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11 – 20 of over 1000Ali J. Chamkha, A.M. Rashad and Humood F. Al‐Mudhaf
The purpose of this paper is to solve the problem of steady, laminar, coupled heat and mass transfer by MHD natural convective boundary‐layer flow over a permeable truncated cone…
Abstract
Purpose
The purpose of this paper is to solve the problem of steady, laminar, coupled heat and mass transfer by MHD natural convective boundary‐layer flow over a permeable truncated cone with variable surface temperature and concentration in the presence of thermal radiation and chemical reaction effects.
Design/methodology/approach
The governing equations are derived and transformed into a set of non‐similar equations which are then solved by an adequate implicit finite difference method.
Findings
It is found that the presence of thermal radiation, magnetic field and chemical reaction have significant effects on the rates of heat and mass transfer. The variation of the wall temperature and concentration exponent contribute to significant changes in the Nusselt and Sherwood numbers as well.
Originality/value
The titled problem with the various considered effects has not been solved before and it is of special importance in various industries. The problem is original.
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Abstract
An analysis of steady laminar mixed convection boundary layer flow along a vertical cone of constant wall temperature is presented. A mixed convection parameter ξ, as proposed by Lin and Chen, is used to serve as a controlling parameter that determines the relative importance of the forced and the free convection flows. New coordinates and dependent variables are then defined in terms of ξ, so that the transformed non‐similar boundary layer equations give computationally efficient numerical solutions which are valid over the entire range of mixed convection flow from the forced convection limit to the free convection limit for fluids of any Prandtl number. The effects of the mixed convection parameter ξ and the Prandtl number Pr on the velocity and temperature profiles as well as on the skin friction and heat transfer coefficients are shown for both cases of buoyancy assisting and buoyancy opposing flow conditions.
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The purpose of this paper is to study steady, laminar, natural convection boundary‐layer flow over a permeable vertical cone embedded in a porous medium saturated with a nanofluid…
Abstract
Purpose
The purpose of this paper is to study steady, laminar, natural convection boundary‐layer flow over a permeable vertical cone embedded in a porous medium saturated with a nanofluid in the presence of uniform lateral mass flux.
Design/methodology/approach
The paper studies steady, laminar, natural convection boundary‐layer flow over a permeable vertical cone embedded in a porous medium saturated with a nanofluid in the presence of uniform lateral mass flux.
Findings
The presence of nanoparticles has significant effects of heat transfer.
Originality/value
The area of nanofluids is very original.
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A steady, two‐dimensional natural convection flow of a viscous, incompressible fluid having temperature‐dependent viscosity and thermal conductivity about a truncated cone is…
Abstract
A steady, two‐dimensional natural convection flow of a viscous, incompressible fluid having temperature‐dependent viscosity and thermal conductivity about a truncated cone is considered. We use suitable transformations to obtain the equations governing the flow in convenient form and integrate them by using an implicit finite difference method. Perturbation solutions are employed to obtain the solution in the regimes near and far away from the point of truncation. The results are obtained in terms of the local skin friction and the local Nusselt number. Perturbation solutions are compared with the finite difference solutions and found to be in excellent agreement. The dimensionless velocity, viscosity and thermal conductivity distributions are also displayed graphically, showing the effects of various values of the pertinent parameter for smaller values of Prandtl number.
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ORTHOGONAL projections are commonly used for representing three dimensional figures on a sheet of paper, and their object is usually that of conveying shape and dimensions to…
Abstract
ORTHOGONAL projections are commonly used for representing three dimensional figures on a sheet of paper, and their object is usually that of conveying shape and dimensions to craftsmen, in order to permit manufacture of mechanical parts.
Amir Reza Mogharrebi, Ali Reza D. Ganji, Khashayar Hosseinzadeh, So Roghani, Armin Asadi and Amin Fazlollahtabar
The purpose of the study is to indicate a three-dimensional convective heat transfer properties evaluation of magnetohydrodynamics nanofluid flow, comprising motile oxytactic…
Abstract
Purpose
The purpose of the study is to indicate a three-dimensional convective heat transfer properties evaluation of magnetohydrodynamics nanofluid flow, comprising motile oxytactic microorganisms and nanoparticles, passing through a rotating cone.
Design/methodology/approach
The imposed technique for solving the governing equations is the Runge–Kutta fifth-order method. The main point of this survey is to diagnosis the influence of diverse factors on velocity, temperature distributions and concentration profile. Furthermore, appending the magnetic field, thermal radiation and viscous dissipation in calculations; also, simultaneous involvement of heat absorption and excretion has been represented as novelties.
Findings
The results elucidate that by changing the Peclet number from 1 to 2, the dimensionless concentration of the microorganisms has been diminished by about 34.37%. In addition, variation of the magnetic parameter from 0 to 1 has been resulted in reducing the temperature distribution by about 3.11%.
Originality/value
Recently, attention has been absorbed to adding the motile microorganisms to nanofluid for enhancement of heat transfer and avoiding aggregation of particles. In this regard, the hydrothermal flow of microorganisms has been investigated in this study.
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Majid Siavashi and Shirzad Iranmehr
The purpose of this study is to analyze a new idea for external flow over a cylinder to increase the heat transfer and reduce pressure drop. Using wedge-shaped porous media in the…
Abstract
Purpose
The purpose of this study is to analyze a new idea for external flow over a cylinder to increase the heat transfer and reduce pressure drop. Using wedge-shaped porous media in the front and wake regions of the cylinder can improve its hydrodynamic, and the rotating flow in the wake region can enhance the heat transfer with increased porous–liquid contact. Permeability plays a vital role, as a high-permeable medium improves heat transfer, whereas a low-permeable region improves the hydrodynamic.
Design/methodology/approach
Therefore, in the current research, external forced convection of nanofluid laminar flow over a bundle of cylinders is simulated using a two-phase mixture model. Four cases with different porous blocks around the cylinder are assessed: rectangular porous; wedge shape in trailing edge (TEP); wedge shape in leading and trailing edges (LTEP); and no porous block case. Also, three different lengths of wedge-shaped regions are considered for TEP and LTEP cases.
Findings
Results are presented in terms of Nusselt (Nu), Euler (Eu) and the performance evaluation criterion (PEC) numbers for various Reynolds (Re) and Darcy (Da) numbers.
Originality/value
It was found that in most situations, LTEP case provides the highest Nu and PEC values. Also, optimal Re and porous medium length exist to maximize PEC, depending on the values of Da and nanofluid volume fraction.
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P. Sudarsana Reddy and P. Sreedevi
Steady-state mixed convection boundary layer flow, heat and mass transfer characteristics of Buongiorno's model nanofluid over an inclined porous vertical plate with thermal…
Abstract
Purpose
Steady-state mixed convection boundary layer flow, heat and mass transfer characteristics of Buongiorno's model nanofluid over an inclined porous vertical plate with thermal radiation and chemical reaction are presented in this analysis.
Design/methodology/approach
The governing nonlinear partial differential equations represent the flow model that can be converted into system of nonlinear ordinary differential equations using the similarity variables and are solved numerically using finite element method.
Findings
The rates of nondimensional temperature and concentration are both decelerate with the higher values of thermophoresis parameter (Nt).
Originality/value
The work carried out in this paper is original.
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Ashraf Muhammad, Ali J Chamkha, S Iqbal and Masud Ahmad
The purpose of this paper is to report a numerical solution for the problem of steady, two dimensional boundary layer buoyant flow on a vertical magnetized surface, when both the…
Abstract
Purpose
The purpose of this paper is to report a numerical solution for the problem of steady, two dimensional boundary layer buoyant flow on a vertical magnetized surface, when both the viscosity and thermal conductivity are assumed to be temperature-dependent. In this case, the motion is governed by a coupled set of three nonlinear partial differential equations, which are solved numerically by using the finite difference method (FDM) by introducing the primitive variable formulation. Calculations of the coupled equations are performed to investigate the effects of the different governing parameters on the profiles of velocity, temperature and the transverse component of magnetic field. The effects of the thermal conductivity variation parameter, viscosity variation parameter, magnetic Prandtl number Pmr, magnetic force parameter S, mixed convection parameter Ri and the Prandtl number Pr on the flow structure and heat transfer characteristics are also examined.
Design/methodology/approach
FDM.
Findings
It is noted that when the Prandtl number Pr is sufficiently large, i.e. Pr=100, the buoyancy force that driven the fluid motion is decreased that decrease the momentum boundary layer and there is no change in thermal boundary layer is noticed. It is also noted that due to slow motion of the fluid the magnetic current generates which increase the magnetic boundary layer thickness at the surface. It is observed that the momentum boundary layer thickness is increased, thermal and magnetic field boundary layers are decreased with the increase of thermal conductivity variation parameter =100. The maximum boundary layer thickness is increased for =100 and there is no change seen in the case of thermal boundary layer thickness but magnetic field boundary layer is deceased. The momentum boundary layer thickness shoot quickly for =40 but is very smooth for =50.There is no change is seen for the case of thermal boundary layer and very clear decay for =40 is noted.
Originality/value
This work is original research work.
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Rajesh Vemula, A J Chamkha and Mallesh M. P.
The purpose of this paper is to focus on the numerical modelling of transient natural convection flow of an incompressible viscous nanofluid past an impulsively started…
Abstract
Purpose
The purpose of this paper is to focus on the numerical modelling of transient natural convection flow of an incompressible viscous nanofluid past an impulsively started semi-infinite vertical plate with variable surface temperature.
Design/methodology/approach
The problem is governed by the coupled non-linear partial differential equations with appropriate boundary conditions. A robust, well-tested, Crank-Nicolson type of implicit finite-difference method, which is unconditionally stable and convergent, is used to solve the governing non-linear set of partial differential equations.
Findings
The local and average values of the skin-friction coefficient (viscous drag) and the average Nusselt number (the rate of heat transfer) decreased, while the local Nusselt number increased for all nanofluids, namely, aluminium oxide-water, copper-water, titanium oxide-water and silver-water with an increase in the temperature exponent m. Selecting aluminium oxide as the dispersing nanoparticles leads to the maximum average Nusselt number (the rate of heat transfer), while choosing silver as the dispersing nanoparticles leads to the minimum local Nusselt number compared to the other nanofluids for all values of the temperature exponent m. Also, choosing silver as the dispersing nanoparticles leads to the minimum skin-friction coefficient (viscous drag), while selecting aluminium oxide as the dispersing nanoparticles leads to the maximum skin-friction coefficient (viscous drag) for all values of the temperature exponent m.
Research limitations/implications
The Brinkman model for dynamic viscosity and Maxwell-Garnett model for thermal conductivity are employed. The governing boundary layer equations are written according to The Tiwari-Das nanofluid model. A range of nanofluids containing nanoparticles of aluminium oxide, copper, titanium oxide and silver with nanoparticle volume fraction range less than or equal to 0.04 are considered.
Practical implications
The present simulations are relevant to nanomaterials thermal flow processing in the chemical engineering and metallurgy industries. This study also provides an important benchmark for further simulations of nanofluid dynamic transport phenomena of relevance to materials processing, with alternative computational algorithms (e.g. finite element methods).
Originality/value
This paper is relatively original and illustrates the influence of variable surface temperature on transient natural convection flow of a viscous incompressible nanofluid and heat transfer from an impulsively started semi-infinite vertical plate.
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