Investigation on flow electrification of ester-based TiO 2 nanofluids
06 Oct 2020-IEEE Transactions on Dielectrics and Electrical Insulation (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 27, Iss: 5, pp 1492-1500
TL;DR: In this article, the authors showed that the streaming current increases with increasing pressboard thickness, disc diameter, oil temperature and spinning disk velocity, and that the loss tangent of the nanofluid with surfactant and BTA shows an increase with increasing temperature.
Abstract: This study shows that TiO 2 nanofiller and cetyl trimethyl ammonium bromide (CTAB) surfactant in ester oil demonstrates higher corona inception voltage under AC and DC voltages. Flow electrification studies with nano fluid adopting the spinning disk method confirms that the streaming current increases with increasing pressboard thickness, disc diameter, oil temperature and spinning disk velocity. The study also indicates that nanofluids with surfactant have higher streaming currents than its effect without surfactant. It is found that the streaming currents could be suppressed by the addition of aromatic additive 1, 2, 3-benzotriazole (BTA). In addition, the permittivity of the nanofluid is not affected by adding surfactant or BTA but a marginal reduction occurs with increasing temperature. However, the loss tangent of the nanofluid with surfactant and BTA shows an increase with increasing temperature. The rheological studies indicate transition from laminar to turbulent flow in the case of nanofluids.
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TL;DR: In this paper, a review on the research of dielectric fluids, especially commonly used power transformer oils enhanced by nanoparticles, is presented, where the main goal is to present recent research in this field sorted by the used nanoparticles.
Abstract: This review is focused on the research of dielectric fluids, especially commonly used power transformer oils enhanced by nanoparticles, i.e., nanofluids. There are differences between various combinations of base fluids and nanoparticles prepared in different ways. The main goal of this review was to present recent research in this field sorted by the used nanoparticles. Nanofluids based on mineral oils, natural, or synthetic esters were investigated in terms of the nature of nanoparticles, particularly Al2O3, TiO2, Fe2O3, Fe3O4, graphene, fullerene, and others. The combinations of environmentally friendly oils and nanoparticles were presented. Finally, the article focused on the description of current dielectric fluids usable in power transformers and the possibilities of improving new and existing fluids with nanoparticles, especially their physical, dielectric, and chemical properties, but with regard to environmental aspects.
21 citations
TL;DR: In this article , the authors report on the significant enhancement of the thermal properties of the FR3 natural ester dielectric oil after the addition of pentyl-graphene nanosheets, as confirmed by thermal diffusivity and specific heat studies at different concentrations and temperatures.
Abstract: This work reports on the significant enhancement of the thermal properties of the FR3 natural ester dielectric oil after the addition of pentyl-graphene nanosheets, as confirmed by thermal diffusivity and specific heat studies at different concentrations and temperatures (30 °C–90 °C). Experimental results of the dielectric constant demonstrated a constant value in the kHz region while increased in the low-frequency region, decreased with increased temperature, and saturated at 0.008% w/w concentration. In addition, light absorption is used for a better understanding of the properties variation upon changing graphene’s concentration as a method to estimate the agglomeration level. The optimum concentration for its best performance in terms of thermal and dielectric properties is 0.008% w/w, whereby the thermal diffusivity and the dielectric constant increased by 43.04% and 6.18%, respectively.
11 citations
DOI•
TL;DR: In this article , a tropical indigenous non-edible ester such as Pongamia oil (PO) and PO methyl ester (POME) were taken as test samples to develop a nonparametric model for investigations.
Abstract: This research investigates a tropical indigenous nonedible ester such as Pongamia oil (PO). PO and PO methyl ester (POME) were taken as test samples to develop a nonparametric model for investigations. This work implements the empirical cumulative distribution function (eCDF) to develop a PO and POME lifetime model. The lifetime model of the PO and POME acts as a decisive factor in determining the early failure regions corresponding to the bathtub model. On the other hand, the Bayesian theorem calculates the Bayesian inference. This enables one to foresee the variable as a posterior distribution to conclude their correlation in the parameter space. The developed lifetime model of PO and POME supports experimental results over hypothesis and assists one to predict the risk probability. The model predicted early failures of the PO at less than 40 kV and POME at less than 54 kV and life of POME from 41 to 54 kV and POME at 55–65 kV. The useful life of PO and POME will experience a failure rate of 45% and 25%, respectively. Furthermore, such detections aid power engineers to treat insulating fluids to overcome early aging effects and deterioration of oil–paper insulation.
10 citations
TL;DR: In this article , experimental investigations of the effects of different surfactants (CTAB, Oleic acid and Span 80) on silica-based synthetic ester nanofluids were performed.
Abstract: This study reports experimental investigations of the effects of different surfactants (CTAB, Oleic acid and Span 80) on silica based synthetic ester nanofluids. The positive and negative potential observed for the ionic (CTAB) and non-ionic surfactant (Span 80) from zeta potential analysis indicates an improved stability. The optimization of nanofillers and surfactants is performed considering the corona inception voltage measured using ultra high frequency (UHF) technique and fluorescent fiber. Rheological analysis shows no significant variation of properties with shear rate, implying Newtonian behavior even with the addition of surfactant. In addition, the permittivity of the nanofluid is not much affected by adding surfactant but a marginal variation is noticed in the loss tangent with the effect of temperature. The fluorescence spectroscopy shows no change in the emission wavelength with the addition of silica nanofiller and surfactants. Flow electrification studies indicate an increase in the streaming current with the rotation speed and temperature, with a higher current magnitude observed in the case of nanofluids.
9 citations
TL;DR: In this article , a tropical indigenous non-edible ester such as Pongamia oil (PO) and PO methyl ester (POME) were taken as test samples to develop a nonparametric model for investigations.
Abstract: This research investigates a tropical indigenous nonedible ester such as Pongamia oil (PO). PO and PO methyl ester (POME) were taken as test samples to develop a nonparametric model for investigations. This work implements the empirical cumulative distribution function (eCDF) to develop a PO and POME lifetime model. The lifetime model of the PO and POME acts as a decisive factor in determining the early failure regions corresponding to the bathtub model. On the other hand, the Bayesian theorem calculates the Bayesian inference. This enables one to foresee the variable as a posterior distribution to conclude their correlation in the parameter space. The developed lifetime model of PO and POME supports experimental results over hypothesis and assists one to predict the risk probability. The model predicted early failures of the PO at less than 40 kV and POME at less than 54 kV and life of POME from 41 to 54 kV and POME at 55–65 kV. The useful life of PO and POME will experience a failure rate of 45% and 25%, respectively. Furthermore, such detections aid power engineers to treat insulating fluids to overcome early aging effects and deterioration of oil–paper insulation.
8 citations
References
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TL;DR: In this article, the authors summarized the recent progress on the study of nanofluids, such as the preparation methods, the evaluation methods for the stability of nanometrics, and the ways to enhance the stability for nanofl fluids, and presented the broad range of current and future applications in various fields including energy and mechanical and biomedical fields.
Abstract: Nanofluids, the fluid suspensions of nanomaterials, have shown many interesting properties, and the distinctive features offer unprecedented potential for many applications. This paper summarizes the recent progress on the study of nanofluids, such as the preparation methods, the evaluation methods for the stability of nanofluids, and the ways to enhance the stability for nanofluids, the stability mechanisms of nanofluids, and presents the broad range of current and future applications in various fields including energy and mechanical and biomedical fields. At last, the paper identifies the opportunities for future research.
1,320 citations
"Investigation on flow electrificati..." refers background or methods in this paper
...It can be inferred that CIV increases on the addition of a surfactant due to the reduction in Van Der Waals force that encapsulates the active surface area of nanoparticles forming a stable nanofluid [3]....
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...Uniform dispersion and stability are important requirements of nanofillers in liquid and different methods are used in the nanofluid preparation, where the two-step system is most widely used [3]....
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Journal Article•
395 citations
TL;DR: A system for measuring the sensitivity of electric field sensors at UHF using a novel gigahertz transverse electromagnetic (GTEM) cell is described to enable calibration of UHF couplers that are used to detect insulation defects in gas insulated substations.
Abstract: A system for measuring the sensitivity of electric field sensors at UHF using a novel gigahertz transverse electromagnetic (GTEM) cell is described. The system was developed to enable calibration of UHF couplers that are used to detect insulation defects in gas insulated substations. The frequency response of a sensor is determined using fast Fourier transform (FFT) processing of its output voltage when it is subjected to a step electric field with a rise time of less than 300 ps. Provided the step response of the sensor is relatively short, the absorbing termination of the GTEM cell can be dispensed with, simplifying its construction. The need for impedance matching at the cell input can be eliminated by using a signal source that absorbs the reflected energy. In addition, the use of a wire septum offers the potential for improving field uniformity. A description of the measurement system is given, and some typical results are presented.
109 citations
TL;DR: In this article, the authors showed that TiO2 nanoparticles can accelerate the charge dissipation rate and uniform the electric field and increase the shallow trap density in the ester-based nanofluid.
Abstract: In order to improve dielectric performance of natural esters, TiO2 semiconductive nanoparticles were added to obtain an ester-based nanofluid. AC, lightning impulse voltage and partial discharge tests were applied to the natural ester and the ester-based nanofluid to check their dielectric performances. It was found that TiO2 nanoparticles can not only enhance AC breakdown voltage of the ester based nanofluid by a factor of 1.3 but also improve the partial discharge properties of the ester based nanofluid compared to that of the natural ester. Pulse electroacoustic (PEA) and thermally stimulated current (TSC) techniques were applied to investigate charge transport and trap characteristic in natural ester and ester-based nanofluid. It reveals that TiO2 nanoparticles can accelerate the charge dissipation rate and uniform the electric field and increase the shallow trap density in the ester-based nanofluid. It is proposed that electron trapping and de-trapping processes in the shallow traps could be one of the main charge transport processes in the ester based nanofluid.
93 citations
"Investigation on flow electrificati..." refers background in this paper
...In the present study, the performance of an insulation medium comprising titanium dioxide (TiO2) nanoparticles dispersed in ester oil was investigated due to indications of its excellent dielectric properties and improved breakdown voltage [2]....
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Abstract: Transformer oil-based nanofluids have unexpected and distinctive dielectric properties that are different from properties of constituting components. This is believed to be attributed to the effect of interfacial zone between oil and nanoparticles. Accordingly, this paper aims to investigate the role through which the interfacial zone affects the dielectric properties of transformer oil-based nanofluids. Oil-based nanofluids are prepared with two different types of nanoparticles having different surface charging polarity. These types are alumina (Al 2 O 3 ) nanoparticles with cationic surface and titania (TiO 2 ) nanoparticles with anionic surface. For each type of nanoparticles, two groups are prepared with and without a surface modifier, which is called surfactant. Each group consists of four samples having nanoparticles weight fractions of 0.01, 0.04, 0.07 and 0.1 g/L. Surfactant is chosen with charge opposite to that of nanoparticle surface charge to be adsorbed on the nanoparticle surface. For each nanofluid sample, surfactant is distributed through the oil using magnetic stirrer, and then, nanoparticles are mixed and homogenized using magnetic stirrer and ultrasonic processing. After preparation, dielectric properties including breakdown strength and dielectric constant are measured. Based on the obtained results, the role of interfacial zone could be clarified in conjunction to that developed in solid nanodielectrics.
83 citations
"Investigation on flow electrificati..." refers methods in this paper
...Next, the BTA charge suppressant was added and mixed with the magnetic stirrer and the resulting colloidal solution was sonicated for 3 hours using a Sonics Vibra-cell sonicator (500 W, 20 kHz) at 40°C and placed in a vacuum desiccator for 2 hours [8]....
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