Liquid dielectric

About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.

Dielectric fluid motors

Abstract: On the application of high electric fields to a dielectric fluid, a convective motion of the fluid is induced. By controlling the fluid motion in nonuniform dc fields, a new type of fluid motor is developed. An angular velocity of more than 15 s−1 (150 rpm) can be achieved at a dc voltage of 5 kV for a motor with a rotor radius of 10 mm. The efficiency of energy transformation from electric to kinetic energy is about 4%. Since magnetic fields and switching circuits are not required, the advantage of the fluid motor will be enhanced by size reduction. The dielectric fluid motor is attractive as a source of mechanical energy in a micromachine.

An Experimental Determination of the Excess Pressure produced in a Liquid Dielectric by an Electric Field

Abstract: A Schlieren optical system has been used to measure the pressure Δp (by its effect on the refractive index) induced in non-polar isotropic liquid dielectrics by the application of an electric field E. All the results agree with the equation which is derived from the theory due to Helmholtz, Δp = E2(-1)(+2)/24π where is the permittivity of the liquid, and not with the equation based on the theory of Livens.

Dielectric fluid for use in power distribution equipment

Abstract: The present invention comprises a mixture of hydrocarbons having a well-defined chemical composition that is suitable for use as a dielectric coolant in electrical equipment in general, and specifically in transformers. The dielectric coolants of the present invention are particularly suited for use in sealed, non-vented transformers, and have improved performance characteristics, including decreased degradation of the paper insulating layers, as well as a greater degree of safety and environmental acceptability. The present dielectric coolants comprise relatively pure blends of compounds selected from the group consisting of aromatic hydrocarbons, polyalphaolefins, polyol esters, and natural vegetable oils, along with additives to improve pour point, increase stability and reduce oxidation rate.

Drop motion, deformation, and cyclic motion in a non-uniform electric field in the viscous limit

Abstract: Drop motion and deformation of a conducting drop in a perfect (or leaky) dielectric fluid and a leaky dielectric drop in a leaky dielectric fluid, in a non-uniform electric field is presented. The investigated non-uniform electrode configuration is of the pin-plate type. Systematic experiments and comparison with existing analytical models is carried out. The main results are summarized as follows: (i) The dielectrophoretic motion of a conducting drop in a non-uniform electric field is explained reasonably well assuming a spherical drop, although deviations are observed at large deformations. Thus dielectrophoretic motion shows a weak shape dependence. (ii) The deformation of a conducting drop in a non-uniform electric field has comparable contributions from the uniform and the non-uniform components of the applied field. (iii) The leaky dielectric nature of the medium results in three different states for a conducting drop (a) no movement, (b) near electrode cyclic motion, and (c) cyclic motion between the electrodes. The frequency of cyclic motion decreases with electric field for near electrode motion. On the contrary it increases with the applied field for electrode-electrode cyclic motion. The leaky dielectric system showing positive dielectrophoresis leads to the drop getting attached to the pin electrode causing emulsification at large field. A leaky dielectric drop suspended in a dielectric, system exhibiting negative dielectrophoresis shows oblate deformation which is augmented by the plate-drop hydrodynamic interaction.

Electrowetting films on parallel line electrodes

Abstract: A lubrication analysis is presented for the spreading dynamics of a high permittivity polar dielectric liquid drop due to an electric field sustained by parallel line electrode pairs separated by a distance R(e). The normal Maxwell stress, concentrated at the tip region near the apparent three-phase contact line, produces a negative capillary pressure that is responsible for pulling out a thin finger of liquid film ahead of the macroscopic drop, analogous to that obtained in self-similar gravity spreading. This front-running electrowetting film maintains a constant contact angle and volume as its front position advances in time t by the universal law 0.43R(e)(t/T(cap))1/3, independent of the drop dimension, surface tension, and wettability. T(cap)=pi(2)mu(l)R(e)/8(epsilon0epsilonl)V2 is the electrocapillary time scale where mu(l) is the liquid viscosity, epsilon0epsilonl the liquid permittivity, and V the applied voltage. This spreading dynamics for the electrowetting film is much faster than the rest of the drop; after a short transient, the latter spreads over the electrowetting film by draining into it. By employing matched asymptotics, we are able to elucidate this unique mechanism, justified by the reasonable agreement with numerical and experimental results. Unlike the usual electrowetting-on-dielectric configuration where the field singularity at the contact line produces a static change in the contact angle consistent with the Lippmann equation, we show that the parallel electrode configuration produces a bulk negative Maxwell pressure within the drop. This Maxwell pressure increases in magnitude toward the contact line due to field confinement and is responsible for a bulk pressure gradient that gives rise to a front-running spontaneous electrowetting film.