Mass Concentration Of Nanoparticles Research Articles

Heat transfer and hydrodynamic performance of ZrO2 geothermal nanofluids through tubular and plate heat exchangers

The improvement in heat transfer equipment plays a significant role to enhance the overall performance of many systems and a wide variety of industrial processes. Heat exchangers are widely used in many of these applications and, with the aim of limiting the growing of energy demand, further improvement is needed. A low-enthalpy geothermal system is commonly constituted by a ground heat exchanger, a heat pump unit, and indoor heating/cooling units. In the ground heat exchanger circuit, the heat exchange occurs between the fluid of the wellbore and the ground through a tubular section similar to that of the inner tube of a Double-Tube Heat Exchanger (DTHE), and between the fluid of the wellbore and the refrigerant of the heat pump in the evaporator/condenser, which is typically a Plate Heat Exchanger (PHE). The use of new nano-enhanced heat transfer fluids featuring improved properties, known as nanofluids, has been proposed as a potential solution for energy efficiency improvement. This study aims to analyse the feasibility of ZrO2 nanofluids based on a propylene glycol:water 10:90 vol% mixture as working fluids in heat transfer applications, focusing on renewable energy systems such as low-enthalpy geothermal installations. The heat transfer performance and hydrodynamic behaviour of four new ZrO2-based nanofluids at nanoparticle mass concentrations of 0.25, 0.50, 0.75, and 1.0 wt% are analysed and compared with the base fluid. Tests through a PHE and a DTHE were performed, and convective heat transfer coefficients and pressure drops were obtained in laminar and turbulent regimes. Increases of the convective heat transfer coefficients up to 123 % and 8.8 % were found for the nanofluids in comparison to the base fluid for laminar flow in the PHE and for turbulent flow in the DTHE, respectively. Finally, a dimensionless analysis was carried out through Nusselt and Reynolds numbers and Darcy friction factor.

Experimental study of preparing the CoFe2O4 magnetic nanofluid and measuring thermal-fluid characteristics of the stabilized magnetocaloric nanofluid

The purpose of this study was to examine the rheological features of CoFe2O4 superparamagnetic nanoparticles dispersed in water-ethylene glycol (EG) coolant as the basis fluid. The experiments are carried out at temperatures between 10 and 50 degrees Celsius, with five mass fraction concentrations of magnetocaloric nanofluid as well as different shear rates. The solvothermal-produced cobalt ferrite metallic compounds are disseminated in EG-water (50:50) coolant. Evaluation of functional groups and organic compounds, the crystal structure of spinel ferrite, the size and morphology of nanoparticles, and the specific surface area, respectively, were carried out. For the developed magnetocaloric nanofluid, shear rate variation illustrates the non-Newtonian behavior of Bingham plastic. The results show that increasing the mass concentration of nanoparticles from 0.05 % to 0.8 % results in about 80 % increase in viscosity at 10 °C. Additionally, thermal conductivity has increased to a maximum of 9.4 % at 50 °C and is improved by increasing temperature.

Al and A356 Alloy Foam Castings Modified with Low Concentrations of Nano-Sized Particles: Structural Study and Compressive Strength Tests

Aluminum and A356 alloy foam castings are produced using a melt-foaming method. Prior to foaming, the melt is modified with nano-sized particles (SiC, TiN, or Al2O3). The nano-sized particles are mixed with micro-sized Al particles, which are ultrasonically treated and hot-extruded. Thus, the so-called “modifying nano-composition” is obtained. The resulting compositions are introduced into the melt of the Al foam at the following mass concentrations of nanoparticles: SiC: 0.038 wt. %; TiN: 0.045 wt. %; and Al2O3: 0.046 wt. %. For the A356 foam, we use the following concentrations: SiC: 0.039 wt. %; TiN: 0.052 wt. %; and Al2O3: 0.086 wt. %. The macrostructure of the foam castings is investigated by CT scanning and 3D analysis. The pore size distributions and accumulative fraction dependencies are determined for all samples. The microstructure of the foam castings is investigated by SEM-EDS analysis. The results confirmed the presence of individual nano-sized particles, as well as clusters of particles in foam walls. The conducted compression tests show a significant increase in the plateau stress (up to 237%) of the modified aluminum foam castings compared to non-modified castings. However, a similar effect of the nano-compositions on A356 alloy foam castings is not observed. The obtained results show that the above-indicated concentrations of nanoparticles can positively influence the mechanical properties of aluminum foam castings. The novelty of the current study is two-fold: (1) such low concentrations of added nanoparticles have never been used before to alter Al foam’s properties, and (2) an original method of introducing the nanoparticles into the melt is applied in the form of nano-compositions.

Investigation of the processes of additional oil displacement by nanosuspension silicon oxide from a model core

The use of nanosuspensions during reservoir flooding is an alternative to chemical methods for enhancing oil recovery. In this work, the effectiveness of using nanosuspensions as a post-displacement agent after the base agent (water) was shown. Filtration tests for additional oil displacement from model rock samples were carried out. Suspensions of nanoparticles were used for post-displacement. The mass concentration of spherical silicon oxide nanoparticles (SiO2) varied from 0.01 to 0.25%wt, and their size varied from 10 to 35 nm. The permeability of the model core was 50 mD. An experimental measurement of the interfacial tension and the contact angle of wettability was performed. It is shown that with an increase in the concentration of nanoparticles, the interfacial tension of the “oil — suspension” decreases. It has been established that at a fixed concentration of nanoparticles (0.1%), with an increase in the size of nanoparticles, the interfacial tension decreases. It was revealed that when using suspensions, the contact angle of rock wetting with oil changes significantly. As a result of filtration tests, dependences of the oil displacement efficiency on the concentration and size of nanoparticles were obtained. It has been shown that additional volume of oil can be recovered after filtering nanosuspensions.

Tribological Performance of a Paraffinic Base Oil Additive with Coated and Uncoated SiO2 Nanoparticles.

Electric vehicles (EVs) have emerged as a technology that can replace internal combustion vehicles and reduce greenhouse gas emissions. Therefore, it is necessary to develop novel low-viscosity lubricants that can serve as potential transmission fluids for electric vehicles. Thus, this work analyzes the influence of both SiO2 and SiO2-SA (coated with stearic acid) nanomaterials on the tribological behavior of a paraffinic base oil with an ISO VG viscosity grade of 32 and a 133 viscosity index. A traditional two-step process through ultrasonic agitation was utilized to formulate eight nanolubricants of paraffinic oil + SiO2 and paraffinic base oil + SiO2-SA with nanopowder mass concentrations ranging from 0.15 wt% to 0.60 wt%. Visual control was utilized to investigate the stability of the nanolubricants. An experimental study of different properties (viscosity, viscosity index, density, friction coefficient, and wear) was performed. Friction analyses were carried out in pure sliding contacts at 393.15 K, and a 3D optical profilometer was used to quantify the wear. The friction results showed that, for the SiO2-SA nanolubricants, the friction coefficients were much lower than those obtained with the neat paraffinic base oil. The optimal nanoparticle mass concentration was 0.60 wt% SiO2-SA, with which the friction coefficient decreased by around 43%. Regarding wear, the greatest decreases in width, depth, and area were also found with the addition of 0.60 wt% SiO2-SA; thus, reductions of 21, 22, and 54% were obtained, respectively, compared with the neat paraffinic base oil.

Parametric analysis for nanolubricant in vapor compression refrigeration cycle

With the escalating global energy crisis and the consequential surge in energy consumption, particularly attributed to air conditioning (AC) systems in buildings, there arises a pressing need for sustainable solutions to mitigate this escalating demand. Vapor compression refrigeration (VCR) cycles, ubiquitous across residential, commercial, and industrial sectors, represent a significant portion of global electricity consumption, exceeding 10%. This demand is further exacerbated in regions characterized by hot climates. Consequently, there is a critical imperative to address the environmental impact of these systems, particularly in terms of reducing their Global Warming Potential (GWP). In response to this imperative, this study aims to develop a comprehensive numerical model for VCR systems, focusing on the implementation of nanolubricants. The primary objective is to assess the impact of integrating Al2O3 nanoparticles into the lubricating oil (referred to as nanolubricant) on the performance of the VCR cycle. The scope of the study encompasses the investigation of nanolubricants within refrigeration systems, aiming to enhance their efficiency and environmental sustainability. Utilizing the Engineering Equation Solver (EES), a numerical model of a VCR cycle utilizing R-410A refrigerant is developed. The model specifically emphasizes the compressor component, which is flooded with a polyolester (POE) oil base. The study explores various parameters, including ambient conditions, refrigerant-to-oil dissolving ratio, and mass concentration of nanoparticles, to evaluate their influence on system performance. The results indicate a significant enhancement in performance when flooding the base oil before introducing Al2O3 nanoparticles, with further improvements observed upon nanoparticle integration. Specifically, the coefficient of performance (COP) of the VCR system exhibits a notable increase compared to the base case configuration. Additionally, the adoption of eco-friendly refrigerants, such as R-32, demonstrates promising COP values following nanoparticle implementation by up to 4%. Moreover, the study reveals a reduction in compressor discharge temperature by up to 20% with higher oil mass concentrations during nanolubricant implementation, indicating enhanced durability and longevity of the VCR system’s compressor. These findings underscore the potential of nanolubricants to contribute to both the efficiency and environmental sustainability of refrigeration systems. In conclusion, the findings of this study offer valuable insights into the utilization of nanolubricants in VCR cycles, highlighting their potential to enhance system performance and mitigate environmental impact. These advancements hold promise for the development of more sustainable refrigeration technologies in the face of mounting energy challenges.

Study on the active cooling effect and convective heat transfer performance inside the rail

In order to study the impact of different influencing factors on the active cooling effect of electromagnetic rail. The effects of the flow velocity of cooling medium, the geometric shape of the cooling channel, the cooling water inlet temperature and the nanoparticle mass fraction on the cooling effect of rail are experimentally investigated. The results indicate that increasing the flow velocity of cooling medium can enhance the heat transfer effect. But when the flow velocity exceeds 2 m/s, further increasing the flow velocity has little effect on enhancing heat transfer, and the correlation between the Nusselt number and the Reynolds number has been obtained and expressed as Nu=0.316Pr1/3Re0.530. Among the three cooling channel geometries studied in this article, square channel has the best cooling effect. The inlet temperature of cooling water has little effect on the convective heat transfer coefficient, but has a significant impact on the thermal equilibrium temperature of the rail. The mass concentration of nanoparticles has a significant impact on the cooling effect of the rail. The larger the mass fraction of nanoparticles, the greater the convective heat transfer coefficient, and the lower the rail peak temperature after reaching thermal equilibrium. However, if the concentration of nanoparticles continues to increase, the effect of enhancing heat transfer will gradually weaken.

Experimental investigation of thermal energy storage in shell-and-multi-tube unit with nano-enhanced phase change material

This paper deals with thermal energy storage with use of nanoparticle enhanced phase change material in shell-and-multitube unit. The experiments are conducted under atmospheric pressure. Paraffin wax and two different fatty acids are used as base phase change material. Graphite and multi-walled carbon nanotubes serve as nanoparticles. Graphite nanoparticles are tested at the concentrations of 0.1 %, 1 % and 5 % by weight, while multi-walled carbon nanotubes only at 0.1 %wt. Ultrasonic vibration and homogenizer are used in order to stabilize the dispersion of the nanoparticles. Polyvinylpyrrolidone surfactant is used to stabilize the suspension and the tested nano-enhanced phase change material exhibit satisfactory stability. Experimental measurements are performed for a bundle of 7 tubes with outside diameter of 6 mm in a staggered arrangement and a pitch ratio of 4.5. It is found that, regardless of the tested base phase change material, the addition of graphite nanoparticles with mass concentration of 0.1 % does not significantly affect the charging and discharging times compared to base phase change material. The differences in charging and discharging times did not exceed 11 %. For a graphite nanoparticles mass concentration of 5 %, an increase in the charging time by up to 21 % and a reduction in the discharging time by 24 % was observed, depending on the type of base phase change material. An addition of multi-walled carbon nanotubes with mass concentration of 0.1 % shows an increase in charging time regardless of the type base phase change material up to 144 % with negligible influence on the discharging time. It was also observed that adding a surfactant to the produced nano-enhanced phase change material results in a reduction in charging time by up to 83 % depending on the type of base phase change material.

Research on Surface Protection Technology of Aluminum Alloy Heat Sinks in Lithium Battery with Composite Anodic Oxide Film

Aluminum alloy sheets are immersed in a mixed acid electrolyte for anodic oxidation to prepare different types of anodic oxide films. The mass concentration of TiO2 nanoparticles in the electrolyte is appropriately increased, and under the action of liquid flow disturbance, the number of nanoparticles adsorbed on the surface of aluminum alloy specimens increases, which plays a good role in homogenizing current and filling, promoting more uniform film formation and inhibiting local excessive corrosion and dissolution of the anodic oxide film, Gradually generate a composite anodized film with good density. The composite anodized film constructs a protective barrier on the surface of the aluminum alloy heat sink in lithium batteries, which can effectively block corrosive media and has a better protective effect on the heat sink than conventional anodized film and mixed acid anodized film, thereby significantly improving the corrosion resistance of the heat sink.

Ultrafine industrial aerosol as a risk factor for the health of smelting shop workers at a machine-building enterprise

Aim. To evaluate the amount and physicochemical properties of ultrafine industrial aerosol (UIA) in the work zone air (WZA) of smelting shop workers at a machine-building enterprise during various technological processes (melting, welding, and metal machining). Materials and methods. The physical properties of UIA particles were evaluated with NanoScan 3910 scanning spectrometer: the number of particles (number/cm3), particle surface volume (nm3/cm3), particle surface area (nm2/cm2), and nanoparticle mass concentration (μg/cm3) in the WZA of a furnace operator (n = 416), a welder (n = 315), a cutter (n = 286), a grinder (n = 78), and workers of the control group (n = 315). The chemical composition of the air samples was determined by inductively coupled plasma optical emission spectrometry (ICP-OES) using an Optima 2100 DV device. Results. It has been found that the highest concentration of UIA nanoparticles was recorded during metal melting at the workplaces (WP) of furnace operators (4.28 × 104 to 2.41 × 105 particles/cm3) and welders (3.01 × 104 to 3.34 × 105 particles/cm3). During mechanical metal processing, a much smaller number of nanoparticles was produced (for grinders, the number varied from 9.81 × 104 to 1.44 × 105 particles/cm3; for cutters, it varied from 2.71 × 104 to 1.94 × 105 particles/cm3). Indicators of surface area, surface volume and mass concentration at the WPs of furnace operators, welders, grinders and cutters exceeded the corresponding indicators of the control group for almost all sizes of suspended particles with statistically significant differences (p ≤ 0.05). It has been estimated that such metals as Al, Cu, Mg, Mo, Fe, and Ni were present in the workers’ WZA but their content did not exceed the current maximum permissible concentrations. Conclusions. The presence of suspended particles of UIA with a maximum concentration in the range from 20 nm to 70 nm has been confirmed in the WZA during melting, welding of metals and machining. Indicators of concentration, surface area, surface volume, and mass concentration at the workplaces of melting shop workers at the machine-building enterprise significantly exceeded the corresponding indicators in the control group without dust formation processes, showing statistically significant differences (p ≤ 0.05). The evidence of metals in the WZA has suggested their presence in the form of nanoparticles, which are more active and dangerous, thus increasing the risk of their adverse effects on the workers. Ультрадисперсний

Conditions of enhanced evaporation for nanofluids droplet and inhibition of coffee-ring effect under buoyancy and Marangoni convection

Evaporation of nanofluid droplets whose size is larger than capillary length is common in industrial processes, but there is currently a lack of research on the evaporation kinetics and more complex deposition patterns under the combined effects of buoyancy and Marangoni convection of large evaporating droplet. Experimental investigations on evaporation of Al2O3H2O nanofluid sessile droplet with initial contact line diameter of 4 mm on heating PTFE coating substrate are reported. The variation in contact angle, contact radius, and droplet volume over time under different conditions were obtained through experiments. The average evaporation rate is calculated. Internal flow characteristics are inferred through the surface temperature distribution detected by the top view infrared camera. The constant contact radius mode takes place at the beginning of evaporation. Then mixed evaporation mode and stick slip mode may occur for different substrate temperature, nanoparticle mass concentration and nanoparticle size. Increasing nanoparticle size causes a decrease in average evaporation rate. Whether the use of nanofluids can improve evaporation rate and heat transfer or not depends on multiple factors. Convection cells exist, and three kinds of deposition patterns are formed due to the underlying coupled transport phenomena. Under the combined effect of buoyancy and Marangoni convection in this article, the most common coffee-ring pattern does not appear. The deposition patterns are directly affected by the pinning stability, which decrease at higher temperature.

Study on the Wear Resistance of Ni-Co-ZrO2 Composite Coatings with Different ZrO2 Nanoparticle Concentrations Prepared Using Electrodeposition on the Micro-Surface of Spindle Hook Teeth

To improve the wear resistance of the surface of the cotton picker spindle, a Ni-Co-ZrO2 composite coating with different ZrO2 nanoparticle concentrations was prepared using electrodeposition technology on the micro surface of spindle hook teeth, and the morphologies of the surface and cross-section, element contents, grain sizes, microhardness and friction coefficients of the Ni-Co-ZrO2 composite coating were obtained; a simulated wear test was conducted based on the independently developed spindle hook tooth wear device, and the morphologies and elemental distributions of the composite coating before and after wear were obtained; the effects of different ZrO2 nanoparticle concentrations (0, 2, 4, 6, 8 g/L) on the morphology, element content, grain size, microhardness, friction coefficient and wear resistance of the coating were discussed. The test results indicated that compared with Ni-Co coatings, Ni-Co-ZrO2 composite coatings featured a more compact coating structure, a greater coating thickness, and a smaller grain size. The presence of ZrO2 nanoparticles led to further improvement of the coating’s microhardness, friction coefficient and wear resistance. When the mass concentration of ZrO2 nanoparticles reached 4 g/L, the microhardness of Ni-Co-ZrO2 composite coating reached the maximum value, 545.4 Hv0.1, and the friction coefficient decreased to 0.06. At the same time, in the simulated wear test, the composite coating with this concentration had the smallest wear area and the highest wear resistance.

The Impact of Silicon Dioxide Nanoparticle Size on the Viscosity and Stability of Nanofluids: A Comprehensive Study

This study investigated the impact of silicon dioxide nanoparticle size on the viscosity and stability of nanofluids. A comprehensive study was conducted, including the synthesis and characterization of silicon dioxide nanoparticles of varying sizes, as well as the preparation and testing of nanofluids with different nanoparticle concentrations. The results show that nanoparticle size has a significant effect on both the viscosity and stability of nanofluids, with smaller nanoparticles leading to higher viscosity and improved stability. Silicon dioxide nanoparticles were dispersed in deionized water at mass fractions of 0.5% and 3% and average particle diameters of 12 nm and 40 nm using an ultrasonic disperser. The rheological properties of the obtained nanofluids at 304 K were studied depending on the mass concentration and linear size of nanoparticles in the liquid. An analysis of the results showed that the viscosity of the nanofluids increased with decreasing linear size of the nanoparticles. These findings have important implications for the development and optimization of nanofluid-based applications in various industries, such as electronics, energy, and biomedical engineering.

DESARROLLO DE NANOPARTÍCULAS DE QUITOSANO-GELATINA Y QUITOSANO-COLÁGENO PARA LIBERACIÓN DE FÁRMACOS

Polymeric nanoparticles have demonstrated a great potential for biomedical application, especially in drug delivery systems acting as nanocarriers. The polymers obtained from living organisms, known as biopolymers, are promising materials for these purposes since they present biodegradability, biocompatibility and low immunogenicity, which are features required for in vivo applications. In this work, polymeric nanoparticles were prepared from mixtures of biopolymers such as chitosan, collagen and gelatin by ionic reticulation with sodium tripolyphosphate. Picric acid as a model drug was encapsulated into the nanoparticles. Chitosan of 50.4 kDa of molecular weight and 81 % of deacetylation degree was prepared through the deacetylation and depolymerization of chitin extracted from squid pens (Loligo sp). The composition, size distribution, and surface charge of the prepared nanoparticles were evaluated. Moreover, the influence of the nanoparticles mass and picric acid concentration were analyzed during the loading process by determining of the loaded content and the incorporation efficiency. Maximum loaded contents of picric acid were 7.16 % and 6.45 % for chitosan/gelatin nanoparticles and chitosan/collagen nanoparticles, respectively. In vitro release tests showed a quick picric acid release in chitosan/gelatin nanoparticles. The nanoparticles prepared with collagen took longer time to release the picric acid. Kinetic studies, using mathematical models, revealed that the release takes place through a diffusion mechanism.

A comprehensive study of the thermophysical and rheological properties of ZrO2 based nanofluids as geothermal fluids

Geothermal heat pump systems in residential and commercial applications have become popular in many countries over the past years. The heat transfer performance of the ground heat exchangers in these systems has still room for improvement since they have huge influence on the overall efficiency. Likewise, new heat transfer fluids with enhanced properties, known as nanofluids, have been proposed as a potential solution to substitute the conventional working fluids and to improve the heat transfer processes and performance. A reliable and appropriated proposal of nanofluids for a particular application must include a complete fluid dynamic characterization including thermophysical, rheological, heat transfer coefficients, and pressure drops analysis, as well as physical or chemical characterization of the nanomaterial. In this study, a novel proposal of propylene glycol:water (10:90 vol%)-based zirconium oxide nanofluids of different nanoparticle mass concentrations (0.25, 0.50, 0.75, 1.0, and 5.0 wt%) as possible geothermal working fluids and their thermophysical and rheological characterization are performed. Thus, the nanopowder was extensively investigated by means of Transmission Electron Microscopy, High Resolution Transmission Electron Microscopy, X-Ray diffraction, and Ultraviolet visible spectroscopy obtaining the shape, size distribution, d-spacing, electron diffraction pattern, and crystallinity. Then, thermal conductivities, dynamic viscosities, densities, and isobaric heat capacities for base fluid and nanofluids were measured by transient hot wire, rotational rheometry, vibrating tube, and differential scanning calorimetry methods, respectively. Increases in thermal conductivity, dynamic viscosity, and density of the nanofluids up to 2.8%, 13%, and 4.1% were found, respectively, while decreases in heat capacity reached 11% in comparison to the base fluid. Different models and equations were also employed to analyse the experimental data.

Complex Formation Behavior of Silica Nanoparticles and Xanthan

AbstractPolyion complex formation between negatively charged polysaccharide, xanthan, and positively charged silica nanoparticles, Ludox CL is investigated in an acetate buffer at pH 5.0. Appreciable precipitate is found in the composition range cx/cSiNP from 0.056 to 0.58, where cx and cSiNP are the mass concentrations of xanthan and silica nanoparticles, respectively. The sign change of the ζ potential for the mixed solutions is observed in the cx/cSiNP range. Significantly high scattering intensity is detected for the mixed solutions in a wider cx/cSiNP range, clearly showing the complex formation. The scattering profile measured by the small‐angle X‐ray scattering reveals that silica nanoparticles are packed loosely in the complex both when xanthan forms double helix and single chain conformations.

Tribological Performance of Different Concentrations of Al2O3 Nanofluids on Minimum Quantity Lubrication Milling

Nanofluid minimum quantity lubrication (NMQL) is a green processing technology. Cottonseed oil is suitable as base oil because of excellent lubrication performance, low freezing temperature, and high yield. Al2O3 nanoparticles improve not only the heat transfer capacity but also the lubrication performance. The physical and chemical properties of nanofluid change when Al2O3 nanoparticles are added. However, the effects of the concentration of nanofluid on lubrication performance remain unknown. Furthermore, the mechanisms of interaction between Al2O3 nanoparticles and cottonseed oil are unclear. In this research, nanofluid is prepared by adding different mass concentrations of Al2O3 nanoparticles (0, 0.2%, 0.5%, 1%, 1.5%, and 2% wt) to cottonseed oil during minimum quantity lubrication (MQL) milling 45 steel. The tribological properties of nanofluid with different concentrations at the tool/workpiece interface are studied through macro-evaluation parameters (milling force, specific energy) and micro-evaluation parameters (surface roughness, micro morphology, contact angle). The result show that the specific energy is at the minimum (114 J/mm3), and the roughness value is the lowest (1.63 μm) when the concentration is 0.5 wt%. The surfaces of the chip and workpiece are the smoothest, and the contact angle is the lowest, indicating that the tribological properties are the best under 0.5 wt%. This research investigates the intercoupling mechanisms of Al2O3 nanoparticles and cottonseed base oil, and acquires the optimal Al2O3 nanofluid concentration to receive satisfactory tribological properties.

Investigation of the stability of nanofluids based on water and carbon nanoparticles synthesized by the electric arc method

In this work, arc discharge synthesis was carried out by sputtering electrodes of various compositions in a helium medium, as a result of which two types of materials containing carbon globules and graphene flakes were obtained. The synthesized materials were characterized with transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. The effect of the type and concentration of carbon nanoparticles and the type of surfactants on the stability of water-based nanofluids was studied with optical spectroscopy. For carbon globules and water, the mass concentrations of nanoparticles and sodium dodecyl sulfate were determined to obtain a nanofluid based on them stable for 1 month, which are 0.02% and 1%, respectively. It was shown that the use of neonol AF 9-12 at a concentration of 2% didn’t lead to the stabilization of carbon globules with a mass concentration of 0.02% in water. For graphene flakes, the mass concentrations of nanoparticles and stabilizers to obtain a water-based nanofluid stable for 1 month were: 0.02% graphene flakes and 1% SDS, as well as 0.02% graphene flakes and 2% neonol AF 9-12, respectively.

Spray characteristics of fuel with cerium oxide nanoparticles

Combining experiment and simulation, spray characteristics of CeO2 nano-fuels and diesel including penetration distance, cone angle, and Sauter mean diameter (SMD) were investigated at various working conditions to reveal the effect of nanoparticles on the fuel spray. The correlation degree between spray characteristics and injection pressure, ambient pressure, and mass concentration of nanoparticles was assessed using the grey relationship analysis. Due to stronger axial diffusion and relatively weaker radial diffusion, nano-fuels showed a longer spray penetration, a smaller cone angle, and a larger SMD than diesel. The difference in spray characteristics between nano-fuel and diesel widened along with an increase in mass concentration. Additionally, the kinetic energy of spray, air resistance, and entrainment were susceptible to injection and ambient pressures. In general, higher injection pressure increased spray penetration and cone angle while reduced SMD. Oppositely, higher ambient pressure decreased the spray penetration while increased the cone angle and SMD. Among the three factors, the injection pressure had the greatest effect on spray characteristics, followed by ambient pressure and then mass concentration.

Thermophysical Properties of Vegetable Oil-Based Hybrid Nanofluids Containing Al2O3-TiO2 Nanoparticles as Insulation Oil for Power Transformers.

The massive demand in the electrical power sector has resulted in a large demand for reliable, cost efficient, and environmentally friendly insulation oil to reduce the dependency on mineral oil. The hybridization of nanoparticles in vegetable oil is a novel method to enhance the thermal properties of vegetable oil. This study focuses on the experimental investigation of the thermophysical properties of coconut oil, soybean oil, and palm oil-based hybrid nanofluids suspended with Al2O3-TiO2 nanoparticles at a mass concentration of 0.2, 0.4, and 0.6%. The ratio between Al2O3 and TiO2 nanoparticles was maintained constant at 50:50. The main purpose of the study is to evaluate the thermal conductivity, dynamic viscosity, and density of different vegetable base oils suspended with Al2O3-TiO2 in the temperature range of 30 to 60 °C. The influence of temperature on the augmentation of thermophysical properties for different vegetable oil-based hybrid nanofluids is investigated experimentally. The experimental results for thermal conductivity for the three types of base fluids show that the effect of nanoparticle mass concentration in thermal conductivity enhancement is less significant for temperatures more than 50 °C. The palm oil with a 0.6% Al2O3-TiO2 nanoparticle concentration exhibited the highest thermal conductivity with a 27.5% thermal conductivity enhancement relative to the base oil. The effect of nanofluid temperature on density and viscosity augmentation is more distinct compared with the impact of Al2O3-TiO2 nanoparticles concentrations. Among all three types of hybrid nanofluids, palm oil based nanofluids were found to have superior thermophysical properties compared with coconut oil and soybean oil, with the highest thermal conductivity of 0.628 W/m·k and lowest viscosity of 17.772 mPa·s.