Thermal conductivity, viscosity and stability of Al 2 O 3 -diathermic oil nanofluids for solar energy systems

Colangelo, Gianpiero; Favale, Ernani; Miglietta, P.; Milanese, Marco; Risi, Arturo de

doi:10.1016/j.energy.2015.11.032

Cited by 178 publications

(74 citation statements)

References 39 publications

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“…. Furthermore, enhanced heat transfer efficiency in other heat exchange devices using diluted NS, such as solar collectors, cooling systems etc., is often accompanied by the generation of thermal convections2526. The aggregate morphology described by quasi-fractal has been modeled in altering the convection heat transfer performance in nanofluids, and some specialized models for convective heat transfer coefficient, dynamic viscosity etc.…”

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confidence: 99%

Fractal aggregation kinetics contributions to thermal conductivity of nano-suspensions in unsteady thermal convection

Sui

Zhao

Bin‐Mohsin

et al. 2016

Sci Rep

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Nano-suspensions (NS) exhibit unusual thermophysical behaviors once interparticle aggregations and the shear flows are imposed, which occur ubiquitously in applications but remain poorly understood, because existing theories have not paid these attentions but focused mainly on stationary NS. Here we report the critical role of time-dependent fractal aggregation in the unsteady thermal convection of NS systematically. Interestingly, a time ratio λ = tp/tm (tp is the aggregate characteristic time, tm the mean convection time) is introduced to characterize the slow and fast aggregations, which affect distinctly the thermal convection process over time. The increase of fractal dimension reduces both momentum and thermal boundary layers, meanwhile extends the time duration for the full development of thermal convection. We find a nonlinear growth relation of the momentum layer, but a linear one of the thermal layer, with the increase of primary volume fraction of nanoparticles for different fractal dimensions. We present two global fractal scaling formulas to describe these two distinct relations properly, respectively. Our theories and methods in this study provide new evidence for understanding shear-flow and anomalous heat transfer of NS associated non-equilibrium aggregation processes by fractal laws, moreover, applications in modern micro-flow technology in nanodevices.

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confidence: 99%

Fractal aggregation kinetics contributions to thermal conductivity of nano-suspensions in unsteady thermal convection

Sui

Zhao

Bin‐Mohsin

et al. 2016

Sci Rep

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“…Many experimental studies [61], theoretical analysis/modelling [11,61] and molecular dynamics simulations [62][63][64][65][66] have attempted to reveal the complex mechanism of the thermal conductivity of nanofluids and the heat transfer between the fluid and the nanoparticles. There have also been many studies measuring the thermal conductivity of nanofluids; proper correlations provided by these studies are useful for engineering simulations [27,67,68].…”

Section: The Heat Flux Vectormentioning

confidence: 99%

Heat Transfer and Flow of Nanofluids in a Y-Type Intersection Channel with Multiple Pulsations: A Numerical Study

Massoudi

Yan

2017

Energies

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Abstract:In this paper, we study pulsed flow and heat transfer in water-Al 2 O 3 nanofluids in a Y-type intersection channel with two inlets and one outlet. At the two inlets, two sinusoidal velocities with a phase difference of π are applied. We assume that the shear viscosity and the thermal conductivity of the nanofluids depend on the nanoparticles concentration. The motion of the nanoparticles is modeled by a convention-diffusion equation, where the effects of the Brownian motion, thermophoretic diffusion, etc., are included. The effects of pulse frequency, pulse amplitude and nanoparticles concentration on the heat transfer are explored numerically at various Reynolds numbers. The results show that the application of the pulsed flow improves the heat transfer efficiency (Nusselt number) for most of the cases studied. Amongst the four factors considered, the effect of the frequency seems to be the most important.

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“…Other works are related to the coupling with kinematics and rheological response. The effect of viscosity is studied in [9]. The kinematic effects are also studied in [10], where an experimental method of studying the heat transfer behavior of buoyancy-driven nanofluids was addressed.…”

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity of Suspension of Aggregating Nanometric Rods

Ammar

Chinesta

Heyd

2016

Entropy

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Enhancing thermal conductivity of simple fluids is of major interest in numerous applicative systems. One possibility of enhancing thermal properties consists of dispersing small conductive particles inside. However, in general, aggregation effects occur and then one must address systems composed of dispersed clusters composed of particles as well as the ones related to percolated networks. This papers analyzes the conductivity enhancement of different microstructures scaling from clusters dispersed into a simple matrix to the ones related to percolated networks exhibiting a fractal morphology.

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Thermal conductivity, viscosity and stability of Al 2 O 3 -diathermic oil nanofluids for solar energy systems

Cited by 178 publications

References 39 publications

Fractal aggregation kinetics contributions to thermal conductivity of nano-suspensions in unsteady thermal convection

Fractal aggregation kinetics contributions to thermal conductivity of nano-suspensions in unsteady thermal convection

Heat Transfer and Flow of Nanofluids in a Y-Type Intersection Channel with Multiple Pulsations: A Numerical Study

Thermal Conductivity of Suspension of Aggregating Nanometric Rods

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