Search for: magnetic-nanofluids
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    Energetic and exergetic performance enhancement of heat exchangers via simultaneous use of nanofluid and magnetic swirling flow: A two-phase approach

    , Article Thermal Science and Engineering Progress ; Volume 20 , 2020 Bezaatpour, M ; Rostamzadeh, H ; Sharif University of Technology
    Elsevier Ltd  2020
    A high-efficient method has been considered for simultaneously improving the hydrothermal and exergetic performance of heat exchangers. Two-phase Eulerian model is employed in a 3-D numerical study to precisely study the hydrothermal and entropic behaviors of Fe3O4/water ferrofluid, under the effect of a magnetic field inducer. The findings reveal that employing the magnetic field can improve the energetic and exergetic performance by generating a swirling flow in the heat exchanger. The pressure drop and entropy generation minimization are also achieved by the induced flow in comparison with other passive techniques due to the lack of any additional obstacle in the flow path. Results show... 

    Study on The Influence of Nanoparticles and Magnetic Field on The Liquid-Liquid Mass Transfer Coefficients

    , M.Sc. Thesis Sharif University of Technology Vahedi, Amid (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    Magnetite (Fe3O4) nanoparticles were synthesized and coated with Oleic Acid using the co-precipitation method. The particles were characterized using DLS, FT-IR, SEM, XRD, VSM and UV-Vis spectrophotometry analysis. The mean size of particles was 28.8 nm and the FT-IR analysis indicated that Oleic Acid was coated suitably on the nanoparticles. The vsm test indicated no hysteresis loop for the particles, defining the superparamagnetism of them. A nanofluid containing nanoparticles in 5wt% Acetic Acid in Toluene as the base fliud was prepared. The stability of this nanofluid was determined using UV-Vis spectrophotometry to be less more then 95% in the first two hours. This nanofluid is used as... 

    Experimental investigation of thermal resistance of a ferrofluidic closed-loop pulsating heat pipe

    , Article Heat Transfer Engineering ; Vol. 35, issue. 1 , 2014 , pp. 25-33 ; ISSN: 01457632 Mohammadi, M ; Mohammadi, M ; Ghahremani, A. R ; Shafii, M. B ; Mohammadi, N ; Sharif University of Technology
    For the present article, a pulsating heat pipe (PHP) is fabricated and tested experimentally by bending a copper tube. The effects of working fluid, heat input, charging ratio, inclination angle, magnets location, and ferrofluid (magnetic nanofluid) volumetric concentration have been investigated on the thermal performance of this PHP. Experimental results show that using ferrofluid as a working fluid improves the thermal performance of the PHP significantly. Moreover, applying a magnetic field on a ferrofluidic PHP reduces its thermal resistance. By changing the inclination angle of the PHP from vertical mode to angles close to the horizontal mode, the present PHP has a constant and... 

    Effect of non-uniform magnetic field on heat transfer of swirling ferrofluid flow inside tube with twisted tapes

    , Article Chemical Engineering and Processing: Process Intensification ; Volume 117 , 2017 , Pages 70-79 ; 02552701 (ISSN) Mokhtari, M ; Hariri, S ; Barzegar Gerdroodbary, M ; Yeganeh, R ; Sharif University of Technology
    In this article, a three-dimensional numerical simulation is performed to investigate the effect of magnetic field on the heat transfer of ferrofluid inside a tube which is equipped with twisted tape. This work comprehensively focused on the flow feature and temperature distribution of ferrofluid in presence of non-uniform magnetic field while ferrofluid swirled inside a tube with twisted tape. In this study, it is assumed that the ferrofluid is single phase and laminar and constant heat flux is applied on the outside of the tube. The magnetic field is established by wire in parallel direction with the axis of the tube. The base fluid is water with 0.86 Vol% Nano particles (Fe3O4). The... 

    Evaluation and Simulation of using Magnetite as Heat Transfer Medium in Direct Solar Absorption Collectors

    , M.Sc. Thesis Sharif University of Technology Ebrahimi, Mahyar (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    In this study, application of a Magnetic Nanofluid consisting of Magnetite as Nanoparticle and Water as base fluid in DASC systems is investigated. The DASC system is modeled theoretically and behavior of such system is predicted.In this study a comparison between magnetite Nanofluid and some other common Nanofluids is conducted. The study shows that Magnetite Nanofluid has a better performance and efficiency than Water, Al2O3 Nanofluid and SiO2 Nanofluid. Also magnetite Nanofluid and TiO2 Nanofluid function are almost similar.Also effect of external magnetic field on the performance of magnetite Nanofluid is investigated. It is showed that when the magnetic Nanofluid is subjected to an... 

    Mixed Convection of Magnetic Nanofluids in Channels Filled with a Porous Medium in the Presence of External Magnetic Field

    , Ph.D. Dissertation Sharif University of Technology Fadaei, Farzad (Author) ; Molaei, Asghar (Supervisor) ; Shahrokhi, Mohammad (Supervisor)
    In this research work, mixed convection heat transfer of ferrofluids (i.e., magnetite nanoparticle) in a circular pipe fully filled with a porous medium in the presence of constant and alternating magnetic fields has been investigated both numerically and experimentally. The duct was heated by a heating coil and the magnetic field was applied via four electromagnets with U shaped ferrite cores and a frequency inverter. The nanoparticles were synthesized using co-precipitation method and coated with a surfactant (i.e., Tween 80) and doubled distilled water was used as the base fluid. To characterize the synthesized nanoparticles, various analyzing techniques such as VSM, SEM, and XRD were... 

    Open-loop pulsating heat pipes charged with magnetic nanofluids: powerful candidates for future electronic coolers

    , Article Nanoscale and Microscale Thermophysical Engineering ; Volume 18, Issue 1 , 2014 , Pages 18-38 ; ISSN: 15567265 Mohammadi, M ; Taslimifar, M ; Haghayegh, S ; Hannani, S. K ; Shafii, M. B ; Saidi, M. H ; Afshin, H ; Sharif University of Technology
    The present research proposes an effective method to enhance the heat transport capability of conventional electronic coolers and improve their thermal management. Pulsating heat pipes (PHPs) are outstanding heat transfer devices in the field of electronic cooling. In the present study, two sets of open-loop pulsating heat pipes (OLPHPs) for two different magnetic nanofluids (with and without surfactant) were fabricated and their thermal performance was experimentally investigated. Effects of working fluid (water and two types of magnetic nanofluids), heating power, charging ratio, nanofluid concentration, inclination angle, application of a magnetic field, and magnet location are described.... 

    Experimental and Numerical Investigation of Reactive Absorption in the presence of Nanofluid and Magnetic field

    , M.Sc. Thesis Sharif University of Technology Kheirkhah Ravandi, Zahra (Author) ; Molaei Dehkordi, Asghar (Supervisor)
    The importance of gases and liquids absorption in the liquid falling film is mostly due to the wide applications of liquid falling film reactors in the chemical industries. In such a reactor the mass and heat transfer occur simultaneously, but in most cases, the importance of mass transfer is predominant. Therefore, the study of heat transfer in this kind of reactor is neglected. In order to improve the efficiency of absorption, different methods have been employed by researchers. Owing to the rapid growth of nanotechnology, nanofluids have widely been used for increasing the absorption of solution, recently. Magnetic fluids due to their unique combination, among different kinds of... 

    Heat transfer and entropy generation analysis of hybrid graphene/Fe3O4 ferro-nanofluid flow under the influence of a magnetic field

    , Article Powder Technology ; Volume 308 , 2017 , Pages 149-157 ; 00325910 (ISSN) Mehrali, M ; Sadeghinezhad, E ; Akhiani, A. R ; Tahan Latibari, S ; Metselaar, H. S. C ; Kherbeet, A. S ; Mehrali, M ; Sharif University of Technology
    Elsevier B.V  2017
    The heat transfer characteristics and entropy generation rate of hybrid graphene-magnetite nanofluids under forced laminar flow that subjected to the permanent magnetic fields were investigated. For this purpose, a nanoscale reduced graphene oxide-Fe3O4 hybrid was synthesized by using graphene oxide, iron salts and tannic acid as the reductant and stabilizer. The thermophysical and magnetic properties of the hybrid nanofluid have been widely characterized and thermal conductivity has shown an enhancement of 11%. The experimental results indicated that the heat transfer enhancement of hybrid magnetite nanofluid compared to the case of distilled was negligible when no magnetic field was... 

    Experimental investigation of a pulsating heat pipe using ferrofluid (magnetic nanofluid)

    , Article Journal of Heat Transfer ; Volume 134, Issue 1 , 2012 ; 00221481 (ISSN) Mohammadi, M ; Mohammadi, M ; Shafii, M. B ; Sharif University of Technology
    In this work, a four-turn pulsating heat pipe (PHP) is fabricated and tested experimentally. The novelty of the present PHP is the capability to obtain various thermal performances at a specific heat input by changing the magnetic field. The effects of working fluid (water and ferrofluid), charging ratio (40% and 70%), heat input (35, 45, 55, 65, 75, and 85 W), orientation (horizontal and vertical heat mode), ferrofluid volumetric concentration (2.5% and 7%), and magnetic field on the thermal performance of PHPs are investigated. The results showed that applying the magnetic field on the water-based ferrofluid reduced the thermal resistance of PHP in all orientations. In the presence of a... 

    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) Karimi, A ; Sadatlu, M. A. A ; Saberi, B ; Shariatmadar, H ; Ashjaee, M ; Sharif University of Technology
    Elsevier  2015
    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... 

    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) Shahsavar, A ; Salim Pour, M. R ; Saghafian, M ; Shafii, M. B ; Sharif University of Technology
    Korean Society of Mechanical Engineers 
    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.... 

    Experimental study on heat transfer augmentation of graphene based ferrofluids in presence of magnetic field

    , Article Applied Thermal Engineering ; Volume 114 , 2017 , Pages 415-427 ; 13594311 (ISSN) Sadeghinezhad, E ; Mehrali, M ; Akhiani, A. R ; Tahan Latibari, S ; Dolatshahi Pirouz, A ; Metselaar, H. S. C ; Mehrali, M ; Sharif University of Technology
    Elsevier Ltd  2017
    The effect of a permanent magnetic field on the heat transfer characteristics of hybrid graphene-magnetite nanofluids (hybrid nanofluid) under forced laminar flow was experimentally investigated. For this purpose, a reduced graphene oxide-Fe3O4 was synthesized by using two-dimensional (2D) graphene oxide, iron salts and tannic acid as the reductant and stabilizer. Graphene sheets acted as the supporting materials to enhance the stability and thermal properties of magnetite nanoparticles. The thermo-physical and magnetic properties of this hybrid nanofluid have been widely characterized and it shows that the thermal conductivity increased up to 11%. The hybrid nanofluid behaves as a Newtonian... 

    Convective-heat transfer of magnetic-sensitive nanofluids in the presence of rotating magnetic field

    , Article Applied Thermal Engineering ; Volume 116 , 2017 , Pages 329-343 ; 13594311 (ISSN) Fadaei, F ; Molaei Dehkordi, A ; Shahrokhi, M ; Abbasi, Z ; Sharif University of Technology
    Elsevier Ltd  2017
    In this work, forced-convection heat transfer of magnetic-sensitive nanofluids has been investigated in the presence of rotating magnetic field. In this regard, the laminar, Newtonian, incompressible, and two-dimensional (2D) fluid flow in a horizontal duct subject to constant wall temperature boundary condition was modeled. Moreover, the fluid was supposed to be non-electrical conductive and the magnetic field source comprised of two time varying components perpendicular to each other. Influences of magnetic field intensity and frequency, inlet fluid velocity, and spin viscosity on the forced-convection heat transfer of the magnetic nanofluids were investigated. It was found that the... 

    Visualization of pool boiling heat transfer of magnetic nanofluid

    , Article Heat Transfer - Asian Research ; Volume 48, Issue 7 , 2019 , Pages 2700-2713 ; 10992871 (ISSN) Zarei Saleh Abad, M ; Ebrahimi Dehshali, M ; Bijarchi, M. A ; Shafii, M. B ; Moosavi, A ; Sharif University of Technology
    John Wiley and Sons Inc  2019
    To increase heat transfer, ferrofluids have been utilized to study the effective parameters of pool boiling. Changes and possible enhancement of pool boiling heat transfer of magnetic fluids is a function of magnetic field and concentration of nanoparticles. To the best knowledge of the authors, no systematic experiments have been conducted to visualize the phenomena during the boiling of ferrofluids with different concentrations. In this study an experimental investigation has been conducted, by designing and fabricating a novel hele-shaw vessel with glass sides, to explore via visualizations some details in the pool boiling of ferrofluids. Boiling patterns of ferrofluids at various... 

    Hybridization of rotary absorber tube and magnetic field inducer with nanofluid for performance enhancement of parabolic trough solar collector

    , Article Journal of Cleaner Production ; 2020 Bezaatpour, M ; Rostamzadeh, H ; Bezaatpour, J ; Sharif University of Technology
    Elsevier Ltd  2020
    A considerable amount of energy is lost in the parabolic trough solar collectors due to the poor capability of working fluid in full absorption of the concentrated solar irradiation across the receiver tube. A new hybrid method is recommended here to cover up such deficiency by simultaneously using a rotary absorber tube and magnetic field inducer with nanofluid. Results showed that the combination effects of the receiver rotation and the magnetic field improve the convection mechanism in the absorber and increase both energetic and exergetic performance of the collector. The study reveals that there is an optimal rotational speed in the each magnetic field intensity for different... 

    Heat transfer enhancement of Fe3O4 ferrofluids in the presence of magnetic field

    , Article Journal of Magnetism and Magnetic Materials ; Volume 429 , 2017 , Pages 314-323 ; 03048853 (ISSN) Fadaei, F ; Shahrokhi, M ; Molaei Dehkordi, A ; Abbasi, Z ; Sharif University of Technology
    Elsevier B.V  2017
    In this article, three-dimensional (3D) forced-convection heat transfer of magnetic nanofluids in a pipe subject to constant wall heat flux in the presence of single or double permanent magnet(s) or current-carrying wire has been investigated and compared. In this regard, laminar fluid flow and equilibrium magnetization for the ferrofluid were considered. In addition, variations of magnetic field in different media were taken into account and the assumption of having a linear relationship of magnetization with applied magnetic field intensity was also relaxed. Effects of magnetic field intensity, nanoparticle volume fraction, Reynolds number value, and the type of magnetic field source...