Addition Of Hybrid Nanoparticles Research Articles

The effect of adding hybrid nanoparticles (Al2O3–TiO2) on the performance of parabolic trough solar collectors using different thermal oils and molten salts

Enhancing the operational efficiency of parabolic trough solar collector (PTSC) systems is key to the advancement of solar energy technologies that enhance power generation sustainability. In the quest for efficient, environmentally friendly energy sources, solar energy systems have been a major focus of both researchers and industry. Adding hybrid nanoparticles (Al2O3–TiO2) to different base fluids of thermal oil or molten salts and then simulating the PTSC's energetic and exergetic performance is pivotal to efficiency enhancement. The focus of this paper will be on three thermal oils Syltherm-800, Therminol VP-1, and Therminol 75 that are used as base fluids with the addition of hybrid nanoparticles. Molten salts such as Solar Salt, Hitec, and HitecXL, which are considered different base fluid types, are also simulated with the same hybrid nanoparticle combination. The inlet temperature is found to be a determining factor in the choice of the base fluid. Inlet temperatures in the range of 300–650 K for thermal oils with the addition of Al2O3–TiO2 have improved the thermal and exergy efficiency of the PTSC by approximately 0.99 % and 0.59 %, respectively. Therminol VP-1/Al2O3–TiO2 has the highest average thermal efficiency among other thermal oils, with an average percentage of 71.68 %, while Syltherm-800/Al2O3–TiO2 has recorded the highest exergy efficiency of 24.1 %. At higher inlet temperatures above 500 K mixing Al2O3–TiO2 with molten salts has increased both energetic and exergetic PTSC performance by approximately 0.60 %. Solar Salt/Al2O3–TiO2 has the highest average thermal and exergy efficiency of 61.8 % and 36.1 %, respectively.

Influence of nano zirconia on the mechanical and durability properties of high-performance concrete containing nano-silica

High Performance Concrete (HPC) was prepared by reinforcing with hybrid nanoparticles such as nano-SiO2 and nano-ZrO2 and the flowability, strength and durability of the concrete was investigated. Slump study showed that the prepared HPC displayed a slump loss with the addition of hybrid nanoparticles due to the absorption of water by hybrid nanoparticles. Experimental results showed that the inclusion of 10% nano-SiO2 and 5% nano-ZrO2 hybrid nanoparticles (mix code M5) enhanced the compressive strength of concrete and exhibited a maximum of 50.12 MPa and 76.4 MPa at 7 days and 28 days of curing due to the reduction of pore volume. Split tensile strength followed the same trend of variation as compressive strength and the mix code M5 showed the maximum split tensile strength of 5.33 MPa and 7.08 MPa cured at 7 days and 28 days respectively. Flexural study resulted that the mix code M5 exhibited a maximum flexural strength of 5.73 MPa and 7.38 MPa cured at 7 days and 28 days respectively owing to the restriction of crack ignition by reinforced hybrid nanoparticles. Rheological study reported that all the prepared concretes lost the weight by less than 1% and the chloride attack displayed maximum weight loss of 4% whereas alkaline attack showed less weight of concrete.

Natural convection and entropy generation in a trapezoidal region with hybrid nanoliquid under magnetic field

PurposeThis paper aims to study numerically the steady natural convective heat transfer of a hybrid nanosuspension (Ag-MgO/H2O) within a partially heated/cooled trapezoidal region with linear temperature profiles at inclined walls under an effect of uniform Lorentz force. This investigation is useful for researchers studying in the area of cavity flows to know features of the flow structures and nature of hybrid nanofluid characteristics. In addition, a detailed entropy generation analysis has been performed to highlight possible regimes with minimal entropy generation rates.Design/methodology/approachThe governing equations formulated using the Oberbeck–Boussinesq approach and single-phase nanoliquid model are transformed to a non-dimensional form by using non-dimensional variables. The obtained equations with appropriate boundary conditions are resolved by the finite difference technique. The developed code has been validated comprehensively. Analysis has been performed for a wide range of governing parameters, including Rayleigh number (Ra = 105), Prandtl number (Pr = 6.82), Hartmann number (Ha = 0–100), magnetic field inclination angle (φ = 0–?/2) and nanoparticles volume fraction (φhnf = 0 and 2%).FindingsIt has been shown that inclined magnetic field can be used to manage the energy transport performance. An inclusion of nanoparticles without Lorentz force influence allows forming more stable convective regime with descending heat plume in the central zone, while such a regime was performed for clear fluid only for moderate and high Hartmann numbers. Moreover, the average overall entropy generation can be decreased with a growth of the Hartmann number, while an addition of hybrid nanoparticles allows reducing this parameter for Ha = 30 and 50. The average Nusselt number can be increased with a growth of the nanoparticles concentration for low values of the magnetic field intensity.Originality/valueGoverning equations written using the conservation laws and dimensionless non-primitive variables have been resolved by the finite difference approach. The created numerical code has been verified by applying the grid independence test and computational outcomes of other researchers. The comprehensive analysis for various key parameters has been performed.

Thermal analysis of hybrid nanofluid flowing inside the automobile radiator

The demand for high-performance engines has increased as a result of the automobile industry's constant technical improvement. The sustainability of the world requires improving the size and design of automotive radiators to increase their performance. One approach for boosting the cooling rate of the radiator is to employ fins. However, the conventional way of utilising fins to accelerate cooling and tiny channels has hit its limit. In this paper, an analytical study was carried out using water based Al2O3 + Cuo hybrid nanofluid along with ethylene glycol (EG) in a radiator to boost the rate of heat exchange. The concentrations of EG, nanoparticles of Al2O3 and Cuo in base fluid were 30%, 0.1% and 0.1% respectively. A cooling circuit was modelled in ANSYS (version 17) and investigated in the transient regime. The study revealed that the heat transfer rate improves due to the addition of hybrid nanoparticles compared to the base fluid.

Effect of incorporating silica-hydroxyapatite-silver hybrid nanoparticles into the resin-modified glass ionomer on the adhesive remnant index score and shear bond strength of orthodontic metal brackets: An in vitro study

This study aimed to assess the effect of addition of silica-hydroxyapatite-silver (Si-HA-Ag) hybrid nanoparticles to light-cure glass ionomer (GI) on shear bond strength (SBS) of metal brackets bonded with this adhesive and the adhesive remnant index (ARI) score. In this in vitro experimental study, 50 sound extracted premolars were assigned to 5 groups (n=10) for orthodontic metal bracket bonding with BracePaste® composite, Fuji ORTHO™ pure resin modified GI (RMGI), and RMGI reinforced with 2wt%, 5wt% and 10wt% Si-HA-Ag nanoparticles. The SBS of brackets was measured by a universal testing machine. Debonded specimens were inspected under a stereomicroscope at×10 magnification to determine the ARI score. Data were analyzed by one-way ANOVA, Scheffe test, Chi-square test, and Fisher's exact test (alpha=0.05). The maximum mean SBS was recorded in BracePaste® composite followed by 2% RMGI, 0% RMGI, 5% RMGI and 10% RMGI. Only the difference between the BracePaste® composite and 10% RMGI was significant in this regard (P=0.006). The groups were not significantly different regarding the ARI scores (P=0.665). All the SBS values were within the clinically acceptable range. Addition of 2wt% and 5wt% Si-HA-Ag hybrid nanoparticles to RMGI as orthodontic adhesive caused no significant change in SBS of orthodontic metal brackets while addition of 10wt% hybrid nanoparticles significantly decreased the SBS. Nonetheless, all the SBS values were within the clinically acceptable range. Addition of hybrid nanoparticles had no significant effect on the ARI score.

Stability and Thermophysical Properties of GNP-Fe2O3 Hybrid Nanofluid: Effect of Volume Fraction and Temperature

The study focused on the impact of concentration and temperature on the electrical conductivity, viscosity, and thermal conductivity of GNP/Fe2O3 hybrid nanofluids. The study found that nanofluids have better electrical conductivity, viscosity, and thermal conductivity than water. The electrical conductivity and thermal conductivity increase linearly with concentration for a constant temperature. However, the nanofluid's viscosity increases with the addition of the hybrid nanoparticles and decreases as the temperature increases. Furthermore, the study shows that the thermal conductivity of the nanofluid is enhanced with increased addition of hybrid nanoparticles in the base fluid and that the thermal conductivity ratio increases with increased addition of nanoparticles. Overall, the results suggest that GNP/Fe2O3 hybrid nanofluids could be used in various industrial applications to improve the heat transfer and energy efficiency of systems.

Improved heating floor thermal performance by adding PCM microcapsules enhanced by single and hybrid nanoparticles

AbstractA heating floor is a low‐temperature emitter consisting of pipelines in which a fluid circulates between 35°C and 45°C. To ensure energy efficiency, occupant comfort, and building material durability, proper heat management is crucial in buildings. By using phase change materials (PCMs) in building envelopes, the indoor temperature can be regulated through the storage and release of thermal energy, which reduces energy consumption and enhances occupant comfort. In this study, we evaluated numerically a heating floor that incorporates a PCM enhanced by nanoparticles (NePCM). The aim of the numerical analysis is to assess the impact of the addition of single and hybrid nanoparticles in different proportions to the PCM layer on the thermal performance of the PCM‐based floor. Therefore, two main objectives are defined. The primary is to take advantage of the storage capacity of a PCM layer by integrating it into the ground; second, to evaluate the hot water temperature levels effect on the floor's performance. Additionally, we address the low thermal conductivity of PCM by enhancing PCM microcapsules with single and hybrid nanoparticles and comparing them to pure PCM. The numerical results obtained show that positioning the PCM microcapsules above the heating tubes (upper position) provides an optimum improvement in thermal performance. Moreover, the addition of hybrid nanoparticles within the base PCM, 1% of Cu mixed with 4% of Al2O3, allows an increase of 4°C, which relates to a reduction of 18% in the internal temperature amplitude and a phase shift of 6 h 30 min compared with the conventional heated floor in which there is no PCM.

Comprehensive performance evaluation of double-glazed windows containing hybrid nanoparticle-enhanced phase change material

Utilizing hybrid nanoparticle-enhanced phase change material (Nano-PCM) in double-glazed windows can improve the thermal inertia and thermal insulation of windows, but the excessive photothermal conversion capacity causes the window to overheat locally in summer and affects thermal comfort. Moreover, the addition of hybrid nanoparticles also affects the visible light transmittance of liquid PCM, which negatively impacts natural lighting. Therefore, a comprehensive evaluation of the glazed window filled with hybrid Nano-PCM is required. In this study, Al2O3-CuO hybrid Nano-PCMs were first prepared to measure and calculate their optical properties in the full spectral band. The evaluation system of the glazed window containing hybrid Nano-PCM was established from the multi-perspectives of energy-saving, thermal comfort, economy, and daylighting. A numerical simulation model was developed to study the optical and thermal performance of glazed units. The results show that the addition of hybrid Nano-PCM has a positive effect on the energy and economic saving. This positive effect is more profound as the proportion of CuO increases under the range of 0.001 % volume fraction, which can save 2552 kJ/d energy and 2003 CNY in the life cycle of the studied window. The thermal comfort index and natural lighting index increase with the increase of the Al2O3 ratio under the range of 0.001 % volume fraction. The maximum average indoor natural lighting reaches 361.89 lx, and the maximum temperature deviation is 9.31℃. In terms of energy consumption, energy-saving, daylighting, and economic factors, the best comprehensive performance for the window is achieved at CuO: Al2O3 ratio of 4:6.

Development and Laboratory Scale Characterization of a New Hybrid Nano‐enhanced Phase Change Material for Solar Thermal Energy Storage

AbstractThe latent heat thermal energy storage (LHTES) systems using organic phase change materials (PCMs) offer significant advantages, however, they suffer with low thermal conductivity and this limitation restricts their uses in many real applications. This weakness of them has attracted the attention of worldwide researchers. In the present work, a novel hybrid organic phase change material (HOPCMs) using two‐step method is prepared by the addition of copper oxide and titanium oxide nanoparticles in different mass fraction ratio for elevating the thermal conductivity of myristic acid (MA) as base PCM. The findings of this experimental work show that with the addition of 75 % CuO and 25 % TiO2 of total 1 % of combined nanoparticles mass fraction, the thermal conductivity of pure PCM enhances by an amount of 13.16 %. The thermo‐physical properties were obtained using differential scanning calorimetry and they show that by the addition of hybrid nanoparticles, PCM does not loses its latent heat by more than 2 %. The chemical and thermal properties were tested by adopting Fourier transform and infrared spectrometer (FT‐IR), X‐ray diffraction (XRD) technique, and thermogravimetric (TGA) analyzer. The reliability and stability of the HOPCMs were checked by conducting accelerated thermal melt/freeze cycle test for 1000 cycles. The HOPCMs so obtained, reveal the good thermal and chemical properties, and ensure a long‐term performance for medium temperature based LHTES systems.

An experimental study on thermal efficiency of hybrid GO/MWCNTs nanoparticles suspended in a binary mixture of ethylene glycol and water

Energy consumption has a demand growth across the globe due to modernization. However, the use of fossil fuels is creating a huge impact on climate change and has made it essential to harvest solar renewable energy technology. The heat transfer fluid plays an important role in maintaining the optimum temperature of the panel by removing the heat absorbed and transferring to the thermal energy storage medium. Due to the poor thermal conductivity and thermal degradation of conventional heat transfer fluids such as water, ethylene glycol and oil, these pose limitations to be utilised in solar energy technology systems. Thus, to overcome this problem, a hybrid nanofluid is used to boost the thermal conductivity and degradation temperature. However, the addition of hybrid nanoparticles further enhances the thermo-physical properties of the fluids. In this present study, GO/MWCNTs hybrid nanoparticles (0.01 – 0.2 wt%) were dispersed in hybrid base fluid (EG/water) in the ratio of 40:60. The finding shows that for visual stability, MWCNT sediment was faster compared to GO while, hybrid GO/MWCNT, showed higher stability compared to the single nanoparticle. The TGA results show the higher thermal degradation temperature at 0.05 wt% of pure GO, pure MWCNT and hybrid GO/MWCNT with thermal degradation of 122.74 ℃, 118.93 ℃ and 119.26 ℃ respectively. The use of nanofluids acts as a clean fuel for electricity production and decreases CO2 emission, which can further promote sustainable development goals.

Magneto-thermogravitational convection for hybrid nanofluid in a novel shaped enclosure

The proposed work exhibits a numerical simulation of steady thermogravitational convection of Cu–Al2O3(50%−50%) water hybrid magneto-nanofluid in a novel shaped enclosure regulated by magnetic field dependent (MFD) viscosity in presence of flush mounted variable heaters. Various cases (Case-I to Case-IV) have been considered depending on the location of the heaters on the bottom and left boundaries. Pertaining to this analysis, the streamfunction (ψ)- vorticity (ζ) form including the energy transport equation of coupled partial differential equations are evaluated with the help of an efficient higher order compact finite difference scheme. Results are exhibited in terms of streamlines, isotherms and Nusselt numbers to describe the transport phenomena obtained for different physical parametric values to this simulation. The influence of the physical parameters such as, Rayleigh number (104≤Ra≤106), Hartmann number (0≤Ha≤60), hybrid nanoparticles volume fraction (0≤ϕhnp≤0.04), orientation of magnetic field (00≤γ≤600) and magnetic number (0≤δ0≤1) on the hybrid nanofluid flow and energy transfer are analyzed. Obtained results indicate that the combinations of the heaters location and the shaped of the geometry have major impact on all the transport phenomena. Moreover, Cu–Al2O3 hybrid nanoparticles play an essential role to levitate the thermal transmission compared to other physical parameters. An addition of hybrid nanoparticles leads to an increase in the average Nusselt number up to 10.8% in Case-I, 12% in Case-II, 11.66% in Case-III and 11.65% in Case-IV. The novelty of the present work is to examine the rheological properties of hybrid nanoliquid in a novel shaped cavity subjected to magnetic field dependent viscosity (MFDV) along with flush mounted variable heaters.

Thermal Convective Instabilities and Chaos in a Rotating Hybrid Nanofluid Layer with Cattaneo–Christov Heat Flux Model

The linear and nonlinear dynamics of thermal convection of a rotating hybrid nanofluid layer heated from below with the Cattaneo–Christov heat flux model are studied in this paper. Starting from the flow equations of a hybrid nanofluid and exploiting the free boundary conditions, the analytical expressions of the stationary and oscillatory Rayleigh numbers of the base fluid are determined as a function of the dimensionless parameters of the heat transfer fluid and the thermophysical properties of the hybrid nanofluid. The effects of hybrid nanoparticles and Taylor number on the onset of stationary convection in the base fluid are investigated graphically. Then, a numerical study of the transition from natural convection to chaotic behaviour of the hybrid nanofluid is made using the truncated Galerkin approximation. This approximation allowed us to find a novel six-dimensional nonlinear system depending on the parameters of the base fluid and the thermophysical properties of the hybrid nanofluid that can be reduced to five, four, or three dimensions when we tend some parameters to zero. The different results showed that the addition of hybrid nanoparticles (alumina-copper) to a thermal fluid (water) subjected to the rotation force in the presence or absence of the thermal relaxation time allows control of the chaotic convection in the base fluid. On the other hand, the increase of the rescaled Taylor number and the Cattaneo number widens the domain of chaos in the hybrid nanofluid with the increase of the rescaled Rayleigh number of the base fluid.

Two-Dimensional Magnetized Mixed Convection Hybrid Nanofluid Over a Vertical Exponentially Shrinking Sheet by Thermal Radiation, Joule Heating, Velocity and Thermal Slip Conditions

Hybrid nanofluid is an improved kind of nanofluid that typically utilized to enhance the thermal efficiency in fluid flow regimes. It has a wide range of real-world applications. This opened up many new prospects to further investigate the two-dimensional hybrid nanofluid under different body geometries and physical parameters. A numerical study of a two-dimensional magnetized mixed convection hybrid nanofluid flow over a vertical exponentially shrinking sheet is considered in this paper. The main objective of this current study is to examine the influences of volume fraction of copper, mixed convection, and radiation on the reduced skin friction and reduced heat transfer against the effect of suction. Besides, the influences of radiation, volume fraction of alumina, velocity slip, thermal slip, magnetic parameter, and Eckert number on the velocity and temperature profiles are also considered in this paper. The governing system of partial differential equations (PDEs) is transformed into a system of nonlinear ordinary differential equations (ODEs) through exponential similarity variables. Then, the bvp4c solver for MATLAB is used to solve the transformed nonlinear ODEs. Numerous significant results are being observed. As the quantity of mixed convection was raised, the reduced skin friction improved in both solutions, and reduced heat transfer increased in the second solution but with no variation found in the first solution. Besides, the temperature profile grew when the volume fraction of alumina, radiation, magnetic parameter, and Eckert number were raised in both solutions. In terms of heat transfer rate, when the amount of the velocity slip parameter was increased, temperature reduced in the first solution but increased in the second solution. Whilst temperature dropped in both solutions as the thermal slip parameter was enhanced. In conclusion, the addition of hybrid nanoparticles boosted the heat transmission rate. In the assisting flow condition, dual solutions exist when the suction parameter value is greater or equal to its critical point. However, no fluid flow is conceivable when the indicated value is less than this critical point.

Effects of hybrid nanoparticle additives in n-butanol/waste plastic oil/diesel blends on combustion, particulate and gaseous emissions from diesel engine evaluated with entropy-weighted PROMETHEE II and TOPSIS: Environmental and health risks of plastic waste

Due to little industrial use of plastic waste recycling, over 200 million tons are thrown in landfills and more than 15 million tons end up in the ocean every year. This study aimed to investigate the effect of waste plastic pyrolysis oil, n-butanol, hybrid (Al2O3 and TiO2) nanoparticles, and diesel fuel blends on combustion, gaseous emissions, and toxic particulates from CRDI diesel engine at steady-state mode. Experiments were carried out using different fuel ratios blended with hybrid nanoparticles at 20 ppm, 40 ppm, and 60 ppm through the ultra-sonification process. The most optimal blend was determined by Shannon entropy-weighted TOPSIS and PROMETHEE II, and was verified with the experimental results. The result shows that the overall fuels have a definite outline by naphthalene, which account for ∼42.67% of the total organic compounds. With n-bu15W30Hy60, n-bu20W40Hy40 and n-buW40Hy60 fuels, ∼54.9% significantly reduction was observed with n-alkane emissions. Low PAHs value found in particulate samples might reduce the effect of eyes irritants and cancers. Compared to EC, the variation in OC had unclear trend across all blend fuels, except for n-bu20W40Hy40 which averagely reduce by ∼89.47% across the Hy40 fuels. Reduction in CO and HC emissions were observed with Hy60 fuels, while the NOx of Hy40 tend to increase significantly than that of Hy20 and Hy60 by an average of 0.204 g/kWh and 0.401 g/kWh, respectively. However, almost equal pressure peaks were obtained with nano-fuels and their heat release became faster as the nanoparticles volume elevated. The MCDM results confirmed that significant benefit could be attained when the fuel mixtures are under the influence of nanoparticles at relatively higher concentrations. The short answer for waste plastic is to ban unnecessary uses of plastic, encourage alternative materials or fuels, and cut plastic production.

Positional impacts of partial wall translations on hybrid nanofluid flow in porous media: Real Coded Genetic Algorithm (RCGA)

Positions of partially translating walls are highly effective for enhancing heat transfer. The present study intends to appraise the positional effects of partially translating cold walls of a bottom-heated enclosure on thermo-fluid phenomena and associated thermal characterization of Cu−Al2O3/water hybrid nanofluid packed porous matrix imposing an external magnetizing field. The cold walls are located either partly length or over the entire length of the sidewalls; the topmost wall is insulated. This novel configuration explores the enhanced heat transfer due to partially translating cold walls in lieu of whole wall motion under similar parametric conditions. Furthermore, the assessment of the different positions of the partially translating walls is also incorporated. The finite volume-based CFD code is developed to solve the governing equations. The thermo-fluid behaviors are analyzed systematically in an orderly fashion of parametric studies for a variety of relevant parameters like Richardson number (Ri), Reynolds number (Re), Darcy number (Da), Hartmann number (Ha), hybrid nanoparticles volume fractions (ϕ), and the directions and positions of partially translating cold walls. The results show distinct local behaviors allied with better heat exchanges compared to the completely cold sidewall motion. The implementation of partially translating cold walls located in the bottom-bottom position might be a good choice for achieving enhanced heat transportation. Moreover, the thermo-fluid flow phenomenon is greatly influenced by the intensity of the applied magnetic field. It has been also revealed that the addition of hybrid nanoparticles is beneficial for certain concentrations only that can attend an enhanced heat transfer. The downward translational speed with a bottom-bottom position is the superior option for accomplishing better heat exchange ∼ 89.08%. Adopting the Real Coded Genetic Algorithm (RCGA), optimal heat transfer under a wide range of pertinent parameters is scrutinized for the upward and downward directions of translation.

Corrosion, rheology, and thermal ageing behaviour of the eutectic salt-based graphene hybrid nanofluid for high-temperature TES applications

The eutectic salt-based nanofluids have recently been explored as a Thermal Energy Storage (TES) material for high-temperature applications due to their improved thermal properties. However, the investigation of such fluids in corrosion, rheology, and thermal ageing is minimal. This study focused on the effect of newly developed hybrid nanofluids based on GO/TiO2 nanoparticles and the eutectic salt mixture on thermophysical properties for high-temperature applications. The results showed that the SS316 immersed in hybrid nanofluid formed a protective layer to prevent corrosion compared to the eutectic salt mixture after 7 days. The surface morphologies and cross-sections were studied using SEM (Scanning Electron Microscope) and EDX (Energy-dispersive X-ray spectroscopy). The addition of hybrid nanoparticles into the eutectic salt mixture exhibits minimal effect on the viscosity that varies about −0.51–11.05% from 250–400 °C range at a shear rate of 250/s. Moreover, the rheological study displayed a strong correlation (R2 of 0.99) with the experimental data. Comparative studies showed that the viscosity values of both eutectic salt mixture and hybrid nanofluid showed good agreement with the literature. Finally, the thermal ageing behaviour of eutectic salt mixture and hybrid nanofluids was investigated for 15 days, and the samples were collected on the 1st, 7th, and 15th day. The average specific heat capacity of hybrid nanofluids and eutectic salt was reduced by 8.76% and 28.94%, respectively, after 15 days, indicating poor thermal stability of eutectic salt compare to hybrid nanofluids.

Stability, thermo-physical and electrical properties of naphthenic/POME blended transformer oil nanofluids

This study aims to investigate the stability, thermo-physical properties and electrical properties of pure transformer oil (naphthenic), palm oil methyl ester (POME) and blend oils suspended with SiO2-graphene nanoparticles. The hybrid SiO2-graphene was synthesized via sol–gel technique with pH varying from 10 to 12. Simultaneously, the transformer oil blend was prepared by homogenizing transformer oil and POME with various mass ratios ranging from 0 to 100%. Later, the nanofluids were synthesized by dispersing SiO2-graphene nanoparticles via high-speed homogenization (25000 RPM) followed by water bath sonication for 5 h. The stability of the nanofluids was measured by visual observation and UV–Vis spectrometer. Optimization of blend oils and hybrid nanofluids was performed using Minitab 18 for higher thermal conductivity and lower viscosity as the criteria for faster heat dissipation and fluid flow. Hybrid nanoparticles synthesized at pH 10 showed the lowest sedimentation rate than pH 11 and 12 and were therefore selected for further studies. Results show the thermal conductivity of nanofluids increased with hybrid nanoparticle concentration and temperature. The viscosity of nanofluid decreased with temperature with POME-based resulted in the lowest. Oxidation induction time (OIT) decreased with temperature but increased with the addition of hybrid nanoparticles. The optimized nanofluid blend was found to be 81.51 wt% mineral oil, 18.48 wt% POME and 0.10 wt% hybrid nanoparticle concentration. Further, the optimized sample resulted in lower dissipation dielectric factor than pure transformer oil. However, the breakdown voltage and resistivity of pure transformer oil is higher than optimized sample.

Improved tribological behavior of lubricating oil dispersed with hybrid nanoparticles of functionalized carbon spheres and graphene nano platelets

A novel synthesis method of Functionalized Carbon Spheres (FCS) coated with Graphene nanoplatelets (GNP) using a simple sonication technique is reported. The FCS/GNP hybrid nanoparticles were found to be effectively improving the tribological characteristics of lubricating oils. For the synthesis of FCS, Carbon Spheres (CS) synthesized via non-catalytic chemical vapor deposition was functionalized using nitric acid. The hybrid nanoparticles were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Raman spectroscopy. The tribological behavior of CASTROL-20 W 40 engine oil dispersed with different concentrations of FCS and GNP using ultrasonication was investigated using a four-ball tester. The tribological behavior of FCS and GNP were investigated separately to compare the tribological performance of the FCS/GNP hybrid nanoparticles. The neat oil dispersed with 0.275 wt% of FCS/GNP hybrid nanoparticles in 10:1 ratio shows excellent dispersion and stability for 30 days without the addition of any surfactant. The results indicate that the addition of these hybrid nanoparticles causes a remarkable reduction (~18%) in the Coefficient of Friction (COF) of the neat oil. The optical image of wear scar on the ball immersed in neat oil shows a significant reduction in the Wear Scar Diameter from 425.6 µm to 390.0 µm with the addition of hybrid nanoparticles. The Raman mapping of the wear scar on chromium steel ball reveals that the FCS/GNP hybrid nanoparticles remain unseparated after the tribology test.

Numerical analysis of thermal conductive hybrid nanofluid flow over the surface of a wavy spinning disk

A three dimensional (3D) numerical solution of unsteady, Ag-MgO hybrid nanoliquid flow with heat and mass transmission caused by upward/downward moving of wavy spinning disk has been scrutinized. The magnetic field has been also considered. The hybrid nanoliquid has been synthesized in the presence of Ag-MgO nanoparticles. The purpose of the study is to improve the rate of thermal energy transmission for several industrial purposes. The wavy rotating surface increases the heat transmission rate up to 15%, comparatively to the flat surface. The subsequent arrangement of modeled equations is diminished into dimensionless differential equation. The obtained system of equations is further analytically expounded via Homotopy analysis method HAM and the numerical Parametric continuation method (PCM) method has been used for the comparison of the outcomes. The results are graphically presented and discussed. It has been presumed that the geometry of spinning disk positively affects the velocity and thermal energy transmission. The addition of hybrid nanoparticles (silver and magnesium-oxide) significantly improved thermal property of carrier fluid. It uses is more efficacious to overcome low energy transmission. Such as, it provides improvement in thermal performance of carrier fluid, which play important role in power generation, hyperthermia, micro fabrication, air conditioning and metallurgical field.

Synthesis of Hybrid Graphene/TiO2 Nanoparticles Based High-Temperature Quinary Salt Mixture for Energy Storage Application

Abstract High temperature and low melting point eutectic mixtures play a significant role in thermal energy storage (TES) and as a heat transfer fluid (HTF). These eutectic mixtures, when dispersed with nanoparticles, further enhance their thermophysical properties. The hybrid Graphene Oxide and titanium (GO/TiO2) nanoparticles (0.01-0.1 wt%) were synthesised using the hydrothermal technique at 180°C for 12 hours in an autoclave. Eutectic salts from a system of nitrate salt mixture composed of sodium (0.558 wt%), potassium (2.118 wt%), lithium (0.738 wt%), calcium (2.478 wt%), and cesium (4.098 wt%) were dispersed into nanosuspension to form a hybrid eutectic mixture for high-temperature applications via series of sonication and heating procedure. The eutectic point (65 oC) was predicted using the phase diagram and validated with experimental value observed at 61 oC using differential scanning calorimetry (DSC). The enhancement in specific heat in the presence of hybrid nanoparticles ranged from 9.8-19.6% compared to the base salt. Moreover, the addition of 0.05 wt% of hybrid nanoparticle showed the highest specific heat improvement (19.6%) compared to other single nanoparticle concentrations in the literature. The eutectic mixtures showed excellent thermal stability over a temperature range of 580 oC, with no significant decomposition in the presence of hybrid nanoparticles. The samples were characterised for structural and morphological changes using ESEM and EDX that showed well-dispersed nanoparticles into the eutectic mixture. FTIR studies confirmed the presence of O-N-O, NO3, and C=N stretching. The interaction between all the nitrate salts and the addition of hybrid nanoparticles did not alter the morphology of the base salts. Raman spectroscopy highlighted the increase in ID/IG ratio from 0.91 to 1.05 due to the presence/binding of TiO2 nanoparticles on the graphene sheet. Therefore, a new hybrid GO/TiO2 based high temperature quinary salt mixture showed better reliability and stability for energy storage applications.