Mass Fraction Of Nanoparticles Research Articles

Improving the emission properties of graphene–carbon nanotube hybrid nanostructures through functionalization with BaO nanoparticles and laser treatment

This paper presents the manufacturing technology of hybrid nanostructures based on a buffer layer of reduced graphene oxide (rGO) flakes with vertical single-walled carbon nanotubes (SWCNTs) and their bundles functionalized with BaO nanoparticles. Using density functional theory (DFT) calculations, supercells of rGO/SWCNT/BaO films were constructed and the patterns of the electron work function were revealed. It has been demonstrated that the electron work function is influenced by both the mass fraction of BaO nanoparticles and the inter-tube distance. Branched carbon nanostructure was formed using a pulsed laser irradiation. Fragmentation of BaO nanoparticles on the carbon surface was achieved. It was shown that after laser treatment, Ba(NO3)2 particles up to 200 nm in size were fragmented into smaller BaO nanoparticles with sizes of a few nanometers, covering the nanotubes. The field emission current–voltage characteristics (CVCs) were measured and showed a 42-fold increase in emission current compared to the nanostructure without BaO functionalization and laser treatment. BaO-functionalized hybrid carbon nanostructures are predicted to be efficient field cathodes, with a current density of at least 2 A/cm2, for use in X-ray tubes, field emission displays, and vacuum microwave devices.

Preparation and rheological properties of highly stable bidisperse magnetorheological fluids

The utilization of magnetic nanofluids as the base carrier liquid proves to be an effective strategy for enhancing the stability of magnetorheological fluids. However, the preparation method for bidispersed magnetorheological fluids still deserves further investigation. In this study, Fe3O4 nanoparticles were synthesized through chemical co-precipitation, and aviation hydraulic oil-based magnetic nanofluids were prepared using myristic acid as a surfactant. Micron-sized particles, modified with the same surfactant, were dispersed into the magnetic nanofluids, resulting in a novel bidisperse magnetorheological fluid (C-MRFF). The coated particles underwent physical phase analysis and magnetic property testing through an x-ray diffractometer, Fourier infrared spectrometer, transmission electron microscope, scanning electron microscope, and vibrating sample magnetometer. Due to the addition of nanoparticles, C-MRFFs exhibited superior stability to micron-sized particle-based magnetorheological fluids. They demonstrated the best sedimentation stability and redispersibility at a 9% mass fraction of nanoparticles. Thanks to the protection of the micron-sized particle surface coating, C-MRFFs displayed superior sedimentation stability to traditional bidisperse magnetorheological fluids over a wide temperature range. The magnetorheological properties of C-MRFFs were studied. The results indicated that the yield stress of C-MRFFs increased with increasing magnetic field strength or decreasing temperature. The increase in the mass fraction of nanoparticles was beneficial to the increase in yield stress until severe settling of C-MRFFs occurred. In comparison to micron-sized particle-based magnetorheological fluids, C-MRFFs exhibited higher yield stresses. Although the yield stress of C-MRFFs was slightly lower than that of traditional bidisperse magnetorheological fluids due to the surface coating of larger particles, they exhibited stronger shear resistance over a wide temperature range.

Experimental investigation on the stability and heat transfer enhancement of phase change materials composited with nanoparticles and metal foams

Conventional phase change materials (PCMs) possess the challenge of low thermal conductivity, which hinders the energy exchange rate and storage efficiency. PCMs composited nanoparticles and metal foams have been a proven solution to enhance the thermal characteristics of PCMs. In this work, three enhanced PCM composites including nanoparticle/paraffin, metal-foam/paraffin and nanoparticle/metal-foam/paraffin were prepared using fusion blending and vacuum impregnation method. The effects of different nanoparticles with different mass fractions on the stability and heat storage and release characteristics of nanoparticle/paraffin were investigated. Compared with paraffin, the melting time and solidification time of nano-metal/paraffin are reduced by a maximum of 30.18 % and 43.15 %, respectively. In addition, the effect of pore density of metal foam on natural convective heat transfer process was evaluated. The results showed that the stability in descending order is as follows: nano‑aluminum, nano‑copper and nano‑silver. The optimal mass fraction of nanoparticles with good stability was 1.5 wt% (copper), 1.0 wt% (silver), 1.5 wt% (aluminum), respectively. The metal foam makes the internal temperature distribution of PCMs more uniform in the heat transfer process, while inhibiting the convective heat transfer process. With the increase of pore density, the effect on natural convection heat transfer process rises. When the PPI (pores per linear inch) of foamed metal is greater than 40, the natural convection process can be inhibited, obviously. The foam metal has a more significant effect on the heat transfer performance of nanoparticle/metal-foam/paraffin than that of the nanoparticles. The economic benefits of nanoparticle/paraffin, metal-foam/paraffin and nanoparticle and metal foam composite phase change materials are progressively decrease, with MFP being suitable for applications with high economic budgets.

Aqueous Theta-Phase Aluminum Oxide Nanofluid for Energy Applications: Experimental Study on Thermal Conductivity

The use of nanofluids in energy systems allows for increasing efficiency and developing more economic systems. Alumina-water is one of the most common nanofluids used but little information is available about the aqueous theta-phase aluminum oxide. Given the lack of thermal conductivity data for this nanofluid, in this research, this property is experimentally evaluated. Nanofluid is prepared using the two-step method, employing a magnetic stirrer and a sonication bath. A high-precision sensor is employed for measuring thermal conductivity, using the method of transient hot wire. The thermal conductivity measurements for the base fluid (water) are compared with data provided by NIST. Nanoparticle mass fraction in the nanofluid is increased from 1 to 10% and the temperature from 22.1 to 59.3 °C. Three sonication times (1.5, 4 and 16.5 h) are used. A strong dependence between the thermal conductivity and the temperature and nanoparticles concentration has been found, while the sonication time has a negligible influence on the thermal conductivity in the range of times tested. A correlation to obtain the thermal conductivity of the water-based nanofluid using theta-phase aluminum oxide has been developed, including nanoparticle volume concentration and temperature. An excellent agreement is obtained between predicted and experimental data.

Improvement of carbon fiber/phenolic composite properties by low-loading graphene oxide and SiO2 nanoparticles

As an ablative thermal protection material, the mechanical properties and ablative resistance of carbon fiber/phenolic (C-Ph) composite should be improved to meet the high requirements in deep space exploration. Herein, the properties of C-Ph composites were improved by the synergistic effect of low-concentration graphene oxide (GO) solution and low mass fraction of SiO2 nanoparticles. Compared to the unmodified C-Ph composite, the compressive strength of the modified composites was increased by 40.75 % and the linear and mass ablation rates were reduced by 17.78 % and 43.95 %, respectively. The introduction of GO effectively improved the interfacial bonding between the fiber and phenolic resin. Meanwhile, the uniformly dispersed SiO2 nanoparticles resisted the applied loads, thus synergistically enhancing the mechanical properties of the composites. In terms of improving ablation resistance, GO promoted the graphitization of fibers and enhanced the stability of the char layer. Concurrently, SiO2 nanoparticles reacted with the carbon matrix under high temperatures to form ablation-resistant SiC, thus synergistically enhancing the ablative properties of the composite.

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 study on the heat transfer performance of liquid metal high-temperature oscillating heat pipes with diamond nanoparticles

In order to realize effcient thermal dissipation at high temperatures, diamond nanoparticles were added in the sodium–potassium (NaK) alloy liquid metal high-temperature oscillating heat pipes (LMHOHPs) to improve the heat transfer performance. The NaK alloy with different mass fractions (0 wt%, 0.25 wt%, 0.50 wt%, 0.75 wt%, 1.00 wt%) of diamond nanoparticles was used as the working fluids. Under the input power of 2000–3500 W and the inclination angle of 0°, 30°, 60°, and 90°, the start-up characteristics and heat transfer performance of LMHOHPs after adding diamond nanoparticles were measured and analyzed. The results showed that after adding diamond nanoparticles, the LMHOHP started more smoothly and could effectively promote the unidirectional circulation flow of the working fluid. The enhancement effects of diamond nanoparticles were more obvious at low input powers. When the inclination angle was 0°, nanoparticles generally presented an enhancement effect. In this study, there was an optimal nanoparticle concentration of 0.50 wt%, which enhanced the heat transfer performance under all the investigated conditions. When the nanoparticle concentration was 0.75 % and the inclination angle was 30°, the maximum enhancement rate of 15.41 % was reached at the input power was 2250 W.

Investigating heat exchanger tube performance: second law efficiency analysis of a novel combination of two heat transfer enhancement techniques

AbstractIn the study, the focus was on evaluating the second law efficiency of a heat exchanger tube operating under continuous heat flux and turbulent flow conditions. The evaluation involved the use of a hybrid GnP and Fe3O4 and modified coiled wire as passive heat transfer enhancement techniques. The primary objective was to investigate the impact of these combined techniques on thermal and hydraulic performance, entropy generation number, Bejan number and second law efficiency. To achieve this, different mass fractions of GnP and Fe3O4 nanoparticles were used in the hybrid nanofluid, along with two forms of modified coiled wire: barrel type and hourglass type. The experimental results indicated that the utilization of hybrid nanofluids and modified helical inserts led to a noticeable improvement in the second law efficiency of the heat exchanger tube. However, it was observed that the differences in entropy generation number and Bejan number between the barrel and hourglass types were not significant, mainly due to higher frictional losses associated with the latter. The highest recorded second law efficiency was 0.416, while the lowest entropy generation number was 0.118. These values were achieved through the combined use of GnP and Fe3O4 with a mass fraction of 0.4% and a barrel-type coiled wire insert with a pitch ratio of 0.5.

Impact of nanoparticle agglomeration on thermal conductivity of molten salt based nanofluids: Insights from molecular dynamics and lattice Boltzmann methods

The nanoparticle aggregation has significant influence on heat transfer properties. The contradictions between different researches exist and the underlying mechanisms of heat conduction remain unclear. To address these issues, the thermal conductivity of solar salt-SiO2 nanofluids in the non-aggregated and aggregated states was investigated, based on the combination of the advantages of molecular dynamics (MD) in revealing physical insights and lattice Boltzmann method (LBM) in simulating properties for complex structures. LBM models were simplified on the basic of MD results. Different heat transfer physics in nanofluids at nanoscale and mesoscale were compared. The results show that the thermal conductivity of aggregated nanofluid is higher than the non-aggregated nanofluid. By analyzing the diffusion coefficient, number density and vibrational density of states, we found that the previous hypotheses (such as Brownian motion, interfacial layer and interfacial thermal resistance) cannot explain the enhanced thermal conductivity induced by the nanoparticle agglomeration. The heat transfer mechanisms of aggregated nanofluid were further analyzed from new perspectives, i.e., the contributions of different material components and fluctuation modes to heat flux. It is found that the nanoparticle aggregation leads to the nanoparticle contribution increase, indicating the formation of low thermal resistance channels within the aggregates. The heat conduction contributed by collision decreases in the aggregated state, while that contributed by potential energy increases. Moreover, the thermal conductivity of aggregated nanofluid is negatively correlated with temperature, aggregate size and fractal dimension of agglomerates, and positively correlated with mass fraction of nanoparticles, degree of agglomeration, and backbone length of each aggregate.

Regulating droplet impact dynamics of nanoparticle suspension: Phenomena, mechanisms, and implications

Droplet impact on solid substrates is a ubiquitous phenomenon in nature, agriculture, and industrial processes, playing a crucial role in numerous applications including self-cleaning, pesticide utilization, and inkjet printing. As a promising technique, adding nanoparticles into simple fluids to form nanofluids can effectively manipulate droplet impact behaviors. However, a comprehensive understanding of how nanoparticles modify the droplet impact dynamics, especially on the nanoscale, is still far from being fully explored. Hence, in this work, through the combined effort of molecular dynamics simulations and theoretical analysis, we elaborate on the influences of nanoparticles on droplet impact process. Using simple droplets as a control, we summarize four typical droplet impact modes and reveal how nanoparticles alter the impact behaviors of droplets, taking into account the key parameters including substrate wettability, impact velocity, volume fraction, and mass fraction of nanoparticles. We also demonstrate that with appropriate modifications, the theoretical/empirical models to predict the maximum contact diameter and the occurrence of breakup for simple droplets still hold to predict those of nanofluid droplets. Our findings and results enhance the understanding of the impact of nanoparticles on the droplet impact dynamics, with promising possibilities for various applications where regulating droplet impact behaviors is desired.

Experimental study on the dynamic wetting of silica nanofluids

Nanofluids are recently discovered nanomaterials with improved thermophysical properties that can enhance the efficiency and reliability of heat transfer systems. Their relevant properties for describing heat transfer, thin film flows, droplet impingements, or microfluidics are surface tension and wettability. A thorough investigation on this topic of research is crucial to understand the root cause of the factors affecting the degree of wetting of nanofluids on solid surfaces. In the present work, silica (SiO2) nanofluids with different mass fractions and types of surfactants based on deionized water were prepared using a simple and cheap two-step method. The effect of surface tension changes on the lateral friction force of the nanofluid was studied using a solid–liquid interface lateral friction force detection system. According to the findings, an increase in the mass fraction of silica nanoparticles led to the larger surface tension of the nanofluid, resulting in a linear decrease in the lateral friction of the latter on the hydrophobic surface of PDMS. The use of ionic surfactants as dispersants caused a dramatic decrease in surface tension and static angle of SiO2 nanofluid (by 20% and 30% after adding SDS and by 40% and 50% after adding CTAB, respectively). This exerted a noticeable impact on the lateral friction force of the fluid. On the contrary, polymeric surfactants (NaPSS) had a small effect on the lateral friction of SiO2 nanofluid. Meanwhile, the lateral friction after stable motion differed from the maximum static friction to a small extent.

Investigation on the Effects of Nanorefrigerants in a Combined Cycle of Ejector Refrigeration Cycle and Kalina Cycle

Abstract The main objective of this study is to carry out the thermodynamic analysis of a new power/refrigeration combined cycle which consists of an ejector refrigeration cycle (ERC) and a Kalina cycle. In ERC, nanorefrigerants are used as the working fluid. Used nanorefrigerants are homogenous mixtures of different base refrigerants (R134a, R152a, and R290) and nanoparticles (TiO2 and Al2O3) with 0–5 wt% nanoparticle concentration. The effects of variation in system operational parameters (nanoparticle mass fraction, evaporator pressure, condenser pressure) on energy efficiency and exergy efficiency of the combined cycle are reported. Additionally, net power production, refrigeration capacity, heat input to the combined cycle, and their exergy contents are given for the case of TiO2/R290 nanorefrigerant use in ERC. This study is the first ERC analysis in which the effect of R152a and R290 base refrigerants and TiO2 nanoparticle use on ERC performance is investigated. The results show that as the nanoparticle concentration and evaporator pressure increase and condenser pressure decreases, the energy and exergy efficiencies of the cycle increase. Under all the considered operational conditions of the combined cycle, the highest efficiency results are obtained for R290 and the lowest for R134a-based refrigerants.

Heat collection characteristics of nanofluids in direct absorption solar collector with built-in rotors

As for the uneven heating of the working medium in direct absorption solar collector (DASC),this paper proposed the method of optimizing the flow pattern in DASC by inserting combined rotors into the collector tube to improve the heat collection performance. The working medium used in this paper is Chinese ink nanofluid. The heat collection performance of the collector was studied, and the enhanced mechanism was explained through simulations. Results demonstrated that inserting rotors improved the temperature rise rate in the circuit, and the temperature of the medium after inserting rotors increased by about 56 % compared with that before inserting rotors when the mass fraction of nanoparticles was 0.2 %. In some cases, a small number of rotors can achieve an enhancement effect similar to that of enormous rotors, and improve the economic performance of the system. The numerical simulation results showed that the high-temperature medium in the plain tube is concentrated near the light side, while the medium in the centre and backlight side of the tube cannot easily absorb solar radiation. After rotors were inserted into the tube, the back-side and light-side media were displaced and mixed by the turbulence of rotors, which can improve heat collection.

Study on packing characteristics of powders with surface modification by nanoparticles

Powders with coated nanoparticles on the surface as a surface modification technique can alter the surface texture of the particles. This paper explored the additional number of nanoparticles on powder packing characteristics. The adhesion mode of nanoparticles and its influence on the inter-particle force in the system were discussed. The study found that the bulk density first increases and then decreases as the content of nanoparticles increases. The incorporation of nanoparticles reduces the inter-particle force, with the optimal mass fraction of nanoparticles being 0.25%, resulting in a 4.43% increase in bulk density. The attachment mode of nanoparticles was observed and analyzed through SEM, with five possible contact modes between particles identified. The change in the inter-particle force was quantitatively analyzed through the probability of each mode. The Bo number was used to establish a prediction model for bulk density, which yielded a highly accurate prediction.

Exploring Quantum Dots Size Impact at Phase Diagram and Electrooptical Properties in 8CB Liquid Crystal Soft-Nanocomposites.

We explore the influence of functionalized core-shell CdSe/ZnS quantum dots on the properties of the host liquid crystal compound 4-cyano-4'-octylbiphenyl (8CB) through electrooptical measurements. Two different diameters of quantum dots are used to investigate the size effects. We assess both the dispersion quality of the nanoparticles within the mixtures and the phase stability of the resulting anisotropic soft nanocomposites using polarizing optical microscopy. The temperature-mass fraction phase diagrams of the nanocomposites reveal deviations from the linear behavior in the phase stability lines. We measure the birefringence, the threshold voltage of the Fréedericksz transition, and the electrooptic switching times of the nanocomposite systems in planar cell geometry as functions of temperature, mass fraction, and diameter of the quantum dots. Beyond a critical mass fraction of the dopant nanoparticles, the nematic order is strongly reduced. Furthermore, we investigate the impact of the nanoparticle size and mass fraction on the viscoelastic coefficient. The anchoring energy at the interfaces of the liquid crystal with the cell and the quantum dots is estimated.

Detailed experimentation and prediction of thermophysical properties in lauric acid-based nanocomposite phase change material using artificial neural network

The thermal conductivity (TC) of a nanocomposite phase change material (NPCM) may be improved by adding nanostructured materials to a Phase Change Material (PCM). To assess the heat transfer rate during the process of phase change, such as melting and freezing, an accurate TC prediction of NPCM is required. A Field Emission Scanning Electron Microscope (FESEM) was utilized to examine the nanoparticle morphological study, and X-Ray Diffraction (XRD) analysis evaluated the crystalline structure. NPCMs were verified using Fourier Transform Infrared Spectroscopy (FTIR). The goal of this research is to create an Artificial Neural Network (ANN) that guesses the TC and viscosity of Lauric Acid (LA) embedded with dispersed copper oxide (CuO) and aluminium oxide (Al2O3). A multi-layered feed-forward ANN (MLFFANN) is trained using the Levenberg-Marquardt (LM) backpropagation algorithm. There are 130 experimental datasets in total, obtained from experiments with nanoparticle mass fractions ranging from 1.25 to 10 wt%. The minimum mean square error (MSE) for TC and viscosity is 4.6815 × 10−5 and 2.4681 × 10−5, respectively. The average absolute deviation (AAD) for TC and viscosity is 0.004249 and 0.003596, respectively, while the mean absolute percentage error (MAPE) is 2.1835 % and 4.8197 % for TC and viscosity, and the correlation coefficients(R) are 0.992 and 0.975, respectively. The largest percentage variation between experimental values and ANN computed values for the liquid and solid phases, respectively, is 3.54 % and 0.832 %. It demonstrates that the constructed ANN prediction model predicts the increased TC and viscosity of NPCM for different nanoparticle loadings, temperatures, and oxide nanoparticles.

Preparation of HNTs‐e‐POSS hybrid nanoparticles and modification of gallic acid epoxy resin

AbstractGallic acid is a renewable plant phenolic resource, and the polyphenolic bio‐based epoxy resin prepared from it can be used as a substitute for bisphenol A epoxy resin in certain fields. However, bio‐based epoxy resins used in the field of high‐performance composite material matrices often require modification. In this paper, firstly, γ‐(2,3‐epoxypropoxy)propyl trimethoxysilane (KH560) was used as the raw material to prepare epoxy‐based cage silsesquioxanes (E‐POSS). Then, E‐POSS was grafted onto γ‐aminopropyltriethoxysilane (KH550) modified halloysite nanotubes (m‐HNTs) to prepare a novel hybrid nanoparticle HNTs‐e‐POSS. Experimental analysis shows that ring opening reactions of amino and epoxy groups can occur between m‐HNTs and E‐POSS, forming a hybrid nanoparticle system of POSS aggregates on the surface of HNTs. Bio‐based nanocomposites were prepared by adding different mass fractions of hybrid nanoparticles HNTs‐e‐POSS into polyphenol type gallic acid epoxy resin matrix (GAER) and using methyltetrahydrophthalic anhydride as curing agent. The properties and micromorphology of the composite were analyzed and characterized. The research showed that with the addition of HNTs‐e‐POSS nanoparticles, the strength and toughness of the composite resin system show a pattern of first increasing and then decreasing, while the storage modulus(E′), glass transition temperature (Tg), and thermal stability of the composite material increased. Mechanical performance analysis shows that the introduction of 0.5 wt% HNTs‐e‐POSS would increase the tensile strength of the composite by 25.46%, while adding 0.75 wt% HNTs‐e‐POSS can increase the impact strength by 15%. The E′(30°C) increased by 24.2% and Tg increased by 7.7°C when the HNTs‐e‐POSS addition was 0.25 wt%.Highlights Prepared hybrid nanoparticle HNTs‐e‐POSS by grafting POSS onto the HNTs surface. Application of HNTs‐e‐POSS in modification of bio‐based gallic acid epoxy resin. HNTs‐e‐POSS can co‐cured with epoxy matrix to increase the crosslinking degree. The strength, toughness, and modulus of gallic acid epoxy resin are improved. Tg and thermal stability of gallic acid epoxy resin are enhanced.

A new solution to a weakly non-linear heat conduction equation in a spherical droplet: Basic idea and applications

A new analytical solution to a non-linear heat transfer equation in a spherically-symmetric droplet is suggested. All thermophysical properties inside the droplet are considered to be close to their average values. This allows us to consider the non-linearity of this equation as weak. The solution is presented as T=T0+T1, where T0 is the solution to a linear heat conduction equation, and T1≪T0. The equation for T1 is presented as a linear heat conduction equation with a source term depending on the distribution of T0 and its spatial derivatives inside the droplet. The latter equation is solved analytically alongside the linear equation for T0, and the final solution is presented as T=T0+T1. The predictions of the numerical code in which this solution was implemented are verified based on a comparison of those predictions with the predictions of COMSOL Multiphysics code using input parameter values that are typical for nanofluid (water and SiO2 nanoparticles) droplet evaporation in atmospheric conditions. It is demonstrated that for these experiments T1≪T0 which justifies the applicability of the linear heat conduction equation used for the analysis of this process. Small differences in the temperatures predicted by both non-linear and linear models lead to a much more noticeable difference in integral characteristics such as time before the start of the formation of the cenosphere when the mass fraction of nanoparticles at the droplet surface reaches about 40%.

Experimental investigation of usage of POE lubricants with Al2O3, graphene or CNT nanoparticles in a refrigeration compressor.

In this study, the use of nanolubricants containing Al2O3, graphene, and carbon nanotubes (CNTs) at different mass fractions in a refrigeration compressor was experimentally investigated. The required electrical power of the compressor was measured to determine the effect of the use of nanolubricants. Nanoparticles used in the preparation of nanolubricants were gradually added to the lubricant to determine the optimum nanoparticle mass fraction for each nanoparticle type. Thus, it was found that the compressor operated safely and efficiently with nanolubricants. Furthermore, the optimum mass fractions were determined to be 0.750% for Al2O3, 0.250% for graphene, and 0.250% for CNTs for operating conditions of this study. As a result, the required electrical power of the compressor decreased by 6.26, 6.82, and 5.55% with the addition of Al2O3, graphene, and CNT nanoparticles at optimum mass fractions of 0.750, 0.250, and 0.250% to the lubricant, respectively, compared to the compressor using pure oil. Moreover, density and dynamic viscosity of the nanolubricant samples used in the experiments were also measured, and their kinematic viscosity, which is an important parameter for lubricants, was calculated. It was determined that the kinematic viscosity continuously increased with increasing nanoparticle fraction. In conclusion, nanolubricants containing nanoparticles above the optimum mass fraction increase the required electrical power of the compressor. It is concluded that nanoparticle fractions should not be used above the optimum value in nanolubricant applications.

Micro-explosion of emulsion droplets with nanoparticles at high temperature

Compared with traditional fuels, emulsified fuels can improve fuel atomization and combustion, and nanoparticles as additives have the potential to enhance combustion and reduce emissions. Previous studies on micro-explosion mainly considered emulsion droplets, but the role of nanoparticles in emulsion droplets is still unclear. In this study, we experimentally investigate the micro-explosion of emulsion droplets with nanoparticles via high-speed photography, digital image processing, optical microscopy, and scanning electron microscopy. The results show that the presence of nanoparticles can greatly improve the strength and probability of micro-explosion, particularly for carbon nanoparticles. This is mainly because nanoparticles can agglomerate during the evaporation of emulsion droplets, facilitate the absorption of radiation energy, inhibit the diffusion of superheated vapor, and ultimately promote micro-explosion. The effects of nanoparticle mass fraction and water content are also investigated, and the results show that the increase of nanoparticles and water can facilitate micro-explosion.