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An analysis of random perturbations in electrolyzers

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Abstract

A method of analysis of the stochastic behaviour of electrolyzers due to stationary random fluctuations in current and inlet electrolyte concentration is presented. The analysis is illustrated by means of a numerical example.

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Abbreviations

c :

electrolyte concentration;c i inlet electrolyte concentration;c E exit electrolyte concentration (mol dm−3)

F :

Faraday's constant (96487 C mol−1)

I :

current (A)

j :

imaginary unit = √(−1)

K :

equivalent gain

N(A) :

nonlinear function of amplitudeA of an independent variable

n :

number of electrons participating in the electrode process

P(z):

probability density function of random variablez

Q :

electrolyte volumetric flow rate (dm3 min−1)

R z(λ):

autocorrelation function

S z(ω):

power spectrum of random variablez

T 0,T 1 :

Frequency characteristic parameters (obtained from process reaction curve)

u :

shorthand for the product αz 1 (see Equation 30)

V :

active volume of electrolyzer (dm3)

v :

shorthand for the product βz 2 (see Equation 30)

χ:

dimensionless exit electrolyte concentration

z 1 :

dimensionless electrolyte inlet concentration

z 2 :

dimensionless current

α:

lumped parameter defined as-c *i /c *E

β:

lumped parameter defined asI */nFQc *E

γ:

lumped parameter defined as aI */nFVc *E

λ:

dummy' integration variable

σ 2x :

variance (or mean power) of random variablez

τ:

mean residence time in electrolyzer, equal toV/Q (min)

ϕ(jω):

frequency spectrum

ω:

angular frequency

*:

steady state (superscript)

erf:

error function, defined as\(erf (z) = \frac{2}{{\surd \pi }}\int_0^z {\exp ( - \lambda ^2 ) d\lambda }\)

o:

step magnitude (superscript)

H :

Heaviside's shifting function, defined asH(t−τ)=0 fort<τ;H(t−τ)=1 fort≥τ

Γ:

gamma function, defined as\(\Gamma (z) = \int_0^\infty { \lambda ^{z - 1} } \exp ( - \lambda ) d\lambda\)

CSTER:

acronym for continuous flow stirred tank electrolytic reactor

PFER:

acronym for plug-flow electrolytic reactor

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Fahidy, T.Z. An analysis of random perturbations in electrolyzers. J Appl Electrochem 20, 901–906 (1990). https://doi.org/10.1007/BF01019563

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