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nanofluidics
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Thermal characteristics of closed loop pulsating heat pipe with nanofluids
, Article Journal of Enhanced Heat Transfer ; Volume 18, Issue 3 , 2011 , Pages 221-237 ; 10655131 (ISSN) ; Arabnejad, S ; Shafii, M. B ; Saboohi, Y ; Sharif University of Technology
2011
Abstract
In this paper, the effect of different parameters on the thermal operation of a Closed Loop Pulsating Heat Pipe (CLPHP) has been investigated. These parameters include the working fluid, the inclination angle, the filling ratio, and the input heat flux. The effect of nanoparticle mass concentrations has been analyzed as well. It was observed that the CLPHP can decrease thermal resistance up to 11.5 times compared to the same empty copper tube with thermal resistance of 9.4 K/W. Optimum thermal operation for a system with the water-silver nanofluid was achieved at conditions of the 50% filling ratio with thermal resistance of 0.9 K/W, and for the water-titanium oxide system, the optimal...
Experimental investigation of forced convective heat transfer coefficient in nanofluids of Al2O3/EG and CuO/EG in a double pipe and plate heat exchangers under turbulent flow
, Article Experimental Thermal and Fluid Science ; Volume 35, Issue 3 , April , 2011 , Pages 495-502 ; 08941777 (ISSN) ; Oskouie, S. N ; Doosthoseini, A ; Joneidi, A ; Pazouki, M ; Sharif University of Technology
2011
Abstract
Nanofluid is the term applied to a suspension of solid, nanometer-sized particles in conventional fluids; the most prominent features of such fluids include enhanced heat characteristics, such as convective heat transfer coefficient, in comparison to the base fluid without considerable alterations in physical and chemical properties. In this study, nanofluids of aluminum oxide and copper oxide were prepared in ethylene glycol separately. The effect of forced convective heat transfer coefficient in turbulent flow was calculated using a double pipe and plate heat exchangers. Furthermore, we calculated the forced convective heat transfer coefficient of the nanofluids using theoretical...
Effect of temperature and concentration on thermal conductivity and viscosity of ferrofluid loaded with carbon nanotubes
, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; 2015 , Pages 1-9 ; 09477411 (ISSN) ; Saghafian, M ; Salimpour, M. R ; Shafii, M. B ; Sharif University of Technology
Springer Verlag
2015
Abstract
The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The...
Thermal Conductivity of Fe2O3 and Fe3O4 Magnetic Nanofluids Under the Influence of Magnetic Field
, Article International Journal of Thermophysics ; Volume 36, Issue 10-11 , September , 2015 , Pages 2720-2739 ; 0195928X (ISSN) ; Goharkhah, M ; Ashjaee, M ; Shafii, M. B ; Sharif University of Technology
Springer New York LLC
2015
Abstract
In this paper, the thermal conductivity of water-based hematite Fe2O3 and magnetite Fe3O4 nanofluids have been investigated in the absence and presence of a uniform magnetic field. The experiments have been performed in the volume concentration range of 0 % to 4.8 % and the temperature range of 20∘C to 60∘C. The effects of the particle volume fraction, temperature, and magnetic field strength on the thermal conductivity have been analyzed. Results show that the thermal conductivity of iron oxide nanofluids has a direct relation with the particle volume fraction and temperature, without the presence of a magnetic field. But surprisingly, when the magnetic field is applied, it is observed that...
Experimental investigation on thermal conductivity of water based nickel ferrite nanofluids
, Article Advanced Powder Technology ; Volume 26, Issue 6 , November , 2015 , Pages 1529-1536 ; 09218831 (ISSN) ; Sadatlu, M. A. A ; Saberi, B ; Shariatmadar, H ; Ashjaee, M ; Sharif University of Technology
Elsevier
2015
Abstract
Experimental investigations are performed in order to determine the thermal conductivity of NiFe2O4 nanoparticles dispersed in deionized water. The magnetic nanoparticles are synthesized using a microemulsion method. The X-ray diffraction (XRD), transmission electronic microscopy (TEM), and vibration sample magnetometer (VSM) are used to characterize the structure, the size and the magnetic properties of the nanoparticles. The VSM results disclose that the NiFe2O4 nanoparticles are ferromagnetic at room temperature. Experimental measurements on thermal conductivity of the prepared nanofluids are conducted at different volume concentrations between 0% and 2% and in the temperature range of...
An experimental study on the effect of ultrasonication on thermal conductivity of ferrofluid loaded with carbon nanotubes
, Article Thermochimica Acta ; Volume 617 , October , 2015 , Pages 102-110 ; 00406031 (ISSN) ; Salimpour, M. R ; Saghafian, M ; Shafii, M. B ; Sharif University of Technology
Elsevier
2015
Abstract
Nanofluids containing Fe3 O4 and carbon nanotubes nanoparticles emulsified and dispersed using gum arabic (GA) and tetramethylammonium hydroxide (TMAH) were made and characterized for potential use as heat transfer fluids. Due to the interaction between the TMAH and GA molecules, the magnetic nanoparticles and CNTs were physically adsorbed. This paper reports an experimental work on the effect of ultrasonication on thermal conductivity of this aqueous suspension. The characterization and surface morphology of the dried samples were studied by using XRD and TEM measurements. Experiments were conducted in the magnetic nanoparticles mass concentration range 0.494-2.428%,...
A novel method for producing unequal sized droplets in micro- and nanofluidic channels
, Article European Physical Journal E ; Volume 38, Issue 9 , September , 2015 ; 12928941 (ISSN) ; Moosavi, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
Springer New York LLC
2015
Abstract
Abstract: We propose a novel method for producing unequal sized droplets through breakup of droplets. This method does not have the disadvantages of the available methods and also reduces the dependence of the droplets volume ratio on the inlet velocity of the system by up to 26 percent. The employed method for investigating the proposed system relies on 3D numerical simulation using the VOF algorithm and the results have been obtained with various valve ratios for both the micro- and nanoscale. The results indicate that the droplet length during the breakup process increases linearly with time. The droplet length at the nanoscale is smaller than that at the micro scale. It has been shown...
Heat transfer and pressure drop characteristics of nanofluid in unsteady squeezing flow between rotating porous disks considering the effects of thermophoresis and Brownian motion
, Article Advanced Powder Technology ; Volume 27, Issue 2 , March , 2016 , Pages 564–574 ; 09218831 (ISSN) ; Tamim, H ; Sharif University of Technology
Elsevier
2016
Abstract
In this study, the unsteady three dimensional nanofluid flow, heat and mass transfer in a rotating system in the presence of an externally applied uniform vertical magnetic field is investigated. This study has different applications in rotating magneto-hydrodynamic (MHD) energy generators for new space systems and also thermal conversion mechanisms for nuclear propulsion space vehicles. The important effects of Brownian motion and thermophoresis have been included in the model of nanofluid. The governing equations are non-dimensionalized using geometrical and physical flow field-dependent parameters. The velocity profiles in radial, tangential and axial directions, pressure gradient,...
Application of electrostatically actuated carbon nanotubes in nanofluidic and bio-nanofluidic sensors and actuators
, Article Measurement: Journal of the International Measurement Confederation ; Volume 73 , September , 2015 , Pages 127-136 ; 02632241 (ISSN) ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
Elsevier
2015
Abstract
The paper investigates the effects of fluid flow on the static and dynamic behaviors of electrostatically actuated carbon nanotubes using nonlocal elasticity theory. The influences of various parameters of fluid flow including fluid viscosity, velocity, mass and temperature on the mechanical behaviors of the carbon nanotubes under static and step DC voltages are studied using this theory. The results computed from the nonlocal elasticity theory are compared with those estimated using the classical elasticity theorem and the outcomes demonstrate the applicability of the electrostatically actuated carbon nanotubes as nano sensors and nano actuators in nanofluidic systems. The nanosystem can be...
The effect of nanoparticles on the mass transfer in Liquid–Liquid extraction
, Article Chemical Engineering Communications ; Volume 202, Issue 5 , Sep , 2015 , Pages 600-605 ; 00986445 (ISSN) ; Heydari Nasab, A ; Bastani, D ; Seife Kordi, A. A ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
This article investigates the effect of nanoparticles on mass transfer in the liquid–liquid extraction for the chemical system of n-butanol–succinic acid–water. For this purpose, nanofluids containing various concentrations of ZnO, carbon nanotubes (CNT), and TiO2 nanoparticles in water, as base fluid, were prepared. To examine the flow mode effect on mass transfer rate, different fluid modes including dropping and jetting were employed in the process. Results show that mass transfer rate enhancement depends on the kinds and the concentration of nanoparticles and the modes of flow. It was observed that after adding nanoparticles, the mass transfer rate significantly increases up to two-fold...
Simulation of heat transfer in nanoscale flow using molecular dynamics
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010, Montreal, QC ; Issue PARTS A AND B , 2010 , Pages 1563-1568 ; 9780791854501 (ISBN) ; Abbasi, H. R ; Sabouri, M ; Khaledi Alidusti, R ; Sharif University of Technology
2010
Abstract
We investigate heat transfer between parallel plates separated by liquid argon using two-dimensional molecular dynamics (MD) simulations incorporating with 6-12 Lennard-Jones potential between molecule pairs. In molecular dynamics simulation of nanoscale flows through nanochannels, it is customary to fix the wall molecules. However, this approach cannot suitably model the heat transfer between the fluid molecules and wall molecules. Alternatively, we use thermal walls constructed from the oscillating molecules, which are connected to their original positions using linear spring forces. This approach is much more effective than the one which uses a fixed lattice wall modeling to simulate the...
Simulation of polymer chain driven by DPD solvent particles in nanoscale flows
, Article ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels Collocated with 3rd Joint US-European Fluids Engineering Summer Meeting, ICNMM2010, 1 August 2010 through 5 August 2010, Montreal, QC ; Issue PARTS A AND B , 2010 , Pages 1035-1040 ; 9780791854501 (ISBN) ; Zakeri, R ; Schneider, G. E ; Sharif University of Technology
2010
Abstract
In this study, we simulate the motion and reformation of polymer chain in the nanoscale fluid flow motion of the DPD (Dissipative Particle Dynamics) solvent. The behavior of polymer chain through DPD solvent is studied for 2D and 3D considerations. We implement two body forces of Poiseuille flow and electroosmotic flow to the DPD fluid particles. In case of the electroosmotic flow force, we show that the movement of polymer chain via the electroosmotic phenomenon provides less dispersion than that of the Poiseuille flow for the same polymer chain movement
Rheology and colloidal structure of silver nanoparticles dispersed in diethylene glycol
, Article Powder Technology ; Volume 197, Issue 1-2 , 2010 , Pages 49-53 ; 00325910 (ISSN) ; Guenther, B. H ; Sharif University of Technology
Abstract
Rheological behavior of agglomerated silver nanoparticles (~ 40 nm) suspended in diethylene glycol over a wide range of volumetric solids concentrations (φ{symbol} = 0.11-4.38%) was studied. The nanoparticle suspensions generally exhibited a yield pseudoplastic behavior. Bingham plastic, Herschel-Bulkley and Casson models were used to evaluate the shear stress-shear rate dependency. Analyzing the effect of silver concentrations on the yield stress and viscosity of the suspensions followed an exponential form, revealing an increase in the degree of interparticle interactions with increasing solid concentrations. Fractal dimension (Df) was estimated from the suspension yield stress and...
Numerical study of forced convective heat transfer of nanofluids: comparison of different approaches
, Article International Communications in Heat and Mass Transfer ; Volume 37, Issue 1 , 2010 , Pages 74-78 ; 07351933 (ISSN) ; Saboohi, Y ; Rashidi, A. M ; Sharif University of Technology
Abstract
Forced convective of a nanofluid that consists of water and Al2O3 in horizontal tubes has been studied numerically. Computed results were validated with existing well established correlation. Two-phase Eulerian model has been implemented for the first time to study such a flow field. A single-phase model and two-phase mixture model formulations were also used for comparison. The comparison of calculated results with experimental values shows that the mixture model is more precise. It is illustrated that the single-phase model and the two-phase Eulerian model underestimates the Nusselt number. Effects of nanoparticles concentration on the thermal parameters are also discussed
Mass-transfer enhancement in single drop extraction in the presence of magnetic nanoparticles and magnetic field
, Article AIChE Journal ; Volume 62, Issue 12 , 2016 , Pages 4466-4479 ; 00011541 (ISSN) ; Molaei Dehkordi, A ; Fadaei, F ; Sharif University of Technology
John Wiley and Sons Inc
2016
Abstract
Magnetite nanoparticles with an average particle size of 28.8 nm were synthesized, coated with oleic acid, and characterized using various techniques such as DLS, FT-IR, SEM, XRD, VSM, and UV-Vis analysis. A nanofluid consisting of synthesized nanoparticles and 5 wt % acetic acid in toluene as the dispersed phase was prepared and used in the chemical test system, Toluene-Acetic Acid-Water, for the single drop extraction in the presence and absence of an external oscillating magnetic field. Influences of various operating and design parameters such as nanoparticle concentration, drop diameter, and the applied current and frequency on the overall mass-transfer coefficients for the...
Evaluation of viscosity and thermal conductivity of graphene nanoplatelets nanofluids through a combined experimental–statistical approach using respond surface methodology method
, Article International Communications in Heat and Mass Transfer ; Volume 79 , 2016 , Pages 74-80 ; 07351933 (ISSN) ; Mehrali, M ; Sadeghinezhad, E ; Ang, B. C ; Ong, H. C ; Esmaeilzadeh, A ; Sharif University of Technology
Elsevier Ltd
Abstract
In the present study, three influential parameters including concentration, temperature and specific surface area of graphene nanosheets were investigated, which are the effective parameters on the viscosity and thermal conductivity of aqueous graphene nanosheets (GNP) nanofluids. A mathematical model developed by respond surface methodology (RSM) based on a central composite design (CCD). Also, the significance of the models was tested using the analysis of variance (ANOVA). The optimum results of aqueous GNP nanofluid showed that the concentration has a direct effect on the relative viscosity and thermal conductivity. Furthermore, predicted responses proposed by the Design Expert software...
Experimental assessment of convective heat transfer coefficient enhancement of nanofluids prepared from high surface area nanoporous graphene
, Article International Communications in Heat and Mass Transfer ; Volume 78 , 2016 , Pages 127-134 ; 07351933 (ISSN) ; Sattari, S ; Rashidi, A. M ; Sharif University of Technology
Elsevier Ltd
Abstract
In this research convective heat transfer coefficient enhancement of nanofluids prepared from high surface area graphene has been investigated in laminar flow in the developing region. The nanofluid has been prepared from nanoporous graphene with high surface area and with concentration of 0.025 to 0.1 wt.%. Deionized water has been used as the base fluid and a type of Ter-Polymer has been utilized as the surfactant. The results indicate that thermal conductivity of nanofluid with concentration of 0.1 wt.% remains quite constant, with only 3.8% enhancement, while convective heat transfer coefficient improves significantly, with 34% enhancement. The behavior of this enhancement related to the...
Effect of magnetic field on thermal conductivity and viscosity of a magnetic nanofluid loaded with carbon nanotubes
, Article Journal of Mechanical Science and Technology ; Volume 30, Issue 2 , 2016 , Pages 809-815 ; 1738494X (ISSN) ; Salim Pour, M. R ; Saghafian, M ; Shafii, M. B ; Sharif University of Technology
Korean Society of Mechanical Engineers
Abstract
The present work examines experimentally the effect of magnetic field on the viscosity and thermal conductivity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and Gum arabic (GA) coated carbon nanotubes (CNTs). The hybrid nanofluid was prepared by using ultrasonic dispersion method. Magnetic field was created by a pair of spaced apart magnet plates. The effect of temperature on the time variation of thermal conductivity under applied magnetic field was also investigated. According to the results of this study, viscosity of the hybrid nanofluid increases with the strength of magnetic field, while it decreases with the increase of temperature....
A novel approach for energy and water conservation in wet cooling towers by using MWNTs and nanoporous graphene nanofluids
, Article Energy Conversion and Management ; Volume 109 , 2016 , Pages 10-18 ; 01968904 (ISSN) ; Lotfi, R ; Seif Kordi, A ; Rashidi, A. M ; Koolivand, H ; Sharif University of Technology
Elsevier Ltd
Abstract
This study deals with an experimental investigation on the thermal performance of a mechanical wet cooling tower with counter flow arrangement by using multi-walled carbon nanotubes (MWNTs) and nanoporous graphene nanofluids. Stable nanofluids were prepared through two-step procedure by using water with properties taken from a working cooling tower in the South of Iran. Zeta potential revealed suitable stability of MWNTs and nanoporous graphene nanofluids. Thermal and rheological properties of the nanofluids were investigated. It was found that thermal conductivity increases by 20% and 16% at 45°C for MWNTs and nanoporous graphene nanofluids, respectively. The increase in density and...
Nanofluid-assisted gas to hydrate (GTH) energy conversion for promoting CO 2 recovery and sequestration processes in the petroleum industry
, Article Petroleum Science and Technology ; Volume 34, Issue 1 , 2016 , Pages 37-43 ; 10916466 (ISSN) ; Montazeri, V ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
In this work the enhancement of gas to hydrate conversion employing the nanographene oxide (NGO)-based nanofluid regarding CO2 capture and sequestration recovery is investigated. A new series of experiments are carried out at different pressures, temperatures, agitation intensities and NGO promoter concentrations by using a newly developed fully automated GTH (gas to hydrate) energy converter. According to the presented results at the 3 MPa and 275.15 K and in the presence of 30 ppm NGO, it is possible to reach a CO2 gas to hydrate conversion of 95% at a low impeller speed in less than 2.5 h, which is quite interesting from an energy consumption standpoint. The presented approach can have...