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Omid Ali Akbari - One of the best experts on this subject based on the ideXlab platform.

  • Heat transfer of oil/MWCNT nanofluid jet injection inside a Rectangular Microchannel
    Symmetry, 2019
    Co-Authors: Esmaeil Jalali, Omid Ali Akbari, Mohammad Mohsen Sarafraz, Tehseen Abbas, Mohammad Reza Safaei
    Abstract:

    In the current study, laminar heat transfer and direct fluid jet injection of oil/MWCNT nanofluid were numerically investigated with a finite volume method. Both slip and no-slip boundary conditions on solid walls were used. The objective of this study was to increase the cooling performance of heated walls inside a Rectangular Microchannel. Reynolds numbers ranged from 10 to 50; slip coefficients were 0.0, 0.04, and 0.08; and nanoparticle volume fractions were 0–4%. The results showed that using techniques for improving heat transfer, such as fluid jet injection with low temperature and adding nanoparticles to the base fluid, allowed for good results to be obtained. By increasing jet injection, areas with eliminated boundary layers along the fluid direction spread in the domain. Dispersing solid nanoparticles in the base fluid with higher volume fractions resulted in better temperature distribution and Nusselt number. By increasing the nanoparticle volume fraction, the temperature of the heated surface penetrated to the flow centerline and the fluid temperature increased. Jet injection with higher velocity, due to its higher fluid momentum, resulted in higher Nusselt number and affected lateral areas. Fluid velocity was higher in jet areas, which diminished the effect of the boundary layer.

  • increasing heat transfer of non newtonian nanofluid in Rectangular Microchannel with triangular ribs
    Physica E-low-dimensional Systems & Nanostructures, 2017
    Co-Authors: Mohammad Reza Shamsi, Omid Ali Akbari, Davood Toghraie, Ali Marzban, Ramin Mashayekhi
    Abstract:

    Abstract In this study, computational fluid dynamics and the laminar flow of the non-Newtonian fluid have been numerically studied. The cooling fluid includes water and 0.5 wt% Carboxy methyl cellulose (CMC) making the non-Newtonian fluid. In order to make the best of non-Newtonian nanofluid in this simulation, solid nanoparticles of Aluminum Oxide have been added to the non-Newtonian fluid in volume fractions of 0–2% with diameters of 25, 45 and 100 nm. The supposed Microchannel is Rectangular and two-dimensional in Cartesian coordination. The power law has been used to speculate the dynamic viscosity of the cooling nanofluid. The field of numerical solution is simulated in the Reynolds number range of 5

  • the effect of aspect ratios of rib on the heat transfer and laminar water tio2 nanofluid flow in a two dimensional Rectangular Microchannel
    Journal of Molecular Liquids, 2017
    Co-Authors: Qumars Gravndyan, Omid Ali Akbari, Davood Toghraie, Ali Marzban, Ramin Mashayekhi, Reza Karimi, Farzad Pourfattah
    Abstract:

    Abstract In this investigation, the computational fluid dynamics of laminar flow and heat transfer in an indented Microchannel is investigated. The Water/TiO 2 nanofluid has been used as a working fluid. The geometry is a two-dimensional Rectangular Microchannel with the length of L = 6.3 mm and the height of H = 70 μm. Numerical solution was modeled in the Reynolds numbers of 10, 50, 100 and 300 with volume fractions of 0, 2 and 4% for different aspect ratios AR = 10, 15, 20, 25. The results of this research indicate that the increase of TiO 2 nanoparticles causes enhancement of heat transfer, friction factor, and performance evaluation criterion and pressure drop. The results show that the friction factor is approximately independent from the aspects ratio, being dependent on the volume fraction of solid nanoparticles.

  • numerical simulation of heat transfer and turbulent flow of water nanofluids copper oxide in Rectangular Microchannel with semi attached rib
    Advances in Mechanical Engineering, 2016
    Co-Authors: Omid Ali Akbari, Davood Toghraie, Arash Karimipour
    Abstract:

    In this research, the effect of utilizing semi-attached rib on heat transfer and liquid turbulent flow of nanofluid water–copper oxide in three-dimensional Rectangular Microchannel has been investigated. The results of numerical examination of this study in comparison to those of smooth channel have also been evaluated. The range of Reynolds numbers is between 10,000 and 60,000 and the volume fraction of copper oxide nanoparticle in 0%, 2%, and 4% was examined. In this numerical simulation, the effects of the changes in parameters such as dimensions of semi-attached rib, volume fraction of the nanoparticle, and Reynolds number were considered. The results of this study showed that utilizing semi-attached rib in Microchannel with a ratio of 0 < R/W ≤ 0.325 in producing stronger vortices, which causes better mixture in fluid layers, is weaker than that with tooth mode of R/W = 0 ratio. However, the main advantage of using tooth with a ratio of 0 < R/W ≤ 0.325 in comparison to ordinary tooth is the increase ...

  • impact of ribs on flow parameters and laminar heat transfer of water aluminum oxide nanofluid with different nanoparticle volume fractions in a three dimensional Rectangular Microchannel
    Advances in Mechanical Engineering, 2015
    Co-Authors: Omid Ali Akbari, Davood Toghraie, Arash Karimipour
    Abstract:

    This article aims to study the impact of ribs on flow parameters and laminar heat transfer of water–aluminum oxide nanofluid with different nanoparticle volume fractions in a three-dimensional Rectangular Microchannel. To this aim, compulsory convection heat transfer of water–aluminum oxide nanofluid in a rib-roughened Microchannel has been numerically studied. The results of this simulation for rib-roughened three-dimensional Microchannel have been evaluated in contrast to the smooth (unribbed) three-dimensional Microchannel with identical geometrical and heat–fluid boundary conditions. Numerical simulation is performed for different nanoparticle volume fractions for Reynolds numbers of 10 and 100. Cold fluid entering the Microchannel is heated in order to apply constant flux to external surface of the Microchannel walls and then leaves it. Given the results, the fluid has a higher heat transfer with a hot wall in surfaces with ribs rather than in smooth ones. As Reynolds number, number of ribs, and nano...

Suman Chakraborty - One of the best experts on this subject based on the ideXlab platform.

  • maxwell stress induced flow control of a free surface electro osmotic flow in a Rectangular Microchannel
    Microfluidics and Nanofluidics, 2014
    Co-Authors: Manik Mayur, Sakir Amiroudine, Didier Lasseux, Suman Chakraborty
    Abstract:

    Multiphase flow control is a challenging task in microfluidic systems. Application of such ideas in electro-osmotic actuation of multiphase flows, which involves a complex convolution of phenomena ranging from electro-chemistry to hydrodynamics, is even more tricky. Most of the existing studies in the field have limited their scope to the thin electric double layer (EDL) limit, where the role of ionic space charge distribution in the EDL is simplified to provide a slip velocity boundary condition at the substrate, and the role of the fluid–fluid interface is limited to continuity of velocity and hydrodynamic shear stress. In this study, electro-osmotic flow of two immiscible fluids, an electrolytic solution and an inert gas, are studied in a Rectangular Microchannel and the role of interfacial potential and Maxwell stress-generated dynamics is explored in a wide range of EDL thicknesses. A net stress term is used in the transport equations which includes the electric effects by Maxwell stress as well as the hydrodynamic stress. It is observed that the free surface, depending upon its potential may enhance the fluid velocity or act as a rigid wall. With the help of two-dimensional velocity contour plots, the role of various flow parameters on flow profile is discussed. Further, a parametric analysis of flow rate gives interesting insights into the flow rate reversal and control in such microfluidic devices.

  • analytical solutions for velocity temperature and concentration distribution in electroosmotic Microchannel flows of a non newtonian bio fluid
    Analytica Chimica Acta, 2006
    Co-Authors: Siddhartha Das, Suman Chakraborty
    Abstract:

    In this paper, analytical solutions are derived, describing the transport characteristics of a non-Newtonian fluid flow in a Rectangular Microchannel, under the sole influence of electrokinetic forces. Apart from estimating the fully-developed velocity and temperature distributions, an explicit expression is derived for solutal concentration distribution within the Microchannel. Finally, as an illustrative case study, the flow behaviour of a blood sample is analyzed, in which the flow parameters are modeled as functions of the hematocrit fraction in the sample. It is revealed that a higher hematocrit fraction may result in significant reductions in species concentration levels, on account of stronger dispersions in the velocity profiles, characterized by more significant viscous effects. It is also demonstrated that cases in which characteristic length scale of RBC suspensions turns out to be consequential relative to the Microchannel dimensions, a significant augmentation in the electroosmotic transport may occur. Such observations can be of particular significance in the design of electroosmotically actuated bio-microfluidic systems as efficient solutal carriers.

Jun Yue - One of the best experts on this subject based on the ideXlab platform.

  • hydrodynamics and mass transfer characteristics in gas liquid flow through a Rectangular Microchannel
    Chemical Engineering Science, 2007
    Co-Authors: Jun Yue, Guangwen Chen, Quan Yuan, Lingai Luo, Y Gonthier
    Abstract:

    Abstract Researches on two-phase transfer and reaction processes in microchannnels are important to the design of multiphase microchemical systems. In the present work, hydrodynamics and mass transfer characteristics in cocurrent gas–liquid flow through a horizontal Rectangular Microchannel with a hydraulic diameter of 667 μ m have been investigated experimentally. Liquid side volumetric mass transfer coefficients were measured by absorbing pure CO 2 into water and a 0.3 M NaHCO 3 / 0.3 M Na 2 CO 3 buffer solution. Interfacial areas were determined by absorbing pure CO 2 into a 1 M NaOH solution. Two-phase flow patterns and pressure drop data were also obtained and analyzed. This paper shows that two-phase frictional pressure drop in the Microchannel can be well predicted by the Lockhart–Martinelli method if we use a new correlation of C value in the Chisholm's equation. Liquid side volumetric mass transfer coefficient and interfacial area as high as about 21 s - 1 and 9000 m 2 / m 3 , respectively, can be achieved in the Microchannel. Generally, liquid side volumetric mass transfer coefficient increases with the increasing superficial liquid or gas velocity, which can be described satisfactorily by the developed empirical correlations. A comparison of mass transfer performance among different gas–liquid contactors reveals that the gas–liquid Microchannel contactor of this study can provide at least one or two orders of magnitude higher liquid side volumetric mass transfer coefficients and interfacial areas than the others.

Quan Yuan - One of the best experts on this subject based on the ideXlab platform.

  • hydrodynamics and mass transfer characteristics in gas liquid flow through a Rectangular Microchannel
    Chemical Engineering Science, 2007
    Co-Authors: Jun Yue, Guangwen Chen, Quan Yuan, Lingai Luo, Y Gonthier
    Abstract:

    Abstract Researches on two-phase transfer and reaction processes in microchannnels are important to the design of multiphase microchemical systems. In the present work, hydrodynamics and mass transfer characteristics in cocurrent gas–liquid flow through a horizontal Rectangular Microchannel with a hydraulic diameter of 667 μ m have been investigated experimentally. Liquid side volumetric mass transfer coefficients were measured by absorbing pure CO 2 into water and a 0.3 M NaHCO 3 / 0.3 M Na 2 CO 3 buffer solution. Interfacial areas were determined by absorbing pure CO 2 into a 1 M NaOH solution. Two-phase flow patterns and pressure drop data were also obtained and analyzed. This paper shows that two-phase frictional pressure drop in the Microchannel can be well predicted by the Lockhart–Martinelli method if we use a new correlation of C value in the Chisholm's equation. Liquid side volumetric mass transfer coefficient and interfacial area as high as about 21 s - 1 and 9000 m 2 / m 3 , respectively, can be achieved in the Microchannel. Generally, liquid side volumetric mass transfer coefficient increases with the increasing superficial liquid or gas velocity, which can be described satisfactorily by the developed empirical correlations. A comparison of mass transfer performance among different gas–liquid contactors reveals that the gas–liquid Microchannel contactor of this study can provide at least one or two orders of magnitude higher liquid side volumetric mass transfer coefficients and interfacial areas than the others.

  • liquid liquid two phase flow patterns in a Rectangular Microchannel
    Aiche Journal, 2006
    Co-Authors: Yuchao Zhao, Guangwen Chen, Quan Yuan
    Abstract:

    In this work, the flow of immiscible fluids in a PMMA Microchannel 300 mu m wide and 600 pm deep was investigated experimentally. Dyed de-ionized water and kerosene were selected as the test fluids. Flow patterns were observed by using a CCD camera and were identified by examining the video images. Flow patterns obtained at the T-junction and in the Microchannel are presented. Superficial velocities varied between 9.26 x 10(-4) similar to 1.85 m/s for water and 9.26 x 10(-4) similar to 2.78 m/s for kerosene. The formation mechanism of slug, monodispersed droplet and droplet populations at the T-junction was studied. Weber numbers of water and kerosene, We(KS) and We(WS), were used to predict the flow regime transition and the flow patterns map. The experimental data of volume of dispersed phase were successfully correlated as a function of We(KS), We(WS), and hold-up fraction. Considering the uncertainty associated with experimental quantification of the process, the results are in satisfactory agreement over the wide range of 1.90 x 10(-3) < We(WS) < 30.43 and 5.90 x 10(-6) < We(KS) < 0.13 with average absolute deviation of only 16.18%. (c) 2006 American Institute of Chemical Engineers.

Chen Guangwen - One of the best experts on this subject based on the ideXlab platform.

  • Hydrodynamics and local mass transfer characterization under gas–liquid–liquid slug flow in a Rectangular Microchannel
    'Wiley', 2020
    Co-Authors: Liu Yanyan, Yue Jun, Xu Chao, Zhao Shuainan, Yao Chaoqun, Chen Guangwen
    Abstract:

    Gas–liquid–liquid three‐phase slug flow was generated in a glass microreactor with Rectangular Microchannel, where aqueous slugs were distinguished by relative positions to air bubbles and organic droplets. Oxygen from bubbles reacted with resazurin in slugs, leading to prominent color changes, which was used to quantify mass transfer performance. The development of slug length indicated a film flow through the corner between bubbles and the channel wall, where the aqueous phase was saturated with oxygen transferred from bubble body. This film flow results in the highest equivalent oxygen concentration within the slug led by a bubble and followed by a droplet. The three‐phase slug flow subregime with alternate bubble and droplet was found to benefit the overall mass transfer performance most. These results provide insights into a precise manipulation of gas–liquid–liquid slug flow in microreactors and the relevant mass transfer behavior thereof

  • Hydrodynamics and local mass transfer characterization under gas-liquid-liquid slug flow in a Rectangular Microchannel
    WILEY, 2019
    Co-Authors: Liu Yanyan, Yue Jun, Xu Chao, Zhao Shuainan, Yao Chaoqun, Chen Guangwen
    Abstract:

    Gas-liquid-liquid three-phase slug flow was generated in a glass microreactor with Rectangular Microchannel, where aqueous slugs were distinguished by relative positions to air bubbles and organic droplets. Oxygen from bubbles reacted with resazurin in slugs, leading to prominent color changes, which was used to quantify mass transfer performance. The development of slug length indicated a film flow through the corner between bubbles and the channel wall, where the aqueous phase was saturated with oxygen transferred from bubble body. This film flow results in the highest equivalent oxygen concentration within the slug led by a bubble and followed by a droplet. The three-phase slug flow subregime with alternate bubble and droplet was found to benefit the overall mass transfer performance most. These results provide insights into a precise manipulation of gas-liquid-liquid slug flow in microreactors and the relevant mass transfer behavior thereof

  • Characteristics of gas-liquid Taylor flow with different liquid viscosities in a Rectangular Microchannel
    ELSEVIER SCIENCE SA, 2019
    Co-Authors: Yao Chaoqun, Zheng Jia, Zhao Yuchao, Qi Zhang, Chen Guangwen
    Abstract:

    Characteristics of gas-liquid Taylor flow with different liquid viscosities are investigated in a Rectangular Microchannel, aiming at providing knowledge and aid in the design of processes involving viscous fluid, such as polymers and ionic liquids. The effect of liquid viscosity on the bubble formation dynamic, film thickness, bubble velocity, and pressure drop is investigated. The results reveal a specific viscous effect compared to those in square or circular channels. For the same capillary number, both the liquid film thickness at the corners and at the short planes are much larger than in square channels. New correlations are proposed for predicting the film thickness in the Rectangular channel. The bubble shape sheared by the liquid phase is also distinct from literature observations that a smaller radius occurs at the rear cap. For the conditions studied (0.00065 < Ca < 0.0525), increasing the viscosity leads to an increase in the instantaneous flow rate, and also an later shift from filling stage to squeezing stage. As the bubble formation is driven by both squeezing pressure and shearing force, the bubble/slug length is affected by both capillary number and flow rate ratio. The recirculation inside liquid slugs is found to play an important role in the pressure drop, which can be well described by an empirical correlation including dimensionless liquid slug length and capillary number