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High expansion (Hi‐Ex) foam is recommended to suppress the leakage and diffusion of cryogenic liquid due to its light weight and large volume. However, the disadvantages of low stability and high break rate under environmental conditions are all limited the further application in vapor mitigation and fire extinguishing. So that, this paper focus on the effect and mechanism of nanoparticles in stabilizing Hi‐Ex foam. Three kinds of nanoparticles with different concentration were selected to evaluate the effect of foam half‐life and the mechanism of particles on improving the foam stability. The results indicated that different particle concentrations can improve the foam stability to a specific extent, and the maximum improving of half‐life can increase by 95.4% in the presence of the hydrophilic SiO2 at .5 wt%. Meanwhile, the hydrophilicity, size, and morphology of the particles have a specific impact on the foam stability. The foam expansion rate first increased and then decreased. From the microscopic point of view, the bubble size gradually increases with time by two processes of ripening and coalescence and satisfied in a logarithmic distribution. While, the liquid film thickness remarkably decreases due to foam drainage without particles and the adsorption and accumulation of nanoparticles on foam lamella can provide a spatial barrier for the film thinning and the inter bubble diffusion. Finally, the microscopic interaction mechanism on improving the foam stability has been further explored and revealed in these two aspects. [ABSTRACT FROM AUTHOR]

A common issue in studies on liquid-phase chemical processes is that the natural solid nanoimpurities present in reagent-grade chemicals are ignored. Little is known about these impurities' nature, sizes, concentrations, and behavior, yet they significantly affect the efficiency of antiscalants in municipal and laboratory solutions. Recent research has focused on: (i) estimating nanoimpurity concentrations in in-house deionized water and semiconductor-grade isopropanol using "light sheet" optical ultramicroscopy, and (ii) visualizing antiscalant sorption on these impurities. Using a fluorescent-tagged antiscalant aminobis(methylenephosphonic acid) (ADMP-F), we tracked its affinity to particulate matter in deionized water and reagent-grade KCl solutions. Our study showed that the total concentration of nanoparticles with a size larger than 20 nm is about 106 units/mL in deionized water and 105 units/mL in isopropanol. Extrapolation of these values to a size ≥1 nm resulted in concentrations of 1011 and 108 units/mL. The addition of KCl or ADMP-F significantly increased foreign nanoparticle populations. ADMP-F is selectively adsorbed by only some impurities, while most antiscalant molecules remain as true solution. To our knowledge, this is the first instance of fluorescently labeled aminoalkylphosphonates being able to differentiate particulate matter traces in reagent-grade purity solutions. Therefore, the role of nanoparticles as crystallization centers should be seriously reconsidered, especially in their important application in scale inhibition. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the influence of Al2O3 nanoparticle concentration and flow rate on the convective heat transfer coefficient in a heat sink. A testing apparatus was constructed to examine a microchannel heat sink coupled with an Al2O3 nanoparticle fluid. Temperature sensors were strategically placed at the microchannel heat sink's entrance (T-in) and exit (T-out). Furthermore, a heating element (T-heater) was utilized to monitor the temperature of the nanoparticle fluid. This experimental setup allowed for precise temperature measurements in the system. Aluminum oxide (Al2O3) nanoparticles were thoroughly dispersed in water for 15 min using a magnetic stirrer, resulting in a uniform mixture with concentrations ranging from 0.2% to 1%. The experiments involved altering the flow rates within the range of 0.2 to 1.4 L per minute, enabling the monitoring of temperature changes (T). The heat transfer coefficient positively correlated with escalating concentrations of Al2O3 particles. Incorporating nanoparticles up to a concentration of 1% significantly enhanced the heat transfer coefficient by 17.29%. Additionally, a direct relationship was observed between the heat transfer coefficient and the increase in the flow rate of the Al2O3/water nanofluid. Specifically, when the flow rate was increased from 0.2 to 1.4 lpm, a significant enhancement in the heat transfer coefficient of 29.95% was achieved. [ABSTRACT FROM AUTHOR]

Aim: In the present study, the influences of chemical reactions on heat transfer and the peristaltic pumping of nanofluid in a convergent channel are analyzed. This mathematical analysis is looked at under the postulates of greater wavelength and smaller Reynold's number. Research methodology: The governing equations are initially transformed from fixed to a wave frame by using linear transformations. Furthermore, these transformed equations are non-dimensioned with the help of similarity variables. Due to the complex form of non-dimensional flow equations, numerical solutions for velocity profile, stream function, temperature profile, and nanoparticle concentration are obtained with the help of Mathematica 11.0 software. These numerical solutions are described via graphs in Mathematica software. These numerical solutions are plotted for numerous rheological parameters. The transportation of nanofluid is based upon multi-sinusoidal natures (cosine wave, sine wave, triangular wave, square wave, sawtooth wave) of peristaltic waves. Outcomes: It is found that with an increasing heat source parameter, the channel flow is decelerated due to the magnitudes of velocity profile and stream function are reduced. While sharp enhancements are noticed in both temperature and nanoparticle concentration by increasing the heat source parameter under chemical reaction effects. The high temperature is obtained with larger chemical reactions. The contrast among viscous and non-viscous fluids is also addressed. A significant enhancement is observed in both velocity profile and stream function by increasing the electroosmotic parameter. Significances and applications: The study is relevant to nano-cooling systems, drug delivery systems, and microfluidic pumps where laminar flows in convergent domains arise. This model is significant for the thermal enhancement of mechanical and chemical rheological processes.

Currently, there are problems to standardize methods for determining the concentration of nanoparticles and creation of etalon materials for calibrating measured concentrations. Accurate determination of nanoparticle concentration is necessary to assess the maximum dose of administered nanotherapeutics for diagnostics and therapy in vivo, to determine the order of reaction in enzymatic nanoreactors. In addition, this parameter determines biological effects, such as the formation of a protein corona on the outer surface of nanoparticles that precedes nanoparticles' absorption and internalization in cells. This review discusses the most common methods for determining the concentration of nanoparticles based on direct visualization, using microscopy, light absorption or light scattering, direct counting of nanoparticles, and gravimetry. Results may differ from one method to the other. Thus, the use of a combination of several methods provides more reliable results. The advantages, disadvantages and ways to improve accuracy of results are also presented. [ABSTRACT FROM AUTHOR]

This research article presents a computational fluid dynamics (CFD) analysis of the heat transfer enhancement in a radiator using nanofluid. The study investigates the effect of varying the concentration of nanoparticles and the inlet velocity of the fluid on the heat transfer rate and pressure drop. The simulation results show that the use of nanofluids in radiators leads to a significant increase in heat transfer rate compared to traditional fluids. However, the pressure drop also increases with the concentration of nanoparticles, which can affect the overall efficiency of the radiator. The study provides valuable insights into the design and optimization of nanofluid-based radiators using CFD simulations. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the thermal performance of water-based Carbon Nano Material (CNM) nanofluids, particularly in the convective heat transfer coefficient (h) parameter, and to analyze the effects of nanoparticle concentration and flow rate on an experimental heat transfer system. To achieve this, the researchers prepared the nanofluid through a 2-step method. In the first step, we mixed the nanoparticles with the base fluid using a magnetic stirrer to ensure homogenization, with the CNM-Water ratio set at 30, 75, 120, and 150 ppm. In the second step, we characterized the prepared samples, determining their size, composition, and particle morphology through PSA and SEM-EDX examination, as well as measuring their density (ρ) and specific heat (Cp). The experiments were carried out using a flow rate simulation test rig with a data acquisition system, at different flow rates of 0.2, 0.6, 1, and 1.4 L/min. Temperature (T) was measured at the inlet, outlet, and heater to determine the convective heat transfer coefficient value. The study successfully investigated the direct impact of CNM concentration and flow rate, with the results showing a consistent and expected value of the coefficient compared to previous studies. The highest coefficient value was observed at 150 ppm CNM-Water ratio and a flow rate of 1.4 L/min, with a value of 1825.37 W/(m2.K).

This study aimed to investigate the influence of Al2O3 nanoparticle concentration and flow rate on the convective heat transfer coefficient in a heat sink. A testing apparatus was constructed to examine a microchannel heat sink coupled with an Al2O3 nanoparticle fluid. Temperature sensors were strategically placed at the microchannel heat sink’s entrance (T-in) and exit (T-out). Furthermore, a heating element (T-heater) was utilized to monitor the temperature of the nanoparticle fluid. This experimental setup allowed for precise temperature measurements in the system. Aluminum oxide (Al2O3) nanoparticles were thoroughly dispersed in water for 15 min using a magnetic stirrer, resulting in a uniform mixture with concentrations ranging from 0.2% to 1%. The experiments involved altering the flow rates within the range of 0.2 to 1.4 L per minute, enabling the monitoring of temperature changes (T). The heat transfer coefficient positively correlated with escalating concentrations of Al2O3 particles. Incorporating nanoparticles up to a concentration of 1% significantly enhanced the heat transfer coefficient by 17.29%. Additionally, a direct relationship was observed between the heat transfer coefficient and the increase in the flow rate of the Al2O3/water nanofluid. Specifically, when the flow rate was increased from 0.2 to 1.4 lpm, a significant enhancement in the heat transfer coefficient of 29.95% was achieved.

The field synergy study is carried out using three oxide nanofluids impinging circular jet on the horizontal circular disc to analyse the synergetic interaction of cooling processes between temperature and flows fields. The heat transfer effect of the nanofluid is examined by rising the Reynolds number and the nanoparticle concentration depending on field synergy number. For jet impinged cooling process, the scale of synergy between the nanofluid flow speed and temperature is decayed with the increase of Reynolds number. Hence, it is contributed to a lower heat transfer efficiency of the nanofluid. Whereas, the scale of synergy between the nanofluid flow speed and temperature can be enhanced by rising the particle concentration. Thus, the heat transfer efficiency of the nanofluid is increased. Analysis showed that Al2O3 nanofluid has the maximum relative field synergy among selected three oxide nanofluids. It is evident that the nanoparticle concentration, nanoparticle material and Reynolds number have significant effect on the heat transfer augmentation. In addition, the study is explored by varying jet-disk spacing. Moreover, the investigation has shown that the reducing heat transfer effect for the materials is Al2O3, CuO and TiO2 subsequently. It is revealed that the heat enhancement is higher for smaller nanoparticle's diameter (i.e., 20 nm) than bigger nanoparticle's diameter (i.e., 80 nm) of the same material. [ABSTRACT FROM AUTHOR]

We investigated the effects of silica nanoparticle (NP) on nanofluid flooding for enhanced oil recovery. All NPs used in experiments were identically surface modified with PSS-co-MA and a zwitterionic surfactant. In core flooding experiments, the oil production from Berea Sandstone showed an increasing trend as the NP concentration increased within the range of 0.1 to 2.0 wt%. This result was closely associated with variance of interfacial tension (IFT) and contact angle (CA). IFT continued to decrease as the NP concentration increased until 2.0 wt%. However, IFT cannot further decrease with an increase in the NP concentration beyond 2.0 wt%, because total interaction energy may be reduced due to the decrease of electrostatic repulsion force by the closer spacing between NPs. When combined with silica nanofluid soaking, the CA of the rock/oil/nanofluids increased with increasing NP concentration; this indicated wettability alteration to a more water-wet condition caused by an enhanced fluid ability to spread silica NPs along the rock surfaces. Because of this effect, the capillary pressure is expected to be sufficiently reduced by nanofluid flooding, compared with brine flooding. However, at higher NP concentration, the NPs caused permeability reduction and an increased pressure drop attributable to the residual NPs in rock pores. This result implies additional oil recovery attributable to improved sweep efficiency related to the log jamming phenomenon caused by the residual NPs, as well as the IFT reduction and wettability alteration, thus leading to enhanced oil recovery. [ABSTRACT FROM AUTHOR]

Investigating the boiling behavior of nanofluids remains a topic of considerable research interest. The existing theoretical framework often underscores Brownian motion and thermophoresis among the predominant mechanisms that influence nanoparticles' movement within nanofluids. However, most current numerical models addressing nanofluid boiling either neglect these mechanisms or incorporate them inadequately. A comprehensive review of the literature reveals two primary gaps. The larger set of numerical studies on nanofluids boiling does not account for any governing equation for nanoparticle concentration, neglecting the primary mechanisms of nanoparticle movement. The smaller set includes such an equation but limits its application to the vapor domain, thereby overlooking the liquid nanofluid phase. Moreover, in the context of film boiling involving nanofluids, an insulating vapor film forms between the nanofluid and the heated surface. This vapor film is dynamic, experiencing evaporation at its outer boundary, leading to an increase in nanoparticle concentration at the vapor-liquid interface—another aspect always neglected in existing numerical models. To address these research gaps, this study introduces a specialized governing equation employing the Continuous-Species-Transfer method within the framework of Computational Multi-Fluid Dynamics. Importantly, it also incorporates governing equations for thermophoresis and Brownian motion to account for the motion of nanoparticles. The method's efficacy is further corroborated by solving a two-dimensional axisymmetric film boiling problem on a vertical cylinder, with results aligning well with analytical studies that consider Brownian motion and thermophoretic behavior. Overall, the study fills a critical gap in the literature by providing a comprehensive tool for examining complex interfacial behaviors in nanofluid film boiling. • Key gaps in CFD models for nanofluid boiling are highlighted. • Novel nanoparticle concentration equation using the Continuous-Species-Transfer method. • First prediction of increased nanoparticle concentration at the gas-liquid interface. • Noted changes in nanofluids' properties during film boiling. • Insights into heat transfer via nanoparticle concentration in nanofluids. [ABSTRACT FROM AUTHOR]

In this work, we present a quantitative method for determining the concentration of metal oxide nanoparticles (NP) synthesized by laser ablation in liquid. The case study was performed with titanium dioxide nanoparticles (TiO2 NP), which were synthesized by laser ablation of a Ti target in water. After synthesis, a colloidal solution was analyzed with UV-Vis spectroscopy. At the same time, the craters that remained on the Ti target after ablation were evaluated with an optical microscope to determine the volume of the ablated material. SEM microscopy was used to determine the TiO2 NP size distribution. It was found that synthesized TiO2 NP followed a Log-Normal diameter distribution with a maximum at about 64 nm. From the volume of ablated material and NP size distribution, under the assumption that most of the ablated material is consumed to form nanoparticles, a concentration of nanoparticles can be determined. The proposed method is verified by comparing the calculated concentrations to the values obtained from the Beer–Lambert law using the Mie scattering theory for the NP cross-section calculation. [ABSTRACT FROM AUTHOR]

The dynamic development of nanotechnology research has contributed to the fact that various types of nanoparticles are increasingly used on a large scale both for medical and biological purposes, but above all in many industrial fields. Such a wide application of nanoparticles is often connected with the need to estimate their characteristic parameters, such as size, size distribution or concentration. Existing instruments are usually quite expensive and not always available. Therefore, other cheaper and simpler methods based on analytical techniques are sought. In this paper, we have proposed a method to estimate the concentration of nanoparticles in solutions based on destabilization analyses of Pickering emulsions produced with their use. The fact of mutual relationship between emulsion concentration, nanoparticle concentration and emulsion stability was used here. The study was carried out using silica nanoparticles. It was presented how to apply the method and what are its limitations. Moreover, an example of its application for the determination of nanoparticle concentration in an unknown sample, obtained after analysis of the permeability of membranes in diffusion chambers, has been presented. The method can become a useful alternative for the determination of nanoparticle concentration in solution in places where no specialized equipment is available. [ABSTRACT FROM AUTHOR]

The purpose of this work is to apply a new method for the growth behavior of bubble dynamics in N-dimensional turbulent Al2O3/H2O-nanofluid for bubble dynamics applications in polymers and climate change models under the influence of surface tension and viscosity. This paper also investigates the factors affecting the dynamics of vapor bubble growth in N-dimensions for turbulent nanofluid. The turbulent flow of the nanofluid in N-dimensions in this study is examined at Re ranging from 3000 to 5000, and concentration from 4 to 6%. The theoretical analysis is conducted using the MPZ technique considering the initial time of bubble growth. The obtained results reveals that the radius of the bubble is proportional to the thermal diffusivity and inversely proportional to the surface tension, viscosity, critical bubble radius, concentration rate of Al2O3-nanoparticles, and initial void fraction. We also found that the growth of the vapor bubble in a nanofluid turbulent flow is less than that of the Newtonian fluid. To the best of our knowledge, the efficient utilization of N-dimensional turbulent Al2O3 nanoparticles in bubble dynamics leads to more reduction for bubble growth process than other previous models. Additionally, the stability analysis is examined via phase plane algorithm with nonlinear ODEs.

In many applications of heat exchanger, due to the heat convection, the wall temperature of the channel usually varies along the streamwise direction. The present paper reports the analysis of nanofluid flows in the channel with linearly varying wall temperature. The non-uniform equilibrium fluid medium model proposed by Buongiorno is applied, where the Brownian diffusion and thermophoresis of nanoparticles are considered. The numerical solutions of laminar flows are determined by the iteration method in conjunction with the Chebyshev collocation method. The results show that: (1) there is a Gaussian distribution of nanoparticle concentration in the wall-normal direction for convective cooling, while its standard deviation depends on the Peclet number and the ratio of Brownian diffusivity to thermophoretic diffusivity; (2) there are obvious stratifications for the viscosity and thermal conductivity in the flow; (3) the velocity decreases significantly with the increase of nanoparticle concentration for convective heating, while there is only a little decrease for the velocity in the cold region for convective cooling.

In this article, a model is developed for the quantitative and calibration-free determination of the diameter and concentration of colloidal metal nanoparticles synthesized by laser ablation in water. The model is valid under the assumption that all the ablated material is converted into nanoparticles. This is proved by Mie theory under dipole approximation and the Beer–Lambert law using experimentally determined ablated crater volumes, size distributions and photoabsorbances. The novelty of the model is shown through the possibility of determining the diameter and concentration of nanoparticles by using only the volume (or mass) of the ablated crater and the UV–Vis photoabsorbance spectrum. It allows fast, accurate and simple quantitative analysis of colloidal metal nanoparticles without the use of electron microscopy, mass spectrometry or relevant experimental techniques. [ABSTRACT FROM AUTHOR]

We present here a perspective detailing the current state-of-the-art technologies for the characterisation of nanoparticles (NPs) in liquid suspension. We detail the technologies involved and assess their applications in the determination of NP size and concentration. We also investigate the parameters that can influence the results and put forward a cause and effect analysis of the principle factors influencing the measurement of NP size and concentration by NP tracking analysis and dynamic light scattering, to identify areas where uncertainties in the measurement can arise. Also included are technologies capable of characterising NPs in solution, whose measurements are not based on light scattering. It is hoped that the manuscript, with its detailed description of the methodologies involved, will assist scientists in selecting the appropriate technology for characterising their materials and enabling them to comply with regulatory agencies’ demands for accurate and reliable NP size and concentration data.

In the present study, two-phase nanofluid flow in a three-dimensional system is modeled over a stretching infinite solar plate and the heat transfer analysis is performed for this problem. The governing equations are presented based on previous studies and the suitable solution method is recommended due to infinite boundary condition in the problem. Keller Box Method (KBM) using the Maple 15.0 mathematical software is applied as the solution method for the governing equation of the problem. The effect of some parameters existed in the equations (Pr (Prandtl number), Sc (Schmidt number), Nb (Brownian motion parameter), Nt (Thermophoresis parameter), λ=b/a (ratio of the stretching rate along y to x directions) and n (power-law index)), are discussed on the velocities, temperature, and nanoparticles concentration functions. As an important outcome, increasing both n and λ parameters, makes a reduction in shear stress, while it increase the Nusselt number function of heat transfer.

In this work, we present a quantitative method for determining the concentration of metal oxide nanoparticles (NP) synthesized by laser ablation in liquid. The case study was performed with titanium dioxide nanoparticles (TiO2 NP), which were synthesized by laser ablation of a Ti target in water. After synthesis, a colloidal solution was analyzed with UV-Vis spectroscopy. At the same time, the craters that remained on the Ti target after ablation were evaluated with an optical microscope to determine the volume of the ablated material. SEM microscopy was used to determine the TiO2 NP size distribution. It was found that synthesized TiO2 NP followed a Log-Normal diameter distribution with a maximum at about 64 nm. From the volume of ablated material and NP size distribution, under the assumption that most of the ablated material is consumed to form nanoparticles, a concentration of nanoparticles can be determined. The proposed method is verified by comparing the calculated concentrations to the values obtained from the Beer–Lambert law using the Mie scattering theory for the NP cross-section calculation.

Methods for the determination of the optical properties of both conventional and hybrid nanofluids are presented. The optical properties considered included the extinction coefficient, absorptance, transmittance, and reflectivity. Experimental, theoretical, and numerical approaches for the evaluation of the optical properties are reviewed. The effects of nanoparticle concentration, size, and shape on the optical properties are discussed. The influence of the base fluid on the optical properties is examined. The dependence of the optical properties on the wavelength is investigated. Results of various analytical and numerical procedures and their validation with the experimental measurements are presented. It is concluded that the optical behavior of nanofluids can be optimized by simultaneous consideration of proper size, shape, concentration, nanoparticles material, base fluid, weather condition, and the wavelength range. Hybridization is found to be a promising choice for improving the optical properties of nanofluids. Hybrid nanofluids received an increasing attention recently and there is need for further research in the direction of hybrid nanofluids and their optical properties. As water is commonly used as the base fluid extensive literature is found for water base nanofluids. On the other hand, non-water-based nanofluids with enhanced optical properties are still potential future research areas. [ABSTRACT FROM AUTHOR]

The essential advantages of microfluidic studies are the excellent visualization of the processes of oil displacement from the porous medium model, simple cleaning, and the possibility of the repeated use of the microfluidic chip. The present article deals with the process of oil displacement by suspension flooding using a microfluidic chip, simulating a porous medium, and the suspensions of silicon dioxide nanoparticles (22 nm). The mass concentration of nanoparticles in suspensions ranged from 0.1 to 2 wt%. Five mass concentrations (0.125 wt%, 0.25 wt%, 0.5 wt%, 1 wt% and 2 wt%) were considered. The article presents the experimental photographs of the oil displacement process by water and SiO2 suspension. It is shown that, with the increasing concentration of nanoparticles, the oil recovery factor increases. A significant effect is observed at 0.5 wt% concentration of nanoparticles. It is shown that the increase in oil recovery during flooding by SiO2 suspension with the maximum concentration was 16%.

This study focused on the imaging in radiotherapy by finding the relationship between the imaging contrast ratio and appropriate gold, iodine, iron oxide, silver, and platinum nanoparticle concentrations; the relationship between the imaging contrast ratio and different beam energies for the different nanoparticle concentrations; the relationship between the contrast ratio and various beam energies for gold nanoparticles; and the relationship between the contrast ratio and different thicknesses of the incident layer of the phantom including variety of gold nanoparticles (GNPs) concentration. Monte Carlo simulation was used to model the gold, iodine, iron oxide, silver, and platinum nanoparticle concentration which were infused within a heterogeneous phantom (50 cm × 50 cm × 10.5 cm) choosing different concentrations (3, 7, 18, 30, and 40 mg), and beams (100, 120, 130, and 140 kVp) correspondingly that were delivered into the phantom. The results showed obvious connection between the high concentration and having a high imaging contrast ratio, low energy and a high contrast ratio, small thickness, and a high contrast ratio. The superior nanoparticle obtained was GNP, the better concentration was 40 mg, the better beam energy was 100 kVp, and the better thickness was 0.5 cm. It is concluded that our study successfully proved that medical imaging contrast could be improved by increasing the contrast ratio using GNP as the finest choice to accomplish this improvement considering a high concentration, low beam energy, and a small thickness.

The paper studies nanoparticle formation in a glowing wire generator (GWG), in which the gas carrier flows around heated metal wire, producing aerosols from a vapor released from the surface. The device has been customized, enabling the use of a double-wire in different orientations in regard to the gas flow. Such alterations provided different effective distances between wires enabling investigation of their mutual influence. Concentration of particles produced in the GWG at different parameters (applied voltage and a gas flow) was carefully measured and analysed. Different regimes of a nanoparticle nucleation were identified that resulted from the applied voltage variation and the gas flow direction. In particular, independent nucleation of nanoparticles on both parts of the wire occurred in the wire plane’s configuration perpendicular to the gas flow, whilst dependent nucleation of nanoparticles was observed at a certain specific set of parameters in the configuration, in which the wire plane was parallel to the gas flow. Two corresponding functions were introduced in order to quantify those nucleation regimes and they tend to zero when either independent or dependent nucleation occur. The peculiarities found ought to be considered when designing the multi-wire GWGs in order to further extend the device’s range for industrial applications.

• Heat transfer performance (HTP) of hybrid nanofluid is investigated. • Nanoparticle concentration and proportion for effective heat transfer are optimized. • Effectiveness of heat exchanger increases to 124% by using hybrid nanofluid. • 40% increase in Nusselt number for hybrid nanofluid coolants. • Nanoparticle concentration and proportion dominate HTP of hybrid nanofluid. Influence of nanoparticle volume concentration and proportion on heat transfer performance (HTP) of Al 2 O 3 – Cu/water hybrid nanofluid in a single pass shell and tube heat exchanger is analyzed. Multiphase mixture model is adopted to model the flow. Three-dimensional governing equations and associated boundary conditions are solved using finite volume method. The numerical results are validated with the experimental results. Results indicate that optimized nanoparticle volume concentration and proportion dominate HTP of hybrid nanofluid. Heat transfer coefficient and Nusselt number are monotonic increase functions of nanoparticle volume concentration and proportion. The percentage increase in heat transfer coefficient of hybrid nanofluid is 139% than water and 25% than Cu/water nanofluid. At higher Reynolds number, the increment in Number of Transfer Units (NTU) between water and hybrid nanofluid is close to 75%. Maximum enhancement in Nusselt number for hybrid nanofluid exceeds 90% when compared to nanofluid (Al 2 O 3 /Water nanofluid). Consequently, highest heat transfer performance is attained for hybrid nanofluid systems. Effectiveness of heat exchanger increases almost to 124% when hybrid nanofluid is employed. We show that it is higher than water as well (conventional coolant). Results are expected to be helpful in further industrial-scale deployment of nanofluids, which is an area that is currently relevant for ongoing academia-industry partnership efforts worldwide. [ABSTRACT FROM AUTHOR]

This paper deals with the interaction of nanoparticles (NPs) in transformer oil and water in the oil and its effect on the electrical properties of the nanoffuid (NF). The breakdown strength and dielectric spectrum measurements under AC for various concentrations of natural SiO 2 and water in mineral oil were studied. Mineral oil-based SiO 2 NFs exhibit significantly higher breakdown voltage than that of base oil under high water content. However, there is an optimal range of NP concentration and water content for maximum breakdown voltage. The results of dielectric spectrum indicate that the dielectric constants of NFs and base oil are greatly affected by water content. The real relative permittivity of oil samples increases exponentially with water content at decreasing frequency (f≤10 Hz). The imaginary relative permittivity of NFs is less than that of the base oil in all cases. Based the experimental results reported, a model on the interplay between NPs and water in transformer oil is presented. The model can broadly explain the influence of the coexistence of NPs and water on the dielectric properties of transformer oil. [ABSTRACT FROM AUTHOR]

• Nonequilibrium convective thermal characteristics of nanofluids in foam metal are modeled. • Effects of LTNE and non-uniform nanoparticle distribution are especially considered. • The overshoot value of nanofluid velocity in a foam metal tube is obtained. • Effects of Brown motion and thermophoresis on nanofluid transport in foam structures are discussed. • Three network models of thermal resistance for nanofluid convection in foam metals are modeled. Foam metals with micro pores own excellent thermal performance, however, poor heat conductive ability of most heat-transfer fluids restricts further heat transfer improvement. Combination of foam metal and nanofluid with highly conductive nanoparticles is a promising solution. Convective thermal characteristics of nanofluids in porous foams are theoretically investigated in this work. Effects of Brownian motion and thermophoretic diffusion of nanoparticles in the base fluid on thermal performance are considered. The nanoparticle and the base-fluid are considered to be in thermal equilibrium and the temperature difference between the nanofluid and foam ligaments is especially considered. Compared with the base-fluid flow in a duct, the velocity distribution for the nanofluid flow in a porous foam is more uniform with a decreased dimensionless temperature. The pressure drop of the nanofluid increases with an increase in the concentration of the nanoparticles. By employing foam metals and nanofluid, the cross-sectional temperature becomes closer to the wall temperature. Simultaneously, notable difference between solid and fluid temperatures can be observed, revealing the LTNE effect of the nanofluid on the porous foam. It is found that the Nusselt number first increases and then decreases with an increase in nanoparticle concentration. Furthermore, the Nusselt number decreases with an increase in the foam porosity. It is found that the thermal performance of a nanofluid in a plain tube is different from that in the foam metals. [ABSTRACT FROM AUTHOR]

We present here a perspective detailing the current state-of-the-art technologies for the characterisation of nanoparticles (NPs) in liquid suspension. We detail the technologies involved and assess their applications in the determination of NP size and concentration. We also investigate the parameters that can influence the results and put forward a cause and effect analysis of the principle factors influencing the measurement of NP size and concentration by NP tracking analysis and dynamic light scattering, to identify areas where uncertainties in the measurement can arise. Also included are technologies capable of characterising NPs in solution, whose measurements are not based on light scattering. It is hoped that the manuscript, with its detailed description of the methodologies involved, will assist scientists in selecting the appropriate technology for characterising their materials and enabling them to comply with regulatory agencies' demands for accurate and reliable NP size and concentration data. [ABSTRACT FROM AUTHOR]

Superparamagnetic iron oxide nanoparticles (SPIONs) are frequently used for drug targeting, hyperthermia and other biomedical purposes. Recently, we have reported the synthesis of lauric acid-/albumin-coated iron oxide nanoparticles SEONLA-BSA, which were synthesized using excess albumin. For optimization of magnetic treatment applications, SPION suspensions need to be purified of excess surfactant and concentrated. Conventional methods for the purification and concentration of such ferrofluids often involve high shear stress and low purification rates for macromolecules, like albumin. In this work, removal of albumin by low shear stress tangential ultrafiltration and its influence on SEONLA-BSA particles was studied. Hydrodynamic size, surface properties and, consequently, colloidal stability of the nanoparticles remained unchanged by filtration or concentration up to four-fold (v/v). Thereby, the saturation magnetization of the suspension can be increased from 446.5 A/m up to 1667.9 A/m. In vitro analysis revealed that cellular uptake of SEONLA-BSA changed only marginally. The specific absorption rate (SAR) was not greatly affected by concentration. In contrast, the maximum temperature Tmax in magnetic hyperthermia is greatly enhanced from 44.4 °C up to 64.9 °C by the concentration of the particles up to 16.9 mg/mL total iron. Taken together, tangential ultrafiltration is feasible for purifying and concentrating complex hybrid coated SPION suspensions without negatively influencing specific particle characteristics. This enhances their potential for magnetic treatment.

In this paper, the unsteady magnetohydrodynamic (MHD) squeezing flow between two parallel disks (which is filled with nanofluid) is considered. The Galerkin optimal homotopy asymptotic method (GOHAM) is used to obtain the solution of the governing equations. The effects of Hartman number, nanoparticle volume fraction, Brownian motion parameter and suction/blowing parameter on nanofluid concentration, temperature and velocity profiles have been discussed. Furthermore, a comparison between obtained solutions and numerical ones have been provided.

In this study, asymmetric peristaltic nanofluid flow in a two dimensional and divergent wavy channel is modeled and the heat transfer analysis is performed for it. The modeling is performed as two-phase model and it is assumed the magnetic field effects on the nanoparticles as magnetohydrodynamic (MHD) flow. Both upper and lower channel walls are considered in constant temperature and constant nanoparticle concentration. The governing equations were solved by analytical least square method (LSM) using the Maple 15.0 mathematical software and compared to available numerical results. The effect of some parameters existed in the equations (Geometry parameter, Brownian motion parameter, Dufour ( Du ) and Soret ( Sr ) numbers and etc.), are discussed on the velocities, temperature and nanoparticles concentration functions. As an important outcome, increasing in both Dufour ( Du ) and Soret ( Sr ) numbers lead to reduction in nanoparticles concentration while Dufour number increments make larger temperature profiles in the channel. [ABSTRACT FROM AUTHOR]

This study focused on the imaging in radiotherapy by finding the relationship between the imaging contrast ratio and appropriate gold, iodine, iron oxide, silver, and platinum nanoparticle concentrations; the relationship between the imaging contrast ratio and different beam energies for the different nanoparticle concentrations; the relationship between the contrast ratio and various beam energies for gold nanoparticles; and the relationship between the contrast ratio and different thicknesses of the incident layer of the phantom including variety of gold nanoparticles (GNPs) concentration. Monte Carlo simulation was used to model the gold, iodine, iron oxide, silver, and platinum nanoparticle concentration which were infused within a heterogeneous phantom (50 cm × 50 cm × 10.5 cm) choosing different concentrations (3, 7, 18, 30, and 40 mg), and beams (100, 120, 130, and 140 kVp) correspondingly that were delivered into the phantom. The results showed obvious connection between the high concentration and having a high imaging contrast ratio, low energy and a high contrast ratio, small thickness, and a high contrast ratio. The superior nanoparticle obtained was GNP, the better concentration was 40 mg, the better beam energy was 100 kVp, and the better thickness was 0.5 cm. It is concluded that our study successfully proved that medical imaging contrast could be improved by increasing the contrast ratio using GNP as the finest choice to accomplish this improvement considering a high concentration, low beam energy, and a small thickness. [ABSTRACT FROM AUTHOR]

In this work, 3-D and two-phase nanofluid flow and heat transfer is modeled over a stretching infinite solar plate. The governing equations are presented based on previous studies. The infinite boundary condition and shortcoming of traditional analytical collocation method have been overcome in our study by changing the problem into a finite boundary problem with a new analytical method called optimal collocation method. The accuracy of results is examined by fourth order Runge- Kutta numerical method. Effect of some parameters, Prandtl number, Schmidt number, Brownian motion parameter, thermophoresis parameter, λ=b/a (ratio of the stretching rate along y- to x-directions), and power-law index on the velocities, temperature, and nanoparticles concentration functions are discussed. As an important outcome of our 3-D model analysis, it is found that increase in thermophoretic forces can enhance the thickness of both thermal and nanoparticle volume fraction boundary-layers. [ABSTRACT FROM AUTHOR]

The combination of nanoparticles (NPs) and surfactant may offer a novel technique of generating stronger foams for gas mobility control. This study evaluates the potential of silica NPs to enhance the foam stability of three nonionic surfactants. Results showed that the concentration of surfactant and NPs is a crucial parameter for foam stability and that there is certain concentrations for strong foam generation. A balance in concentration between the nonionic surfactants and the NPs can enhance the foam stability as a result of forming flocs in solutions. At fixed surfactant concentration, the addition of NPs at low to intermediate concentrations can produce a more stable foam compared to the surfactant. The production of small population of flocs as a result of mixing the surfactant and NPs can enhance the foam stability by providing a barrier between the gas bubbles and delaying the coalescence of bubbles. Moreover, these flocs can increase the solution viscosity and, therefore, slow the drainage rate of thin aqueous film (lamellae). The measurements of foam half-life, bubble size, and mobility tests confirmed this conclusion. However, the addition of more solid particles or surfactant might have a negative impact on foam stability and reduce the maximum capillary pressure of coalescence as a result of forming extensive aggregates. [ABSTRACT FROM AUTHOR]

Vegetable oil is a low toxic, excellent biodegradable and renewable energy source used as an ideal lubricating base oil in machining. Castor oil exhibits good lubrication performance but poor mobility, which limits its application especially in precision grinding. The main objective of the work presented to obtain optimal mixed vegetable based-oil and optimal nanoparticles adding concentration in grinding Ni-based alloy with minimum quantity lubrication. An experimental investigation is carried out first to study the different vegetable oils with excellent mobility mixed with castor oil. The lubrication property of the oil was evaluated in terms of grinding force, force ratio, specific grinding energy, and surface roughness. Based on the test conditions, it is found that soybean/castor mixed oil obtained the optimal results ( μ = 0.379, U = 83.27 J/mm 3 and R a = 0.325 μm) and lubricating effect compared with castor oil and other mixed base oils. To further explore the lubricating capability of soybean/castor mixed oil, MoS 2 nanoparticles which have excellent lubricating property were added into the soybean/castor mixed oil to prepare different concentrations nanofluids. From the present study, it can be concluded that 8% mass fraction of the oil mixture should be added to obtain the optimal machining results, with the lowest force ratio (0.329), specific energy (58.60 J/mm 3 ), and average grinding temperature (182.6 °C). Meanwhile, better surface microtopography of ground parts and grinding debris morphologies were also observed for the machining conditions. [ABSTRACT FROM AUTHOR]

Early disease diagnostics require rapid, sensitive, and selective detection methods for target analytes. Specifically, early viral detection in a point-of-care setting is critical in preventing epidemics and the spread of disease. However, conventional methods such as enzyme-linked immunosorbent assays or cell cultures are cumbersome and difficult for field use due to the requirements of extensive lab equipment and highly trained personnel, as well as limited sensitivity. Recent advances in nanoparticle concentration have given rise to many novel detection methodologies, which address the shortcomings in modern clinical assays. Here, we review the primary, well-characterized methods for nanoparticle concentration in the context of viral detection via diffusion, centrifugation and microfiltration, electric and magnetic fields, and nano-microfluidics. Details of the concentration mechanisms and examples of related applications provide valuable information to design portable, integrated sensors. This study reviews a wide range of concentration techniques and compares their advantages and disadvantages with respect to viral particle detection. We conclude by highlighting selected concentration methods and devices for next-generation biosensing systems. [ABSTRACT FROM AUTHOR]

In this paper, behavior of low concentration nanofluids (0.1%, 0.5%, 2.5% by vol.) is experimentally studied in a circular channel subjected to a constant heat flux. Two average particle sizes (10 and 20 nm) were also used. The local heat transfer coefficient is measured for water-based nanofluids containing oxide nanoparticles (TiO 2 , Al 2 O 3 , CuO) under the single phase regime and subcooled flow boiling conditions in a vertical channel. In single phase regime, it is found that the convective heat transfer coefficient enhances for nanofluids. Nucleate boiling augmented the rate of heat transfer. However, at the subcooled regime, the rate of heat transfer degrades for nanofluids and it degrades more by increasing concentration of nanoparticles. On the other hand, it can be seen the nanoparticle type has a small effect on this degradation, while the particle size has more effect on heat transfer coefficient variation. Comparisons with correlations present in literature are accomplished and a very good agreement is realized. [ABSTRACT FROM AUTHOR]