Modeling of embedded flow fields and the effect of back-diffusion in electrochemical desalination

Warden, Colby Dalton

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https://hdl.handle.net/2142/129660 Copy

Description

Title

Modeling of embedded flow fields and the effect of back-diffusion in electrochemical desalination

Author(s)

Warden, Colby Dalton

Issue Date

2025-01-31

Director of Research (if dissertation) or Advisor (if thesis)

Smith, Kyle C

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Desalination
• flow fields
• electrode
• mass transport

Abstract

The use of flow fields in electrochemical systems such as redox flow batteries, fuel cells, and desalination systems has been shown to improve flow uniformity and reaction distribution resulting in increased performance. Flow fields help to face one of the primary challenges in these systems which is the low permeability of electrodes used in them. Hence, understanding how to manipulate and design flow fields is important. The body of literature on flow fields is massive and many types and configurations have been tested, but most design principles presented in literature are informed only by hydrodynamics. Although hydrodynamic effects are extremely important to understand in improving flow field performance, understanding of mass transfer is also integral to the operation of flow fields and rarely if ever are mass transfer principles used to inform flow field design. Outside of channel spacing and overall electrode dimensions, another key component of flow field design is the shape and dimension of channels. Channel tapering has been shown to improve flow uniformity within porous electrodes by counteracting regions of low flow. However, the use of channel tapering in the literature is typically done without specific analysis for the design in question, but rather with a presumed notion that it will improve performance. In this work, we present three-dimensional simulation results from flow and mass transport modeling. First, we demonstrate functionality of optimally tapered channels following previous work produced by hydrodynamic analysis. These channels are tapered in such a way that they produce uniform transverse flow in an embedded, micro-interdigitated flow field increasing the total coverage of active material in the electrode. Additionally, mass transport simulations revealed the effect of back-diffusion reducing reaction rate uniformity. We present an analytical mass transport model to account for this effect and test its governing parameters in simulations. These simulations revealed that back-diffusion has a strong dependence on electrode dimensions. The following work attempts to fill a gap in the literature using evidence of design constraints informed and enforced by an analytical mass transfer model capturing the effect of back-diffusion.

Graduation Semester

2025-05

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129660

Copyright and License Information

Copyright 2025 Colby Warden

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