The Experts below are selected from a list of 639 Experts worldwide ranked by ideXlab platform
Asghar Molaei Dehkordi - One of the best experts on this subject based on the ideXlab platform.
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transient and steady state forced convection to power law fluids in the Thermal Entrance region of circular ducts effects of viscous dissipation variable viscosity and axial conduction
Energy Conversion and Management, 2010Co-Authors: Asghar Molaei Dehkordi, Mohammad MemariAbstract:A numerical study 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 with taking into account the effects of viscous dissipation, axial conduction, and variations of viscosity with temperature. In this regard, the unsteady-state Thermal energy and momentum equations were solved numerically using a finite-difference method, whereas the steady-state Thermal energy equation with constant wall heat flux as the boundary condition was solved analytically as the initial condition of the former. The numerical procedure used in the present work was validated with an analytical solution for the special case of Newtonian fluids. The effects of the power-law index, axial conduction, wall heat flux, and variations of fluid viscosity on the local Nusselt number and Thermal Entrance Length were investigated. Moreover, the local Nusselt number values of steady-state conditions were correlated as a function of the power-law index and wall heat flux. Furthermore, a correlation was derived for the Thermal Entrance Length as a function of the power-law index and wall heat flux.
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Transient forced convection with viscous dissipation to power-law fluids in Thermal Entrance region of circular ducts with constant wall heat flux
Energy Conversion and Management, 2009Co-Authors: Asghar Molaei Dehkordi, Ali MohammadiAbstract: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 Nusselt number of steady state conditions was correlated in terms of the power-law index and wall heat flux and compared with literature data, which were obtained by an analytic solution for Newtonian fluids. Furthermore, a relationship was proposed for the Thermal Entrance Length.
Mostafa Barigou - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation of transverse vibration effects on radial temperature profile and Thermal Entrance Length in laminar flow
Aiche Journal, 2011Co-Authors: M Eesa, Mostafa BarigouAbstract:Radial heat transfer in laminar pipe flow is characterized by a wide temperature distribution over the pipe cross-section. We use a validated Computational Fluid Dynamics (CFD) model to show that the superimposition of a transverse vibration on the steady laminar flow of a Newtonian fluid moving in a pipe with an isoThermal wall, generates considerable chaotic flow and radial mixing which result in a large enhancement in wall heat transfer as well as a considerably more uniform radial temperature field. Transverse vibration also causes the temperature profile to develop very rapidly in the axial direction reducing the Thermal Entrance Length by a large factor. These effects are dependent on vibration amplitude and frequency, and fluid viscosity. © 2010 American Institute of Chemical Engineers AIChE J, 2011
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Enhancing radial temperature uniformity and boundary layer development in viscous Newtonian and non-Newtonian flow by transverse oscillations: A CFD study
Chemical Engineering Science, 2010Co-Authors: M Eesa, Mostafa BarigouAbstract:Radial heat transfer in laminar pipe flow is limited to slow Thermal conduction which results in a wide temperature distribution over the pipe cross-section. This is undesirable in many industrial processes as it leads to an uneven distribution of fluid heat treatment. Often the fluids involved are relatively viscous and processing them under turbulent conditions is impractical and/or uneconomical. On the other hand, the use of static in-line mixers to promote radial mixing may be prohibited in hygienic processes because they are difficult to keep clean. In this paper, we use a validated Computational Fluid Dynamics (CFD) model to show that the imposition of a transverse vibration motion on a steady laminar flow generates sufficient chaotic fluid motion which leads to considerable radial mixing. This results in a large enhancement in wall heat transfer as well as a near-uniform radial temperature field accompanied by a substantial heating of the inner region of the flow. Vibration also causes the temperature profile to develop very rapidly in the axial direction reducing the Thermal Entrance Length by a large factor, so that much shorter pipes could in principle be used to achieve a desired temperature at the outlet. The effects are quantitatively demonstrated for Newtonian and non-Newtonian pseudoplastic fluids of different viscosities, for a wide range of vibration amplitudes and frequencies. For processes where vibrational motion can be implemented the benefits can be very significant.
Ali Mohammadi - One of the best experts on this subject based on the ideXlab platform.
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Transient forced convection with viscous dissipation to power-law fluids in Thermal Entrance region of circular ducts with constant wall heat flux
Energy Conversion and Management, 2009Co-Authors: Asghar Molaei Dehkordi, Ali MohammadiAbstract: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 Nusselt number of steady state conditions was correlated in terms of the power-law index and wall heat flux and compared with literature data, which were obtained by an analytic solution for Newtonian fluids. Furthermore, a relationship was proposed for the Thermal Entrance Length.
M Eesa - One of the best experts on this subject based on the ideXlab platform.
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cfd simulation of transverse vibration effects on radial temperature profile and Thermal Entrance Length in laminar flow
Aiche Journal, 2011Co-Authors: M Eesa, Mostafa BarigouAbstract:Radial heat transfer in laminar pipe flow is characterized by a wide temperature distribution over the pipe cross-section. We use a validated Computational Fluid Dynamics (CFD) model to show that the superimposition of a transverse vibration on the steady laminar flow of a Newtonian fluid moving in a pipe with an isoThermal wall, generates considerable chaotic flow and radial mixing which result in a large enhancement in wall heat transfer as well as a considerably more uniform radial temperature field. Transverse vibration also causes the temperature profile to develop very rapidly in the axial direction reducing the Thermal Entrance Length by a large factor. These effects are dependent on vibration amplitude and frequency, and fluid viscosity. © 2010 American Institute of Chemical Engineers AIChE J, 2011
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Enhancing radial temperature uniformity and boundary layer development in viscous Newtonian and non-Newtonian flow by transverse oscillations: A CFD study
Chemical Engineering Science, 2010Co-Authors: M Eesa, Mostafa BarigouAbstract:Radial heat transfer in laminar pipe flow is limited to slow Thermal conduction which results in a wide temperature distribution over the pipe cross-section. This is undesirable in many industrial processes as it leads to an uneven distribution of fluid heat treatment. Often the fluids involved are relatively viscous and processing them under turbulent conditions is impractical and/or uneconomical. On the other hand, the use of static in-line mixers to promote radial mixing may be prohibited in hygienic processes because they are difficult to keep clean. In this paper, we use a validated Computational Fluid Dynamics (CFD) model to show that the imposition of a transverse vibration motion on a steady laminar flow generates sufficient chaotic fluid motion which leads to considerable radial mixing. This results in a large enhancement in wall heat transfer as well as a near-uniform radial temperature field accompanied by a substantial heating of the inner region of the flow. Vibration also causes the temperature profile to develop very rapidly in the axial direction reducing the Thermal Entrance Length by a large factor, so that much shorter pipes could in principle be used to achieve a desired temperature at the outlet. The effects are quantitatively demonstrated for Newtonian and non-Newtonian pseudoplastic fluids of different viscosities, for a wide range of vibration amplitudes and frequencies. For processes where vibrational motion can be implemented the benefits can be very significant.
Mohammad Memari - One of the best experts on this subject based on the ideXlab platform.
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transient and steady state forced convection to power law fluids in the Thermal Entrance region of circular ducts effects of viscous dissipation variable viscosity and axial conduction
Energy Conversion and Management, 2010Co-Authors: Asghar Molaei Dehkordi, Mohammad MemariAbstract:A numerical study 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 with taking into account the effects of viscous dissipation, axial conduction, and variations of viscosity with temperature. In this regard, the unsteady-state Thermal energy and momentum equations were solved numerically using a finite-difference method, whereas the steady-state Thermal energy equation with constant wall heat flux as the boundary condition was solved analytically as the initial condition of the former. The numerical procedure used in the present work was validated with an analytical solution for the special case of Newtonian fluids. The effects of the power-law index, axial conduction, wall heat flux, and variations of fluid viscosity on the local Nusselt number and Thermal Entrance Length were investigated. Moreover, the local Nusselt number values of steady-state conditions were correlated as a function of the power-law index and wall heat flux. Furthermore, a correlation was derived for the Thermal Entrance Length as a function of the power-law index and wall heat flux.