Date of Award

5-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Qiao, Rui

Committee Member

Vahidi , Ardalan

Committee Member

Xuan , Xiangchun

Abstract

The charging kinetics of Electric Double Layer Capacitors (EDLC) were studied using a continuum model based on the Poisson-Nernst-Planck (PNP) Equations, with the additional modeling of the bulk fluid motion in the electrolyte using the Navier-Stokes Equations. The results demonstrate that the addition of bulk flow modeling yields a faster charging rate and higher charging current due to the additional convective component of the current resulting from the bulk fluid motion. A parametric study was conducted to determine the effect of various physical parameters of the EDLC system on the charging kinetics. Decreased fluid viscosity results in a faster charging rate as the fluid velocities and, therefore, the convective current, becomes larger. Reduced ion mobility enhances the flow modeling effect by reducing the remaining non-convective components of the current, thus causing the convective current to represent a greater portion of the total current, but the penalty is lower overall current and correspondingly slower charging. Increased wall slip enhances the convective current by reducing friction at the walls and increasing the flow velocities. Widening the electrode pore bores increases charging rate by providing a greater cross-sectional area for the ion current to pass. Deepening the electrode pores slows the charging by requiring more ions to enter the pore in order to reach the steady-state charged condition.

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