FRVT - Artículos en Revistas
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Item Indigo Carmine Degradation in Water Induced by a Pulsed Positive Corona Discharge in Air: Discharge and Postdischarge Effects.(2022) Ferreyra, Matías; Fina, Brenda; Milardovich, Natalio; Chamorro, Juan Camilo; Santamaría, Brenda; Balestrasse, Karina; Prevosto, LeandroIn recent years, one of the fastest growing technological applications in the field of nonthermal plasmas is the degradation of organic contaminants of water. In this work, the degradation of indigo carmine (IC) in water induced by a pulsed positive corona discharge operating in ambient air is reported. Degradation levels in different volumes of IC in solution with distilled water treated with different plasma exposure times immediately after discharge (0 h), and in the postdischarge up to 24 h were examined. To explain the IC discoloration in the postdischarge phase, a chemical model was developed. The stability of the reactive species in solution nitrate (NO3 −), nitrite (NO2 −) and hydrogen peroxide (H2O2 ), as well as the properties of the solution (electrical conductivity, pH) were also measured. The results suggest that the hydroxyl radical (OH˙) as well as ozone (O3 ) are the main oxidizing species during the discharge phase, being primarily formed in the gas phase through plasma-mediated reactions and then transferred to the liquid by diffusion, while the OH˙ production in the bulk liquid through the decomposition of peroxinitrous acid (O=NOOH) plays a major role in the IC degradation during the postdischarge. These results are associated with a noticeably increase in the energy-yield values observed at 24 h post-treatment.Item On the reduction of the third-order harmonic losses in low–voltage power cables used for feeding large LED and CFL lighting loads.(2017) Milardovich, Natalio; Prevosto, Leandro; Lara, Miguel Ángel; Milardovich, DiegoAn experimental investigation of diversity factors for LED (light emitting diode) in combination with CFL (compact fluorescent lamps) and LED lamps is presented in this paper. Attention was paid to the reduction of low–order harmonic currents, especially the third one; which is mainly responsible for the strong increase in power losses in the neutral conductor of low–voltage installations. The harmonic currents drawn by several LED and CFL lamps with nominal powers < 25 W were first measured to investigate the electrical characteristics of individual lamps. The results showed a sensible reduction of the harmonic current of third order and therefore a marked reduction of the power losses associated with them. The convenience of having LED lamps designed to operate as two–phase loads is suggested for certain applications of significant power demand.Item Descargas en contacto con líquidos: caracterización eléctrica de una descarga corona pulsada.(2021) Milardovich, Natalio; Ferreyra, Matías; Chamorro, Juan Camilo; Prevosto, LeandroLa gran cantidad de trabajos publicados en los últimos años sobre descargas no-térmicas en (y en contacto con) líquidos,evidencia el creciente interés en este particular campo de las descargas eléctricas debido al gran número de aplicacio-nes tecnológicas. En particular, una de las aplicaciones emergentes de mayor crecimiento es el tratamiento de agua,tanto para su potabilización como para su activación, con vistas a realizar el tratamiento indirecto de alimentos y semi-llas con descargas no-térmicas; sin el agregado de sustancias químicas. En este trabajo, se presenta la caracterizaciónexperimental de una descarga corona en contacto con agua operando en régimen pulsado. Se usó una geometría tipoalambre-plano con el electrodo plano sumergido en agua. La descarga fue alimentada a través de una fuente pulsadatipo capacitiva, capaz de proveer un tren periódico de pulsos de alto voltaje (∼15 kV) y corta duración∼100 ns), conuna frecuencia de repetición de 40 pulsos/s. Se reportan y discuten resultados de las mediciones de voltaje y corrientede la descarga para diferentes condiciones de operación, y se infieren la potencia instantánea y la energía disipada en elplasma generado. Se muestran además fotografías con largos tiempos de exposición de la descarga pulsada. The large number of works published in recent years on non-thermal discharges in (and in contact with) liquids, showsthe growing interest in this particular field of electric discharges due to the large number of technological applications.In particular, one of the fastest growing emerging applications is the treatment of water, both for its purification andfor its activation, with a view to carrying out the indirect treatment of food and seeds with non-thermal discharges;without the addition of chemicals. In this work, the experimental characterization of a corona discharge in contact withwater operating in a pulsed regime is presented. A flat-wire type geometry was used with the flat electrode immersedin water. The discharge was powered through a pulsed capacitive type source, capable of providing a periodic train ofhigh voltage pulses (∼15 kV) with short duration (∼100 ns), with a repetition frequency of 40 pulses/s. The resultsof discharge voltage and current measurements are reported and discussed for different operating conditions, and theinstantaneous power and energy dissipated in the generated plasma are inferred. Photographs in the visible with longexposure times of the pulsed discharge are also shown.Item Plasma Cutting of Concrete: Heat Propagation and Molten Material Removal From the Kerf.(2019) Chamorro, Juan Camilo; Prevosto, Leandro; Cejas, Ezequiel; Milardovich, Natalio; Mancinelli, Beatriz; Fischfeld, GerardoAn experimental investigation of heat propagation in the case of plasma cutting of concrete is reported. The experiments were carried out by using a high-enthalpy nitrogen plasma jet generated in a dc vortex-stabilized nontransferred arc torch. Concrete plates of different thicknesses up to 52 mm and with and without steel reinforcement were used. The plates were placed horizontally while cutting. The heat conduction losses inside the material were estimated by comparing thermocouple measurements and theoretical temperatures obtained with an analytical model of the heat propagation in the material. The influence of the molten concrete layer that separates the plasma to the solid material due to the high viscosity of the liquid concrete was accounted for. The power losses below the material in the extinguishing plasma have also been determined from calorimet ric measurements. For different plate thicknesses and cutting velocities, a complete power balance of the process is performed with the calculation of the cutting efficiency on the basis of various relevant power terms. In addition, the hydrodynamics of the molten concrete layer in the kerf is analyzed. For a mean power level of 11.2 kW and a nitrogen gas flow rate of 25 Nl/min, the torch is able to cut a concrete plate of 52 mm in thickness with a speed of 20 mm/min and a whole efficiency of about 30%. The viscosity force is the main limiting factor on the cutting velocity in thick plates.Item Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads.(2014) Milardovich, Natalio; Prevosto, Leandro; Lara, MarcelaA numerical investigation on the harmonic disturbances in low-voltage cables feeding large LED loads is reported. A frequency domain analysis on several commercially available LEDs was performed to investigate the signature of the harmonic current injected into the power system. Four-core cables and four single-core cable arrangements (three phases and neutral) of small, medium, and large conductor cross sections, with the neutral conductor cross section approximately equal to the half of the phase conductors, were examined. The cables were modelled by using electromagnetic finite-element analysis software. High harmonic power losses (up to 2.5 times the value corresponding to an undistorted current of the same rms value of the first harmonic of the LED current) were found. A generalized ampacity model was employed for re-rating the cables. It was found that the cross section of the neutral conductor plays an important role in the derating of the cable ampacity due to the presence of a high-level of triplen harmonics in the distorted current. The ampacity of the cables should be derated by about 40 %, almost independent of the conductor cross sections. The calculation have shown that an incoming widespread use of LED lamps in lighting could create significant additional harmonic losses in the supplying low-voltage lines, and thus more severe harmonic emission limits should be defined for LED lamps.