCIENCE
Volume 196, Issue -, Pages 104-115

Publisher

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ces.2018.10.049

Keywords

Electrospun electrodes; Numerical modelling; X-ray computed tomography; Redox flow battery; Mass transfer coefficient; Fibrous media

Funding

  1. EPSRC [EP/L014289/1, EP/N032888/1]
  2. STFC Extended Network in Batteries and Electrochemical Energy Devices [ST/N002385/1]
  3. Royal Academy of Engineering
  4. Natural Science and Engineering Research Council (NSERC) of Canada
  5. Eugenie Ulmer Lamothe Endowment
  6. Vadasz Family Doctoral Fellowship
  7. McGill University's Graduate Mobility Award
  8. EPSRC [EP/S003053/1, EP/N032888/1, EP/L014289/1] Funding Source: UKRI
  9. STFC [ST/N002385/1] Funding Source: UKRI

Ask authors/readers for more resources

A numerical method for calculating the mass transfer coefficient in fibrous media is presented. First, pressure driven flow was modelled using the Lattice Boltzmann Method. The advection-diffusion equation was solved for convective-reacting porous media flow, and the method is contrasted with experimental methods such as the limiting current diffusion technique, for its ability to determine and simulate mass transfer systems that are operating at low Reynolds number flows. A series of simulations were performed on three materials; specifically, commercially available carbon felts, electrospun carbon fibers and electrospun carbon fibers with anisotropy introduced to the microstructure. Simulations were performed in each principal direction (x,y,z) for each material in order to determine the effects of anisotropy on the mass transfer coefficient. In addition, the simulations spanned multiple Reynolds and Peclet numbers, to fully represent highly advective and highly diffusive systems. The resulting mass transfer coefficients were compared with values predicted by common correlations and a good agreement was found at high Reynolds numbers, but less so at lower Reynolds number typical of cell operation, reinforcing the utility of the numerical approach. Dimensionless mass transfer correlations were determined for each material and each direction in terms of the Sherwood number. These correlations were analyzed with respect to each materials' permeability tensor. It was found that as the permeability of the system increases, the expected mass transfer coefficient decreases. Two general mass transfer correlations are presented, one correlation for isotropic fibrous media and the other for through-plane flow in planar fibrous materials such as electrospun media and carbon paper. The correlations are Sh = 0.879 Re-0.402 Sc-0.390 and Sh = 0.906 Re-0.432 SC0.432 respectively. (C) 2018 Elsevier Ltd. All rights reserved.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.6
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available