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Open AccessFeature PaperArticle

Modeling the Effect of Channel Tapering on the Pressure Drop and Flow Distribution Characteristics of Interdigitated Flow Fields in Redox Flow Batteries

1
Departamento de Ingeniería Térmica y de Fluidos, Universidad Carlos III de Madrid, 28911 Leganés, Spain
2
Department of Mechanical Engineering, Energy Engineering Graduate Program, University of Massachusetts Lowell, Lowell, MA 01854, USA
3
Unidad de Procesos Electroquímicos, Instituto IMDEA Energía, Avda. Ramón de La Sagra 3, 28935 Móstoles, Spain
*
Author to whom correspondence should be addressed.
Processes 2020, 8(7), 775; https://doi.org/10.3390/pr8070775
Received: 4 June 2020 / Revised: 25 June 2020 / Accepted: 26 June 2020 / Published: 1 July 2020
(This article belongs to the Special Issue CFD Applications in Energy Engineering Research and Simulation)
Optimization of flow fields in redox flow batteries can increase performance and efficiency, while reducing cost. Therefore, there is a need to establish a fundamental understanding on the connection between flow fields, electrolyte flow management and electrode properties. In this work, the flow distribution and pressure drop characteristics of interdigitated flow fields with constant and tapered cross-sections are examined numerically and experimentally. Two simplified 2D along-the-channel models are used: (1) a CFD model, which includes the channels and the porous electrode, with Darcy’s viscous resistance as a momentum sink term in the latter; and (2) a semi-analytical model, which uses Darcy’s law to describe the 2D flow in the electrode and lubrication theory to describe the 1D Poiseuille flow in the channels, with the 2D and 1D sub-models coupled at the channel/electrode interfaces. The predictions of the models are compared between them and with experimental data. The results show that the most influential parameter is γ , defined as the ratio between the pressure drop along the channel due to viscous stresses and the pressure drop across the electrode due to Darcy’s viscous resistance. The effect of R e in the channel depends on the order of magnitude of γ , being negligible in conventional cells with slender channels that use electrodes with permeabilities in the order of 10 12 m 2 and that are operated with moderate flow rates. Under these conditions, tapered channels can enhance mass transport and facilitate the removal of bubbles (from secondary reactions) because of the higher velocities achieved in the channel, while being pumping losses similar to those of constant cross-section flow fields. This agrees with experimental data measured in a single cell operated with aqueous vanadium-based electrolytes.
Keywords: modeling; interdigitated flow field; channel tapering; pressure drop; flow distribution; lubrication theory; redox flow battery modeling; interdigitated flow field; channel tapering; pressure drop; flow distribution; lubrication theory; redox flow battery
MDPI and ACS Style

García-Salaberri, P.A.; Gokoglan, T.C.; Ibáñez, S.E.; Agar, E.; Vera, M. Modeling the Effect of Channel Tapering on the Pressure Drop and Flow Distribution Characteristics of Interdigitated Flow Fields in Redox Flow Batteries. Processes 2020, 8, 775.

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