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This study explores how electroosmosis and buoyancy forces affect flow regimes in electrokinetic systems within rectangular capillaries and how these regimes shape concentration profiles under varying temperature and non-symmetric conditions caused by uneven wall convection. The advective impact of Joule heating and convection on solute migration is investigated, with emphasis on determining which force dominates and how non-symmetric environments influence flow regimes and dispersion—key considerations for designing efficient electrokinetic devices and effective soil-remediation protocols. Using generalized (Robin-type) boundary conditions, the study introduces a skewness parameter 𝑅2 to help predict flow reversal behavior and mixing issues based on system parameters. The analysis applies heat-transfer modeling, solves the Navier–Stokes equation for buoyancy-driven cases limited by 𝑅2, and solves the molar species continuity equation to obtain concentration profiles across scenarios of 𝑅2 values and Joule heating. The area-averaging method is used for the advective case and limiting scenarios (including insulation and uneven environments) are reported, along with reverse-flow conditions and their mixing impact on concentration profiles.
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Impact and Role of Temperature on Electrostatic Potentials and Velocity Profiles Prediction
Electrostatic potential profiles are vital for understanding and controlling electroosmosis as well as particle mixing. The shape and magnitude of this profile—particularly a key parameter called the zeta potential (ζ)—directly dictate the speed and direction of fluid flow when an electric field is applied. The role of temperature in modifying this important parameter has not been analyzed from a mathematical approach, and it is relevant for improving the design of microfluidic devices and technologies involving capillary electrophoresis for non-isothermal systems. In this study, two electrophoretic cell geometries are investigated under non-isothermal conditions. A heat-transport model (with heat generation and Dirichlet boundary conditions) is coupled into the Poisson–Boltzmann equation to obtain zeta potential profiles for different temperature distributions. In addition, the Navier–Stokes equation for the electroosmotic case is solved to obtain velocity profiles, including examples of flow reversal under temperature development. Numerical analysis for rectangular and cylindrical geometries indicates that large temperature gradients produce significant zeta-potential changes and can induce multiple flow reversals; effects are more pronounced at high Joule-heating values, while small temperature differences yield approximately linear electrostatic potential behavior and typical laminar profiles.
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- Award ID(s):
- 2345379
- PAR ID:
- 10662908
- Publisher / Repository:
- American Institute of Chemical Engineers (AIChE)
- Date Published:
- Edition / Version:
- 1
- Page Range / eLocation ID:
- 1-2
- Subject(s) / Keyword(s):
- zeta potential joule heating flow reversal
- Format(s):
- Medium: X Size: 128KB Other: pdf
- Size(s):
- 128KB
- Location:
- Boston, MA, USA
- Sponsoring Org:
- National Science Foundation
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