Boehmite Alumina Nanoparticles Research Articles

Analysis of spiral plate heat exchanger used to cool vegetable oil with nanofluid consisting of water and non-spherical boehmite alumina nanoparticles

The objective is to use dimensionless analysis through the thermal efficiency method to determine the thermohydraulic performance of a spiral plate heat exchanger (SPHE) used to cool sunflower oil. The coolant consists of water as a base fluid and non-spherical Boehmite Alumina nanoparticles with a defined volume fraction. The concept of thermal efficiency for heat exchangers is used to determine the main quantities used in the analysis. Graphical results are presented for the number of thermal units (NTU), thermal efficiency, thermal effectiveness, hot fluid outlet temperature, thermal and viscous irreversibilities, and Bejan number. The analyzed heat exchanger provides excellent thermal performance for refrigerants consisting of water and non-spherical nanoparticles in platelets or cylindrical, with a volume fraction equal to 12%. Viscous dissipation significantly increases concerning the dissipation associated with pure water, but the cost-benefit is within reason for the proposed objective, within the flow rate under analysis.

Theoretical analysis using thermal efficiency concept in straight micro channel printed circuit heat exchanger

The objective is to analyze the thermal and hydraulic performance in a Micro Channel Straight Printed Circuit Heat Exchanger. Counterflow and parallel flow configurations were analyzed for water cooling using ethylene glycol-based fluid and platelet-shaped non-spherical Boehmite alumina nanoparticles. The work presents results from applying a dimensionless theory that uses the concepts of thermal efficiency of heat exchangers and quantities associated with the second law of thermodynamics. Thermal efficiency, thermal effectiveness, thermal and viscous irreversibilities, thermodynamic Bejan number, and outlet water temperatures are presented in graph form. The data obtained allow us to conclude that the heat exchanger can work in a range of water and refrigerant flow rates below the design parameters. With the inclusion of nanoparticles with a volume fraction equal to 5.0%, the flow rates of the refrigerant fluid can be significantly reduced. The analysis performed shows that the use of nanoparticles improves the operational cost-benefit of the heat exchanger with a significant reduction in the hot water outlet temperature.

Effect of boehmite alumina nanoparticles on the physical and chemical characteristics of eco-friendly sodium alginate/polyvinyl alcohol bio-nanocomposite film

In the present work, bio-nanocomposite films of sodium alginate/polyvinyl alcohol (SA/PVA) blend with different loadings of boehmite alumina (BA) nanoparticles were developed via the film-casting technique. The bio-nanocomposite films obtained, containing boehmite alumina nanoparticles, are highly transparent and eco-friendly. The morphological characterization, by using TEM, AFM and SEM, indicate the fact that the BA nanoparticles showed a homogeneous dispersion at low BA loading, with rod-like features and plates with cubic crystal shapes morphology. Conversely, BA agglomeration was observed at higher BA loading. The mechanical properties indicate improvements in the tensile strength and elongation-at-break and flexibility in the 3 wt% BA nanoparticles loading. This (3 wt%) is stable with homogeneous dispersion of BA nanoparticles in the SA/PVA blend matrix, which is confirmed by SEM and TEM analysis. Additionally, the contact angle of the blend matrix was observed to be 34.7° and with the incorporation of boehmite alumina (BA) of between 3 to 9 wt % to the hydrophilic blend matrix, the results in contact angles of the nanocomposite films in increasing hydrophobic order of 47.9–67.9°, respectively. Furthermore, the incorporation of BA nanoparticles shows that the SA/PVA blend matrix have desirable thermal stability. From the present study, the novel ternary SA/PVA/BA bio-nanocomposite films could be a potential candidate to be used in the fields of biomedical (such as wound healing) and packaging applications.

Effect of nanoparticles shape on turbulent nanofluids flow within a solar collector by using hexagonal cross-section tubes

This paper investigates the turbulent flow of nanofluid (NFs) in which boehmite-alumina nanoparticles with different shapes of platelet, brick, blade, and cylinder suspended in a mixture of W/EG in a flat plate solar collector (FPSC). A hexagonal cross-sectional tube is used in the FPSC and compared with a simple one. The problem variables include flow rate (FR) (0.25–1 kg / s), shape and volume percentage (φ) of nanoparticles (NPs) (0–4%), tube shape (circular and hexagonal) and FPSC material (copper and steel). The influence of these variables on the FPSC output temperature (TCOUT), Nusselt number (Nu) and heat transfer coefficient (h) is investigated. The results reveal that copper FPSC can provide higher TCOUT but has lower convective coeffient and Nu than steel FPSC. The outlet fluid temperature is 1.86 °C higher when pure fluid flows in copper tubes. The addition of NPs, particularly bricks, causes the temperature of the fluid at the outlet to rise. This increase is about 1°for φ = 4%. The use of a hexagonal tube enhances the temperature of the fluid at the outlet relative to a circular one. For copper and steel FPSCs, this increase is 2.67 and 1.75 °C for pure fluid, respectively. The addition of NPs reduces the amount of heat transfer and Nu for the FPSCs.

Numerical study on performance enhancement of the fin and tube heat exchanger using different nanoparticle shapes

The effects of various shapes of boehmite alumina nanoparticles including platelets, blades, cylindrical and bricks, mixed with water, on the thermo-economic characteristics of a fin tube heat exchanger (FTHE) are explored. Multi-objective optimization is applied for two objective functions including effectiveness and total annual cost (TAC). For this aim, nine design variables involving particle concentration are considered. Variations of nanofluid properties including viscosity, conductivity and Prandtl number versus particle volume fraction for various nanoparticle shapes are investigated. It is resulted that in the high range of effectiveness (e > 0.6), Pareto fronts of bricks shape are almost dominated on the other shapes of nanoparticles. It is also demonstrated that Pareto fronts of blades are completely captured on the other Pareto fronts in the fixed value of TAC for the region with medium effectiveness (0.4 < e < 0.6). Finally, the impacts of design parameters on the effectiveness are discussed for the optimum Pareto fronts.

Blasius and Sakiadis slip flow of H2O–C2H6O2 (50:50) based nanoliquid with different geometry of boehmite alumina nanoparticles

The geometry of the nanoparticles in nanoliquids has significant influence in many engineering and bio medical applications and also the classical flow problems such as Blasius and Sakiadis problems are important in industrial applications. In view of this, an investigation on the flow of H2O–C2H6O2 (50:50) mixture based nanoliquid with different geometry of boehmite alumina nanoparticles is carried out in the presence of viscous dissipation effects. Spherical, blades, bricks, platelets and cylindrical geometries of the nanoparticels are considered. Both Blasius and Sakiadis flow types are analysed for slip and no-slip cases. The thermal and velocity slip boundary conditions are included as a function of nanoparticle volume fraction. Mathematical model is solved numerically by the Iterative Power Series (IPS) method and shooting strategy with the thermo-physical properties of different geometries nanoparticles. It is observed that the thermal boundary layer thickness is increased for cylindrical nanoparticles and decreased for spherical nanoparticles in both slip and no-slip cases of Blasius and Sakiadis flows. The reduced Nusselt number is increased with nanoparticle volume fraction for all shapes of boehmite alumina nanoparticles except spherical nanoparticles.

The effect of boehmite alumina nanoparticles on the properties of polylactide/polypropylene blend composites

The effect of boehmite alumina nanofiller on properties of polylactide/polypropylene blend compatibilized with 3% maleic anhydride grafted polypropylene was investigated. Boehmite alumina nanoparticles were finely dispersed in polylactide/polypropylene/boehmite alumina blend up to 7 wt.% to form blend nanocomposites which were prepared by twin-screw melt compounding. The morphology, thermal, mechanical, heat distortion temperature, thermomechanical and degradation characteristics were investigated. Scanning electron microscopy indicated a tubular morphology with increasing boehmite alumina in the blend matrix particularly at 5 and 7 wt.% of boehmite alumina loadings with few agglomerates. Transmission electron microscopy indicated a highly dispersed boehmite alumina in the blend nanocomposites. Boehmite alumina nanoparticles significantly influenced the thermal properties and a nucleation of the blend matrix. A significant improvement in the tensile modulus and tensile strength upon addition of boehmite alumina in the blend nanocomposites was obtained. However, beyond 3 wt.% of boehmite alumina addition, there was a clear deterioration in mechanical properties.

First and second laws analysis of a minichannel-based solar collector using boehmite alumina nanofluids: Effects of nanoparticle shape and tube materials

This paper evaluates the first and second laws for a flat plate minichannel-based solar collector where the working fluid is a suspension of boehmite alumina nanoparticles in a mixture of water and ethylene glycol. Four different shapes of nanoparticles, including platelets, blades, cylinders, and bricks are selected for this study. The results of Nusselt number, heat transfer coefficient, outlet temperature, and entropy generation are presented for different shapes of nanoparticles and volume concentrations up to 4% in turbulent flow. Two different solar collectors are investigated so that in one of them the tubes and absorber plate are made of copper and in another the material is of steel. It is found that the platelet shaped nanoparticles show the lowest heat transfer coefficient while bricks, except at the highest volume fraction, i.e. 4%, display the highest heat transfer coefficient. The heat transfer coefficient for copper tubes is lower than that of steel tubes. The findings indicate that, independent of nanoparticle shape, the outlet temperature increases by adding the nanoparticles but the rate of increase for platelets is lowest. The results of entropy generation analysis for copper tubes elucidate that the entropy generation rate is minimized by using brick shaped particles with volume fraction of 2%, while for steel tubes the minimum entropy generation is achieved by using blade shaped particles with volume fraction of 4%. In mass flow rate of 0.5kg/s, the entropy generation rate for steel tubes is, on average, about 11% higher than copper tubes and this value attains 18% when the mass flow rate increases from 0.5 to 0.75kg/s.

Thermal, viscoelastic and mechanical behavior of polypropylene with synthetic boehmite alumina nanoparticles

Effects of nanofiller concentration and surface treatment on the morphology, thermal, viscoelastic and mechanical behavior of polypropylene copolymer (PP)/boehmite alumina (BA) nanocomposites were investigated. Both untreated BA particles and those treated with octylsilane (OS) or sulphonic acid compound (OS2) were added at up to 10 wt% to produce nanocomposites by melt mixing followed by film blow molding and hot pressing. Dispersion of BA was studied by scanning electron microscopy. Differential scanning calorimetry and wide-angle X-ray scattering were adopted to detect changes in the crystalline structure of PP. Thermooxidative degradation of the nanocomposites was assessed by thermogravimetrical analysis. Dynamic mechanical analysis served for studying the viscoelastic properties, whereas quasi-static tensile, creep and Elmendorf tear tests were used to detect changes in the mechanical performance. BA nanoparticles were finely dispersed in PP up to 10 wt%, even when they were not surface modified. The resistance to thermal degradation was markedly improved by BA nanomodification. Since the crystalline characteristics of the PP matrix did not practically change with BA modification, changes observed in the mechanical properties were attributed to BA dispersion, filler/matrix interactions and related effects.

Mechanical and rheological response of polypropylene/boehmite nanocomposites

In this study, the influence of synthetic boehmite alumina nanoparticles with various surface treatments on the morphology, crystallization behavior and mechanical properties of polypropylene copolymer nanocomposites was studied. In particular, a series of polypropylene/boehmite alumina nanocomposites, containing up to 10 wt% of untreated and of octylsilane-functionalized boehmite alumina nanoparticles, were prepared by melt compounding and film blowing. A third type of composite was produced by incorporation of boehmite alumina nanoparticles treated with benzene sulfonic acid. Scanning electron microscopy indicated that boehmite alumina nanoparticles were finely and uniformly dispersed, though agglomerated, in the polypropylene nanocomposites. Surface-treated boehmite alumina nanoparticles were better dispersed in the matrix than the untreated boehmite alumina nanocomposites. The melt viscosity of nanocomposites remained unaltered or decreased by nanofiller incorporation at low concentration (2.5 and 5 wt%), while it slightly increased at higher concentrations (10 wt%). Uniaxial tensile tests indicated that the nanoparticles can induce a remarkable stiffening effect even at a rather low filler content, especially in the case of surface-treated particles. The plane stress fracture toughness of the material, evaluated by the essential work of fracture approach, showed a noticeable improvement due to boehmite alumina incorporation, with an optimal effect for a filler concentration of about 2.5 wt%.

Viscoelastic behaviour and fracture toughness of linear-low-density polyethylene reinforced with synthetic boehmite alumina nanoparticles

Aim of the present study is to investigate how synthetic boehmite alumina (BA) nanoparticles modify the vis- coleastic and fracture behaviour of linear low-density polyethylene. Nanocomposites containing up to 8 wt% of untreated and octyl silane-functionalized BA nanoparticles, were prepared by melt compounding and hot pressing. The BA nanoparticles were finely and unformly dispersed within the matrix according to scanning electron microscopy inspection. The results of quasi-static tensile tests indicated that nanoparticles can provide a remarkable stiffening effect at a rather low filler content. Short term creep tests showed that creep stability was significatively improved by nanofiller incorporation. Concurrently, both storage and loss moduli were enhanced in all nanocomposites, showing better result for surface treated nanoparticles. The plane-stress fracture toughness, evaluated by the essential work of fracture approach, manifested a dramatic increase (up to 64%) with the BA content, with no significant differences among the various types of BA nanoparticles.

The role of emulsifier in stabilization of emulsions containing colloidal alumina particles

This paper focuses on the study on rheological behaviour of emulsions, stabilized by both differently modified dispersible colloidal Boehmite alumina nanoparticles and a non-ionic emulsifier. Hysteresis loop measurements and dynamic rheological measurements were carried out in linear and non-linear regimes on two different emulsion systems – water-in-oil (W/O) and oil-in-water (O/W) emulsions.Emulsion stabilized by a combination of moderately hydrophobic particles and a non-ionic emulsifier is an O/W emulsion. The addition of emulsifier improved the stability, however, did not show a significant influence on the emulsion flow behaviour. The emulsion, stabilized by both – nanoparticles and emulsifier – showed a complicated behaviour, i.e. sometimes it exhibited thixotropy or antithixotropy and sometimes both of them.Emulsion stabilized by rather hydrophobic particles and a non-polar emulsifier is a W/O emulsion. The emulsion is very homogenous and exhibited very weak thixotropy. Dynamic measurements showed that G’ was almost equal to G” and both parameters were frequency-dependent, indicating a viscous liquid-like system with little network structure if any. With addition of emulsifier, the rather elastic solid-like emulsion structure may be changed into the viscous liquid-like structure.In order to get a better understanding of relationships between rheological behaviour and microstructure, differential scanning calorimetry (DSC) results and optical microscopic images of the emulsions studied were discussed.

Effect of Boehmite Alumina Nanofiller Incorporation on the Morphology and Thermal Properties of Functionalized Poly(propylene)/Polyamide 12 Blends

AbstractA composite of boehmite alumina nanoparticles and a PP/PA12 blend is prepared. WAXD and SEM suggest that a low filler loading enhances the coalescence of PA12, whereas a higher loading reverses the situation. DSC, DMA and TGA reveal that the final properties of the blend composites such as crystallization temperatures, flexural storage moduli, or thermal degradation temperatures improve with increasing nanoparticle loading. The data are compared with the neat polymers and the compatibilized blend, and the results show that the compatibility increases only at high nanoparticle loading, and most of the thermal properties improve with increasing nanoparticle content in the blends. The presence of interfacial interactions between the polymer matrices and the filler was confirmed via FTIR.magnified image

Dielectric relaxation phenomena and dynamics in polyoxymethylene/polyurethane/alumina hybrid nanocomposites

AbstractTernary hybrid composites composed of polyoxymethylene (POM), polyurethane (PU) and boehmite alumina nanoparticles were produced by melt blending with and without latex pre‐compounding. PU latex pre‐compounding was employed for the fine dispersion of both the PU and alumina particles within the POM matrix. In this study the electrical properties of the POM/PU/boehmite alumina nanocomposites were examined by means of broadband dielectric spectroscopy over a wide temperature (−100 to 150 °C) and frequency (10−1 to 106 Hz) range. Data were analysed by means of the electric modulus formalism. The recorded relaxations include contributions from both polymers and the inorganic reinforcing phase. In the ternary hybrid systems five distinct relaxation processes were detected. Relaxations were assigned and interpreted by considering the morphology of the corresponding composite. In particular, they were attributed to the γ‐mode of POM and/or of PU, the α‐mode of PU, the α‐mode of POM and to the interfacial polarization process. Finally, the dynamics of all the recorded processes are examined and discussed. Copyright © 2011 Society of Chemical Industry

Influence of the particle type on the rheological behavior of Pickering emulsions

In order to get a better understanding of potential relationships among the microstructure and stability of Pickering emulsions, rheological studies were performed using differently modified disperable colloidal Boehmite alumina nanoparticles. Hysteresis loop measurements and dynamic (oscillatory) rheological measurements on two different emulsion systems were carried out in linear and non-linear regime at different storage time. Differential scanning calorimetry (DSC) results, transmission electron microscopy (TEM) and optical microscopy images of these emulsion systems were additionally analysed in respect to reveal the emulsions type and their microstructure. Pickering emulsion stabilized by moderately hydrophobic particles exhibited inhomogeneous structure, relative large yield stresses and thixotropic flow behavior, indicating a formation of a three-dimensional network. Emulsion stabilized by rather hydrophobic particles with a contact angle around 90°, was revealed to be an oil-in-water-in-oil multiple emulsion. The emulsion was homogenous and showed thixotropy, indicating the presence of a three-dimensional network. However, a phase separation slightly occurred in the storage time evaluated meaning that the stability of this emulsion need be improved.

Structure and creep response of toughened and nanoreinforced polyamides produced via the latex route: Effect of nanofiller type

Ternary composites composed of polyamide-6 (PA-6), hydrogenated nitrile rubber (HNBR) and sodium fluorohectorite (FH) or boehmite alumina (BA) were produced by melt blending with latex precompounding. The latter served for the predispersion of the FH and BA nanoparticles. The related masterbatch (MB) was produced by mixing the HNBR latex with water dispersible BA or water swellable FH. The dispersion of the nanofillers in the composites was studied by scanning and transmission electron microscopy techniques (SEM and TEM, respectively) and discussed. The thermomechanical and creep properties of the composites were determined in short-time creep tests (performed at various temperatures) and dynamic mechanical thermal analysis (DMTA), respectively. The melt flow of the composites was characterized in a plate/plate rheometer. PA-6/HNBR/FH composites produced by the MB technique outperformed the PA-6/HNBR/BA systems in respect to most of the mechanical and viscoelastic characteristics. This was attributed to the preferred location of FH in the PA-6 matrix and to its higher aspect ratio compared to BA.