The Experts below are selected from a list of 9801 Experts worldwide ranked by ideXlab platform

Ching-yang Cheng - One of the best experts on this subject based on the ideXlab platform.

  • Double-Diffusive Free Convection over Arbitrarily Inclined Plates with Nonuniform Surface Temperature and Concentration in Porous Media
    2014
    Co-Authors: Ching-yang Cheng
    Abstract:

    This work studies the double-diffusive free convection over arbitrarily inclined plates in fluid saturated porous media with nonuniform surface temperature and concentration. The governing equations are transformed into a set of nonsimilar differential equations, and the obtained boundary layer equations are then solved by the cubic spline collocation method. The heat and mass transfer characteristics are presented as functions of surface temperature exponent, surface concentration exponent, inclination variable, Lewis Number, and buoyancy ratio. Results show that an increase in the Lewis Number leads to a decrease in the Local Nusselt Number and an increase in the Local Sherwood Number. Moreover, increasing the buoyancy ratio tends to increase both the Local Nusselt Number and the Local Sherwood Number. For the positive inclination, as the inclination variable increases, the Local Nusselt Number and the Local Sherwood Number first decrease, reach minima, and then increase. The minima are where the tangential and normal components of buoyancy force are comparable.

  • Soret and Dufour Effects on Mixed Convection Heat and Mass Transfer from a Vertical Wedge in a Porous Medium with Constant Wall Temperature and Concentration
    Transport in Porous Media, 2012
    Co-Authors: Ching-yang Cheng
    Abstract:

    This work studies the Soret and Dufour effects on the boundary layer flow due to mixed convection heat and mass transfer over a downward-pointing vertical wedge in a porous medium saturated with Newtonian fluids with constant wall temperature and concentration. A suitable coordinate transformation is performed, and the obtained nonsimilar equations are solved by cubic spline collocation method. The effects of the Dufour parameter, Soret parameter, wedge angle parameter, mixed convection variable, and buoyancy ratio on the heat and mass transfer characteristics has been studied. The Local Nusselt Number is found to decrease when the Dufour parameter is increased. Moreover, an increase in the Soret Number leads to a decrease in the Local Sherwood Number. For natural-convection-dominated regime, an increase in the Soret Number leads to an increase in the Local Nusselt Number for buoyancy assisting flows and a decrease for buoyancy opposing flows. As the wedge angle parameter is increased, the Local Nusselt Number and the Local Sherwood Number increases for forced convection and forced-convection-dominated mixed convection. The wedge angle parameter is insignificant for natural convection or natural-convection-dominated mixed convection.

  • natural convection boundary layer flow over a truncated cone in a porous medium saturated by a nanofluid
    International Communications in Heat and Mass Transfer, 2012
    Co-Authors: Ching-yang Cheng
    Abstract:

    Abstract This work studies the natural convection boundary layer flow over a truncated cone embedded in a porous medium saturated by a nanofluid with constant wall temperature and constant wall nanoparticle volume fraction. The effects of Brownian motion and thermophoresis are incorporated into the model for nanofluids. A suitable coordinate transformation is performed, and the obtained nonsimilar equations are solved by the cubic spline collocation method. The effect of the Brownian motion parameter and thermophoresis parameter on the temperature, nanoparticle volume fraction and velocity profiles are discussed. The effects of the thermophoresis parameter, Brownian parameter, Lewis Number, and buoyancy ratio on the Local Nusselt Number have been studied. Results show that an increase in the thermophoresis parameter or the Brownian parameter tends to decrease the Local Nusselt Number. Moreover, the Local Nusselt Number increases as the buoyancy ratio or the Lewis Number is decreased.

  • Free convection boundary layer flow over a horizontal cylinder of elliptic cross section in porous media saturated by a nanofluid
    International Communications in Heat and Mass Transfer, 2012
    Co-Authors: Ching-yang Cheng
    Abstract:

    Abstract This work studies the free convection boundary layer flow over a horizontal cylinder of elliptic cross section in porous media saturated by a nanofluid with constant wall temperature and constant wall nanoparticle volume fraction. The effects of Brownian motion and thermophoresis are incorporated into the model for nanofluids. A coordinate transformation is performed, and the obtained nonsimilar governing equations are then solved by the cubic spline collocation method. The effects of the Brownian motion parameter and thermophoresis parameter on the profiles of the temperature, nanoparticle volume fraction and velocity profiles are presented. The Local Nusselt Number is presented as a function of the thermophoresis parameter, Brownian parameter, Lewis Number and the aspect ratio when the major axis of the elliptical cylinder is vertical (slender orientation) and horizontal (blunt orientation). Results show that the Local Nusselt Number is increased as the thermophoresis parameter or the Brownian parameter is decreased. The Local Nusselt Number increases as the buoyancy ratio or the Lewis Number is decreased. Moreover, the Local Nusselt Number of the elliptical cylinder with slender orientation is higher than those of the elliptical cylinder with blunt orientation over the lower half cylinder.

  • soret and dufour effects on heat and mass transfer by natural convection from a vertical truncated cone in a fluid saturated porous medium with variable wall temperature and concentration
    International Communications in Heat and Mass Transfer, 2010
    Co-Authors: Ching-yang Cheng
    Abstract:

    This work studies the Soret and Dufour effects on the natural convection heat and mass transfer near a vertical truncated cone with variable wall temperature and concentration in a fluid-saturated porous medium. A coordinate transform is used to obtain the nonsimilar governing equations, and the transformed boundary layer equations are solved by the cubic spline collocation method. Results for Local Nusselt Number and the Local Sherwood Number are presented as functions of Soret parameters, Dufour parameters, surface temperature and concentration exponents, buoyancy ratios, and Lewis Numbers. Results show that increasing the Dufour parameter tends to decrease the Local Nusselt Number, while it tends to increase the Local Sherwood Number. An increase in the Soret Number leads to an increase in the Nusselt Number and a decrease in the Sherwood Number from a vertical truncated cone in a fluid-saturated porous medium. The Local Nusselt Number and the Local Sherwood Number of the truncated cones with higher surface temperature and concentration exponents are higher than those with lower exponents.

K. A. Yih - One of the best experts on this subject based on the ideXlab platform.

  • Radiation effect on mixed convection over an isothermal cone in porous media
    Heat and Mass Transfer, 2001
    Co-Authors: K. A. Yih
    Abstract:

    The radiation effect on the mixed convection flow of an optically dense viscous fluid adjacent to an isothermal cone embedded in a saturated porous medium with Rosseland diffusion approximation is numerically investigated. The entire regime of the mixed convection is included, as the mixed convection parameter of χ varies from 0 (pure free convection) to 1 (pure forced convection). The transformed nonlinear system of equations is solved by using an implicit finite difference method. Numerical results are given for the dimensionless temperature profiles and the Local Nusselt Number for various values of the mixed convection parameter χ, the cone angle parameter m, the radiation-conduction parameter R d and the surface temperature parameter H. The Local Nusselt Number decreases initially, reaches a minimum in the intermediate value of χ and then increases gradually. It is apparent that increasing the cone angle parameter m enhances the Local Nusselt Number. The Local Nusselt Number is significantly increased for the large values of the radiation-conduction parameter R d and the surface temperature parameter H, i.e., radiation effect becomes pronounced.

  • Blowing/Suction Effect on Combined Convection in Stagnation Flow Over a Vertical Plate Embedded in a Porous Medium
    Journal of Mechanics, 1999
    Co-Authors: K. A. Yih
    Abstract:

    Blowing/suction effect on steady two-dimensional laminar combined convection owing to the stagnation flow against a vertical flat plate with linear wall temperature with distance in a saturated porous medium is numerically analyzed. The nonlinear coupled boundary-layer equations were transformed and the resulting ordinary differential equations were solved by Keller box method. Numerical results for the Local friction coefficient and the Local Nusselt Number are presented for various parameters. In general, it is observed that in the buoyancy assisting (opposing) flow both the Local friction coefficient and the Local Nusselt Number increase (decrease) because of the increase of buoyancy parameter, blowing/suction parameter and permeability parameter. The Local Nusselt Number becomes nearly constant when Ω is very small (pure fluid flow) and Ω is very large (pure Darcy flow).

  • Coupled heat and mass transfer in mixed convection over a VHF/VMF wedge in porous media: The entire regime
    Acta Mechanica, 1999
    Co-Authors: K. A. Yih
    Abstract:

    Coupled heat and mass transfer in mixed convection about a wedge embedded in saturated porous media has been analyzed by nonsimilar solutions for the case of variable heat flux (VHF) and variable mass flux (VMF). The entire regime of the mixed convection is included, as the mixed convection parameter χ* varies from 0 (pure free convection) to 1 (pure forced convection). The transformed nonlinear system of equations is solved by using an implicit finite difference method. The dimensionless temperature profiles, the dimensionless concentration profiles, the Local Nusselt Number and the Local Sherwood Number are presented. The decay of the dimensionless temperature profiles and the dimensionless concentration profiles has been observed in all cases. The Local Nusselt Number and the Local Sherwood Number increase for the increase in buoyancy ratioN*, wall heat/mass flux exponents and for the decrease in wedge angle parameter λ. The variations of the Local Nusselt Number and the Local Sherwood Number with the increase of χ* have the phenomenon of minimum. For a positive (negative)N*, increasing the Lewis Number decreases (increases) the Local Nusselt Number. On the other hand, the Local Sherwood Number enhances as the Lewis Number increases. Moreover, it is observed that the Lewis Number has a more pronounced effect on the Local Sherwood Number than it has on the Local Nusselt Number.

  • Coupled heat and mass transfer by free convection over a truncated cone in porous media: VWT/VWC or VHF/VMF
    Acta Mechanica, 1999
    Co-Authors: K. A. Yih
    Abstract:

    The heat and mass transfer characteristics of natural convection about a truncated cone embedded in a saturated porous medium subjected to the coupled effects of thermal and mass diffusion is numerically analyzed. The surface is maintained at variable wall temperature/concentration (VWT/VWC) or variable heat/mass flux (VHF/VMF). The transformed governing equations are solved by Keller box method. Numerical data for the dimensionless temperature profiles, the dimensionless concentration profiles, the Local Nusselt Number and the Local Sherwood Number are presented for wide range of dimensionless distance ξ, the Lewis Number Le, the exponent λ, and buoyancy ratioN (orN*). In general, it has been found that when the buoyancy ratio is increasing both the Local Nusselt Number and the Local Sherwood Number increase. Increasing the value of λ and ξ increases the Local surface heat and mass transfer rates. The Local Nusselt (Sherwood) Number increases (decreases) with decreasing the Lewis Number. Furthermore, it is shown that the Local Nusselt Number and the Local Sherwood Number of the truncated cone approach those of inclined plate (full cone) for the case of ξ=0 (ξ→∞).

  • Effect of radiation on natural convection about a truncated cone
    International Journal of Heat and Mass Transfer, 1999
    Co-Authors: K. A. Yih
    Abstract:

    Abstract A boundary layer analysis is presented to investigate numerically the effect of radiation on natural convection flow of an optically dense viscous fluid over an isothermal truncated cone in this paper. The nonsimilar governing equations are obtained by using a suitable transformation and solved by the Keller box method. Numerical results for the dimensionless velocity profiles, the dimensionless temperature profiles, the Local friction coefficient and the Local Nusselt Number are graphically presented for the dimensionless distance ξ, the Prandtl Number Pr=0.7, the radiation–conduction parameter Rd and the surface temperature parameter H. It is shown that increasing ξ, Rd and H increases the Local Nusselt Number. The Local friction coefficient decreases with increasing the above three parameters. Whereas, for the larger value of Rd and H, the variation of the Local friction coefficient with ξ has the phenomenon of maximum. Furthermore, the Local friction coefficient and the Local Nusselt Number of the truncated cone approach those of the inclined plate (full cone) for the case of ξ=0 (ξ→∞).

Sameer Khandekar - One of the best experts on this subject based on the ideXlab platform.

  • Local Nusselt Number enhancement during gas liquid taylor bubble flow in a square mini channel an experimental study
    International Journal of Thermal Sciences, 2013
    Co-Authors: Abhik Majumder, Balkrishna Mehta, Sameer Khandekar
    Abstract:

    Abstract Taylor bubble flow takes place when two immiscible fluids (liquid–liquid or gas–liquid) flow inside a tube of capillary dimensions within specific range of volume flow ratios. In the slug flows where gas and liquid are two different phases, liquid slugs are separated by elongated Taylor bubbles. This singular flow pattern is observed in many engineering mini-/micro-scale devices like pulsating heat pipes, gas–liquid–solid monolithic reactors, micro-two-phase heat exchangers, digital micro-fluidics, micro-scale mass transfer process, fuel cells, etc. The unique and complex flow characteristics require understanding on Local, as well as global, spatio-temporal scales. In the present work, the axial streamwise profile of the fluid and wall temperature for air–water (i) isolated single Taylor bubble and, (ii) a train of Taylor bubbles, in a horizontal square channel of size 3.3 mm × 3.3 mm × 350 mm, heated from the bottom (heated length = 175 mm), with the other three sides kept insulated, are reported at different gas volume flow ratios. The primary aim is to study the enhancement of heat transfer due to the Taylor bubble train flow, in comparison with thermally developing single-phase flows. Intrusion of a bubble in the liquid flow drastically changes the Local temperature profiles. The axial distribution of time-averaged Local Nusselt Number ( Nu ¯ z ) shows that Taylor bubble train regime increases the transport of heat up to 1.2–1.6 times more as compared with laminar single-phase liquid flow. In addition, for a given liquid flow Reynolds Number, the heat transfer enhancement is a function of the geometrical parameters of the unit cell, i.e., the length of adjacent gas bubble and water plug.

  • Local Nusselt Number enhancement during gas–liquid Taylor bubble flow in a square mini-channel: An experimental study
    International Journal of Thermal Sciences, 2013
    Co-Authors: Abhik Majumder, Balkrishna Mehta, Sameer Khandekar
    Abstract:

    Abstract Taylor bubble flow takes place when two immiscible fluids (liquid–liquid or gas–liquid) flow inside a tube of capillary dimensions within specific range of volume flow ratios. In the slug flows where gas and liquid are two different phases, liquid slugs are separated by elongated Taylor bubbles. This singular flow pattern is observed in many engineering mini-/micro-scale devices like pulsating heat pipes, gas–liquid–solid monolithic reactors, micro-two-phase heat exchangers, digital micro-fluidics, micro-scale mass transfer process, fuel cells, etc. The unique and complex flow characteristics require understanding on Local, as well as global, spatio-temporal scales. In the present work, the axial streamwise profile of the fluid and wall temperature for air–water (i) isolated single Taylor bubble and, (ii) a train of Taylor bubbles, in a horizontal square channel of size 3.3 mm × 3.3 mm × 350 mm, heated from the bottom (heated length = 175 mm), with the other three sides kept insulated, are reported at different gas volume flow ratios. The primary aim is to study the enhancement of heat transfer due to the Taylor bubble train flow, in comparison with thermally developing single-phase flows. Intrusion of a bubble in the liquid flow drastically changes the Local temperature profiles. The axial distribution of time-averaged Local Nusselt Number ( Nu ¯ z ) shows that Taylor bubble train regime increases the transport of heat up to 1.2–1.6 times more as compared with laminar single-phase liquid flow. In addition, for a given liquid flow Reynolds Number, the heat transfer enhancement is a function of the geometrical parameters of the unit cell, i.e., the length of adjacent gas bubble and water plug.

Abhik Majumder - One of the best experts on this subject based on the ideXlab platform.

  • Local Nusselt Number enhancement during gas liquid taylor bubble flow in a square mini channel an experimental study
    International Journal of Thermal Sciences, 2013
    Co-Authors: Abhik Majumder, Balkrishna Mehta, Sameer Khandekar
    Abstract:

    Abstract Taylor bubble flow takes place when two immiscible fluids (liquid–liquid or gas–liquid) flow inside a tube of capillary dimensions within specific range of volume flow ratios. In the slug flows where gas and liquid are two different phases, liquid slugs are separated by elongated Taylor bubbles. This singular flow pattern is observed in many engineering mini-/micro-scale devices like pulsating heat pipes, gas–liquid–solid monolithic reactors, micro-two-phase heat exchangers, digital micro-fluidics, micro-scale mass transfer process, fuel cells, etc. The unique and complex flow characteristics require understanding on Local, as well as global, spatio-temporal scales. In the present work, the axial streamwise profile of the fluid and wall temperature for air–water (i) isolated single Taylor bubble and, (ii) a train of Taylor bubbles, in a horizontal square channel of size 3.3 mm × 3.3 mm × 350 mm, heated from the bottom (heated length = 175 mm), with the other three sides kept insulated, are reported at different gas volume flow ratios. The primary aim is to study the enhancement of heat transfer due to the Taylor bubble train flow, in comparison with thermally developing single-phase flows. Intrusion of a bubble in the liquid flow drastically changes the Local temperature profiles. The axial distribution of time-averaged Local Nusselt Number ( Nu ¯ z ) shows that Taylor bubble train regime increases the transport of heat up to 1.2–1.6 times more as compared with laminar single-phase liquid flow. In addition, for a given liquid flow Reynolds Number, the heat transfer enhancement is a function of the geometrical parameters of the unit cell, i.e., the length of adjacent gas bubble and water plug.

  • Local Nusselt Number enhancement during gas–liquid Taylor bubble flow in a square mini-channel: An experimental study
    International Journal of Thermal Sciences, 2013
    Co-Authors: Abhik Majumder, Balkrishna Mehta, Sameer Khandekar
    Abstract:

    Abstract Taylor bubble flow takes place when two immiscible fluids (liquid–liquid or gas–liquid) flow inside a tube of capillary dimensions within specific range of volume flow ratios. In the slug flows where gas and liquid are two different phases, liquid slugs are separated by elongated Taylor bubbles. This singular flow pattern is observed in many engineering mini-/micro-scale devices like pulsating heat pipes, gas–liquid–solid monolithic reactors, micro-two-phase heat exchangers, digital micro-fluidics, micro-scale mass transfer process, fuel cells, etc. The unique and complex flow characteristics require understanding on Local, as well as global, spatio-temporal scales. In the present work, the axial streamwise profile of the fluid and wall temperature for air–water (i) isolated single Taylor bubble and, (ii) a train of Taylor bubbles, in a horizontal square channel of size 3.3 mm × 3.3 mm × 350 mm, heated from the bottom (heated length = 175 mm), with the other three sides kept insulated, are reported at different gas volume flow ratios. The primary aim is to study the enhancement of heat transfer due to the Taylor bubble train flow, in comparison with thermally developing single-phase flows. Intrusion of a bubble in the liquid flow drastically changes the Local temperature profiles. The axial distribution of time-averaged Local Nusselt Number ( Nu ¯ z ) shows that Taylor bubble train regime increases the transport of heat up to 1.2–1.6 times more as compared with laminar single-phase liquid flow. In addition, for a given liquid flow Reynolds Number, the heat transfer enhancement is a function of the geometrical parameters of the unit cell, i.e., the length of adjacent gas bubble and water plug.

Anuar Mohd Ishak - One of the best experts on this subject based on the ideXlab platform.

  • unsteady boundary layer flow of a nanofluid over a stretching shrinking sheet with a convective boundary condition
    Journal of the Egyptian Mathematical Society, 2016
    Co-Authors: Syahira Mansur, Anuar Mohd Ishak
    Abstract:

    Abstract The unsteady boundary layer flow of a nanofluid past a stretching/shrinking sheet with a convective surface boundary condition is studied. The effects of the unsteadiness parameter, stretching/shrinking parameter, convective parameter, Brownian motion parameter and thermophoresis parameter on the Local Nusselt Number are investigated. Numerical solutions to the governing equations are obtained using a shooting method. The results for the Local Nusselt Number are presented for different values of the governing parameters. The Local Nusselt Number decreases as the stretching/shrinking parameter increases. The Local Nusselt Number is consistently higher for higher values of the convective parameter but lower for higher values of the unsteadiness parameter, Brownian motion parameter and thermophoresis parameter.

  • Unsteady boundary layer flow of a nanofluid over a stretching/shrinking sheet with a convective boundary condition
    Journal of the Egyptian Mathematical Society, 2016
    Co-Authors: Syahira Mansur, Anuar Mohd Ishak
    Abstract:

    Abstract The unsteady boundary layer flow of a nanofluid past a stretching/shrinking sheet with a convective surface boundary condition is studied. The effects of the unsteadiness parameter, stretching/shrinking parameter, convective parameter, Brownian motion parameter and thermophoresis parameter on the Local Nusselt Number are investigated. Numerical solutions to the governing equations are obtained using a shooting method. The results for the Local Nusselt Number are presented for different values of the governing parameters. The Local Nusselt Number decreases as the stretching/shrinking parameter increases. The Local Nusselt Number is consistently higher for higher values of the convective parameter but lower for higher values of the unsteadiness parameter, Brownian motion parameter and thermophoresis parameter.

  • Three-Dimensional Flow and Heat Transfer Past a Permeable Exponentially Stretching/Shrinking Sheet in a Nanofluid
    Journal of Applied Mathematics, 2014
    Co-Authors: Syahira Mansur, Anuar Mohd Ishak, Ioan Pop
    Abstract:

    The three-dimensional flow and heat transfer of a nanofluid over a stretching/shrinking sheet is investigated. Numerical results are obtained using bvp4c in MATLAB. The results show nonunique solutions for the shrinking case. The effects of the stretching/shrinking parameter, suction parameter, Brownian motion parameter, thermophoresis parameter, and Lewis Number on the Local skin friction coefficient and the Local Nusselt Number are studied. Suction increases the solution domain. Furthermore, as the sheet is shrunk in the -direction, suction increases the skin friction coefficient in the same direction while decreasing the skin friction coefficient in the -direction. The Local Nusselt Number is consistently lower for higher values of thermophoresis parameter and Lewis Number. On the other hand, the Local Nusselt Number increases as the Brownian motion parameter increases.

  • The Magnetohydrodynamic Boundary Layer Flow of a Nanofluid past a Stretching/Shrinking Sheet with Slip Boundary Conditions
    Journal of Applied Mathematics, 2014
    Co-Authors: Syahira Mansur, Anuar Mohd Ishak
    Abstract:

    The magnetohydrodynamic (MHD) boundary layer flow of a nanofluid past a stretching/shrinking sheet with velocity, thermal, and solutal slip boundary conditions is studied. Numerical solutions to the governing equations were obtained using a shooting method. The skin friction coefficient and the Local Sherwood Number increase as the stretching/shrinking parameter increases. However, the Local Nusselt Number decreases with increasing the stretching/shrinking parameter. The range of the stretching/shrinking parameter for which the solution exists increases as the velocity slip parameter and the magnetic parameter increase. For the shrinking sheet, the skin friction coefficient increases as the velocity slip parameter and the magnetic parameter increase. For the stretching sheet, it decreases when the velocity slip parameter and the magnetic parameter increase. The Local Nusselt Number diminishes as the thermal slip parameter increases while the Local Sherwood Number decreases with increasing the solutal slip parameter. The Local Nusselt Number is lower for higher values of Lewis Number, Brownian motion parameter, and thermophoresis parameter.

  • Three-dimensional flow and heat transfer of a nanofluid past a permeable stretching sheet with a convective boundary condition
    2014
    Co-Authors: Syahira Mansur, Anuar Mohd Ishak
    Abstract:

    The three-dimensional flow and heat transfer of a nanofluid over a stretching sheet is studied. Numerical solutions are obtained using the boundary value problem solver bvp4c in MATLAB. It is noted that the results obtained for three-dimensional flow are similar to the results obtained in most two-dimensional flow problems. The suction and stretching parameter decrease the skin friction coefficient. On the other hand, increasing the stretching parameter is to increase the Local Nusselt Number. Although Biot Number encourages the heat transfer rate at the surface, increasing thermophoresis parameter and Brownian motion parameter causes the Local Nusselt Number to decrease.