Patrice Estellé

University of Rennes | UR1 · Laboratoire de Génie Civil et Génie Mécanique (LGCGM)

The thermo-physical properties of water-based nanofluids containing carbon nanotubes, stabilized by SDBS as surfactant, are experimentally studied. The effect of low nanoparticle volume fraction, ranging from 0.0055% to 0.278%, on density, thermal conductivity and viscosity of nanofluids is investigated for temperature range of 20°C to 40°C. Enhanc...

Experimental results on the steady state viscosity of carbon nanotubes water-based nanofluids are presented considering the influence of particle volume fraction and temperature ranging from 0 to 40°C. The suspensions consist of multi-walled carbon nanotubes dispersed in de-ionized water and they are stabilized by a surfactant. The aspect ratio of...

Thermal conductivity measurement of carbon nanotubes water-based nanofluids is here reported. We have considered in particular the influence of nanoparticle volume fraction, temperature, carbon nanotube aspect ratio and different kind of surfactant (SDBS, Lignin, Sodium polycarboxylate) on thermal conductivity enhancement of nanofluids. The experim...

In this work, natural convection heat transfer and fluid flow is reviewed in different types of enclosures with localized heating, considering the working fluid as a simple fluid or a nanofluid. Experimental findings are considered in addition to two and three dimensional numerical studies. The common objective of the reviewed work is to investigat...

We report here the thermal conductivity measurement of carbon nanotubes water-based nanofluids stabilized by sodium dodecylbenzene sulfonate as a function of volume fraction and temperature. For the first time, we further show the existence of a sharp peak in thermal conductivity at very small volume fraction below theoretical percolation threshold...

The performance improvement of a thermosyphon for disseminating heat is significant for the thermal management of a system. Furthermore, the water as the working liquid in a thermosyphon has an operating limit. Therefore, adding particles in the nanofluids as a working liquid could improve the thermal properties of thermosyphon and boiling temperat...

The exceptional properties of high-grade graphene make it an ideal candidate for thermal dissipation and heat exchange in energy applications and nanofluid development. Here, we present a comprehensive study of few-layer graphene (FLG) nanofluids prepared in an industrial context. FLG nanofluids were synthesized through an ultrasound-assisted mecha...

Applying nanofluids in heat transfer systems is an innovative approach to improve the weak thermal characteristics of thermal oils. In this work, the thermal performance of a parabolic trough solar collector using Dowtherm A oil-based nanofluid along with Pd, Au, and NiO nanoparticles as an operating fluid within the receiver tube was numerically i...

Nanofluid-based spectral beam splitting (SBS) hybrid photovoltaic/thermal (PV/T) systems are a promising and efficient way to achieve full-spectrum utilization of solar energy. It utilizes the spectrum above bandgap of PV cells for power generation and the other sunlight for thermal output, decoupling PV and PT while having high total conversion ef...

The evolution in nanofluid technology in the last few decades has proved the prodigious potential in several applications, especially thermal management and lubrication. An extensive investigation of nanofluid’s rheological profile is vital to characterize the fluid flow behavior. This study signifies the rheological aspects of graphene and its hyb...

Nanofluids are an emerging class of heat transfer fluids that are engineered by dispersing nanoparticles in conventional fluids. They represent a promising, multidisciplinary field that has evolved over the past two decades to provide enhanced thermal features, as well as manifold applications in thermal management, energy, transportation, MEMs and...

Nanofluids have emerged as powerful instruments in heat transfer applications due to their improved thermophysical properties. Additionally, many heat transfer equipments are started to be operated within the range of transitional flow regions in the advances in thermal management enhancement techniques. However, up to date, the friction factor and...

In this study, the combined impact of carbon nanotube volume fractions and the electric field on the enhancement of dielectric oil heat transfer is investigated. The geometry studied is an annular layer filled with the dielectric oil and bounded by two eccentric or concentric cylinders. A temperature gradient and an electrical potential difference...

A hybrid solar photovoltaic-thermal collector is the combination of a solar thermal unit and a photovoltaic panel for the simultaneous generation of heat and electricity. In these systems, a fluid is used to cool photovoltaic panels and, thus, prevent their reduction of electrical efficiency. The hot fluid leaving the system can also be used in var...

Nanofluids are considered as a new generation of heat transfer fluids since they exhibit thermophysical properties improvements compared with conventional heat transfer fluids. The high thermal conductivity of nanofluids and even the isobaric specific heat enhancements over conventional liquids make these colloidal suspensions very attractive in ma...

The microchannel heat sink (MCHS) has become the most relevant micro-heat exchanger for a small area in need of an effective high heat removal system. However, heat dissipation from the microchips where the MCHS is utilized—the microprocessor and microcontroller—is getting higher with the sizes getting smaller. A more effective coolant is needed to...

While numerical modelling of different types of nanofluids in various microchannel heat sink geometry under different flow conditions are many, few involved utilizations of experimental data. Reports so far have indicated the potential cooling capability of nanofluids in general, yet none have investigated the effects of the surfactant alone on the...

A parametric numerical investigation has been performed of three-dimensional combined thermal–solutal capillary and buoyancy convection performances of micropolar multi-walled carbon nanotubes-water nanofluid. The governing equations are given based on vorticity-vector potential formulation and numerically resolved with finite volume method. The ef...

The main aim of the present study is to evaluate the influence of multi-walled carbon nanotubes (MWCNTs) and TiO2 nanoparticles (NPs) on lubricant and fluid flow within natural gas turbine meters. In light of this purpose, disparate concentration of TiO2 NPs (0.1, 0.2, and 0.3 wt%), various volume flow rates 0.14, 0.35, and 0.12 cm3S were employed...

This editorial note is dedicated to the Virtual Special Issue about the "Advances in Rheological Behavior of Nanofluids and Ionanofluids". After a brief presentation of the objectives of this VSI, the contributions published in the Journal of Molecular Liquids are introduced. Since their introduction in the early 1990s, nanofluids have been an attr...

By a combination of semi-analytical Boltzmann transport and first-principles calculations, we systematically investigate thermoelectric properties of semiconducting (gapped) materials by varying the degrees of polynomials in their energy dispersion relations, in which either the valence or conduction energy dispersion depends on the wave vector rai...

Nanofluids containing titanium oxide nanoparticles are one of the most often investigated by researchers and their properties such as viscosity or thermal conductivity were largely reported. On the other hand, electrical conductivity of this type of nanofluids are often omitted. Therefore, this paper reports experimental data on the electrical cond...

Natural circulation loops with double pipe heat exchangers at heating and cooling ends have a potential to be used in the refrigeration systems as an alternative to suction line heat exchangers. The heat transfer capability of such natural circulation loops depends on the geometrical parameters as well as thermophysical properties of the working fl...

The objective of this research is to examine how ultrasonication time affects agglomeration, stability, thermal conductivity, and viscosity of CuO nanofluid. Using different reaction conditions, distinct shaped CuO nanoparticles are synthesised and dispersed in an EG: DW (70:30) ratio with 0.3 vol%. Microscopic and TEM images are used to analyze co...

The study was performed on the effect of adding covalently functionalized-hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) and non-covalently-functionalized MWCNTs on the breakdown voltage and thermal properties of transformer oil in a rectangular chamber. The novelty of the present study is the use of covalently functionalized hydroxylated a...

We theoretically investigate the thermoelectric properties of semiconducting (gapped) materials by varying the degrees of polynomials in their energy dispersion relations, in which either the valence or conduction energy dispersion depends on the wave number raised to the power of two, four, and six. The thermoelectric transport coefficients such a...

Thermosyphons are heat transfer devices characterized by high efficiency due to simultaneous phase changes occurring in the evaporation-condensation cycle of working fluid. One of the most promising solutions to enhance their heat transfer capacity of the device is the use of nanofluids – suspensions of particles with at least one dimension below 1...

This paper reports the influence of surfactant Triton X-100 on boron nitride nanotubes (BNNTs) nanofluid in non-optimized and optimized microchannel heat sink (MCHS) at 30 °C and 50 °C. The MCHS performance was evaluated in terms of thermal resistance and pressure drop, utilizing experimental thermo-physical properties of distilled water, a mixture...

Nanofluids which consist of nanoparticles added to conventional fluids (or base fluids) are considered as promising heat transfer fluids. Compared to metal, metal oxide nanoparticles and carbon nanotubes, graphene with its extremely high intrinsic thermal conductivity became the best candidate to design nanofluids. Such nanofluids have the potentia...

This work investigates the convective heat transfer enhancement of water-based nanofluids in pipe heat exchanger used for the ethanol condensation process. The nanofluids were produced with different nature of nanoparticles, Cu, Fe3O4, MWCNT, and graphene, in the volume concentration 0.01-0.1%, using different surfactants. These nanoparticles are c...

A computational analysis has been performed in this study to solve three-dimensional thermo-solutal natural convection in a differentially heated cubical enclosure filled with micropolar CNT/water nanofluid stabilized by two types of surfactants lignin and sodium polycarboxylate. The work is carried out for different pertinent parameters as Rayleig...

Concentrating solar power (CSP) technology can become a very valuable contributor to the transformation and decarbonization of our energy landscape, but for this technology to overcome the barrier toward market deployment, significant enhancements in the solar-to-thermal-to-electric energy conversion efficiency are needed. Here, an in-depth experim...

: Concerns over the exponential increase in the heat produced per unit area in chips have driven advanced research into the nanofluid capability as a coolant. Generally reported for its improved thermal conductivity in particular at higher concentrations, different types of surfactant normally added used to stabilize the nanofluid have reported dif...

In this research, two different diesel oil-based nanofluids were prepared and the influence of temperature and nanoparticle content were examined on viscosity, tribological, and physicochemical features of diesel oil. The kinematic viscosity of samples was experimentally evaluated based on standard ASTM D445. The greatest viscosity increment was di...

This experimental study aims to energetically and exergetically compare the performance of a PVT system with sheet-and-plain serpentine tube collector (base PVT system) with two cases of modified PVT systems. The modified PVT systems are the replacements of plain serpentine tube with rifled serpentine tube with 3 ribs (3-start rifled PVT system) an...

Recent advancements in thermo-fluid technology assisted with highly thermal conductive nanomaterials have shown assuring outcomes. It is also proven that thermal conductivity alone cannot define the overall heat transfer characteristics, and the viscous properties are equally significant towards thermal management. Therefore, this research involves...

The paper summarized results of experimental studies on thermophysical and electrical properties of ethylene glycol based nanofluids containing carbon black nanoparticles. Two types of nanoparticles differing in size and specific surface area were used to develop nanofluids. During examination the thermal conductivity, isobaric heat capacity, mass...

Graphene derivatives are promising nanomaterials for producing nanofluids due to their excellent intrinsic characteristics. Among thermophysical profile, and in addition to thermal properties, relevant property to evaluate the potential of graphene-based nanofluids as efficient and reliable heat transfer fluids is viscosity, and rheological behavio...

Nowadays, different types of strategies are proposed and tested to find the best scenario for upgrading the productivity of heat transfer fluids, especially nanofluids. Some optimum empirical conditions demonstrated that the best size, shape, and nature of nanoparticles and their appropriate dispersion have positive influences on nanofluid thermal...

We report in this study the experimental investigation of the dynamic viscosity of purified multi-walled carbon nanotubes (MWCNT) water and water-propylene glycol based nanofluids in the temperature range 10-80 °C. Four weight concentrations of MWCNTs are considered, between 0.005 and 0.1 wt.%. Triton X-100, a common nonionic surfactant, is used to...

We report the shear flow behavior of few layer graphene (FLG) based nanofluids produced with a commercial mixture of water and propylene glycol and three nonionic surfactants, Triton X-100, Pluronic® P123, and Gum Arabic respectively. The flow properties of these nanofluids were experimentally investigated between 283.15 and 323.15 K and for FLG co...

Volumetric properties such as density and isobaric thermal expansivity, and surface tension are of paramount importance for nanofluids to evaluate their ability to be used as efficient heat transfer fluids. In this work, the nanofluids are prepared by dispersing few-layer graphene in a commercial heat transfer fluid Tyfocor ® LS (40:60 wt.% propyle...

High-quality graphene is an especially promising carbon nanomaterial for developing nanofluids for enhancing heat transfer in fluid circulation systems. We report a complete study on few layer graphene (FLG) based nanofluids, including FLG synthesis, FLG-based nanofluid preparation, and their thermal conductivity. The FLG sample is synthesized by a...

Recently, many scientists have been making remarkable efforts to enhance the efficiency of direct solar thermal absorption collectors that depends on working fluids. There are a number of heat transfer fluids being investigated and developed. Among these fluids, carbon nanomaterial-based nanofluids have become the candidates with the most potential...

This paper presents the preparation and thermal/physical characterization of phase change materials (PCMs) based on poly(ethylene glycol) 400 g·mol−1 and nano-enhanced by either carbon black (CB), a raw graphite/diamond nanomixture (G/D-r), a purified graphite/diamond nanomixture (G/D-p) or nano-Diamond nanopowders with purity grades of 87% or 97%...

This editorial note is dedicated to the 1st International Conference on Nanofluids (ICNf19), which was organized under the auspices of Nanouptake COST Action in June 2019, in Castelló (Spain). After a brief report about the conference issues, the successful selected contributions to this Special Issue of Energies about the ICNf19 are introduced.

This study compares the tribological and thermophysical features of the lubricating oil using MoS2 and ZnO nano-additives. The average size of MoS2 and ZnO nanoparticles were 90 nm and 30 nm, respectively. The nanoparticles were suspended using Triton X-100 in three different concentrations (0.1, 0.4 and 0.7 wt.%) in commercial diesel oil. Tribolog...

This study reports the synthesis and the characterization of ethylene glycol silver-based nanofluids produced from the polyol process. This synthesis process is based on the reduction of silver nitrate (AgNO3) with the presence of the aqueous emulsion of latex copolymer, used here for the first time along with ethylene glycol. The influence of late...

Nanofluids are considered as promising alternative in heat exchange processes to the classical fluids, which usually present poor thermal properties. One interesting application for nanofluids is as heat transfer fluid in solar thermal applications plants. Boron nitride nanotubes present interesting thermophysical properties for use in nanofluids....

In the present work, Fe3O4 nanoparticles produced by the ultrasonic precipitation method and characterized by XRD, SEM, and BET methods are used to produce nanofluids using a mixture of water and ethylene glycol (WEG 50:50) as a base fluid and both sodium dodecyl sulfonate and oleic acid as surfactants. The thermal conductivity, dynamic viscosity a...

Introduction: Nowadays, the increased tendency to further reducing the size of the electronic devices has demanded high rates of heat transfer, larger than 100W from a surface of only a few square centimeters, which is a serious engineering challenge.

Nano-colloidal suspensions of nanomaterials in a fluid, nanofluids, are appealing because of their interesting properties related to heat transfer processes. Whilst nanomaterials based on transition metal chalcogenides (TMCs) have been widely studied in catalysis, sensing, and energy storage applications, there are few studies of nanofluids based o...

The main objective of this study is to design and characterize silver suspensions based on poly(ethylene glycol) PEG400, Ag/PEG400, as energy storage media for low-temperature applications. A polyvinylpyrrolidone (PVP) treatment was applied to ~22 nm silver nanoparticles to ensure good stability in poly(ethylene glycol). An array of different exper...

Wettability is the ability of the liquid to contact with the solid surface at the surrounding fluid and its degree is defined by contact angle (CA), which is calculated with balance between adhesive and cohesive forces on droplet surface. Thermophysical properties of the droplet, the forces acting on the droplet, atmosphere surrounding the droplet...

In this study, a series of low-concentration carbon nanotubes (CNT) water-based nanofluids (0.0055, 0.055, 0.111 and 0.278 vol%) were used as coolants in a shell and tube cooler of the residue fluid catalytic cracking gasoline product to analyze their effects on heat performance of the heat exchanger. The coolants and gasoline flow in tube side and...

This work analyzes the dynamic viscosity, surface tension and wetting behavior of phase change material nano–emulsions (PCMEs) formulated at dispersed phase concentrations of 2, 4 and 10 wt.%. Paraffin–in–water samples were produced using a solvent–assisted route, starting from RT21HC technical grade paraffin with a nominal melting point at ~293–29...

Nanofluids which consist of the addition of nanoparticles in a base fluid are envisaged for a large domain of applications. For many of them, the surface tension (ST) behavior of the prepared nanofluids is a key parameter to exploit their thermophysical properties. Due to their remarkable properties, carbon nanotubes (CNTs) are commonly used to dev...

This paper focuses on an experimental study of the surface tension of nanofluids based on ethylene glycol with various types of nitride nanoparticles. Samples were prepared using a two-step method with mass content between 1 and 5% of particles. Nanofluids contain three types of nitride nanoparticles: aluminum nitride, silicon nitride and titanium...

Experimental investigations of the dynamic viscosity of stable nanofluids water EG based are studied. For all temperatures, except for lower ones, a Newtonian behaviour is reported in the range-20°C to 20°C. No significant increase in viscosity was noticed for MWCNT nanofluids while a decrease in viscosity with nanoparticle content is observed for...

The stability of the flow induced by the extrusion forming process of a cement based material is largely influenced by the relative migration between the lubricating liquid phase and the granular skeleton. In the present work, we propose linking rheological concepts and soil mechanics (consolidation theory, Darcy's law) to reach a simple criterion...

A new procedure is described to convert the vane torque and rotational velocity data into shear stress vs shear rate relationships. The basis of the procedure consists in considering locally the sheared material as a Bingham fluid and computing a characteristic shear rate from Couette analogy. The approach is first applied to experimental vane data...

A new method is developed to determine the rheological and tribological behaviour of viscoplastic fluids using a back extrusion test. In back extrusion geometry, the material is forced to flow in the gap between the inner and the outer cylinder. Such a flow is modelled by a Bingham constitutive law under different wall boundary conditions (stick, s...

A high torque vane rheometer is used to measure the yield stress of cement-based materials. It is shown that this apparatus is suitable for the evaluation of the yield stress of various concretes and mortars in the fresh state in comparison with slump tests realized with ASTM Abrams cone. Then, the rheological properties (yield stress and shear flo...

This paper provides a new model to evaluate the yield stress of suspensions, slurries or pastes, based on the release of a finite volume of material onto a horizontal surface. Considering the height (h) and the radius (R) of the sample at the flow stoppage, two asymptotic regimes, where h>R or h<R, lead to different analytical models that allow the...

Highlights • Comparison of optimized thermal and hydrodynamic performances of a circular and square microchannel heat sink cooled with carbon nanotube nanofluid, using experimentally obtained data. • Analysis of surfactant and viscosity effects on CNT nanofluid performance. • Utilization of multi-objective genetic algorithm (MOGA) to simultaneously...

Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids – suspensions containing nanometre-sized particles – can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume a...

Thermal oils due to their high ability in cooling and lubricating have many applications in high-tech industries such as the automotive industry. Dispersing nanoparticles in a thermal oil (which the resulted new liquid is called nanofluid) can modify further the cooling and lubrication efficiencies. This review paper aims to present the recent adva...

Modeling and simulation of nanofluid flows is crucial for applications ranging from the cooling of electronic devices to solar water heating systems, particularly when compared to the high expense of experimental studies. Accurate simulation of a thermal-fluid system requires a deep understanding of the underlying physical phenomena occurring in th...

It has been more than two decades since the discovery of nanofluids-mixtures of common liquids and solid nanoparticles less than 100 nm in size. As a type of colloidal suspension, nanofluids are typically employed as heat transfer fluids due to their favorable thermal and fluid properties. There have been numerous numerical studies of nanofluids in...

Nowadays, the use of nanofluids as alternative to commonly-used industrial heat transfer fluids is a topic of increasing interest. Analysing the improved efficiency of heat transfer processes according to advanced nanomaterials and obtaining stable nanofluids is one of the most interesting challenges. This paper presents a study of nanofluids based...