Adding Al2O3 Nanoparticles Research Articles

Enhancing soot emission control and performance in biodiesel-powered diesel engine through Al2O3 nanoparticle

Abstract Interest in biodiesel as a diesel fuel substitute has increased due to the growing need for sustainable energy sources. The blends of biodiesel, such B20, have become more popular because they can lessen the need for fossil fuels and greenhouse gas emissions. The blends of biodiesel, however, may pose problems with emissions, performance, and combustion efficiency. The objective of this study is to investigate the effects of blending ethanol (C2H6OH) and aluminium oxide (Al2O3) into B20 biodiesel blend in order to improve engine performance. The study examines the effects of adding C2H6OH (5% of vol.) and Al2O3 (75 ppm) to the B20 biodiesel mix on its essential features and combustion. To fully assess the performance and emissions characteristics of the single cylinder diesel engine, experimental evaluations include a wide range of engine operating loads. The findings show that adding C2H6OH to the B20 blend increases its volatility and oxygen content, which promotes better ignition and combustion characteristics. Additionally, adding Al2O3 nanoparticles to the blend shows promise for improving combustion efficiency by enhancing fuel atomization and lowering soot emission. The synergy of adding both Al2O3 and C2H6OH to B20 significantly reduces CO, HC, and smoke levels of the diesel engine by 33.04, 28.13, and 12.88%, respectively. The results of this study offer important new information about how C2H6OH and Al2O3 additives might improve the B20 biodiesel blend's emissions performance and combustion efficiency, increasing the fuel's potential as a greener alternative for the transportation industry.

Study of the influence of adding Al2O3 nanoparticles to biodiesel on the performance and emissions characteristics of a diesel engine

The use of biodiesel in compression ignition (CI) engines has great potential to reduce emissions and the dependence on fossil fuels. However, the complete adoption of biodiesel in CI engines is limited by several drawbacks. A promising solution to these problems is the addition of nanoparticles to biodiesel or diesel-biodiesel blends. Hence, this paper studies the impact of adding aluminum oxide (Al2O3) nanoparticles on the performance and emission characteristics of a diesel engine running on biodiesel and a mixture of diesel and biodiesel. Al2O3 nanoparticles were added at concentrations of 50, 100 and 150 ppm to biodiesel (B100) and a mixture of 50 % biodiesel and 50 % commercial diesel (B50). The results indicated an increase in fuel conversion efficiency and a reduction in specific fuel consumption. The highest fuel conversion efficiency was 26.5 % for B50 with 100 ppm of Al2O3, indicating an improvement of around 28.6 % compared to diesel fuel (B0). In general, CO emissions were reduced with the addition of nanoparticles, with a maximum reduction of 42.8 % for B100 with 50 ppm Al2O3 compared to B0. The highest reduction in NOX emissions was 30.3 % for B50 with 100 ppm Al2O3 compared to pure diesel B0.

Mechanical properties and corrosion behavior of titanium surface biocomposites reinforced with Al2O3 particles fabricated by friction stir processing

This study aims to investigate the effects of Al2O3 micro and nanoparticles on the microstructure, mechanical, and corrosion properties of the pure titanium surface biocomposites fabricated by friction stir processing (FSP). The microstructure, mechanical, and corrosion properties of samples were evaluated using optical microscopy (OM), electron-backscattered diffraction system (EBSD), hardness tests, tensile tests, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) analyses. The OM and EBSD analyses proved the highest amount of grain refinement associated with the formation of strain-free recrystallized grains by applying FSP at the presence of Al2O3 nanoparticles. However, the amount of micro-strain and grain size of FSPed titanium without particles and with Al2O3 microparticles were much higher than that of samples with Al2O3 nanoparticles. Notably, the hardness values improved by about 33 % and 52 % by introducing Al2O3 microparticles and nanoparticles, respectively. Mechanical tests demonstrated a noticeable enhancement in the tensile strength of the samples, from 200 MPa for the sample processed without Particles to the highest amount of 294 MPa for that processed in presence of nanoparticles. The corrosion test results revealed a significant improvement in the corrosion resistance of the titanium samples by adding Al2O3 nanoparticles in which the corrosion potential increased from 0.244 to 0.192 V and charge transfer resistance from 394 to 794 kΩ cm2.

Effect of Al2O3 nanoparticle dispersion on the thermal properties of a eutectic salt for solar power applications: Experimental and molecular simulation studies

Thermophysical properties of molten salts aid in determining the storage efficiency of thermal energy storage (TES) systems in concentrating solar power plants. In this research, a novel ternary molten salt (4NaCl–37KCl–59LiNO3, mol%) was utilized as the phase change material (PCM), while Al2O3 nanoparticles (NPs) were employed as a thermal conductivity enhancer. Experimental measurements and molecular dynamics simulations were conducted to confirm that the introduction of Al2O3 NPs as dopants enhanced the specific heat, thermal conductivity, and energy storage density of the eutectic salt. Specifically, at an Al2O3 NP content of 0.5 wt%, the composite PCM exhibited a 44.23 % increase in liquid-state specific heat and a 40.82 % increase in liquid-state thermal conductivity, along with a 15.73 % increase in storage density. This study demonstrates that the enhanced thermal properties of eutectic salts by adding Al2O3 NPs are primarily attributed to the emergence of nanostructures and alterations in atomic potential energy, as evidenced by both experimental and simulated microstructural analyses. These findings offer valuable insight into the selection of thermal storage materials and additives, as well as their implementation in medium-temperature TES systems, with the objective of optimizing the efficient utilization of solar energy.

Nanofluids in microchannel heat sinks for efficient flow cooling of power electronic devices

Nanofluids hold significant potential in the field of heat transfer intensification. The objective of this paper is to investigate the thermal-hydraulic characteristics of Ag, SiO2, and Al2O3 nanofluids in rectangular (MC-R), trapezoidal (MC-T), and omega-shaped (MC-O) microchannel heat sinks (MCHSs) through conjugate numerical simulations under a constant heat flux of 100 W/cm2. Water was used as the base fluid, and nanoparticle volume fraction ranged from 0 to 6 %. The average heat transfer coefficient (HTC), Nusselt number, thermal resistance, pressure drop, and pump power as a function of Reynolds number are studied for different nanofluids and cross-sectional shapes in microchannels. The overall performance is also characterized by thermal performance factor, coefficient of performance (COP), and entropy generation analysis. The simulation results show that adding Al2O3 nanoparticles with a volume fraction of 6 % in MC-R at a Reynolds number of 500 results in a substantial 12.3 % increase in the average HTC and an approximately 8 % reduction in total thermal resistance compared to pure water. For the same nanofluid, MC-O exhibits the highest convective HTC, the highest Nusselt number, and the lowest maximum heat sink temperature. The total entropy generation in the MCHSs decreases obviously with increasing Reynolds number. MC-O has the smallest total entropy generation, meaning it has the optimal flow and heat transfer irreversibility. These findings can not only provide valuable guidance for the rational design of MCHSs but also hold significant implications for the effective cooling of microelectronic components via nanofluid-based thermal management technology.

Hot corrosion resistance of Al2O3 nanoparticles reinforced CoNiCrAlY coatings deposited by LPPS and HVOF processes in molten Na2SO4-V2O5 at 850[formula omitted

In this research, satellited CoNiCrAlY/nano-Al2O3 feedstocks with 2 and 4 wt% oxide nanoparticles and conventional CoNiCrAlY powder were deposited through the HVOF and LPPS processes on Inconel 738 substrates. The hot corrosion test was done in molten Na2SO4-55wt.%V2O5 salt at 850 °C for 24 h. The microstructure and phase composition of the as-sprayed and corroded coatings were characterized by the FESEM and XRD. The results showed that by adding Al2O3 nanoparticles in the HVOF CoNiCrAlY coatings up to 4 wt%, the porosity increased from 0.6 to 2.7 vol% and the surface roughness increased from 4.4 to 7.1 μm. By adding Al2O3 nanoparticles in the LPPS CoNiCrAlY coatings up to 4 wt%, the porosity increased from 2 to 3.76 vol%, and the surface roughness increased from 6.1 to 7.5 μm. Penetration of corrosive salt in the conventional and composite HVOF coatings, including 2 and 4 wt% nanoparticles, was obtained as 72, 16, and 140 μm, respectively. Penetration of the corrosive species in the conventional and composite LPPS coatings consisting of 2 and 4 wt% nanoparticles was measured as 91, 125, and 170 μm, respectively. The hot corrosion mechanism was basic and acidic fluxing, creating (Co, Ni)2V2O7, Na(AlO2), CoCo2O4, and NiCr2O4 corrosion products.

Thermal stabilization and energy harvesting in a solar PV/T-PCM-TEG hybrid system: A case study on the design of system components

In PV cells consisting of p-type and n-type semiconductor materials, electricity is produced with part of the solar radiation coming to the cell surfaces, while the rest causes the cells to rise in temperature, thus decreasing the conversion efficiency. Therefore, controlling the cell temperature is very important in terms of conversion efficiency. In this paper, passive cooling was performed by storing the heat acting on the PV panel with a 40 W harvesting capacity in the phase change material (PCM) in contact with the back surface. Simultaneously, active cooling was achieved by transferring the heat stored in the PCM to the hot-side surface of the integrated thermoelectric generator (TEG) with the help of the heat transfer fluid circulated in the copper pipes inside the PCM. Thus, the base hybrid system (PV/T-PCM-TEG) design (Case_1), which increases thermal stabilization of cells, was realized. While 20 thermoelectric modules are used in TEG, RT55 paraffin wax is used as PCM in the empty space on the back surface of the PV panel. In addition, to improve the PV/T-PCM-TEG system efficiency, three different cases were created by adding Al2O3 nanoparticles into the PCM (Case_2) and by placing copper fins around the copper pipes (Case_3). As a result, the power output of PV/T-PCM-TEG is 10.29%, 12.73%, and 14.22% higher for Case_1, Case_2, and Case_3, respectively, than the standard PV panel. In addition, the maximum PV panel efficiency is 30%, while the efficiency of PV/T-PCM-TEG increased to 32.8% with Case_1, 33.9% with Case_2, and 35.2% with Case_3.

Squeezed flow of MHNF (modified hybrid nanofluid) with thermal radiation and C-C (Cattaneo-Christov) heat flux: A numerical study via FDM

In this work, we have focused on the analysis of aluminum oxide(Al2O3),graphene oxide(GO),and silver(Ag)nanoparticles submerged in water enclosed between two parallel walls (plates) of infinite length. The lower wall is fixed and satisfies the convective boundary condition.The upper wall is placed at a distance and squeezes towards the lower wall. The energy equation comprises the thermal radiation effect. Heat transport is explored in presence of Cattaneo-Christov heat flux instead of Fourier heat flux. Here, water is taken as base fluid while generating a mixture of nanofluids (NF) consisting of Ag nanoparticles in the base fluid. Hybrid nanofluid is obtained by adding GO nanoparticles in the NF(Ag + water). Modified hybrid nanofluid (MHNF) is synthesized by addingAl2O3 nanoparticles in HNF(GO + Ag + water).The partial differential equations (PDEs) associated with the considered problem are modeled through Navier Stokes equations. These PDEs are then non-dimensionalized through adequate dimensionless variables and solved through the finite difference method (FDM). Influences of parameters related to the problem of velocities and temperature are visualized graphically in the flow of base fluid, HNF(GO + Ag + water),NF(Ag + water), and MHNF(Al2O3 + GO + Ag + water). It is seen that the thermal boundary layer thickness is more for MHNF as compared to NF and HNF cases due to variation in Biot number.

Biodegradable and reprocessable cellulose-based polyurethane films for bonding and heat dissipation in transparent electronic devices

It is challenging and attractive to prepare the bio-based polymers with comparable or even improved properties in terms of sustainability and economics. Here, the cellulose-based polyurethane films with ethyl cellulose as a soft segment to fully substitute polyether polyols were prepared in a facile and environmentally friendly preparation process. Moreover, the selected sample exhibited high transparency (transmittance of 84.4%), good shape memory behavior (shape fixation ratio of 95% and shape recovery ratio of 94.4%), tensile strength (9.2 MPa), good biodegradability (degradation half-life (t1/2) of 38 d) and excellent reprocessability (recycled 10 times). Especially, the cellulose-based polyurethane films performed the role of adhesive bonding with the different substrates. In addition, by adding Al2O3 nanoparticles, the EC-PU composites not only exhibited high transparency and excellent adhesive strength but also improved thermal conductivity. At a low filler loading (2.5 wt%) of Al2O3 nanoparticles (30 nm), the Al2O3-EC-PU4 film not only maintained higher transmittance of 73.6% but also had excellent lap-shear strength of 3.04 MPa. Moreover, both the thermal conductivity and thermal diffusivity of Al2O3-EC-PU4 film reached as high as 0.92 W/mK and 14.81 mm2/s, which are 146% and 1048% higher than the blank sample. Therefore, it has great potential in developing high performance bio-based plastics and transparent electronic fields.

Effect of Temperature and Al2O3 NanoFiller on the Stress Field of CFRP/Al Adhesively Bonded Single-Lap Joints

In this paper, the effect of aluminum oxide, Al2O3, nanoparticles’ inclusion into Epocast 50-Al/946 epoxy adhesive at different temperatures, subjected to quasi-static tensile loading, is numerically investigated. The single-lap adhesive joint with two different types of material adherends (composite fiber-reinforced polymer (CFRP) and aluminum (Al) 5083 adherends) and adhesive Epocast 50-A1/hardener 946 were modeled in ABAQUS/CAE. A numerical methodology was proposed to analyze the effect on peel stress and shear stress by adding Al2O3 nanoparticles into the neat adhesive at 25 °C, 50 °C, and 75 °C temperatures at four different locations of the adhesive regions: the interface of the adhesive and aluminum adherend (location A), the middle plane of the adhesive region (location B), the middle longer edge (along the length of the adhesive, location C), and the middle shorter edge (along the width of the adhesive, location D). The results showed that adding nanoparticles into the neat adhesive improves joint strength at room and elevated temperatures. High peel and shear stresses were recorded near both edges of the locations (A, B, C, and D). For location A, adding nanofillers into the adhesive resulted in the reduction in peak peel stress by 1.3% for 25 °C; however, it increased by 2.7% and 10.7% for 50 °C and 75 °C temperatures, respectively. Furthermore, the peak shear stress observed a considerable reduction of 19.6% for 25 °C, but it increased by 7.7% and 8.7% for 50 °C and 75 °C temperatures, respectively, for location A. The same trend was also observed for other locations (i.e., B, C, and D). This signified that adding aluminum oxide nanoparticles in the adhesive resulted in increased stiffness at higher temperatures and increased ductility of the joint, as compared to the joint with neat adhesives at room temperature. Moreover, it was observed that locations A and B were more vulnerable to damage initiation, as the peak of stresses lay near the edges, indicating that the crack initiation would take place close to the edges and propagate towards the center, leading to ultimate failure.

Analyzing the combustion and emissions of a DI diesel engine powered by primary alcohol (methanol, ethanol, n-butanol)/diesel blend with aluminum nano-additives

The study investigates the effects of the primary alcohol (methanol, ethanol, n-butanol) and aluminum (Al2O3) nano-additive on combustion and emission characteristics of a direct injection diesel engine at 30% (low) and 80% (high) engine loads of a constant engine speed. The alcohol/diesel nanofuels were made by adding Al2O3 nanoparticles (25, 100 ppm) into the alcohol/diesel blend (the same oxygen content level) with ultrasonic mixing and surfactant assistance. The results revealed that an extension in the ignition delay was induced by the substitution of primary alcohol fuel, among which methanol showed the most apparent regardless of engine load. Under high load, the addition of methanol in diesel aroused the most obvious promotion effects on peak heat release rate (HRRmax) and peak cylinder gas pressure (CGPmax), while under low load, the addition of n-butanol had the most obvious promotion effect. The addition of Al2O3 nanoparticles to the alcohol/diesel blend significantly improved the combustion process, with the results of decreased ignition delay, increased CGPmax and HRRmax, and shortened combustion duration, especially for the cases in high nanoparticles dosage (with a few exceptions). Under both loading conditions, the addition of methanol led to the least emissions of CO, NOX, and smoke opacity among the three alcohol fuels, while HC emissions presented just the opposite trends. Compared to pure diesel fuel, the engine powered by alcohol/diesel nanofuels emitted less CO, HC, and smoke emissions with a reduction amplitude of 36.2–77.8%, −8.8–10.7%, and 24.2–55.6%, respectively. However, Al2O3 nanoparticles addition brought more NOX emission with the increment of 6.2–17.5%, especially for the methanol/diesel nanofuels.

Insights into the thermophysical properties and heat conduction enhancement of NaCl-Al2O3 composite phase change material by molecular dynamics simulation

In concentrated solar power (CSP) applications, the thermal energy storage (TES) system with molten salt is widely utilized. However, molten salts usually suffer from relatively low thermal conductivity. In this regard, adding nanoparticles has been considered as an effective way to improve the thermal conduction of molten salt. In the present work, the thermophysical properties of NaCl-Al2O3 composite phase change material (PCM), including the melting point, specific heat capacity, melting enthalpy, self-diffusion coefficient as well as thermal conductivity, are first examined by using molecular dynamics simulations. Simulation results show that the thermal conductivity of base salt NaCl can be significantly improved by adding Al2O3 nanoparticles. An enhancement of 17.94% has been observed with 5.565 wt% addition of Al2O3 nanoparticles. The results also suggest the doped nanoparticles can reduce the melting point and melting enthalpy but increase the specific heat capacity of base salt. The increase in self-diffusion coefficient of composite PCM with temperature indicates the existence of micro-convection around nanoparticles in base salt. Furthermore, the microscopic mechanism of thermal performance enhancement by adding nanoparticles into molten salt has been revealed. The results indicate that the interfacial thermal resistance is greatly related to the type of base salt and nanoparticles. Based on energy analysis, it is concluded that the variation of ion collision frequency in base salt due to the addition of nanoparticles plays a major role in the enhancement of thermal conductivity of NaCl-Al2O3 composite phase change material.

Polymer composites with high energy density and charge–discharge efficiency at high temperature using aluminum oxide particles

Polymer-based dielectric capacitors with excellent elevated-temperature capacitive performances are highly demanded in next-generation electronic power systems. Here, we design an effective and low-cost way to fabricate high-temperature polymer capacitors via adding Al2O3 nanoparticles (NPs) into polyetherimide (PEI) nanocomposites. Benefited from good thermal stability, high thermal conductivity of Al2O3 NPs and high glass transition temperature of PEI, the Joule heat caused by high temperature and large electric field, dissipate quickly. Therefore, the nanocomposites present low dielectric loss and superior high-temperature capacitive properties. Consequently, even at 150 °C, the Al2O3 NPs/PEI nanocomposite delivers still slim electric displacement-electric field (D-E) loops, small remnant electric displacement (Dr), and large maximum electric displacement (Dmax). Thus, it results in an ultra-high discharged energy density (Ue) of 6.68 J cm−3, which far exceeds the state-of-the-art polymer and polymer composites, and high efficiency (η) of 84.77% at 150 °C. This work addresses the paradox that large Ue and high η cannot be simultaneously achieved in high-temperature polymer composites.

Effect of Concentration of Al2O3 Nanoparticles on Electrical Properties of Mineral Oil

This study aimed to compare the electrical characteristics of mineral oil-based nanoparticles to those of pure mineral oil. Mineral oil used in distribution transformers was mixed with aluminum oxide (Al2O3) nanoparticles, which serve as an insulator, with 0.01, 0.03, and 0.05 % mineral oil volume concentrations. The moisture content in mineral oil was measured beforehand, and the electrical tests were subsequently conducted in accordance with international standards. The moisture content test revealed that the combination of nanoparticles and mineral oil resulted in an increase in moisture content. As regards the test of AC withstanding voltage and negative polarity lightning impulse voltage, it was found that the mineral oil mixed with the nanoparticles had higher dielectric strength than the original mineral oil. In addition, the test results of positive polarity lightning impulse voltage demonstrated that with a mixture of mineral oil and the nanoparticles at a 0.01 % concentration, the positive polarity lightning impulse dielectric strength of the mineral oil increased. However, at concentrations of 0.03 and 0.05 %, it did not rise, regardless of the increasing volume of nanoparticles. The results, thus, showed promising directions for applications of nanoparticles in the development of electrical properties of mineral oil. HIGHLIGHTS The addition of Al2O3 nanoparticles to the mineral oil resulted in an increase in the oil moisture content. However, it was found that the moisture content in the mineral oil tended to decrease with the increase in the amount of nanoparticles The optimum nanofluid combination in terms of increased AC breakdown strength was created by adding Al2O3 nanoparticles to mineral oil at a rate of 0.05 vol% The Al2O3 nanoparticles being added to the mineral oil can give an increase in the impulse breakdown voltage with the negative polarity For the positive polarity of the impulse breakdown voltage, the best nanofluid mixture in terms of increased breakdown strength was produced by the addition of Al2O3 nanoparticles at a rate of 0.01 vol% to the mineral oil GRAPHICAL ABSTRACT

Stability, surface tension, and thermal conductivity of Al2O3/water nanofluids according to different types of alcohol and their proportion

In this study, the stability, surface tension, and thermal conductivity of Al2O3/water nanofluids with different types of alcohol fluids were investigated. Different types of alcohols (butanol, pentanol, and hexanol) were added to the Al2O3/water nanofluid. From the UV–vis spectroscopy results, Al2O3/water nanofluids did not show a significant absorbance difference for concentrations more than 0.5 wt%. From 0.1 to 0.5 wt% the absorbance enhancement ratio was 101.3%; however, it was 9.0% from 0.5 to 0.9 wt%. Therefore, 0.5 wt% Al2O3 nanofluids are effective in terms of fluid dispersibility. During the zeta potential measurement of the nanofluid stability, increasing the Al2O3 in the nanofluids caused more instability. However, the type and concentration of the aqueous alcohol solutions without Al2O3 did not significantly affect the stability characteristics. The contact angle of the alcohol-based nanofluids at saturated concentrations showed a decrease of at least 18.7%. Adding Al2O3 nanoparticles to the alcohol-based nanofluids increased the surface tension by an average of 3.4%. The thermal conductivity of the alcohol-based nanofluids was lower than that of distilled water. However, the addition of Al2O3 can enhance their thermal conductivity. The thermal conductivity lowered by the alcohol-based fluids enhanced by an average of 73.4% after adding Al2O3.

Experimental investigation of the effect of Al2O3 nanoparticles as additives to B20 blended biodiesel fuel: Flame characteristics, thermal performance and pollutant emissions

Palm oil biodiesel has been identified as a renewable energy source with a huge potential to replace liquid fossil fuels in the future. The current experimental work investigates the effect of using Al2O3 nanofuel produced by adding Al2O3 nanoparticles to 20 % blend of palm oil biodiesel with diesel fuel on the flame characteristics, radiation, temperature and pollutant emissions in an oil burner. A homogeneous suspension was prepared from Al2O3 nanoparticles, of the concentration of 500 ppm, in B20 blended biodiesel fuel. The Infrared Radiation (IR) of the flame, the flame temperature, luminosity, radiative heat flux and CO and NOx pollutant emissions were measured and compared with those of B20 fuel. The results indicate that Al2O3 nanoparticles enhance the evaporation rate of nanofuel droplets and shift the maximum flame temperature to the upstream region. Al2O3 nanoparticles favor scattering of heat over heat absorption, which accelerates flame heat transfer and decreases its temperature. Nevertheless, Al2O3 nanoparticles improve soot particles nucleation and surface growth and increase the highly emissive intermediate soot particles in the flame reaction zone. These intermediate soot particles enhance the luminosity and IR and total radiation heat transfer of the flame. The enhancement rate for average flame radiation of B20 blend fuel was as much as 10 % and higher concentrations of nanoparticles led to a substantial increase in the radiation heat flux. However, they cause an increase in the CO emission from 48 to 62 ppm which is in the standard level. Finally, the use of the nanofuel instead of B20 fuel decreases the NOx emission by 11 %.

Thermal performance of nanofluid with employing of NEPCM in a PVT-LFR system

A photovoltaic thermal- linear Fresnel reflector (PVT-LFR) modified with integration of phase change material (PCM) was investigated numerically in current paper. The impact of the different mass flow rates and influence of adding Al2O3 nanoparticles to the coolant and PCM on the performance of collector is evaluated. In order to model the PVT-LFR system a transient solver is chosen. The governing equations of the PVT-LFR are solved using CFD (computational fluid dynamic) approach. The SIMPLE algorithm was applied for coupling of velocity and pressure. The simulation is done under the constant solar radiation of 750 W/m2 for 20,000 s. The results show, that electrical efficiency of the system is reduced by decreasing mass flow rate and adding nanoparticles to the PCM, however, with adding nanoparticles to coolant, the electrical performance of the system is enhanced. The thermal output of the system enhances with increasing mass flow rate. Furthermore, adding nanoparticles to the water and phase change material has positive effect on the thermal output of collector.

Analysis of turbulent two-phase flow and heat transfer using nanofluid

Finite element analysis of turbulent two-phase flow and heat transfer was conducted in the present investigation to analyze the effect of adding Al2O3 nanoparticles to the minimum quantity lubrication (MQL) cooling fluid on the cutting tool temperature distribution. Discrete phase model (DPM) was used to describe the trajectory of the mist in the fluid domain. The numerical results presented in this investigation were in good correlation with the experimental results. The findings of this investigation demonstrated that the average temperature of the cutting tool was found to decrease with adding Al2O3 nanoparticles. Further, the results demonstrated that the temperature variation was significant in the vicinity of the tool tip compared to a faraway point. The compressed air pressure was found to have a profound effect on the temperature of the cutting tool. This study was an effort to determine the performance of the cutting tool using MQL based nanofluid and utilizing discrete phase model.

Simulation of Natural Convection around an Inclined Heating Triangular Cylinder Using Lattice Boltzmann Method: On the Stabilization of the Oscillatory Regime by Using Nanoparticles

Natural convection heat transfer in an inclined outer square cylinder confining a heated triangular cylinder is studied numerically using the Lattice Boltzmann method. The working fluid (pure water or Al2O3-water nanofluid) is confined in the space between the heated triangular body and an outer square cylinder. The cooling process of the system is ensured through two opposite isothermal cold walls of the external cylinder. The parameters governing the present problem are the Rayleigh number (103 ≤ Ra ≤ 106), the inclination of the configuration (0° ≤ θ ≤ 180°), and the volume fraction of nanoparticles (0 ≤ φ ≤ 0.04). The results obtained are presented in terms of streamlines, isothermes, intensities of the flow cells, and Nusselt numbers. This study shows that the inclination of the studied configuration has an important effect on the flow structure, the flow cells’ intensities, the amount of heat evacuated through each of the two cold walls and on the steadiness of the final state of the flow (steady or unsteady). It is shown that the inclination of the system has a moderate effect on the global quantity of heat leaving the block ( undergoes a maximum variation of 12.2% when the inclination is varied in its range). In addition, we show that it is possible to eliminate the Hopf’s instabilities and bring the flow to the steady regime by adding Al2O3 nanoparticles with certain volume fraction in the base fluid.

Experimental analysis on tribological properties and lubricating mechanisms of oil-based Al2O3 nanofluids applied on steel-brass frictional pairs

The present research studied the tribological properties of Al2O3 nanofluids applied on steel-brass contacts. It was found that the coefficient of friction could be stabilized and reduced by approximately 40.7% after adding Al2O3 nanoparticles. The wear width and wear depth could be reduced by up to 39.6% and 69.3% while using 1 wt% Al2O3 nanofluid. By examining the worn surfaces, Al2O3 nanoparticles were embedded into brass by external load to form a hard case, which could protect the brass surfaces from wear loss. In addition, some black spots with low shear resistance containing high carbon content were formed which were the result of the presence of oleic acid. In summary, the excellent lubricating performance of Al2O3 nanofluids was mainly associated with the physical embedment of Al2O3 nanoparticles and tribo-films of oleic acid. The results obtained in this research can be used to enhance the performance and extend the service life of some engineering components such as journal bearings with inner brass bushings.