Nanofluid Samples Research Articles

Effect of particle size on SiO2 nanofluid viscosity determined by a two-step method

AbstractAccording to review of the literature, the influence of nanoparticle diameter with irregular shapes on viscosity requires further research since there is no relation between particle size and nanofluid stability. In this study, SiO2/EG–water-based nanofluid samples were prepared, and their viscosities were experimentally determined. SiO2 nanoparticles had sizes of 7, 15, and 40 nm, and the base fluid was a 50% ethylene glycol and 50% water mixture. Nanofluid samples were prepared using a two-step technique. Viscosity change was measured every 10 °C from 20 to 60 °C. The maximum viscosity values were observed for 7, 15, and 40 nm particles over an entire concentration range. Considering all measurements, the highest viscosity increase was 60.51% for 3% SiO2 (7 nm) at 60 °C, and the lowest viscosity change was 7.72% for 1% SiO2 (40 nm) at 40 °C. The most stable sample of the current study was 1% SiO2 (15 nm), and its Zeta potential was − 35.6 mV. Finally, a new empirical equation that included temperature, particle diameter, and concentration terms is suggested to predict dynamic viscosity, with R adj 2 = 0.98. It was also compared with previous correlations.

Comparison between pool boiling system of graphene quantum dots and nitrogen-doped graphene quantum dots suspended in binary base fluids

Using nanofluids instead of conventional heat transfer fluids as a passive method is a well-established and widely used technique by researchers to increase the rate and thermal performance of engineering equipment. In this study, the hydrothermal method with a bottom-up approach was used for the synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots. Then, nanofluid samples were prepared in a two-step process, by adding nanoparticles to binary base fluids of deionized water and ethylene glycol in volume concentrations of (50:50) and (60:40), in four concentrations of 100, 200, 500, and 1000 ppm. In order to better understand the boiling heat transfer mechanism and measure its characteristics such as critical heat flux and heat transfer coefficient, an experimental system was designed and built. Nanofluids based on graphene quantum dots have unique features such as compatibility with the environment, economic efficiency, high stability and suitable heat transfer capability. For this reason, their selection in the pool boiling heat transfer process, in addition to saving energy, is introduced as one of the most effective options for improving CHF and HTC. The tests were performed under saturated conditions, atmospheric pressure, and on a vertical flat and polished copper thermal plate. Prepared nanofluids GQDs and N: GQDs based on DI-water maintained their apparent stability for two months. For GQDs nanofluids at an optimal concentration of 500 ppm with a volume ratio of (60:40) DI-water and EG, compared to DI-water, the greatest increase in CHF and HTC is 90.69, 85.011 % and for N: GQDs at a concentration of 500 with a volume ratio (50:50) DI-water and EG, 75.37 and 78.17 % compared to DI-water.

Experimental and statistical investigation on the dielectric breakdown of magneto nanofluids for power applications

The insulating oil serves the dual purpose of providing insulation and cooling within transformers. This investigation aims to explore the impact of various nanoparticles on the dielectric breakdown voltage (BDV) of dielectric oils. The study examines the effect of the concentration of magnetic nanoparticles on the dielectric breakdown voltage of insulating oils. Nanoparticles such as iron (II, III) oxide (Fe3O4), cobalt (II, III) oxide (CO3O4), and ferrous phosphide (Fe3P) were utilized to create nanofluids with carrier mediums consisting of mineral oil and synthetic ester oil. BDV determination was conducted using a VDE and S–S electrode system according to IEC 60156 standards. Nanofluid were prepared using a two-step method, and their concentrations ranged from 0.01 g/L, 0.02 g/L, and 0.04 g/L in base oils. Twelve iterations were conducted for each prepared nanofluid, and breakdown voltage measurements were recorded. The results indicate a noteworthy enhancement in the breakdown voltage of nanofluids. The statistical analysis was performed on the dielectric property of nanofluid samples for better breakdown accuracy. The maximum enhancement at specific nanoparticle concentrations was shown by each nanofluid. The results show that under the S–S electrode configuration, the greatest overall enhancement was observed for Fe3P in mineral oil, with an enhancement of 70.05%, and Fe3O4 in synthetic ester oil, with an enhancement of 46.29%.

Nanofluidic Platform for Studying the First-Order Phase Transitions in Superfluid Helium-3

The symmetry-breaking first-order phase transition between superfluid phases 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He-A and 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He-B can be triggered extrinsically by ionising radiation or heterogeneous nucleation arising from the details of the sample cell construction. However, the role of potential homogeneous intrinsic nucleation mechanisms remains elusive. Discovering and resolving the intrinsic processes may have cosmological consequences, since an analogous first-order phase transition, and the production of gravitational waves, has been predicted for the very early stages of the expanding Universe in many extensions of the Standard Model of particle physics. Here we introduce a new approach for probing the phase transition in superfluid 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He. The setup consists of a novel stepped-height nanofluidic sample container with close to atomically smooth walls. The 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He is confined in five tiny nanofabricated volumes and assayed non-invasively by NMR. Tuning of the state of 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He by confinement is used to isolate each of these five volumes so that the phase transitions in them can occur independently and free from any obvious sources of heterogeneous nucleation. The small volumes also ensure that the transitions triggered by ionising radiation are strongly suppressed. Here we present the preliminary measurements using this setup, showing both strong supercooling of 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He-A and superheating of 3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}He-B, with stochastic processes dominating the phase transitions between the two. The objective is to study the nucleation as a function of temperature and pressure over the full phase diagram, to both better test the proposed extrinsic mechanisms and seek potential parallel intrinsic mechanisms.

Characterization of TiO2 nanoparticles for nanomaterial applications: Crystallite size, microstrain and phase analysis using multiple techniques

This study aimed to verify the suitability of TiO2 nanoparticles as nanomaterials in terms of crystallite size, microstrain and phase. The TiO2 nanoparticles were tested experimentally in suspensions of mono ethylene glycol and distilled water (MEG-DW) at ratios of 10:90, 25:75, and 40:60. The nanoparticles were dispersed in the base liquid via a two-step process, resulting in the formation of TiO2-3%/MEG-10, TiO2-3%/MEG-25, and TiO2-3%/MEG-40 nanofluids. The results revealed average crystallite sizes of approximately 20.10, 22.10, and 39.6 nm for the three nanofluid samples, as determined by the Scherrer equation, Williamson–Hall (W–H) plot, and TEM-ImageJ software. These results confirm that the TiO2 nanoparticles meet the nanomaterial criteria with a sub-100 nm size. The microstrain analysis yielded values of 0.000020, 0.000299, and 0.001386 for the three samples and further investigation confirmed the presence of rutile. The high-temperature stability of the rutile phase makes the TiO2 nanofluids suitable for use in industrial heating systems.

Experimental investigation of photothermal performance in nanofluid-based direct absorption solar collection for solar-driven water desalination

As the demand for energy continues to rise unabated, an examination of the constraints posed by finite fossil fuel reserves becomes crucial. There is need to explore and underscore the imperative shift towards renewable energy resources, where, solar energy is widely available and can readily be used in different applications, especially in water desalination applications. In the present research, photothermal performance of water based nanofluids containing graphene oxide (GO), zinc oxide (ZnO), iron oxide (FeO), and their composites (GO-ZnO and GO-FeO) have been studied under the natural sun to determine the potential for water desalination applications. All type of the nanofluid are prepared through a two-step method and are characterized morphologically using a scanning electron microscope (SEM). UV–visible spectroscopy is used to assess the optical absorbance of prepared nanofluids. The outcomes of this study show that pure GO nanofluids exhibited excellent absorption in the visible and near-infrared regions as compared to other nanofluids used in this research study, which makes them efficient nanofluids in converting solar energy into heat. For more assessment, a direct or volumetric solar thermal collector was used to evaluate the photothermal efficiency of water based nanofluids GO, ZnO, FeO, and their binary composites of GO-ZnO, and GO-FeO under natural solar flux at weight concentrations (0.01 wt%). The sensible heating efficiency due to the rise in temperature and latent heat of evaporation efficiency due to mass loss of nanofluid samples contributed towards photothermal efficiency. Pure GO nanofluids showed the highest photothermal efficiency, which is 71 % among all the nanofluids used in this study due to their carbon-based structure, highest optical absorption peak, excellent dispersion stability, and highest thermal conductivity. This experimental work also revealed that binary nanofluids containing composites of (GO-ZnO) and (GO-FeO) showed higher photothermal efficiency as compared to individual nanofluids ZnO and FeO except graphene oxide GO. According to the results and observation of this experimental work, pure GO-based nanofluids are potential candidates for direct absorption solar collection used in water desalination applications.

Enhanced Stability, Superior Anti-Corrosive, and Tribological Performance of Al2O3 Water-based Nanofluid Lubricants with Tannic Acid and Carboxymethyl Cellulose over SDBS as Surfactant

In this research work, the stability, tribological, and corrosion properties of a water-based Al2O3 nanofluid (0.5 wt%) formulated with tannin acid (TA) and carboxymethyl cellulose (CMC) as dispersants or surfactants were investigated. For comparative purposes, sodium dodecylbenzene sulfonate (SDBS) was also incorporated. The stability of the nanofluid was assessed through zeta potential measurements and photo-capturing, revealing the effectiveness of TA and CMC in preventing nanoparticle agglomeration. Tribological properties were examined using a pin-on-disk apparatus, highlighting the tribofilm of Al2O3 that enhanced lubricating properties of the nanofluid by the SEM, resulting in reduced friction and wear of the contacting surfaces. Sample with the addition of both TA and CMC exhibited the best tribological performance, with a ~ 20% reduction in the friction coefficient and a 59% improvement in wear rate compared to neat nanofluid without TA and CMC. Additionally, the corrosion resistance of the nanofluids were evaluated via weight loss and electrochemical impedance spectroscopy. The nanofluid sample containing both TA and CMC exhibited the lowest corrosion rate, with 97.6% improvement compared to sample without them. This study provides valuable insights into the potential applications of TA and CMC-based Al2O3 nanofluids as effective and environmentally friendly solutions for coolant or lubrication in cutting processes.

Synthesis of thermal and physical properties of biodegradable hybrid nano fluid using two step method

In the presence of green technology or biodegradable options, vegetable oils emerged as replacements for mineral oil as base oils due to their properties of high viscosity index, high flash point, low toxicity, low volatility, and high biodegradability. Nano fluids were a relatively new class of fluids that consisted of a base fluid with nano-sized particles (1–100 nm) suspended within them. The synthesis and characterization of biodegradable hybrid nano fluids and their combination with base materials were carried out in this paper, playing a vital role in machining operations. SiC and TiO2 were used as nano particles, with the base fluid being palm oil, and sodium dodecyl sulphate (SDS) was employed as a surfactant to maintain fluid stability. All samples were prepared in individual and hybrid modes, including palm oil as the base fluid without any emulsifier/surfactant, palm oil + SiC with nano particle concentrations of 0.1%, 0.2%, and 0.3% by volume, palm oil + TiO2 with nano particle concentrations of 0.1%, 0.2%, and 0.3% by volume, and palm oil + SiC + TiO2 with nano particle concentrations of 0.1%, 0.2%, and 0.3% by volume. The FTIR results showed that the SiC + palm oil and SiC + TiO2 + palm oil samples had better chemical composition and surface characterization as biodegradable hybrid nano fluids. The zeta potential values were observed to increase at volume concentrations of 1%, 2%, and 3%. Particularly, the biodegradable hybrid nano fluid samples (palm oil + 1% Vol. SiC + TiO2) and (palm oil + 2% Vol. SiC) demonstrated increased stability as well as enhanced physical, thermal, and rheological properties in machining applications.

Measurement of electrical conductivity of transformer oil based nanofluid

In this article, an attempt was made to evaluate the electrical conductivity of ananofluid based on transformer oil. For this purpose, several nanofluid samples with different concentrations of dielectric silicon dioxide nanoparticles and conductive zinc nanoparticles were prepared. The dielectric permittivity and electrical conductivity of the obtained nanofluids were measured experimentally. After processing the experimental results, a theoretical calculation was made using the Nielsen formula. After the calculation, the results were compared with the experimental data. In the process of comparative analysis, the correspondence of the calculated and experimental values of the dielectric permittivity was noted. There was also a discrepancy between the experimental and calculated values of electrical conductivity. An explanation is proposed for the discovered discrepancy between the calculated and experimental values. Presumably, the main reason for the decrease in electrical conductivity in the experiment is the adsorption of ion particles in the dielectric.

Enhancing Thermal Performance of Evacuated Tube Solar Collector using Novel Graphene Oxide Nanofluid

The research article investigates the thermal performance of heat pipe-based evacuated tube solar collector (ETSC) experimentally using graphene oxide (GO) and deionised (DI) water as working fluid with a mass flow rate of 0.5 lit/min, 0.75 lit/min, and 1 lit/min. The different volumetric concentrations of 0.001%, 0.002%, and 0.003% graphene oxide nanofluid samples were prepared in the deionised water. The X-ray diffraction (XRD) was used to determine the structural properties of graphene oxide and the morphology of graphene oxide was studied by scanning electron microscope (SEM). To evaluate the stability of nanofluid samples, the Zeta potential analysis was carried out which showed that prepared nanofluid samples remain stable for up to 30 days. The effect of different nanofluid concentrations on various thermo physical properties of nanofluid was studied and discussed. The thermal performance of ETSC was investigated by considering the effect of volumetric concentrations of nanofluid and mass flow rates. According to the findings, there is a significant increment in temperature difference and energy gain by using nanofluid samples, and the maximum thermal efficiency of ETSC was found to be 37.1% for a volumetric concentration of 0.003% at 1 lit/min mass flow rate as compared to water.

Dielectric response of vegetable oil-based nanofluid and impregnated Kraft paper for high voltage transformer insulation

Methyl ester from vegetable oil has been considered a potential replacement for mineral oil used for power transformer cooling and insulating applications. However, some pertinent properties in making this liquid a better transformer oil based on the laydown standards need to be enhanced to maximize the use of this insulating liquid. Technology involving nano-modification can enhance the properties of these ester liquids placing them in a better position as a good alternative. In this study, we aim to investigate the performance of methyl ester liquid from neem seed oil, a non-food grade oil, when modified with SiO2 insulating nanoparticles at several concentrations. Furthermore, Kraft paper compatibility has also been analyzed to observe their compatibility after impregnation. The breakdown strength, temperature-dependent dissipation loss factor, dielectric constant, and viscosity of both pure and nanofluid samples of neem ester liquid have been measured per standard methods. The nanofluid's dielectric performance has been significantly enhanced by the presence of SiO2 nanoparticles according to results obtained from the experiment. For instance, the dielectric dissipation factor at an operating frequency of 60 Hz has been improved by 96%, 89%, and 79% at 30 °C, 50 °C, and 70 °C respectively relative to the base neem liquid. This remarkable improvement has been attributed to the SiO2 nanoparticle's ability to polarize, trap, and de-trap mobile electrons develop in nanofluid when an electric field is applied.

Soft computing approaches for prediction of specific heat capacity of hybrid nanofluids

AbstractNanofluids are thermoelectric substance with a greater thermal transmission effectiveness than traditional thermal fluids. Nanofluid's specific heat capacity (SHC) is a crucial thermophysical parameter since it controls the fluid's heat transfer coefficient. Surprisingly few research investigations have been done on the prognostic modelling of the specific heat capacity of fusion nanofluids, despite the fact that numerous experiments have been conducted on the heat transfer capacitance of blended nanofluids. This study focuses on the use of algorithms based on machine learning procedures (MLP) to estimate the SHC of blended nanofluids. Numerous numbers of hybrid nanofluids are investigated in this investigation. Total of 984 samples of hybrid nanofluids for specific heat capacity has been collected from nine experimental research papers. Various MLP techniques were utilized in this analysis, including extreme boost gradient boost regression (XGB), support vector regression augmented with a genetic algorithm (support vector regression [SVR]‐genetic algorithm [GA]), grid search optimized based gradient boost regression algorithm (GBR) (GBR‐GSO), and voting ensemble procedure (VE). The obtained correlation coefficients of the SVR‐GA, XGB, VE and GBR‐GSO models for the testing dataset are 98.43%, 96.29%, 94.4% and 96.55% respectively. The SVR‐GA model showed a better predictive accuracy relative to other ML models. This SVR‐GA anticipated model could be used for quick and reliable prediction of the SHC of blended nanofluids which reduces the burden associated with experimental measurement possible future work includes applying a machine‐learning strategy to the problem of determining the diffusivity of hybrid nanofluids.

A comprehensive experimental study on thermal conductivity of ZrO2-SiC /DW hybrid nanofluid for practical applications: Characterization, preparation, stability, and developing a new correlation

This study mainly intended to identify changes in the thermal conductivity of distilled water (DW) because of the addition of Zirconium oxide (ZrO2) and Silicon carbide (SiC) nanoparticles. Keeping this in view, the study considered hybrid nanofluid samples developed with the help of ZrO2 (dp: 20 nm)-SiC (dp: 45––60 nm) nanoparticles. Initially, the research involved conducting XRD, TEM, EDX and FESEM tests which allowed for conducting phase and structural analysis and also facilitated the study of nanoparticles’ microstructure. In the next step, a magnetic stirrer and ultrasonic vibrator were used in sequential steps for dispersing and homogenizing Nanomaterials in distilled water. The volume concentration (φ) was kept between 0.025 and 0.1 % during the synthesis of samples. Then the samples were checked to evaluate their thermal conductivity through the transient hot wire method. In this way, the thermal conductivity of all samples was evaluated for temperatures between 20 and 60 °C. The results indicated a positive association of the thermal conductivity of nanofluid with parameters like temperature and solid volume fraction. It was noted that ZrO2-SiC/DW hybrid nanofluid depicted a nearly 25.75 % increase in thermal conductivity at a 0.1 % volume fraction of nanoparticles and a temperature of 60 °C. The value of the thermal conductivity ratio of ZrO2-SiC/DW was determined using the proposed mathematical correlation. The fitting method was applied to experimental data which depicted the R-Square value of 0.9906 which is considerably high. It was found that the proposed equation gave an acceptable value of the maximum margin of deviation (i.e.,1.15 %).

Functionalization and characterization of iron oxide nanoparticles recovered from acid mine drainage and application in the enhanced oil recovery

Oil is one of the most intensively used energy sources in the world and, as a fossil fuel, it is a finite resource. Different methods have been explored to increase oil recovery from mature fields, particularly using enhanced oil recovery (EOR) with the help of nanofluids. This study performed EOR tests using iron oxide nanoparticles added to brine and sodium dodecyl sulfate solutions. Three types of iron oxide nanoparticles were examined: commercial (IO), derived from the acid drainage of an underground coal mine (SIO), and temperature-sensitive functionalized (TSIO). The nanoparticles were well characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, high-resolution X-ray photoelectron spectroscopy, and transmission electron microscopy. The nanofluids were evaluated through dynamic light scattering measurements and determination of the viscosity, turbidity, contact angle and surface tension. There was not significant variation in the surface tension of the samples, which ranged between 25.46 and 28.28 mN m−1. However, the contact angle exhibited notable fluctuations depending on the nanoparticles concentration, ranging from 7.39° to 24.43°. Furthermore, the zeta potential suggests that the stability of the nanofluid samples falls within the moderate to medium range. An improvement in oil recovery reached 10% with the commercial nanoparticles (0.50 wt%), followed by 8.5% using the synthesized (0.25 wt%) and 7.5% using the functionalized (0.25 wt%). Moreover, all nanofluids showed good stability for up to 30 days, and their viscosity showed a direct relationship with the enhancement in oil recovery.

Experimental Investigation on Thermal Conductivity of Palm Oil and Zinc Oxide PFAE-based Nanofluids

Vegetable oil (VO) have been constantly researched as an alternative to the conventional mineral oil (MO) in the application of transformer insulation liquid. VO is deemed as a suitable replacement for MO as they are a renewable source, cheaper in price, and have a high thermal conductivity, high flashpoint, and high breakdown voltage value. In addition, the trending interest in nanofluids has made it possible to further improved the insulating properties of VOs. This paper reports the experimental results of thermal conductivity test of Palm oil-based nanofluids and Palm fatty acid ester (PFAE)-based nanofluids. The nanoparticles used in this work is Zinc Oxide (ZnO) <50nm nano powder and the nanofluid (NF) samples are varied by low, medium and high concentrations. The test was conducted at 9 different temperatures from 25°C to 65°C with 5°C gap. The result shows that a low and medium concentration nanofluid has an improvement in thermal conductivity value, up to 42.6% and 59.5% respectively for palm oil-based nanofluid. Meanwhile, the high concentration palm oil-based nanofluid has lower enhancement in thermal conductivity value at certain temperatures. As for PFAE-based nanofluids, the thermal conductivity value has improved by up to 27% and 14.4% for medium and high concentration respectively. Nanofluids with medium concentration of ZnO, has the highest enhancement in insulating and cooling properties for both palm oil and PFAE-based nanofluids. This observation is supported by the kinematic viscosity value of the mentioned nanofluid.

Analysis of heat transfer performance and thermo-hydraulic characteristics of graphene nanofluids: impact of sedimentation effects

This study investigates the heat transfer performance and thermo-hydraulic characteristics of nanofluids containing graphene nanoparticles in a water and ethylene glycol mixture. Results show that both nanofluid samples, with concentrations of 0.15% and 0.10% by volume, experience increased heat transfer coefficients (h) compared to the base fluid under various operating conditions, with average reductions of approximately 21% and 26%, respectively. Additionally, the nanofluids exhibit higher friction losses and pressure drops compared to the base fluid. The friction factor and head loss increased by 8.7% and 7.7% for the 0.15% concentration sample and 12.7% and 12.4% for the 0.10% concentration sample. These findings indicate that the thermo-hydraulic performance of the nanofluids is unsatisfactory, offering limited advantages over the base fluid. Surprisingly, the sedimentation of nanoparticles in the test section leads to unexpected results. Contrary to typical observations, the higher concentration sample shows a lower head loss. This discrepancy is attributed to nanoparticle sedimentation, increasing friction factors, and pressure drops. The study also examines the thermal conductivity and viscosity of the nanofluids. It is found that even at low concentrations, graphene nanofluids exhibit higher thermal conductivity than the base fluid. The dynamic viscosity slightly increases with concentration, aligning well with theoretical models. Further research is needed to optimize nanofluid performance and address these issues in practical applications.

Comprehensive analysis of dispersion and aggregation morphology of nanoparticles on the thermophysical properties of water-based nanofluids using molecular dynamics simulation

BackgroundIn recent decades, using nanofluids (NFs) to improve the thermal properties of the NFs was widely considered. MethodsIn the current study, molecular dynamics (MD) simulation was used to examine the effects of dispersion and morphology of nanoparticle aggregation (NA), solid volume fraction (SVF), temperature (Temp), nanoparticle size (NS), and nanoparticle shape on the thermal properties of water/Nickel nanofluid (NF). The thermophysical properties of the NFs were simulated and studied using MD simulation, which was a common computational method because of the high cost and limitations of experimental approaches, particularly at molecular dimensions. LAMMPS software package, and the EAM potential function were used to simulate the structure. In the present simulation, three NF samples containing Ni with SVF of 1, 2, and 3% with two shape of spherical (SN) and cylindrical (CN) and in two different Temp of 313 to 358 K were considered. Also, the nanoparticles (NPs) with the radii of 8, 10, and 12 Å were considered in the simulation box. The results show that by increasing Temp and SVF, the diffusion coefficient (Dnf) of NFs would increase and decrease, respectively. From a numerical point of view, by increasing Temp from 313 K to358 K in 1% SVF, thermal conductivity (knf) and Dnf increased from 0.25656 to 0.99688 W/mK and 0.34786075 to 0.68396948, respectively. Moreover, by increasing SVF and T, the viscosity (µnf) of NF increased and decreased, respectively. Significant findingsAs the radius of NPs increased, the Dnf of the water-based NFs increased. This is because larger NPs can provide more surface area for water molecules to interact with, which can increase the overall mobility of water molecules and enhance the Dnf. Also, the µnf decreased. This is because larger NPs can reduce the overall µnf of the NF by increasing the mobility of water molecules and reducing the degree of hydrogen bonding between water molecules. Besides, NFs containing CN had a lower Dnf than NFs created by SN. On the other hand, suspensions containing CN had a greater µnf and knf.

Effects of PVP surfactant on nanosuspension stability and optical, dielectric, and rheological properties of zinc oxide nanoparticles dispersed alcohols mixture based nanofluids

Nanofluids (NFs) are state-of-the-art engineered promising properties soft materials which found vital applications in thermal management and electrical insulation, and also gaining much attention in the advances of soft optoelectronic and microelectronic device technologies. The longer-time functionality of the NF material depends on particle suspension stability which can be maintained up to some extent with the addition of appropriate surfactants. Here, we report the promising properties of the semiconductor NF (SNF) samples consisting of a highly rich ethylene glycol (EG) mixture with glycerol (Gly) (90/10 vol%) as base fluid, zinc oxide (ZnO) nanosuspension, and poly(vinyl pyrrolidone) (PVP) surfactant. These formulated 90EG + 10Gly/x wt% (ZnO + PVP) SNFs with varying concentrations (x wt%) of ZnO and PVP are characterized by employing ultraviolet-visible (UV–Vis) spectrophotometer (wavelength range 200–800 nm), precision inductance-capacitance-resistance (LCR) meter (frequency range 50 Hz to 1 MHz), and rotational rheometer (shear rate range 13–132 s−1). The UV–Vis absorbance spectra, recorded on the freshly prepared and aged SNF samples, confirmed that the added PVP enhances longer time suspension stability for ZnO nanoparticles in the H-bonded 90EG + 10Gly viscous base fluid, and also promoted the photosensitivity, electronic transition, and radiation blocking performance of these materials. The dielectric spectra revealed a huge contribution of the electrode and interfacial polarization processes to the dielectric permittivity of the SNFs at low frequencies and their dynamics is explored from the intense relaxation peaks observed in the loss angle tangent spectra. The higher experimental frequency range dielectric permittivity remains frequency independent and it is marginally affected by the ZnO and PVP concentrations in these SNFs, at 298.15 K. The electric modulus and impedance spectra of these SNFs are also provided and analyzed for the charge conductivity and interfacial relaxation processes. The ac electrical conductivity of these materials obeys the power law behaviour along with the dc conductivity part in the range from 5.4 to 6.8 × 10–7 S⋅cm−1. The rheological measurements on these SNFs, in the 303.15 K to 323.15 K, categorized them as Newtonian-type fluids with a considerable increase in dynamic viscosity by PVP dissolution. These materials showed the Arrhenius behaviour of viscous flow having activation energies in the range of 25–27 kJ⋅mol−1. The experimental results of various techniques on these green-formulated SNFs revealed their multifunctionality with great potential for the future generation of soft device technologies, in addition to highlighting their current applications of manageable heat transfer in the flow systems.

Experimental and CFD analysis of fluid flow in rectangular strip based micro channel with nano fluid

Comparative analysis is conducted between nano fluid Al2O3 + CuO + H2O and water as basic fluid through simulation technique and validate it through experimental result. The effect of nano fluid (NF) and water were acknowledge which were flowing inside rectangular shape micro channel (RSMC) internally and externally time to time as per decided experiment sets with or without rectangular-strip micro-insert (RSMI), for observing the fluid flow behaviour, heat transfer attributes and performance characteristics. During preparation of nano fluid 0.05% − 0.1% volume fraction (vol.%), 10–20 nm size nano particles (NP) were taken with 0.5–0.75 ml CTAB as surfactant. Experimentation were conducted for diverse operating condition/parameters under counter-flow conditions, where NF is moving inside micro channel of less than 1 mm diameter having flow rate 0.0001562 to 0.006255 kg/sec. Hot fluid as water is moving inside the concentric-tube of 3.6 cm diameter with flow rate of 0.000782 kg/sec. The operating temperature of NF and hot fluid as water were 308 K and 323 K. As per observation, the results of proposed samples of NF with 0.1 vol% showed better performance than 0.05 vol% NF and water. It happens due to higher rate of thermal-conductivity achieved because NF gain extra molecular area with an addition of diverse NP with base fluid, where as better optimum results were observed with an enhancement of 8%-9% in case of RSMC with micro insert (M.I.) compared with other geometric model because high turbulency received due to extra-exposed area of M.I.. A close error percentage near about 4–5% was developed between experimental and simulation work. Thus it validates the present investigation.

Analysis of tool wear and chip morphology under different machining environments in turning operation

A large supply of coolant can raise machining costs and be potentially harmful to the environment. Therefore, other techniques are needed to solve the issues that arise while using coolant. In this study, the effects of cutting speed, feed, depth of cut, and lubrication conditions (dry: no lubrication, cotton seed oil-based nano fluid: alumna is used during machining). The surface roughness and cutting force were investigated during the turning of 304 stainless steels with minimum quantity lubrication (MQL). L9 orthogonal array was used for the experiments. The findings show that dry may be replaced by alumina nanofluids with MQL. In order to assess the machinability of hardened AISI 304 steel, cutting force and surface roughness are taken into account as technological performance criteria. Al2O3 is combined with cotton seed oil for creating nanofluid sample.