Viscosity and thermal conductivity of ZnO–water-based nanofluids stabilized by grafted SMA-g-MPEG comb-shaped copolymer for heat transfer applications
TL;DR: In this paper, the effect of poly(styrene-co-maleic anhydride)-grafted methoxy (polyethylene glycol) (SMA-g-MPEG) copolymer as dispersants on the viscosity and thermal conductivity of zinc oxide (ZnO)-water-based nanofluids was studied.
Abstract: In this work, the effect of poly(styrene-co-maleic anhydride)-grafted methoxy (polyethylene glycol) (SMA-g-MPEG) copolymer as dispersants on the viscosity and thermal conductivity of zinc oxide (ZnO)–water-based nanofluids was studied. Various molecular weight MPEGs were grafted to SMA copolymer by esterification reaction, and ZnO nanoparticles (NPs) were prepared by microwave irradiation method. Prepared ZnO NPs and copolymers were characterized by UV, FESEM, TEM, XRD, FTIR, NMR and TGA techniques. The grafted copolymer was used to enhance the dispersibility of ZnO–water-based nanofluids. The effect of SMA-g-MPEG comb-shaped copolymer on the viscosity and thermal conductivity of the suspensions was investigated at different concentrations (0.1, 0.3 and 0.5 wt%) and solid volume fractions of ZnO NPs (φ = 0.5–3.0%). The suspension with SMA-g-MPEG 2000 dispersant showed improved stabilization at higher particle concentration. The variation of viscosity with shear rate showed the nanofluids behaved as a non-Newtonian fluid at the lower shear rate and Newtonian behaviour with the increase in shear rate. However, thermal conductivities of the ZnO–water-based nanofluids increased with increasing of the particle volume concentration and decreased with increase in the chain length of the grafted molecules. The average chain length of the grafted molecule exhibited enhanced thermal conductivity as compared with that of the base fluids. Finally, experimental values of the thermal conductivity and viscosity were compared with the estimations done by several simple theoretical models.
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01 Apr 2020
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TL;DR: In this paper, the application of polyvinyl alcohol (PVA) supported sol-gel self-propagation route for the synthesis of ZnO-based binary metal oxides nanocomposites (BMONCs) was reported.
Abstract: The present work reports the application of poly (vinyl alcohol) (PVA) supported sol-gel-self-propagation route for the synthesis of ZnO-based binary metal oxides nanocomposites (BMONCs). The DRS–U...
23 citations
Cites background from "Viscosity and thermal conductivity ..."
...Among several metal oxides, ZnO is confirmed to be abundant, low cost, biocompatible, and less toxic materials.([2]) It also listed as an antimicrobial agent and safe material as food preservation of foodborne diseases by the U....
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21 Dec 2022
TL;DR: In this article , the underlying physics behind nanofluid destabilization and identifies significant factors that dictate the destabilization process are explored. And the desired properties for attaining long-term stability and identifies different challenges associated with the stability of nanoflids are discussed.
Abstract: A nanofluid is a colloidal suspension of nanoparticles in any base fluid that displays a plethora of improved properties based on its field of applications, i.e., heat transfer, lubrication, and biomedical applications, over those of nanoparticles alone. Despite their improved properties, the real-world applications of nanofluids remain limited due to their gradual destabilization with time. Therefore, the stability of nanofluids remains a significant bottleneck that preventing their widespread application in numerous fields. Since a nanofluid is a colloidal suspension, Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO theory have been utilized to elucidate the process of nanofluid destabilization. This chapter explores the underlying physics behind nanofluid destabilization and identifies significant factors that dictate the destabilization process. The roles of nanoparticle and base fluid properties, preparation method, external forces, operating conditions, and stabilizer presence on nanofluid stability have been examined in great detail. Different nanofluid stabilization strategies and stability evaluation methods are also discussed in the present chapter. This chapter discusses the desired properties for attaining long-term stability and identifies different challenges associated with the stability of nanofluids. Upon consideration of the abovementioned factors, the chapter provides summarized guidelines to ensure long-term nanofluid stability. This chapter concludes with a discussion on future research direction in nanofluid stabilization.
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TL;DR: In this article , an aqueous carbon black slurry was prepared by esterifying polystyrene-maleic anhydride with isobutanol as a dispersant for carbon black.
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TL;DR: In this article, the authors used a Brookfield rotating viscometer to measure the viscosities of the dispersed fluids with γ-alumina (Al2O3) and titanium dioxide (TiO2) particles at a 10% volume concentration.
Abstract: Turbulent friction and heat transfer behaviors of dispersed fluids (i.e., uttrafine metallic oxide particles suspended in water) in a circular pipe were investigated experimentally. Viscosity measurements were also conducted using a Brookfield rotating viscometer. Two different metallic oxide particles, γ-alumina (Al2O3) and titanium dioxide (TiO2), with mean diameters of 13 and 27 nm, respectively, were used as suspended particles. The Reynolds and Prandtl numbers varied in the ranges l04-I05 and 6.5-12.3, respectively. The viscosities of the dispersed fluids with γ-Al2O3 and TiO2 particles at a 10% volume concentration were approximately 200 and 3 times greater than that of water, respectively. These viscosity results were significantly larger than the predictions from the classical theory of suspension rheology. Darcy friction factors for the dispersed fluids of the volume concentration ranging from 1% to 3% coincided well with Kays' correlation for turbulent flow of a single-phase fluid. The Nusselt n...
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"Viscosity and thermal conductivity ..." refers background in this paper
...Experimentally calculated thermal conductivity data are compared with the three theoretical models viz., Hamilton–Crosser, Pak and Cho and Timofeeva....
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... 5), Pak and Cho (Eq....
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...(5) Knf Kbf = Kp + (n − 1)Kbf − (n − 1) (Kbf − Kp) Kp + (n − 1)Kbf + (Kbf − Kp) , Pak and Cho [40] developed a thermal conductivity correlation model for Al2O3 and TiO2 nanofluids, which was expressed as follows: Timofeeva et al....
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...Kp + (n − 1)Kbf + (Kbf − Kp) , Pak and Cho [40] developed a thermal conductivity correlation model for Al2O3 and TiO2 nanofluids, which was expressed as follows:...
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3,019 citations
"Viscosity and thermal conductivity ..." refers methods in this paper
...The Hamilton and Crosser (HC) model (1962) [39] developed for determining the effective thermal conductivity of a two-phase mixture which is given as follows:...
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TL;DR: Together, these results imply that the geometry, agglomeration state, and surface resistance of nanoparticles are the main variables controlling thermal conductivity enhancement in nanofluids.
Abstract: In recent years many experimentalists have reported an anomalously enhanced thermal conductivity in liquid suspensions of nanoparticles. Despite the importance of this effect for heat transfer applications, no agreement has emerged about the mechanism of this phenomenon, or even about the experimentally observed magnitude of the enhancement. To address these issues, this paper presents a combined experimental and theoretical study of heat conduction and particle agglomeration in nanofluids. On the experimental side, nanofluids of alumina particles in water and ethylene glycol are characterized using thermal conductivity measurements, viscosity measurements, dynamic light scattering, and other techniques. The results show that the particles are agglomerated, with an agglomeration state that evolves in time. The data also show that the thermal conductivity enhancement is within the range predicted by effective medium theory. On the theoretical side, a model is developed for heat conduction through a fluid containing nanoparticles and agglomerates of various geometries. The calculations show that elongated and dendritic structures are more efficient in enhancing the thermal conductivity than compact spherical structures of the same volume fraction, and that surface (Kapitza) resistance is the major factor resulting in the lower than effective medium conductivities measured in our experiments. Together, these results imply that the geometry, agglomeration state, and surface resistance of nanoparticles are the main variables controlling thermal conductivity enhancement in nanofluids.
700 citations
TL;DR: A review of green and biological synthesis methods of ZnO-NPs and investigation of their biomedical applications is presented in this paper, where the authors summarize the green-and biological-based synthesis methods and their applications.
548 citations
TL;DR: ZnO nanorods were fabricated by a simple low-temperature hydrothermal process in high yield (about 85%), starting with Zn(OH) 4 2− aqueous solution in the presence of CTAB, the CTA board serving as a structure director, and no calcination process was needed as discussed by the authors.
Abstract: ZnO nanorods were fabricated by a simple low-temperature hydrothermal process in high yield (about 85%), starting with Zn(OH) 4 2− aqueous solution in the presence of CTAB, the CTAB serving as a structure director, and no calcination process was needed. The morphology and crystal structure of the prepared ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM) and Transmission electron microscope (TEM). The ZnO nanorods were then used to construct a gas sensor for ethanol detection at different operating temperature. The as-prepared ZnO nanorod gas sensor exhibited a high, reversible and fast response to ethanol, indicating its potential application as a gas sensor to detect ethanol.
436 citations