Effect of interfacial thermal resistance and nanolayer on estimates of effective thermal conductivity of nanofluids

Khodayari, Ali; Fasano, Matteo; Bigdeli, Masoud Bozorg; Mohammadnejad, Shahin; Chiavazzo, Eliodoro; Asinari, Pietro

doi:10.1016/j.csite.2018.06.005

Cited by 29 publications

(13 citation statements)

References 60 publications

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“…At the same time, a great number of models are based on the hypothesis of the presence of a nanostructure of a certain type around the nanoparticles [ 20 , 21 ]. The fluid molecules that are close to the nanoparticles can form an ordered layer, an almost solid structure, called a nanolayer.…”

Section: Introductionmentioning

confidence: 99%

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Modelling Thermal Conduction in Nanoparticle Aggregates in the Presence of Surfactants

2020

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Many theoretical and experimental studies have shown that the addition of nanoparticles into conventional fluids may generate nanofluids with significantly improved heat transfer properties. In the present work, the effect of nanoparticle aggregation on the thermal conductivity of nanofluids is studied, considering also the effect of surfactants that are typically added to stabilise the nanofluid. A method for simulating aggregate formation is developed here that allows tailoring of the fractal dimension and the number density of the nanoparticles to desired values. The method is shown to be computationally simple and fast. Data that are extracted from electron microscope images are compared with simulation results regarding surface porosity and the autocorrelation function. The surfactants are modelled as a layer around the particles, and the effective thermal conductivity is calculated with a meshless numerical technique. Significant increase in conductivity is observed for small values of the fractal dimension and for large number density of particles in the aggregate. The simulations are in good agreement with experimental results. It is also concluded that prediction of the conductivity of such nanofluids requires the knowledge of the type and the amount of the surfactant added.

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Section: Introductionmentioning

confidence: 99%

“…The thickness

is considered to be between

. Subsequent research has focused on determining the thickness of the nanolayer and its thermal conductivity [ 21 , 22 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

Modelling Thermal Conduction in Nanoparticle Aggregates in the Presence of Surfactants

2020

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“…It was reported that the high TC of nanoparticles, Brownian motion and Kapitza resistance all affect the TC of MSBNFs. 25,49 Khodayari et al 50 and Serebryakova et al 51 pointed out that the estimation of ETC of nanofluids significantly depends on the Kapitza resistance formed by phonon scattering at the interface layer. The Kapitza resistance decreases with the increase of nanoparticle diameter, which has the opposite effect on the ETC.…”

Section: Comparison Of Overall Thermophysical Propertiesmentioning

confidence: 99%

Effects of interface layer on the thermophysical properties of solar salt‐SiO ₂ nanofluids: A molecular dynamics simulation

Rao

Wang

et al. 2021

Int J Energy Res

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The microstructure and behaviors of the interface layer around the nanoparticle are strongly related to the overall thermophysical properties of molten salt-based nanofluids (MSBNFs). Understanding this link may enable the advanced heat transfer fluid (HTF) for concentrated solar power and other applications. In this study, a molecular dynamics (MD) model for solar salt (60 wt% NaNO 3 /40 wt% KNO 3 )-SiO 2 nanofluid system is developed to estimate the characteristics of the interface layer and their effects on the overall specific heat capacity (SHC) and effective thermal conductivity (ETC) of MSBNFs. The results show that the SHC and thermal conductivity (TC) of the interface layer in MSBNFs are, respectively, 1.44-1.85 and 1.05-1.97 times higher than those of pure solar salt. The SHC of the interface layer has a significant effect on the overall SHC of the MSBNFs, but the interface layer is not the dominant influencing factor for the ETC enhancement of MSBNFs and thus has less effect on the overall ETC.

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“…Short-wavelength high-frequency phonons are responsible for the thermal behaviour of nanolayers. Therefore, it can be inferred that the thermal conductivity decreases exponentially across the nanolayer thickness: 44,45 k nl ðrÞ ¼ k * p þ k bf À k * where, m is a real positive value, usually with value of 2 (ref. 45) and r is the radial distance from the surface of the nanoparticle; r p , to the outer boundary of the adsorbed nanolayer; r p + t. In addition, the average thermal conductivity of the nanolayer can be determined as: 44,45 k nl ¼ t…”

Section: Equivalent Thermal Conductivity Of Dispersed Nanoparticlesmentioning

confidence: 99%

Thermal conductivity and molecular heat transport of nanofluids

et al. 2019

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Fluid media such as water and ethylene glycol are usually quite poor conductors of heat. Nanoparticles can improve the thermal properties of fluids in a remarkable manner. Despite a plethora of experimental and theoretical studies, the underlying physics of heat transport in nanofluids is not yet well understood.Furthermore, the link between nanoscale energy transport and bulk properties of nanofluids is not fully established. This paper presents a thermal conductivity model, encapsulating solid-liquid interfacial thermal resistance, particle shape factor and the variation of thermal conductivity across a physisorbed fluidic layer on a nanoparticle surface. The developed model for thermal conductivity integrates the interfacial Kapitza resistance, the characteristics of a nanolayer, convective diffusion and surface energy with capillary condensation. In addition, the thickness of the nanolayer is predicted using the Brunauer-Emmett-Teller (BET) isotherms and micro/nano-menisci generated pressures of condensation. Such a comprehensive model for thermal conductivity of nanoparticles and systematic study has not hitherto been reported in the literature. The thermal conductivity model is evaluated using experimental data available in open literature.

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Effect of interfacial thermal resistance and nanolayer on estimates of effective thermal conductivity of nanofluids

Cited by 29 publications

References 60 publications

Modelling Thermal Conduction in Nanoparticle Aggregates in the Presence of Surfactants

Modelling Thermal Conduction in Nanoparticle Aggregates in the Presence of Surfactants

Effects of interface layer on the thermophysical properties of solar salt‐SiO ₂ nanofluids: A molecular dynamics simulation

Thermal conductivity and molecular heat transport of nanofluids

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Effect of interfacial thermal resistance and nanolayer on estimates of effective thermal conductivity of nanofluids

Cited by 29 publications

References 60 publications

Modelling Thermal Conduction in Nanoparticle Aggregates in the Presence of Surfactants

Modelling Thermal Conduction in Nanoparticle Aggregates in the Presence of Surfactants

Effects of interface layer on the thermophysical properties of solar salt‐SiO 2 nanofluids: A molecular dynamics simulation

Thermal conductivity and molecular heat transport of nanofluids

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Product

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Effects of interface layer on the thermophysical properties of solar salt‐SiO ₂ nanofluids: A molecular dynamics simulation