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    An approximate analytical solution for electro-osmotic flow of power-law fluids in a planar microchannel

    , Article Journal of Heat Transfer ; Volume 133, Issue 9 , July , 2011 ; 00221481 (ISSN) Sadeghi, A ; Fattahi, M ; Hassan Saidi, M ; Sharif University of Technology
    2011
    Abstract
    The present investigation considers the fully developed electro-osmotic flow of power-law fluids in a planar microchannel subject to constant wall heat fluxes. Using an approximate velocity distribution, closed form expressions are obtained for the transverse distribution of temperature and Nusselt number. The approximate solution is found to be quite accurate, especially for the values of higher than ten for the dimensionless Debye-Huckel parameter where the exact values of Nusselt number are predicted. The results demonstrate that a higher value of the dimensionless Debye-Huckel parameter is accompanied by a higher Nusselt number for wall cooling, whereas the opposite is true for wall... 

    Mixed electroosmotically and pressure-driven flow with temperature- dependent properties

    , Article Journal of Thermophysics and Heat Transfer ; Volume 25, Issue 3 , Sep , 2011 , Pages 432-442 ; 08878722 (ISSN) Sadeghi, A ; Yavari, H ; Saidi, M. H ; Chakraborty, S ; Sharif University of Technology
    2011
    Abstract
    The present work reports the outcome of a comprehensive parametric study on mixed electroosmotically and pressure-driven flow in slit microchannels with constant wall heat fluxes. Special attention is given to disclose the applicability ranges of usual assumptions in simplified analyses. The governing equations for fully developed conditions are first made dimensionless and then solved by means of an implicit finite difference method. The results reveal that the assumption of constant thermophysical properties does not leadto significant errors in practical applications. Although the Debye-Huckel linearization may successfully be used to evaluate velocity profiles up to the zeta potentials... 

    An experimental comparison of SiO2/water nanofluid heat transfer in square and circular cross-sectional channels

    , Article Journal of Thermal Analysis and Calorimetry ; 2017 , Pages 1-10 ; 13886150 (ISSN) Pourfayaz, F ; Sanjarian, N ; Kasaeian, A ; Razi Astaraei, F ; Sameti, M ; Nasirivatan, S ; Sharif University of Technology
    Springer Netherlands  2017
    Abstract
    In this paper, with the aim of enhancing the thermal conductivity of the fluid, a nanofluid is prepared based on SiO2. A series of experimental tests were carried out for both laminar and forced convection regimes in a horizontal tube with two different geometric shapes (circular and square cross section) subjected to constant wall heat flux (4735 W m−2). A comparative study has been done to investigate the effect of the geometry on the convective heat transfer. Moreover, the effect of the volume concentration on the behavior of the nanofluid and the base fluid was evaluated by comparing various volume concentrations (0.05, 0.07 and 0.2%). The experiments were done under two different... 

    An experimental comparison of SiO2/water nanofluid heat transfer in square and circular cross-sectional channels

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 131, Issue 2 , 2018 , Pages 1577-1586 ; 13886150 (ISSN) Pourfayaz, F ; Sanjarian, N ; Kasaeian, A ; Razi Astaraei, F ; Sameti, M ; Nasirivatan, S ; Sharif University of Technology
    Springer Netherlands  2018
    Abstract
    In this paper, with the aim of enhancing the thermal conductivity of the fluid, a nanofluid is prepared based on SiO2. A series of experimental tests were carried out for both laminar and forced convection regimes in a horizontal tube with two different geometric shapes (circular and square cross section) subjected to constant wall heat flux (4735 W m−2). A comparative study has been done to investigate the effect of the geometry on the convective heat transfer. Moreover, the effect of the volume concentration on the behavior of the nanofluid and the base fluid was evaluated by comparing various volume concentrations (0.05, 0.07 and 0.2%). The experiments were done under two different... 

    Heat transfer characteristics of mixed electroosmotic and pressure driven flow of power-law fluids in a slit microchannel

    , Article International Journal of Thermal Sciences ; Volume 53 , 2012 , Pages 71-79 ; 12900729 (ISSN) Babaie, A ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
    2012
    Abstract
    Thermal transport characteristics of electroosmotic flow of power-law fluids in the presence of pressure gradient through a slit microchannel are studied in this paper. Considering a fully developed flow with a constant wall heat flux as the boundary condition, the governing equations are numerically solved by means of the finite difference method. A complete parametric study is done in order to investigate the effects of different flow parameters on the thermal behaviors of the flow. The results show that the non-Newtonian characteristic of the fluid can influence the thermal behaviors of the flow by affecting the rate of heat convection and viscous dissipation; however, its influence... 

    Heat transfer due to electroosmotic flow of viscoelastic fluids in a slit microchannel

    , Article International Journal of Heat and Mass Transfer ; Volume 54, Issue 17-18 , August , 2011 , Pages 4069-4077 ; 00179310 (ISSN) Sadeghi, A ; Saidi, M. H ; Mozafari, A. A ; Sharif University of Technology
    2011
    Abstract
    The bio-microfluidic systems are usually encountered with non-Newtonian behaviors of working fluids. The rheological behavior of some bio-fluids can be described by differential viscoelastic constitutive equations that are related to PTT and FENE-P models. In the present work, thermal transport characteristics of the steady fully developed electroosmotic flow of these fluids in a slit microchannel with constant wall heat fluxes have been investigated. The Debye-Huckel linearization is adopted and the effects of viscous dissipation and Joule heating are taken into account. Analytical solutions are obtained for the transverse distributions of velocity and temperature and finally for Nusselt... 

    Three dimensional heat transfer modeling of gas-solid flow in a pipe under various inclination angles

    , Article Powder Technology ; Vol. 262, Issue. 1 , 2014 , pp. 223-232 ; ISSN: 0032-5910 Pishvar, M ; Saffar Avval, M ; Mansoori, Z ; Amirkhosravi, M ; Sharif University of Technology
    Abstract
    The turbulent heat transfer in gas-solid flows through an inclined pipe under various inclination angles is studied with constant wall heat flux. The hydrodynamic k- τ and kθ- τθ thermal two phase model is used in a lagrangian/Eulerian four way approach. The numerical results agreed reasonably with available experimental data in vertical and horizontal pipe flows. The effects of inclination angles on the flow patterns are reported. The pressure drop and Nusselt number are enhanced significantly as the inclination increases up to a certain angle. The mass loading ratio has influence on the optimal inclination angle. With increasing loading ratio, the optimal inclination angle of maximum... 

    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
    Abstract
    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... 

    Transient forced convection with viscous dissipation to power-law fluids in thermal entrance region of circular ducts with constant wall heat flux

    , Article Energy Conversion and Management ; Volume 50, Issue 4 , 2009 , Pages 1062-1068 ; 01968904 (ISSN) MolaeiDehkordi, A ; Mohammadi, A. A ; Sharif University of Technology
    2009
    Abstract
    A numerical investigation was conducted on the transient behavior of a hydrodynamically, fully developed, laminar flow of power-law fluids in the thermally developing entrance region of circular ducts taking into account the effect of viscous dissipation but neglecting the effect of axial conduction. In this regard, the unsteady state thermal energy equation was solved by using a finite difference method, whereas the steady state thermal energy equation without wall heat flux was solved analytically as the initial condition of the former. The effects of the power-law index and wall heat flux on the local Nusselt number and thermal entrance length were investigated. Moreover, the local... 

    Heat transfer in turbulent nanofluids: separation flow studies and development of novel correlations

    , Article Advanced Powder Technology ; Volume 31, Issue 8 , August , 2020 , Pages 3120-3133 Montazer, E ; Shafii, M. B ; Salami, E ; Muhamad, M. R ; Yarmand, H ; Gharehkhani, S ; Chowdhury, Z. Z ; Kazi, S. N ; Badarudin, A ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    Convective heat transfer plays a significant role in numerous industrial cooling and heating applications. This method of heat transfer can be passively improved by reconfiguring flow passage, fluid thermophysical properties, or boundary conditions. The broader scope of nanotechnology introduced several studies of thermal engineering and heat transfer. Nano-fluids are one of such technology which can be thought of engineered colloidal fluids with nano-sized particles. In the present study, turbulent forced convection heat transfer to nanofluids in an axisymmetric abrupt expansion heat exchanger was investigated experimentally. During heat transfer investigation, the functionalized...