Effects of Frequency and Joule Heating on Height Rise between Parallel Electrodes with AC Electric Fields

Abstract

High strength AC electric fields generate a body force on a dielectric medium confined between two electrodes. The body forces are due to two factors. First is the variation in permittivity across an interface such as liquid–air present between the electrodes. The second is a change in the dielectric property of the medium due to a variation in the thermodynamic properties such as temperature. The height rise of a dielectric medium between two electrodes is one of the consequences of these electrical body forces and is used here as a comparatively simple way to study these forces. In an aqueous solution with finite conductivity, the effects of the frequency of the supplied voltage source and the temperature change due to Joule heating on height rise have never been studied in this context. This study focuses on systems where the contributions of surface forces are negligible and highlights the interplay between solution conductivity, applied electric field, and the solution height/temperature behavior. Using a generic thermodynamic model for an aqueous solution under the application of an alternating current electric field, it is shown that for low conductivity solutions the resulting temperature and height rise change weakly with the applied field frequency and strongly with the applied electric field. For higher conductivity solutions, the behavior becomes more complex with respect to the electric field strength. As compared to Pellat’s original model, the height rise varies from strongly suppressed to enhanced.

Novel Raman Spectroscopy Method for Solutions in Uniform, High-Strength Electric Field

“…25 The measured conductivity of a 40% w/w water–ethanol mixture (∼ 0.1 mS/m) was higher compared to a pure alcohol (∼ 0.01 mS/m) by an order of magnitude. The significantly higher conductivity of the 40% ethanol solution results in much higher resistive losses within the solution at an alternating electric field strength of 1.0 MV/m, 19 raising its temperature by ∼ 20°C from the prior temperature at 0.8 MV/m as shown Fig. 7.…”

“…We applied a sinusoidal voltage with varying peak-to-peak voltages at a frequency of 5000 Hz as this maximizes the effective electric field across the liquid. 19 We estimated the potential drop across the channel by modeling the system, including the solution and the insulation layers, as a series of capacitors. We applied five different voltages for each solution of the water-ethanol mixtures, resulting in an effective electric field strength varying from 0 to 1 MV/m across the 10 μm solution.…”

Dielectric polarization-based separations in an ionic solution

“…The first being the inability of the model to account for the microscopic structural changes resulting from the application of E-field on the solution confined between two electrodes. 39 The change in permittivity with concentration in eqn (6) was measured at low electric-field strengths because rapid transport witnessed here varies the concentration making high electric-field permittivity measurements impossible. Structural changes induced by the high electric-fields may alter the change in permittivity with concentration in ways that are not accounted for in our model.…”

“…This relatively high ow rate is several times higher than is currently possible using electrophoretic methods in a single channel. 33 A thermodynamic model under the application of an external E-eld developed earlier 32 is used to predict the equilibrium concentration change for the uorescein sodium (NaFl) dye solution conned in a channel. For such a system, i.e., a closed system which is subjected to an external E-eld, the Helmholtz free energy (dF ′ ) is given by eqn (1), where, S represents entropy, E is E-eld strength, V is volume, 3 is permittivity of the solution, T is temperature, c i is concentration of species i in molarity, p is pressure, u is frequency, D is electrical displacement vector, m i is chemical potential of species i in absence of Ẽ, and n i is number of moles of species i.…”

Thermodynamic Study of the Electric Field Effect on Liquid–Vapor Mixture at Equilibrium: An Analysis on a Water–Ethanol Mixture

“…Various methods have been employed in previous studies to calculate the change in internal energy caused by E -fields. In this manuscript, we adopt the approach of Anand et al to establish a relationship for U E . − This energy is dependent on the strength of the E -field, E , the entropy under the influence of the E -field, S E , the volume, V , the displacement vector, D⃗ , and the permittivity, ε. By applying eq and considering that E⃗ = D⃗ /ε, U E is expressed as U E = prefix∫ S E T normald S E + prefix∫ V ∫ 0 D⃗ E⃗ · normald D⃗ normald V = T S E + D⃗ · D⃗ 2 ε V …”