Electrical Conductivity Of Nanofluids Research Articles

Electrical conductivity of nanofluids with single- and multi-walled carbon nanotubes. Experimental study

The object of this paper is to experimental study the electrical conductivity of nanofluids with carbon nanotubes (CNT). Nanofluids based on water, ethylene glycol and isopropyl alcohol with single-walled (SWCNT) and multi-walled (MWCNT) carbon nanotubes are considered. In some cases, surfactants were used to prepare the nanofluid. CNT concentrations varied from 0.05% to 1%. It was shown that the electrical conductivity of all nanofluids much more than that of base fluids. The influence of surfactants on the electrical conductivity of nanofluids is studied and analyzed. The use of surfactants in all cases increases the electrical conductivity of the initial base fluids. The greatest excess of the electrical conductivity was achieved when using ionic surfactants. For the first time, the electrical conductivity of nanofluids with SWCNTs and MWCNTs is systematically compared. The same base fluids are used for this. It was shown that electrical conductivity of nanofluids with SWCNTs significantly exceeds that of nanofluids with MWCNTs. The effect of aspect ratio on electrical conductivity of nanofluids with SWCNTs and MWCNTs are studied. In conclusion, the possible mechanisms of electrical conductivity of the considered nanofluids are discussed.

Exploring the role of biopolymers and surfactants on the electrical conductivity of water-based CuO, Fe3O4, and hybrid nanofluids

The research on the application of nanofluids in the thermal management of electric components is gaining widespread attention. In this context, and as past studies on nanofluids mainly focus on thermal properties, the investigation of the electrical properties of nanofluids has become important. The role of dispersants on the electrical conductivity of nanofluids stabilized using two biopolymer dispersants, chitosan, and gum arabica (GA), and a synthetic dispersant Sodium Dodecyl Benzoic Sulfate (SDBS) is investigated in this work. The nanofluids are prepared with water, nanoparticles (0.1 wt%), and dispersants (0.05 and 0.5 wt%), and the electrical conductivity is measured to examine the role of nanoparticle materials (CuO, Fe3O4, and CuO + Fe3O4), dispersants, and temperatures (25–40 °C). According to observations, the dispersants significantly affect the electrical conductivity, while nanoparticle material has a minimal impact. At 0.5 wt% concentration, SDBS stabilized nanofluids have electrical conductivity 708.7 times higher than water, whereas, with chitosan and GA, it is 144.2 and 12.8 times higher than water, respectively. CuO-water nanofluids show relatively higher electrical conductivity than Fe3O4 and hybrid CuO + Fe3O4 water nanofluids. Measured electrical conductivity is used for regression analysis using response surface methodology (RSM). Three quadratic nonlinear polynomial equations are developed to predict the electrical conductivity based on the input parameters (dispersant concentration and temperature). The predicted and measured values were in excellent agreement with each other. The current study offers a novel perspective on the electrical behavior of nanofluids with biopolymer dispersants and provides a prediction model for nanofluid electrical conductivity.

Effects of ultasonication and surfactant on the thermal and electrical conductivity of water – Solar glycol mixture based Al2O3 nanofluids for solar-thermal applications

The present experimental work aims to prepare nanofluid using Al2O3 nanomaterials as dispersant into a solar glycol (SG) – water mixture (80:20) and investigate its stability, density, thermal conductivity, electrical conductivity, and viscosity at three differing volume percentages, namely 0.15, 0.3, and 0.45. Oleic acid (OA) was used as a surfactant to increase the stability of the nanofluid. The concentrations of Al2O3 and OA used were, 0.15, 0.3, 0.45 vol%, and 2 ml, 3 ml, 5 ml, and 10 ml, respectively, while the ultasonication time was varied between 30 and 70 min. The stability of the prepared nanofluid was confirmed using the UV–Vis spectrometer, zeta potential, and by visual inspection. The Al2O3–SG/water-mixture-based nanofluids thermal conductivity was augmented by 26.36% at 0.45 vol% and 30 °C, within ± 5% deviation error. The dynamic viscosity of the Al2O3-based nanofluids was increased by ∼ 1.85 times compared to the SG-water mixture at 0.45 vol%. At 0.45 vol% of Al2O3 with 5 ml of OA, the nanofluid electrical conductivity was enhanced by 87.87% at a temperature of 50 °C, within ± 5% deviation error. The enhancement coefficient ratio increases with an increase in volume concentration and a reduction in temperature. It is concluded that the highly stable conductive nanofluid with excellent thermo-physical properties would be helpful to improve the overall performance and energy efficiency solar-thermal units.

Thermodynamical analysis for mixed convective peristaltic motion of silver-water nanoliquid having temperature dependent electrical conductivity

The development of advanced-performance thermal frameworks for increased heat transport has proved to be of remarkable interest these days. Therefore, present attempt is intended to deal with entropy generation and heat transfer analysis for the peristaltic flow of an electrically conducting silver-water nanoliquid through a symmetric channel. System is supposed to be affected by an external magnetic field and electrical conductivity of nanofluid is considered to vary with temperature. Mixed convection, joule heating aspects along with thermal and velocity slip conditions are considered in analysis. Two phase model of nanofluids is adopted. Mathematical modeling for entropy generation is carried out via second law of thermodynamics. Making use of numerical solver NDSolve, graphical analysis for entropy generation, heat transfer, Bejan number and velocity is presented. Results reveal that by enhancing electrical conductivity parameter entropy generation increases. It is further deduced that entropy generation can be minimized by addition of silver nanoparticles. Bejan number increases by increasing Grashoff number. For large values of Hartman number temperature increases. Temperature of nanofluid increases by enhancing thermal slip parameter. Increase in Grashoff number provides better rate of heat transport at the boundary. Moreover, velocity decreases by enhancing velocity slip parameter.

Experimental Studies on Thermophysical and Electrical Properties of Graphene–Transformer Oil Nanofluid

The thermophysical and electrical properties of graphene–transformer oil nanofluid at three weight percentage concentrations (0.01%, 0.03%, and 0.05%) were experimentally studied. Experiments conducted to find viscosity, surface tension, density, specific resistance, electrical conductivity, and dielectric dissipation at various temperatures ranging from 20 °C to 90 °C. It was noted that the nanofluid with 0.05% concentration showed an enhancement of 2.5% and 16.6% for density and viscosity, respectively, when compared to transformer oil. In addition, an average reduction in surface tension is noted to be 10.1% for the maximum concentration of nanofluid. Increase in heat load and concentration improves Brownian motion and decreases the cohesive force between these particles, which results in a reduction in surface tension and increases the heat-transfer rate compared to transformer oil. In addition, for the maximum concentration of nanoparticles, the electrical conductivity of nanofluid was observed to be 3.76 times higher than that of the transformer oil at 90 °C. The addition of nanoparticles in the transformer oil decreases the specific resistance and improves the electrical conductivity thereby enhancing the breakdown voltage. Moreover, the thermophysics responsible for the improvement in thermophysical and electrical properties are discussed clearly, which will be highly useful for the design of power transmission/distribution systems.

Review on the electrical conductivity of nanofluids: Recent developments

This review paper focuses on the recent developments in theoretical and experimental research studies carried out to examine the electrical conductivity of different types of nanofluids. Based on it, various parameters that affect the electrical conductivity of nanofluids, namely the structure/shape and size of nanomaterials, temperature, preparation methods, instruments, surfactant, and volume concentration has been studied. It was found that the rise in volume fraction and the temperature of nanomaterials generally led to increment in electrical conductivity of all nanofluids.

A Review on Electrical Conductivity of Nanoparticle-Enhanced Fluids.

This review discusses exclusively the recent research on electrical conductivity of nanofluids, correlations and mechanisms and aims to make an important step to fully understand the nanofluids behavior. Research on nanoparticle-enhanced fluids’ electrical conductivity is at its beginning at this moment and the augmentation mechanisms are not fully understood. Basically, the mechanisms for increasing the electrical conductivity are described as electric double layer influence and increased particles’ conductance. Another idea that has resulted from this review is that the stability of nanofluids can be described with the help of electrical conductivity tests, but more coordinated research is needed. The purpose of this article is not only to describe the aforementioned studies, but also to fully understand nanofluids’ behavior, and to assess and relate several experimental results on electrical conductivity. Concluding, this analysis has shown that a lot of research work is needed in the field of nanofluids’ electrical characterization and specific applications.

A comprehensive presentation on nanoparticles electrical conductivity of nanofluids: Statistical study concerned effects of temperature, nanoparticles type and solid volume concentration

In this paper, the effect of base fluid, temperature, solid volume concentration and nanoparticle type on electrical conductivity of nanofluid is reviewed for the first time. The work involves discussing the effect of base fluid, temperature, solid volume concentration and nanoparticle type on electrical conductivity of nanofluid among academic analysis of recent studies. The achievements imply that the electrical conductivity generally increases as temperature and solid volume fraction increases. Moreover it should be mentioned that the influence of temperature improvement is not as effective as the nanoparticles concentrations.

Electrical Conductivity of New Nanoparticle Enhanced Fluids: An Experimental Study.

In this research, the electrical conductivity of simple and hybrid nanofluids containing Al2O3, TiO2 and SiO2 nanoparticles and water as the base fluid was experimentally studied at ambient temperature and with temperature variation in the range of 20–60 °C. A comparison of the experimental data with existing theoretical models demonstrated that the theoretical models under-predict the experimental data. Consequently, several correlations were developed for nanofluid electrical conductivity estimation in relation to temperature and volume concentration. The electrical conductivity of both simple and hybrid nanofluids increased linearly with both volume concentration and temperature upsurge. More precisely, by adding nanoparticles to water, the electrical conductivity increased from 11 times up to 58 times for both simple and hybrid nanofluids, with the maximum values being attained for the 3% volume concentration. Plus, a three-dimensional regression analysis was performed to correlate the electrical conductivity with temperature and volume fraction of the titania and silica nanofluids. The thermo-electrical conductivity ratio has been calculated based on electrical conductivity experimental results and previously determined thermal conductivity. Very low figures were noticed. Concluding, one may affirm that further experimental work is needed to completely elucidate the behavior of nanofluids in terms of electrical conductivity.

Chemical Treatment and Dispersant Characteristics of CNTs Particle and its Applications on Nanofluid

The present study aimed to evaluate simple, efficient approach to improve dispersion and electrical conductivity of nanofluid. In this study, chemical treatment and dispersion technique used to develop the dispersion and electrical conductivity of MWCNTs in aqueous. The surface of MWCNTs was modified by chemical oxidation with potassium persulfate/sodium hydroxide (K2S2O8/NaOH) to achieve more hydrophilic MWCNTs. NC (nanoCellulose) used as the dispersion for nanofluid. As a result, dispersion characteristics examined by UV-Visible spectrophotometer revealed that best dispersion of MWCNTs obtained for chemically modified MWCNTs with K2S2O8/NaOH. From the electrical conductivity measurement, chemically treated MWCNTs with dispersant showed highest conductivity 210μS/cm. With the overall results, chemical treatment and dispersion method can play significant role in improving the dispersion and electrical conductivity of MWCNTs nanofluids.

Effect of Ceramic Nanoparticles on Nanofluids Electrical Conductivity

In this study, an extensive experimental evaluation is conducted on the electrical conductivity of water based nanofluids containing three types of ceramic nanoparticles of (Al2O3, CuO and ZrO2) with different nanoparticles concentrations of (0.05, 0.1, 0.15 and 0.2 vol. %) and for various temperatures ranged by (20-80 °C) by using deionized water as a base fluid. The nanofluids volume (water/nanoparticles) is used at (200 ml). The nanofluid sample mixes slowly by stirring and ultrasonic vibration sonicator with power of (50 W) for a maximum time of (15-20 minutes) to break up any particle aggregates with no any surfactant that is added into the nanofluids to avoid reunion. The electrical conductivity of nanofluids is measured by electrical conductivity meter. Results indicate that the effect of solution temperature on the nanofluids electrical conductivity has little effect in the range of 20–40 °C, but the effect of temperature is increased in the temperature range of 40–80 °C. Also, the percent of electrical conductivity enhancement is 80%, 75% and 50 % when using the nanofluids of CuO, Al2O3 and ZrO2 respectively. Finally, the theoretical model of Maxwell is used to compare with the present experimental results and it gives an agreements.

Magnetic and electrical conductivity studies of zinc doped cobalt ferrite nanofluids

To synthesize stable nanofluids of zinc-doped cobalt ferrite (ZnxCo(1-x)Fe2O4) with various dopant concentrations (x = 0, 0.1, 0.2, 0.3 and 0.4), a two-step method is adopted. X-ray diffraction pattern was used to confirm the phase purity of the ferrite whereas EDAX analysis was performed to determine the chemical composition. The magnetic studies performed on the samples reveal that they show monodomain structure and superparamagnetic nature. The electrical conductivity of the undoped and zinc doped cobalt ferrite nanoparticles is studied and is explained through hopping mechanism. The electrical conductivity of all the nanofluids is higher than that of water, the base fluid, due to the formation of electrical double layer (EDL) in the dispersion. An increase of 90% in electrical conductivity is reported in the Zn0.2Co0.8Fe2O4 sample at room temperature compared to base fluid, which is due to higher surface charge and zeta potential. The effect of temperature on electrical conductivity of nanofluids is elucidated using percolation effect of ferrite nanoparticles in the base fluid. Also, it is noted that magnetic field has no effect over the formation of EDL, and hence, there is no change in electrical conductivity with respect to applied field. The experimental values are compared with Maxwell and Shen's models, which are found compactible with the framework of Shen's model.

Free convection of copper–water nanofluid in a porous gap between hot rectangular cylinder and cold circular cylinder under the effect of inclined magnetic field

Natural convection heat transfer of copper–water nanofluid in a porous gap between hot internal rectangular cylinder and cold external circular cylinder under the effect of inclined uniform magnetic field has been investigated. Domain of interest is a porous sector, where horizontal and vertical adiabatic borders are the external circular cylinder radii. Governing equations formulated in dimensionless stream function, vorticity and temperature variables using the Brinkman-extended Darcy model for the porous medium, single-phase nanofluid model with Brinkman correlation for the nanofluid viscosity and Hamilton and Crosser model for the nanofluid thermal conductivity have been solved numerically by the control volume finite element method. Effects of the Rayleigh number, Hartmann number, Darcy number, magnetic field inclination angle, nanoparticles volume fraction, nanoparticles shape factor, nanoparticles material, nanofluid thermal conductivity and dynamic viscosity models and nanofluid electrical conductivity correlation on streamlines, isotherms, local and average Nusselt numbers have been studied. Obtained results have shown the heat transfer enhancement with the Rayleigh number, Darcy number, nanoparticles volume fraction and nanoparticles shape factor, while the heat transfer rate reduces with the Hartmann number and magnetic field inclination angle. At the same time, the average Nusselt number increases at about 16% when nanoparticles volume fraction rises from 0 till 4% for Ra = 105, Ha = 25, while for Ha = 0 one can find the heat transfer rate augmentation at about 9% for the same conditions. In the case of different nanofluid thermal conductivity and dynamic viscosity models, it has been found that KKL model reflects the heat transfer rate reduction with nanoparticles volume fraction, while for the Hamilton–Crosser–Brinkman model, the heat transfer rate increases. Comparison between the Maxwell correlation for the nanofluid electrical conductivity and the base fluid electrical conductivity illustrates an intensification of the convective heat transfer rate for high values of the Rayleigh number (Ra ≥ 104) in the case of Maxwell correlation for the nanofluid electrical conductivity. At the same time, the effect of the nanoparticles volume fraction becomes more significant when nanofluid electrical conductivity is a function of nanoparticles volume fraction.

Experimental study on thermal conductivity and electrical conductivity of diesel oil-based nanofluids of graphene nanoplatelets and carbon nanotubes

In this study the performance of diesel oil using carbon-based nano additives evaluated. Since carbon nanostructures are unstable in diesel oil (DO), covalent and noncovalent bonds can solve this challenge to a large extent. Here, nanoparticles containing graphene nanoplatelets (GNP) as well as multi-walled carbon nanotubes (MWCNT) in the form of non-covalent with surfactant oleic acid (OA) and covalent with hexylamine (HA) have been synthesized and their thermal and electrical conductivity have investigated in the laboratory. For this purpose, individually, GNP and MWCNT are functionalized with hexylamine. Then, nanofluids include HA-GNP/DO, HA-MWCNT/DO, OA-GNP/DO, OA-MWCNT/DO and a hybrid of OA-GNP and MWCNT/DO at weight concentrations of 0.05%, 0.1%, 0.2%, and 0.5% were synthesized. The thermal conductivity and electrical conductivity of above suspensions, were studied at temperatures of 5 °C to 100 °C. The results showed increasing in thermal conductivity and electrical conductivity of all nanofluids in all weight concentrations compared to the pure diesel oil at the constant temperature. In addition, with increasing temperature, thermal conductivity and electrical conductivity increased for all weight concentrations.

Tuning the electrical conductivity of exfoliated graphite nanosheets nanofluids by surface functionalization.

The electrical conductivity of exfoliated graphite in water nanofluids has been experimentally determined, and compared with the same property when the dispersed nanosheets have been oxidized. The effect of oxidation on this property is different if compared with the case of sintered dry nanosheets. In any case, for the sintered raw material the conduction behaves as expected in a metal, while for the nanofluid it shows values and trends typical of a weak electrolyte solution. The effect of oxidation on the electrical conductivity of exfoliated graphite can be explained as being caused by the dissociation in the fluid phase of the moieties resulting from the chemical functionalization process. This opens the possibility of designing a functionalization process to tune the nanofluid electrical conductivity.

Effect of Polymeric Additives on Thermal and Electrical Conductivity of Nanofluids

Effect of Polymeric Additives on Thermal and Electrical Conductivity of Nanofluids

Методы управления свойствами углеводородных жидкостей в задачах обеспечения пожарной безопасности

When assessing the level of fire danger of technological process it is necessary to consider the rate of evaporation of the combustible substances and materials, the expiration settings for liquids and gases, concentrated limits of flame propagation for the combustible mixtures in technological devices and equipment. There are presented the Raman spectra of multilayer carbon nanotubes (CNT) used in the experiments. It’s demonstrated reorientation of multiwalled carbon nanotubes external influence variable frequency-modulated potential by atomic force microscopy, that eliminates one of the causes of physical and chemical anisotropy in nanofluids system. The electrical conductivity nanofluids of ethanol-based with multilayer carbon nanotubes increases by 2.5 times by increasing the concentration of CNTs, their functionalization and increasing defects. Presumably the electrical conductivity of nanofluids with low volume fraction of CNTs has a percolation nature, according to which the nanotubes in conjunction with each other to form a base fluid system of conducting channels. In conditions at low content of small orientational ordering additive increases the conductivity. The expiration time of the liquid hydrocarbon with multiwalled nanotubes is increased by 20-35 % with an increase in the CNT concentration. The rate of change of pressure in the saturated ethanol vapor modifications multiwall carbon nanotubes and subjected to the influence of the frequency-modulated potential during the first 15 minutes decreases in average 1.5 times. The rate of weight loss is significantly reduced, which increases fire protection fluid with additives CNT. The mass of evaporated nanofluids with ethanol-based multilayer CNT generally decreased by 30-60 % compared to the base fluid that causes nanofluids stability to thermal degradation index and determines the rheological properties. The mechanism controlling the properties of nanofluids depends on the physical properties of fluid and nanoparticles, as well as the parameters of external influence. The development of nanotechnology methods of controlling the properties of hydrocarbon liquids (creation bottom with adjustable parameters of nanoparticles and chemical free option) will allow you to solve a number of tasks to ensure fire safety in the storage and transportation of flammable liquids and combustible liquids.

Synthesis and experimental investigation of the electrical conductivity of water based magnetite nanofluids

In this study, magnetite, Fe3O4, nanoparticles were synthesized by chemical co-precipitation technique at different conditions. The products were characterized using X-ray diffraction, transmission electronic microscopy, and Fourier transform infrared spectroscopy. The electrical conductivity of nanofluids was nvestigated at different volume fractions and temperatures. Experimental measurements indicated considerable enhancement of electrical conductivity of Fe3O4 nanofluids with increase in both volume fraction and temperature under our experimental conditions. The results were compared with Shen's model, an electrical conductivity model previously developed for nanofluids. Survey results indicated that this model is largely able to explain the mechanism of Fe3O4 nanofluid electrical conductivity especially at low concentrations.

Experimental Investigation of Thermal Conductivity and Electrical Conductivity of Al2O3 Nanofluid in Water - Ethylene Glycol Mixture for Proton Exchange Membrane Fuel Cell Application

Nanofluid is an alternative promising cooling liquid with superior performance characteristic compared to conventional cooling liquid for Proton Exchange Membrane fuel cell (PEMFC). In this paper, new findings on ratio of thermal conductivities and electrical conductivities of nanofluids in water: ethylene glycol (EG) mixtures are established. Thermal conductivities and electrical conductivities of base fluids which are water: EG mixtures with concentration ranging from 0 % ethylene glycol up to 100 % ethylene glycol were measured. These base fluids are then dispersed with Al2O3 at 0.1, 0.3 and 0.5 % of volume concentration and thermal conductivities and electrical conductivities are then measured at temperature of 20°C. The result demonstrates that thermal conductivities reduced as the EG content percentage increases in the water: EG mixture. Thermal conductivities for 0.5 % volume concentration of Al2O3 is 0.6478W/m.K and 0.2816W/m.K for 0 and 100 % EG content in water: EG mixture. However, at a specific EG percentage, thermal conductivities also increased as a function of volume concentration. Electrical conductivities measured in 0.1, 0.3 and 0.5 % volume concentration of Al2O3 in base fluid also observed to decrease as the EG concentration increased even though the base fluids’ electrical conductivity behave differently. Thermo-electrical conductivity ratio (TEC) has also been established based on both thermal and electrical conductivity findings.

Preparation, characterization, viscosity, and thermal conductivity of nitrogen-doped graphene aqueous nanofluids

Nanofluids perform a crucial role in the development of newer technologies ideal for industrial purposes. In this study, Nitrogen-doped graphene (NDG) nanofluids, with varying concentrations of nanoparticles (0.01, 0.02, 0.04, and 0.06 wt%) were prepared using the two-step method in a 0.025 wt% Triton X-100 (as a surfactant) aqueous solution as a base. Stability, zeta potential, thermal conductivity, viscosity, specific heat, and electrical conductivity of nanofluids containing NDG particles were studied. The stability of the nanofluids was investigated by UV–vis over a time span of 6 months and concentrations remain relatively constant while the maximum relative concentration reduction was 20 %. The thermal conductivity of nanofluids was increased with the particle concentration and temperature, while the maximum enhancement was about 36.78 % for a nanoparticle loading of 0.06 wt%. These experimental results compared with some theoretical models including Maxwell and Nan’s models and observed a good agreement between Nan’s model and the experimental results. Study of the rheological properties of NDG nanofluids reveals that it followed the Newtonian behaviors, where viscosity decreased linearly with the rise of temperature. It has been observed that the specific heat of NDG nanofluid reduced gradually with the increase of concentration of nanoparticles and temperature. The electrical conductivity of the NDG nanofluids enhanced significantly due to the dispersion of NDG in the base fluid. This novel type of fluids demonstrates an outstanding potential for use as innovative heat transfer fluids in medium-temperature systems such as solar collectors.