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    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 of extra-long pulsating heat pipe application in solar water heaters

    , Article Experimental Thermal and Fluid Science ; Volume 42 , 2012 , Pages 6-15 ; 08941777 (ISSN) Arab, M ; Soltanieh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier  2012
    In this study, the aim is to investigate the application of pulsating heat pipes (PHPs) as a heat transfer tool in a solar water heater (SWH). For this purpose, an extra-long pulsating heat pipe (ELPHP) is designed, constructed and installed in a thermosyphon solar water heater. In this work the ELPHPs are made of copper tubes of internal diameter 2.0. mm. The number of meandering turns is 6 and the working fluid employed is distilled water. The lengths of condenser and evaporator sections are 0.8 and 0.96. m, respectively. The length of adiabatic section varies between 0.7 and 1.8. m. Inclination of the ELPHPs varies between 15° and 90° but is 45° for evaporator section. Four different... 

    Thermodynamic analysis of a novel combined power and refrigeration cycle comprising of EKalina and ejector refrigeration cycles

    , Article International Journal of Refrigeration ; Volume 104 , 2019 , Pages 291-301 ; 01407007 (ISSN) Behnam, P ; Faegh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2019
    A novel combined power and refrigeration cycle is introduced and analyzed from the thermodynamic standpoint. The proposed cycle is an integration of a Kalina cycle equipped with an ejector (EKalina) and an ejector refrigeration cycle (ERC). In order to enhance the overall cycle performance, the possibility of employing two-phase ejectors in combined power and refrigeration cycles is studied. A parametric analysis is conducted to investigate the effects of the key thermodynamic parameters namely turbine inlet pressure, split ratio, basic ammonia concentration, heat source and evaporator temperatures on the cycle performance. The developed model is also verified with available data and it is... 

    Experimental examination of utilizing novel radially grooved surfaces in the evaporator of a thermosyphon heat pipe

    , Article Applied Thermal Engineering ; Volume 169 , 2020 Bahmanabadi, A ; Faegh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2020
    The application of heat pipes with flat evaporators in cooling electronic devices has attracted a lot of attention in recent years. Increasing the rate of heat transfer in their evaporator by utilizing structured surfaces is considered as a prominent method for reducing the thermal resistance of the heat pipes. In this study, the performance of a thermosyphon heat pipe with novel radially rectangular-grooved and radially inclined triangular-grooved evaporator surfaces was evaluated experimentally. It is hypothesized that the radial grooves may enhance the performance by inducing rotational motions and increasing the heat transfer coefficients. Based on the results, the optimum filling ratio... 

    Optical and thermal analysis of a parabolic trough solar collector for production of thermal energy in different climates in Iran with comparison between the conventional nanofluids

    , Article Journal of Cleaner Production ; Volume 175 , 2018 , Pages 294-313 ; 09596526 (ISSN) Marefati, M ; Mehrpooya, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2018
    Optical and thermal analysis of the most well-known solar concentrator system; parabolic trough collector (PTC) are investigated and analyzed. To evaluate performance of the PTC, four cities of Iran with different weather conditions are chosen as case studies. Effective parameters such as concentration ratio, incident angle correction factor, collector mass flow rate are considered. The main objective of this work is evaluation of the solar energy potential using PTC in under consideration cities with different climates. Numerical modeling of the analysis is done using MATLAB software. Simulation results shows that Shiraz, with an average annual thermal efficiency of 13.91% and annual useful... 

    Numerical investigation on the effect of external varying magnetic field on the mixing of ferrofluid with deionized water inside a microchannel for lab-on-chip systems

    , Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; 2020 Saadat, M ; Ghassemi, M ; Shafii, M. B ; Sharif University of Technology
    Taylor and Francis Inc  2020
    Energy-efficient mixing is vital for chemical and fuel processes. To this end, a flow-focusing configuration is proposed to investigate the effect of a uniform magnetic field on the mixing of a water-based ferrofluid with two streams of deionized water. An external and varying magnetic field is imposed on a straight microchannel, and the mixing between the ferrofluid and deionized waters is qualitatively and quantitatively measured. A commercial code based on the finite-element method is used, and the simulations are validated by two experimental studies in the literature. For a magnetic flux density of 10 mT, a signal frequency of 1 Hz, a duty cycle of 0.3, an inlet velocity of 500 µm/s,... 

    Experimental study of evaporator surface area influence on a closed loop pulsating heat pipe performance

    , Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM, 8 July 2012 through 12 July 2012, Rio Grande ; Volume 2 , 2012 , Pages 233-238 ; 08888116 (ISSN) ; 9780791844762 (ISBN) Tabatabaee, M. H ; Mohammadi, M ; Shafii, M. B ; Sharif University of Technology
    Pulsating Heat Pipes are an effective mean for heat removal with the potential for a widespread application in electronic packaging. An experimental study a Closed Loop Pulsating Heat Pipe (CLPHP) constructed of copper tubes formed into four meandering turns is presented. Once configured in a vertical orientation the lower portion of the CLPHP comes in contact with a heat source (called the evaporator) from which it will remove heat through the pulsating action of the two-phase mixture contained within the initially evacuated copper tubes eventually transfer the heat to a heat sink (known as the condenser). Heat fluxes can be measured using temperature data gathered from experiments.... 

    Experimental examination of a natural vacuum desalination system integrated with evacuated tube collectors

    , Article Desalination ; Volume 467 , 2019 , Pages 79-85 ; 00119164 (ISSN) Abbaspour, M. J ; Faegh, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2019
    A solar natural vacuum desalination system was experimentally investigated. Using a barometric water column and creating an equilibrium with atmospheric pressure and gravity, vacuum conditions were maintained inside the evaporation chamber throughout the day, which led to the beginning of evaporation at lower temperatures and as a result, lower energy consumption compared to conventional methods. Solar evacuated tubes were used to more efficiently absorb solar radiation and raise the temperature of saline water. In addition, at the system startup, a vacuum pump was utilized to fill the water column and create vacuum conditions. Then, the existing vacuum in the system was maintained naturally... 

    Design and construction of a two-phase fluid piston engine based on the structure of fluidyne

    , Article Energy ; Volume 127 , 2017 , Pages 660-670 ; 03605442 (ISSN) Moazami Goudarzi, H ; Yarahmadi, M ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2017
    Engines that extract energy from low-grade heat sources, e.g., from other processes, have received considerable attention recently. The use of Fluidyne, which is a liquid piston Stirling engine, is quite popular. Herein, we explore the use of liquid-to-vapor phase change in a Fluidyne. This provides two considerable differentiators; (1) exploitation of very low temperature difference ΔT≈30 K, and (2) relatively low temperature ΔT≈330 K heat sources, for producing mechanical work, and thus electrical energy. The influence of three operating parameters, i.e., input heat flux, working fluid, and filling ratio, on the performance of the engine was characterized. Their optimum values, which yield... 

    Ferrofluid droplet formation from a nozzle using alternating magnetic field with different magnetic coil positions

    , Article Journal of Magnetism and Magnetic Materials ; Volume 498 , 2020 Favakeh, A ; Bijarchi, M. A ; Shafii, M. B ; Sharif University of Technology
    Elsevier B.V  2020
    Ferrofluid has been used in many fields, such as microfluidics, droplet formation, and heat transfer, due to its potential to be attracted in the presence of a magnetic field. Droplet formation, itself, has many applications such as emulsions, 3D micro-printers, MEMS, and electro-sprays. In this study, the mechanism of ferrofluid droplet formation from the nozzle in the presence of an alternating magnetic field was investigated. The magnetic coil was fixed at different angles with respect to gravity and the effect of the alternating magnetic field and the angle of the magnetic coil axis with respect to gravity on the produced droplet volume, satellite droplet, and droplet formation frequency... 

    The effect of a non-uniform pulse-width modulated magnetic field with different angles on the swinging ferrofluid droplet formation

    , Article Journal of Industrial and Engineering Chemistry ; Volume 84 , 2020 , Pages 106-119 Bijarchi, M. A ; Favakeh, A ; Shafii, M. B ; Sharif University of Technology
    Korean Society of Industrial Engineering Chemistry  2020
    In this study, ferrofluid droplet formation from a nozzle in the presence of a non-uniform Pulse-Width Modulated (PWM) magnetic field with different angles was studied experimentally. A Drop-on-Demand platform was introduced and three different regimes of droplet formation were observed. The regime map of the droplet formation was presented. A new type of droplet formation evolution was observed in which the droplet is formed while it is swinging around the nozzle, and the satellite droplet is not generated in this regime. The effects of five important parameters including magnetic flux density, applied magnetic frequency, duty cycle, distance between the nozzle and the center of the upper... 

    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) Karimi, A ; Goharkhah, M ; Ashjaee, M ; Shafii, M. B ; Sharif University of Technology
    Springer New York LLC  2015
    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... 

    A comparative study of various machine learning methods for performance prediction of an evaporative condenser

    , Article International Journal of Refrigeration ; Volume 126 , 2021 , Pages 280-290 ; 01407007 (ISSN) Behnam, P ; Faegh, M ; Shafii, M. B ; Khiadani, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Evaporative condensers are regarded as highly-efficient and eco-friendly heat exchangers in refrigeration systems. Data-driven methods can play a key role in performance prediction of evaporative condensers, conducted without the complexity of theoretical analysis. In this study, four machine learning models including multi-layer perceptron artificial neural network (ANNMLP), support vector regression (SVR), decision tree (DT), and random forest (RF) models have been employed to predict heat transfer rate and overall heat transfer coefficient of a small-scale evaporative condenser functioning under a wide range of working conditions. A set of experimental tests were conducted, where inlet... 

    Splitting dynamics of ferrofluid droplets inside a microfluidic T-junction using a pulse-width modulated magnetic field in micro-magnetofluidics

    , Article Soft Matter ; Volume 17, Issue 5 , 2021 , Pages 1317-1329 ; 1744683X (ISSN) Bijarchi, M. A ; Dizani, M ; Honarmand, M ; Shafii, M. B ; Sharif University of Technology
    Royal Society of Chemistry  2021
    Micro-magnetofluidics offers a promising tool for better control over the ferrofluid droplet manipulation which has been vastly utilized in biomedical applications in recent years. In this study, the ferrofluid droplet splitting under an asymmetric Pulse-Width-Modulated (PWM) magnetic field in a T-junction is numerically investigated using a finite volume method and VOF two-phase model. By utilizing the PWM magnetic field, two novel regimes of ferrofluid droplet splitting named as Flowing through the Same Branch (FSB) and Double Splitting (DS) have been observed for the first time. In the FSB regime, the daughter droplets move out of the same microchannel outlet, and in the DS regime, the... 

    Correlation for Nusselt number in pure magnetic convection ferrofluid flow in a square cavity by a numerical investigation

    , Article Journal of Magnetism and Magnetic Materials ; Volume 322, Issue 22 , November , 2010 , Pages 3607-3613 ; 03048853 (ISSN) Ashouri, M ; Ebrahimi, B ; Shafii, M. B ; Saidi, M. H ; Saidi, M. S ; Sharif University of Technology
    Magnetic convection heat transfer in a two-dimensional square cavity induced by magnetic field gradient is investigated numerically using a semi-implicit finite volume method. The side walls of the cavity are heated with different temperatures, the top and bottom walls are isolated, and a permanent magnet is located near the bottom wall. Thermal buoyancy-induced flow is neglected due to the nongravity condition on the plane of the cavity. Conditions for the different values of non-dimensional variables in a variety of ferrofluid properties and magnetic field parameters are studied. Based on this numerical analysis, a general correlation for the overall Nusselt number on the side walls is... 

    Experimental study of internal forced convection of ferrofluid flow in porous media

    , Article Defect and Diffusion Forum ; Vol. 348 , April , 2014 , pp. 139-146 ; ISSN: 10120386 ; ISBN: 9783038350002 Sehat, A ; Sadrhosseini, H ; Shafii, M. B ; Sharif University of Technology
    This work presents an experimental study of the effect of a magnetic field on laminar forced convection of a ferrofluid flowing in a tube filled with permeable material. The walls of the tube are subjected to a uniform heat flux and the permeable bed consists of uniform spheres of 3-mm diameter. The ferrofluid synthesis is based on reacting iron (II) and iron (III) in an aqueous ammonia solution to form magnetite, Fe3O4. The magnetite is mixed with aqueous tetra methyl ammonium hydroxide, (CH3) 4NOH, solution. The dependency of the pressure drop on the volume fraction, and comparison of the pressure drop and the temperature distribution of the tube wall is studied. Also comparison of the... 

    Experimental study of a novel Magneto Mercury Reciprocating (MMR) micropump, fabrication and operation

    , Article Sensors and Actuators, A: Physical ; Volume 194 , 2013 , Pages 277-284 ; 09244247 (ISSN) Karmozdi, M ; Salari, A ; Shafii, M. B ; Sharif University of Technology
    Today, MEMS have wide applications in modern technologies. Magneto hydro dynamic (MHD) micropumps play an important role in the MEMS industry and have been thoroughly studied in the recent years. In this study, the idea of classic reciprocating micropumps was combined with magneto hydro dynamics (MHD) to develop a novel Magneto Mercury Reciprocating (MMR) micropump. To attain this goal, the Lorentz force, as the actuation mechanism, was used to move a conductive liquid (mercury) slug in a reciprocating manner in order to suck the working fluid (air) from the inlet and pump it to the outlet. The performance of the fabricated MMR micropump was examined in terms of parameters such as pressure... 

    Breakup of microdroplets in asymmetric T junctions

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 5 , 2013 ; 15393755 (ISSN) Samie, M ; Salari, A ; Shafii, M. B ; Sharif University of Technology
    Symmetric T junctions have been used widely in microfluidics to generate equal-sized microdroplets, which are applicable in drug delivery systems. A newly proposed method for generating unequal-sized microdroplets at a T junction is investigated theoretically and experimentally. Asymmetric T junctions with branches of identical lengths and different cross sections are utilized for this aim. An equation for the critical breakup of droplets at asymmetric T junctions and one for determining the breakup point of droplets are developed. A good agreement was observed between the theories (present and previous) and the experiments  

    A novel reciprocating micropump based on Lorentz force

    , Article Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 7 February 2015 through 9 February 2015 ; Volume 9320 , 2015 ; 16057422 (ISSN) ; 9781628414103 (ISBN) Salari, A ; Hakimsima, A ; Shafii, M. B ; Sharif University of Technology
    SPIE  2015
    Lorentz force is the pumping basis of many electromagnetic micropumps used in lab-on-a-chip. In this paper a novel reciprocating single-chamber micropump is proposed, in which the actuation technique is based on Lorentz force acting on an array of microwires attached on a membrane surface. An alternating current is applied through the microwires in the presence of a magnetic field. The resultant force causes the membrane to oscillate and pushes the fluid to flow through microchannel using a ball-valve. The pump chamber (3 mm depth) was fabricated on a Polymethylmethacrylate (PMMA) substrate using laser engraving technique. The chamber was covered by a 60 μm thick hyper-elastic latex rubber... 

    Effect of magnetic field on internal forced convection of ferrofluid flow in porous media

    , Article Experimental Heat Transfer ; Volume 29, Issue 1 , 2016 , Pages 1-16 ; 08916152 (ISSN) Sadrhosseini, H ; Sehat, A ; Shafii, M. B ; Sharif University of Technology
    Taylor and Francis Ltd  2016
    Enhancement of heat transfer is investigated in an experimental study of ferrofluid flow in a tube subjected to a constant and uniform heat flux on its wall, filled with permeable material under the effect of magnetic field. Effect of ferrofluid volume fraction, Reynolds number, and different frequencies of various magnetic field modes on heat transfer is examined by measuring the temperature on the wall. Using ferrofluid under the effect of magnetic field improves the heat transfer, and porous media makes the temperature distribution more uniform. Volumetric percentage of nano-particles has the greatest effect on the heat transfer