Boundary layer flow of nanofluids to analyse the heat absorption/generation over a stretching sheet with variable suction/injection in the presence of viscous dissipation
TL;DR: In this paper, the heat and mass transfer characteristics in boundary layer flow about a stretching sheet in a porous medium filled with TiO2 -water and Al2O3 -water-based nanofluids, in...
Abstract: In this investigation, the heat and mass transfer characteristics in boundary layer flow about a stretching sheet in a porous medium filled with TiO2 – water and Al2O3 – water-based nanofluids, in ...
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TL;DR: In this paper, the heat and mass transportation for the bioconvection transient rotating flow of Maxwell nanofluid over Riga plate is inspected in the present investigation, and the authors used the Cattano-Christov theory, Buongiorno model, binary chemical reaction, and activation energy are incorporated.
Abstract: The heat and mass transportation for the bioconvection transient rotating flow of Maxwell nanofluid over Riga plate is inspected in the present investigation The bioconvection is utilized alongside nanofluids to provide stability to improved thermal transportation Further, Cattano-Christov theory, Buongiorno model, binary chemical reaction, and activation energy are incorporated The unsteady three dimensional partially differentiate formulation is simplified in the form of two independent coordinates ( ζ , η ) For steady-state solution ( ζ = 1 ) , Glerikin discretization in used to employ finite element simulation in MATLAB environment The buoyancy ratio parameters, unsteady parameter, rotating parameter, thermophoresis, and Brownian motion parameter escalated the nanofluid temperature field Modified electromagnetic parameter M H accelerated the primary flow velocity and activation energy augmented the volume fraction of nanoparticles in the boundary layer region The larger modified Hartmaan number M H reduces the coefficient of skin friction in primary direction but the magnitude of coefficient of skin friction in secondary direction is augmented The local Nusselt number Re x 1 / 2 Nu x is directly proportional to M H and β 2 but it is inversely related to β 1 and α T
37 citations
TL;DR: In this paper, the authors explored the heat transfer and boundary layer flow of a hybrid nanofluid past an inclined stretching/shrinking sheet with suction and buoyancy force effects.
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Cites methods from "Boundary layer flow of nanofluids t..."
...(17) → ∞ → → → ς l ς m ς β ς As ; ′( ) 0, ( ) 0, ( ) 0, (18)...
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...The transformed nonlinear ordinary differential Equations (14) to (16) with boundary conditions (17) to (18) are numerically solved by the spectral quasi‐linearization method....
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References
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01 Jan 1995
7,263 citations
"Boundary layer flow of nanofluids t..." refers background in this paper
...Choi (1995) is the first who introduced the term nanofluids to refer to the fluid with suspended nanoparticles....
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TL;DR: In this article, the authors considered seven slip mechanisms that can produce a relative velocity between the nanoparticles and the base fluid and concluded that only Brownian diffusion and thermophoresis are important slip mechanisms in nanofluids.
Abstract: Nanofluids are engineered colloids made of a base fluid and nanoparticles (1-100 nm) Nanofluids have higher thermal conductivity' and single-phase heat transfer coefficients than their base fluids In particular the heat transfer coefficient increases appear to go beyond the mere thermal-conductivity effect, and cannot be predicted by traditional pure-fluid correlations such as Dittus-Boelter's In the nanofluid literature this behavior is generally attributed to thermal dispersion and intensified turbulence, brought about by nanoparticle motion To test the validity of this assumption, we have considered seven slip mechanisms that can produce a relative velocity between the nanoparticles and the base fluid These are inertia, Brownian diffusion, thermophoresis, diffusioplwresis, Magnus effect, fluid drainage, and gravity We concluded that, of these seven, only Brownian diffusion and thermophoresis are important slip mechanisms in nanofluids Based on this finding, we developed a two-component four-equation nonhomogeneous equilibrium model for mass, momentum, and heat transport in nanofluids A nondimensional analysis of the equations suggests that energy transfer by nanoparticle dispersion is negligible, and thus cannot explain the abnormal heat transfer coefficient increases Furthermore, a comparison of the nanoparticle and turbulent eddy time and length scales clearly indicates that the nanoparticles move homogeneously with the fluid in the presence of turbulent eddies so an effect on turbulence intensity is also doubtful Thus, we propose an alternative explanation for the abnormal heat transfer coefficient increases: the nanofluid properties may vary significantly within the boundary layer because of the effect of the temperature gradient and thermophoresis For a heated fluid, these effects can result in a significant decrease of viscosity within the boundary layer, thus leading to heat transfer enhancement A correlation structure that captures these effects is proposed
5,329 citations
TL;DR: In this article, an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat-transfer fluids, which are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluid, and they represent the best hope for enhancing heat transfer.
Abstract: Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in many industrial applications. In this paper we propose that an innovative new class of heat transfer fluids can be engineered by suspending metallic nanoparticles in conventional heat transfer fluids. The resulting {open_quotes}nanofluids{close_quotes} are expected to exhibit high thermal conductivities compared to those of currently used heat transfer fluids, and they represent the best hope for enhancement of heat transfer. The results of a theoretical study of the thermal conductivity of nanofluids with copper nanophase materials are presented, the potential benefits of the fluids are estimated, and it is shown that one of the benefits of nanofluids will be dramatic reductions in heat exchanger pumping power.
4,634 citations
TL;DR: In this paper, an expression for the viscosity of solutions and suspensions of finite concentration is derived by considering the effect of the addition of one solute-molecule to an existing solution, which is considered as a continuous medium.
Abstract: An expression for the viscosity of solutions and suspensions of finite concentration is derived by considering the effect of the addition of one solute‐molecule to an existing solution, which is considered as a continuous medium.
3,724 citations
"Boundary layer flow of nanofluids t..." refers background or methods in this paper
...Choi (1995) is the first who introduced the term nanofluids to refer to the fluid with suspended nanoparticles....
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...Choi (1995) is the first who introduced the term nanofluids to refer to the fluid with suspended nanoparticles. Choi et al. (2001) reported that the addition of a small amount of nanoparticles to conventional heat transfer liquids notably increases the thermal conductivity of the fluid up to approximately two times....
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...The effective dynamic viscosity of the nanofluid was given by Brinkman (1952) as:...
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...The effective density of the nanofluids is given as: ρn f = (1 − φ)ρf + φρs (7) The effective dynamic viscosity of the nanofluid was given by Brinkman (1952) as: μn f = μf (1 − φ)2.5 (8) where φ is the solid volume fraction of nanoparticles....
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TL;DR: In this paper, it was shown that the presence of many of these minute spheres to a wave-length of light in the glass will account for all the optical properties of "regular" gold ruby glass, and that the irregularities in colour and in polarisation effects sometimes exhibited by gold glass are due to excessive distance between consecutive gold particles or to excessive size of such particles.
Abstract: The present paper contains a discussion of some optical properties of a medium containing minute metal spheres. The discussion is divided into two Parts: the first Part dealing with colours in metal glasses, in which the proportion of volume occupied by metal is small; the second Part dealing with metal films, in which this proportion may have any value from zero to unity. In Part I. the observations of Siedentopf and Zsigmondy beyond the limit of microscopic vision (‘Ann. der Phys.,’ January, 1903) are discussed. It is shown that the particles seen in a gold ruby glass are particles of gold which, when their diameters are less than 0.1μ, are accurately spherical. I have endeavoured to show that the presence of many of these minute spheres to a wave-length of light in the glass will account for all the optical properties of “regular” gold ruby glass, and that the irregularities in colour and in polarisation effects sometimes exhibited by gold glass are due to excessive distance between consecutive gold particles or to excessive size of such particles, the latter, however, involving the former. It is also shown that the radiation from radium is capable of producing in gold glass the ruby colour which is generally produced by re-heating. The method adopted enables us to predict from a knowledge of the metal present in metallic form in a glass what colour that glass will be in its “regular” state.
3,519 citations