Mass Concentration Of Nanoparticles Research Articles

Heat Transfer in a Loop Heat Pipe using Diamond-H2O Nanofluid

ABSTRACTThe main aim of this study is to enhance the thermal performance of loop heat pipe (LHP) charged with nanofluid as the working fluid. Thus, experiments are conducted to investigate heat transfer characteristics of using diamond-H2O nanofluid with nanoparticle mass concentration ranged from 0% to 3% in a LHP as a working medium for heat input range from 20 W to 60 W. The three-dimensional model, laminar flow and heat transfer governing equations are solved using the finite volume method. The simulations are carried out with three-dimensional model based on the characterization of the working fluid inside the LHP to give an insight into the heat transfer and fluid flow mechanism. The LHP performance is evaluated in terms of temperature distributions and total thermal resistance of LHP. It is inferred that the temperatures obtained at all points in evaporator side of LHP charged with diamond-H2O nanofluid are lower and reach their steady state faster than LHP charged with pure water. At the constant heat input, test results showed the average decrease of 5.7%−10.8% at nanoparticle mass concentrations ranging from 0.5% to 3% in Rth of LHP as compared with pure water (0%).

Separating excess surfactant from silver and gold nanoparticles in micellar concentrates by means of nonaqueous electrophoresis

It is shown by physicochemical means (IR Fourier spectroscopy, CHN-analysis with preliminary sorption of surfactant on SiO2) that the content of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in an electrophoretic concentrate remains unchanged during the electrophoretic concentration of silver and gold nanoparticles. Diluting the concentrate and carrying out the second stage of electrophoresis reduces the concentration of surfactant from 0.25 to 0.015 M while maintaining the mass concentration of nanoparticles. Nanoparticles in organosols before and after electrophoresis are characterized by means of photon correlation spectroscopy, phase analysis light scattering, and spectrophotometry. Conducting films on glass substrates are obtained from concentrates with a different contents of surfactant via water–alcohol treatment and thermolysis.

Effect of Temperature and Mass Concentration of SiO₂ Nanoparticles on Electrical Conductivity of Ethylene Glycol

Effect of Temperature and Mass Concentration of SiO₂ Nanoparticles on Electrical Conductivity of Ethylene Glycol

Experimental study of the sensible heat storage in the water/TiO2 nanofluid enclosed in an annular space

This article is devoted to an experimental study of heat transfer during a sensible heat storage cycle (charging/discharging) in a vertical cylindrical system. The experimental setup consists of two cylindrical tanks filled respectively with hot and cold water, a test bench, and measurement instruments. The test bench, thermally insulated with glass wool, is also composed of two vertical concentric tubes whose annular space contains the used nanofluid (the mixture of distilled water and titanium dioxide nanoparticles). The heat transfer fluid (HTF) flows in the upward direction of the inner tube (HTF pipe). Adequate methods were used to prepare titanium dioxide nanoparticles for which the diameter is less than 20nm. Both convective heat transfer coefficient between external inner tube wall and nanofluid, and heat flux densities during storage cycle, were evaluated. The effect of nanofluid mass concentration (0.005, 0.01, 0.02 and 0.03wt%) and the HTF mass flow rate on thermal heat transfer coefficient and hence heat flux densities were analyzed. Experimental results show that the average convective heat transfer coefficient increases with increasing the mass flow rate, and it is improved by comparison with the fluid base (distilled water) when the nanofluid is considered. Furthermore, it has been observed that there is an optimal nanoparticles mass concentration corresponding to a maximal average convective heat flux and also a maximal recovered heat flux density. Consequently, convective heat transfer coefficient has a strong influence on the sensible heat during a storage cycle (charging/discharging).

Optical properties of PVP/ZnO composite thin films

Purpose: The aim of the work was the preparation of thin composite layers from PVP polymer doped by ZnO nanoparticles using the spin coating method and the analysis of the applied reinforcing phase on the morphology and optical properties of obtained composites. Design/methodology/approach: To analyse the morphology of thin coatings a technique of surface topography imaging using the atomic force microscopy (AFM) was applied. Analysis of the optical properties was conducted using absorbance spectrum in function of wavelength for all produced thin coatings using UV-Vis spectroscopy. Findings: AFM results show that mass concentration of ZnO nanoparticles of 10% in a solution of PVP/EtOH polymers has a meaningful influence on the morphology of the surface of the PVP/ZnO composite coatings. Using obtained absorbance spectra, the width of the band gap of the manufactured composite coatings were determined which were compared with a band gap values of pure polymer and used reinforcing phase. Practical implications: The analysis of the values of the energy band gap of the manufactured materials showed that both for pure polymer and composite coatings values of energy band gap are similar approx. 4 eV at the same time decrease the degree of absorption of electromagnetic radiation caused by the increasing concentration of the reinforcing phase, which indicates the broad possibilities of application of this type of the material.

Comparative toxicity of Cd, Mo, and W sulphide nanomaterials toward E. coli under UV irradiation

In this study, the phototoxicity of cadmium sulfide (CdS), molybdenum disulfide (MoS2), and tungsten disulfide (WS2) nanoparticles (NPs) toward Escherichia coli (E. coli) under UV irradiation (365 nm) was investigated. At the same mass concentration of NPs, the toxicity of three NPs decreased in the order of CdS > MoS2 > WS2. For example, the death rates of E. coli exposed to 50 mg/L CdS, MoS2, and WS2 were 96.7%, 38.5%, and 31.2%, respectively. Transmission electron microscope and laser scanning confocal microscope images of E. coli exposed to three NPs showed the damage of cell walls and release of intracellular components. The CdS-treated cell wall was more extensively damaged than those of MoS2-treated and WS2-treated bacteria. WS2 and MoS2 generated superoxide radical (O2−), singlet oxygen (1O2), and hydroxyl radical under UV irradiation, CdS produced only O2− and 1O2. CdS and WS2 released ions under UV irradiation, while MoS2 did not. Reactive oxygen species (ROS) generation and toxic ion release jointly resulted in the antibacterial activities of CdS and WS2. ROS generation was the dominant toxic mechanism of MoS2 toward the bacteria. This study highlighted the importance of considering the hazardous effect of sulfide NPs after their release into natural waters under light irradiation condition.

Influence of collagen/fibroin scaffolds containing silver nanoparticles on dermal regeneration of full-thickness skin defect wound in rat

Objective: To explore the influence of collagen/fibroin scaffolds containing silver nanoparticles on dermal regeneration of full-thickness skin defect wound in rat. Methods: Eighty-one collagen/fibroin scaffolds containing silver nanoparticles (with the mass concentration of silver nanoparticles as 10 mg/L) and 81 collagen/fibroin scaffolds without silver nanoparticles were produced respectively with freeze-drying method and enrolled as silver nanoparticles scaffold group (SNS) and control scaffold group (CS). Nine scaffolds in each group were cultured with human fibroblasts. At post culture hour (PCH) 2, 12, and 24, the human fibroblasts adherent to the scaffolds (n=3) in two groups were counted. Four full-thickness skin defect wounds were reproduced on the back of each one of the 36 SD rats. The rats were divided into groups SNS (wounds were transplanted with collagen/fibroin scaffolds containing silver nanoparticles) and CS (wounds were transplanted with collagen/fibroin scaffolds without silver nanoparticles) according to the random number table, with 18 rats in each group. In post surgery week (PSW) 1, 2, and 4, 6 rats in each group were sacrificed respectively for general observation, observation of histological structure, inflammatory cell infiltration, and collagen deposition with HE staining, count of CD68 positive cells with immunohistochemical staining, and mRNA expressions of interleukin-6 (IL-6) and IL-10 with real-time fluorescent quantitative reverse transcription polymerase chain reaction. Data were processed with analysis of variance of factorial design, t test, and Bonferroni correction. Results: (1) At PCH 2, 12, and 24, the numbers of human fibroblasts adherent to the scaffolds in the two groups were close (with t values from 1.77 to 2.60, P values above 0.05). (2) In PSW 1, no obvious symptom of infection was observed in wound or wound edge of rats in group SNS with obvious vascularization of scaffolds, while obvious symptoms of infection were observed in wounds of rats in group CS with some scaffolds exfoliated. In PSW 2, the scaffolds were firmly attached to the wounds of rats in group SNS, while obvious contracture was observed in the wounds of rats in group CS with a lot of scaffolds exfoliated. In PSW 4, the scaffolds covered the wounds of rats in group SNS with obvious epithelization on the surface of the scaffolds, while all the scaffolds exfoliated, leaving obvious contracture of residual wounds of rats in group CS. (3) In PSW 1 and 2, compared with those in group CS, more collagen secretion and tissue regeneration and less inflammatory cell infiltration in the scaffolds were observed in the wounds of rats in group SNS. In PSW 4, obvious epithelization was observed in the wounds of rats in group SNS, while inflammatory cell infiltration was observed without obvious epithelization in the wounds of rats in group CS. (4) In PSW 1, the number of CD68 positive cells in the wounds of rats in group SNS [(54±10) /mm(2)] was similar to that in group CS [(78±7) /mm(2,) t=1.52, P>0.05]. In PSW 2 and 4, the numbers of CD68 positive cells in the wounds of rats in group SNS [(154±10) and (77±7) /mm(2)] were significantly less than those in group CS [(268±16) and (136±13) /mm(2,) with t values respectively 7.31 and 3.83, P values below 0.01] respectively. (5) Except for the expression in PSW 4 (t=1.23, P>0.05), the mRNA expressions of IL-6 in the wounds of rats in group SNS in PSW 1 and 2 were significantly lower than those in group CS (with t values respectively 13.12 and 4.65, P values below 0.01). Except for the expression in PSW 1 (t=3.08, P<0.05), the mRNA expressions of IL-10 in PSW 2 and 4 in the wounds of rats in the two groups were similar (with t values respectively 2.14 and 0.49, P values above 0.05). Conclusions: Besides good biocompatibility, collagen/fibroin scaffolds containing silver nanoparticles have obvious effect in modulating inflammation, thus they can accelerate dermal regeneration induced by collagen/fibroin scaffolds for wound repair.

Heat Transfer in a Loop Heat Pipe Using Fe2NiO4-H2O Nanofluid

Nanofluids are stable suspensions of nano fibers and particles in fluids. Recent investigations show that thermal behavior of these fluids, such as improved thermal conductivity and convection coefficients are superior to those of pure fluid or fluid suspension containing larger size particles. The use of enhanced thermal properties of nanofluids in a loop heat pipe (LHP) for the cooling of computer microchips is the main aim of this study. Thus, the Fe 2 NiO 4 -H 2 O served as the working fluid with nanoparticle mass concentrations ranged from 0 to 3 % in LHP for the heat input range from 20W to 60W was employed. Experimental apparatus and procedures were designed and implemented for measurements of the surface temperature of LHP. Then, a commercial liquid cooling kit of LHP system similar as used in experimental study was installed in real desktop PC CPU cooling system. The test results of the proposed system indicate that the average decrease of 5.75oC (14%) was achieved in core temperatures of desktop PC CPU charged with Fe 2 NiO 4 -H 2 O as compared with pure water under the same operating conditions. The results from this study should find it’s used in many industrial processes in which the knowledge on the heat transfer behavior in nanofluids charged LHP is of uttermost importance.

Hydrophobically modified nanoparticle suspensions to enhance water evaporation rate

The evaporation rates of water can be enhanced by adding the hydrophobically modified nanoparticles as a suspension. The magnitudes of enhancement are related to the diameter and mass concentration of nanoparticles. In particular, a 15% enhancement was achieved after adding the modified Al2O3 nanoparticle with a diameter of 13 nm and mass percentage of 0.02%. A theoretical model was established in order to estimate the evaporation rates of hydrophobic particle-based nanofluids. The obtained results indicate that the enhanced evaporation rates are attributed to the elevated saturated vapor pressures of the nanofluids. These results may have important applications for energy-efficient enhancement of water evaporation rates.

Thermal evaluation of water-based alumina nanofluid in an electronic heat sink application

An experimental study was conducted to investigate the thermal performance of a water-based Al2O3 nanofluid in an electronic heat sink application. Heat transfer tests were carried out using 20 nm alumina particles at a concentration of 5% by mass, and a coolant temperature ranging from 47 to 57 oC. The results were compared to a baseline case using deionized water as a coolant. Thermal conductivity and viscosity tests conducted on alumina nanofluids show both parameters increase with nanoparticles mass concentration. Alumina nanofluid with 5% nanoparticles mass concentration behaves as a shear thinning fluid. Tests conducted on an electronic heat sink show heat flux and coolant heat transfer coefficient increase with bulk mass flow rate. Compared to cooling by deionized water, the average increase in the heat transfer coefficient using water-based alumina nanofluid as a coolant was about 20%, while the average increase in heat flux was about 24%. An additional decrease in the heated wall cross-section temperature between 4.1 and 4.9 oC is also seen. For the same pumping power, the presence of nanoparticles in the base fluid is shown to have a significant effect on the increase in heat transfer coefficient.

A Systematic Review of Reported Exposure to Engineered Nanomaterials.

Engineered nanomaterials (ENMs) have a large economic impact in a range of fields, but the concerns about health and safety of occupational activities involving nanomaterials have not yet been addressed. Monitoring exposure is an important step in risk management. Hence, the interest for reviewing studies that reported a potential for occupational exposure. We systematically searched for studies published between January 2000 and January 2015. We included studies that used a comprehensive method of exposure assessment. Studies were grouped by nanomaterial and categorized as carbonaceous, metallic, or nanoclays. We summarized data on task, monitoring strategy, exposure outcomes, and controls in a narrative way. For each study, the strength of the exposure assessment was evaluated using predetermined criteria. Then, we identified all exposure situations that reported potential occupational exposure based on qualitative or quantitative outcomes. Results were synthesized and general conclusion statements on exposure situations were formulated. The quality of evidence for the conclusion statements was rated as low, moderate, or high depending on the number of confirmed exposure situations, the strength of the exposure assessment, and the consistency of the results. From the 6403 references initially identified, 220 were selected for full-text screening. From these, 50 studies describing 306 exposure situations in 72 workplaces were eligible for inclusion (27 industrial-scale plants and 45 research or pilot-scale units). There was a potential for exposure to ENMs in 233 of the exposure situations. Exposure occurred in 83% (N = 107) of the situations with carbonaceous ENMs, in 73% (N = 120) of those with metallic ENMs and in 100% (N = 6) of those with nanoclay. Concentrations of elemental carbon in the workers' breathing zone ranged from not detected (ND) to 910 µg m(-3) with local engineering controls (LEC), and from ND to 1000 µg m(-3) without those controls. For carbon nanofibres (CNFs), particle counts ranged from ND to 1.61 CNF structures cm(-3) with LEC, and from 0.09 to 193 CNF structures cm(-3) without those controls. The mass concentrations of aluminium oxide, titanium dioxide, silver, and iron nanoparticles (NPs) were ND, 10-150, 0.24-0.43, and 32 µg m(-3) with LEC, while they were <0.35, non-applicable, 0.09-33, and 335 µg m(-3) without those controls, respectively. Regarding the potential of exposure in the workplace, we found high-quality evidence for multiwalled carbon nanotubes (CNTs), single-walled CNTs, CNFs, aluminium oxide, titanium dioxide, and silver NPs; moderate-quality evidence for non-classified CNTs, nanoclays, and iron and silicon dioxide NPs; low-quality evidence for fullerene C60, double-walled CNTs, and zinc oxide NPs; and no evidence for cerium oxide NPs. We found high-quality evidence that potential exposure is most frequently due to handling tasks, that workers are mostly exposed to micro-sized agglomerated NPs, and that engineering controls considerably reduce workers' exposure. There was moderate-quality evidence that workers are exposed in secondary manufacturing industrial-scale plants. There was low-quality evidence that workers are exposed to airborne particles with a size <100nm. There were no studies conducted in low- and middle-income countries.

Effect of nanoparticles on condensation of humid air in vertical channels

In this paper, the effect of uniform surface injection of nanoparticles on humid air condensation, as a main type of vapor condensation in the presence of non-condensable gas (NCG), is numerically investigated. Various inlet conditions (velocity and relative humidity) of vertical CONAN type classical test section were modeled. Two mass concentrations of different nanoparticles were examined and the behavior of filmwise condensation was studied under different parameters of heat and mass transfer, such as: Reynolds number and mean Nusselt number of the condensed film, and local and mean Sherwood number. Finally, by using response surface methodology, the statistical interpretation (objective function) of the numerical results are provided for other inlet conditions. As shown in the results, an increase in the nanoparticles mass concentration has direct influence on condensate Reynolds number and Sherwood number of the humid air. At higher relative humidities (ω), using nanoparticles has more impact and the maximum improvement of the condensate Reynolds number (at the outlet), mean Nusselt number of the condensed film and mean Sherwood number are 11.4, 4.5 and 6%, respectively. It is observed that, under best conditions (ω = 100%, Uin = 3 m/s), 0.5% of nanoparticles mass concentration improves the total heat flux by more than 10.4%.

An empirical study on the mixed convection transfer and pressure drop of HTO/CuO nanofluid in inclined tubes

In this paper, the mixed convective flow of heat transfer oil (HTO)–CuO nanofluid in inclined tubes is studied experimentally. The flow regime is laminar and the surface temperature is constant. The effect of nanoparticles mass concentration on the heat transfer rate and the pressure drop is studied as Richardson number is between 0.1 and 0.7, and the nanoparticles mass concentration is 0%, 0.5%, 1.0% and 1.5%. The experiments were performed in four inclination angles, e.g. 0°, 30°, 60°, and 90°. The results show that the combined free and forced convection heat transfer rate increases significantly by the nanoparticle concentration. According to the experimental results, two new correlations are proposed to predict nanofluid flow Nusselt number in terms of Richardson number and nanoparticles mass concentration with the maximum error of 16%. The pressure drop of heat transfer oil (HTO)–CuO nanofluid flow is also investigated and a new correlation is extracted to estimate the flow Darcy friction factor in inclined tubes. As the heat transfer enhancement methods usually accompany with an increase in the pressure drop, the system performance index is also presented. Accordingly, the maximum performance index is 1.58 which is achieved with 1.5% nanoparticles mass concentration and an inclination angle of 30° at Richardson number of 0.7. This result shows that using nanoparticles is more in favor of the heat transfer enhancement rather than in the increase of the pressure drop.

Simultaneous Determination of Size and Quantification of Gold Nanoparticles by Direct Coupling Thin layer Chromatography with Catalyzed Luminol Chemiluminescence.

The increasing use of metal-based nanoparticle products has raised concerns in particular for the aquatic environment and thus the quantification of such nanomaterials released from products should be determined to assess their environmental risks. In this study, a simple, rapid and sensitive method for the determination of size and mass concentration of gold nanoparticles (AuNPs) in aqueous suspension was established by direct coupling of thin layer chromatography (TLC) with catalyzed luminol-H2O2 chemiluminescence (CL) detection. For this purpose, a moving stage was constructed to scan the chemiluminescence signal from TLC separated AuNPs. The proposed TLC-CL method allows the quantification of differently sized AuNPs (13 nm, 41 nm and 100 nm) contained in a mixture. Various experimental parameters affecting the characterization of AuNPs, such as the concentration of H2O2, the concentration and pH of the luminol solution, and the size of the spectrometer aperture were investigated. Under optimal conditions, the detection limits for AuNP size fractions of 13 nm, 41 nm and 100 nm were 38.4 μg L−1, 35.9 μg L−1 and 39.6 μg L−1, with repeatabilities (RSD, n = 7) of 7.3%, 6.9% and 8.1% respectively for 10 mg L−1 samples. The proposed method was successfully applied to the characterization of AuNP size and concentration in aqueous test samples.

Combined free and forced convection heat transfer of the copper oxide-heat transfer oil (CuO-HTO) nanofluid inside horizontal tubes under constant wall temperature

In this paper, the combined free and forced convection heat transfer of the heat transfer oil-copper oxide (HTO-CuO) nanofluid flow in horizontal tubes is studied experimentally. The flow regime is laminar and the surface temperature is constant. The effect of nanoparticle mass concentration and microfin tube on the heat transfer rate is investigated as Richardson number is between 0.1 and 0.7. The results show that the combined free and forced convection heat transfer rate increase significantly with the increase in nanoparticle concentration from 0% to 1.5%. As shown in the results, three new correlations are presented to predict the mixed heat transfer rate based on increasing the Richardson number from 0.04 to 0.7. The maximum deviation of both correlations is less than 10%. In addition, a new correlation is suggested to assess the Nusselt number based on the Rayleigh number in horizontal tubes from 1656000 to 8200000. The maximum deviation of the correlation is almost 5%.

Performance improvement of wire-bonded mesh screen flat heat pipe using water-based nanofluid

An experimental study was conducted to investigate the thermal performances of a new type of wire-bonded mesh screen flat heat pipe using water and nanofluid as working fluid to find better structure and the working fluid based on the present flat heat pipes. The influences of the kind of working fluid, mass concentration of nanofluid and operating pressure on the thermal performance of the heat pipe were investigated under the three steady operating pressures. It is found from the results that the thermal performance of wire-bonded mesh screen heat pipe are superior to that of wire-bonded flat heat pipe either using water or using nanofluid as working fluid; the thermal resistance of the former reduces distinctly and the maximum power increases obviously. Moreover, using nanofluid can significantly enhance the thermal performance of this heat pipe; enhanced ratios of the both heat transfer coefficient and maximum heat flux gradually increase with increasing the nanoparticle mass concentration in the nanofluid at the same operating pressure, peaking at the 1.0 wt%. Then, they will gradually reduce with further increase of mass concentration of nanofluid.

Investigations of Electron Properties of Carbon Nanotubes Decorated with Platinum Nanoparticles with Their Varying Fraction

The paper presents the outcomes of investigations into electron properties and a qualitative and quantitative analysis of the chemical composition of unmodified carbon nanotubes with comparison to nanotubes decorated with platinum nanoparticles. The fabricated nanocomposite materials of the CNT-Pt type differed in a varying mass concentration of platinum nanoparticles (5, 10, and 20% of Pt). X-ray photoelectron spectroscopy (XPS) was employed to examine the structure and to analyse chemical composition. Survey spectra measurements within a wide range of the binding energy of 0–1400 eV were performed in the first phase of the investigations. The core lines of C1s carbon, Pt4f platinum, and O1s oxygen and a valence band were then measured. The chemical composition of the studied materials was determined based on the measured spectra of the core lines. The purpose of the investigations is to determine the effect of platinum nanoparticles on the structure and electron properties of the fabricated CNT-Pt nanocomposites.

Experimental Investigation and Optimization of Nanoparticle Mass Concentration and Heat Input of Loop Heat Pipe

Experimental Investigation and Optimization of Nanoparticle Mass Concentration and Heat Input of Loop Heat Pipe

Studies on Characteristics and Formation of Soot Nanoparticles in an Ethylene/Air Inverse Diffusion Flame

AbstractAn ethylene/air inverse diffusion flame burner was assumed to generate a stable flame, and soot samples were captured at different locations around the outer edge along the height of the flame. The soot samples were then analyzed with transmission electron microscopy (TEM), gas chromatography-mass spectrometry (GC-MS), and other detection means, and a photoacoustic analyzer was introduced to detect the mass concentration of soot nanoparticles after inception based on their optical features. The results showed that the plot of soot concentration had the same tendency as the gas temperature’s, which increased first and then declined with the increase in flame height, but these two curves had two different turning points. As to the measurements of TEM, the morphology of soot particles exhibited diverse shapes and structures at different flame heights. Alkanes, cycloalkanes, olefins, benzene, anthracene, pyrene, and aromatic compounds were determined as the main components of soot by the detection of ...

Optimization of SiO2 nanoparticle mass concentration and heat input on a loop heat pipe

This study presents the effect of nanoparticle mass concentration and heat input based on the total thermal resistance (Rth) of loop heat pipe (LHP), employed for PC-CPU cooling. In this study, silica nanoparticles (SiO2) in water with particle mass concentration ranged from 0% (pure water) to 3% is considered as the working fluid within the LHP. The experimental design and optimization is accomplished by the design of experimental tool, Response Surface Methodology (RSM). The results show that the nanoparticle mass concentration and the heat input have significant effect on the Rth of LHP. For a given heat input, the Rth is found to decrease with the increase of the nanoparticle mass concentration up to 0.5% and increased thereafter. It is also found that the Rth is decreased when the heat input is increased from 20 W to 60W. The results are optimized with the objective of minimizing the Rth, using Design-Expert software, and the optimized nanoparticle mass concentration and heat input are 0.48% and 59.97W, respectively, the minimum Rth being 2.66 (ºC/W). The existence of an optimum nanoparticle mass concentration and heat input are the predominant factors for the improvement in the thermal performance of nanofluid-charged LHP.