The growth rate and uniformity of Carbon Nano Tubes (CNTs) based on Chemical Vapor Deposition (CVD)
technique is investigated by using a numerical model. In this reactor, inlet gas mixture, including xylene as
carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal CVD reactor at
atmospheric pressure. Based on the gas phase and surface reactions, released carbon atoms are grown as CNTs on the iron catalysts at the reactor hot walls. The effect of inlet gas-mixture flow rate, on CNTs growth rate and its uniformity is discussed. In addition the velocity and temperature profile and also species concentrations throughout the reactor are presented.
Computational Analysis of Natural Convection in Spherical Annulus Using FEVIJMER
HEAT transfer by natural convection from a body to its finite enclosure is of importance
in nuclear reactor technology, electronic instrumentation packaging, aircraft cabin design, the
analysis of fluid suspension gyrocompasses, and numerous other practical situations. The steady
natural convection heat transfer of fluids between two concentric isothermal spheres is investigated
computationally with the help of FEV in ANSYS 14.5. The inner wall is subjected to a higher
temperature and outer is at room temperature. The steady behavior of the flow field and its
subsequent effect on the temperature distribution for different Rayleigh numbers and radius ratios
are analyzed.
Bossious boundary condition is taken for natural convection and which is solved in fluent
module. Steady solutions of the entire flow field is obtained for Rayleigh number (5x101<ra><105),><rr><3). The result shows that the Rayleigh number and
radius ratio have a profound influence on the temperature and flow fields and Prandlt number has
very negligible effect. The results of average Nusselt numbers are also compared with those of
previous numerical investigations. Excellent agreement is obtained.
Effect of Radiation on Mixed Convection Flow of a Non-Newtonian Nan fluid ove...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
Thermal Energy on Water and Oil placed Squeezed Carreau Nanofluids FlowMOHAMMED FAYYADH
this research work is focused on the numerical study regarding Carreau nanofluids’ squeezed flow via a permeable sensor surface. The nanofluids’ thermal conductivity is considered to be dependent on temperature. A convenient transformation is employed to reorganize governing equations into ordinary differential equations. The Runge–Kutta method and shooting technique are employed to accurately solve the boundary layer momentum as well as heat equations. Graphical and tabular aids are used to evaluate the solutions of applicable parameter with regards to temperature as well as the rate of heat transfer. In this work, a comparison is done from three nanofluids, i.e. copper, oxide aluminum and SWCNTs (nanoparticles) based fluids (water, crude oil and ethylene glycol) to improve heat transfer. It is found that the temperature dimensionless was dropped and dominated with the squeezed flow parameter and nanoparticle volume fraction parameter. That is for all nanomaterials. When compared with water and ethylene glycol, crude oil is cooler and a thinner thermal boundary layer is presented. For the rate of heat transfer (Nusselt number) was higher in: Ethylene glycol- SWCNT with high permeable velocity parameter 0.2, Ethylene glycol- SWCNT with low squeeze flow parameter 0.1 and Ethylene glycol- oxide aluminum with low nanoparticle volume fraction 0.05
Heat transefer of a dusty fluid over a stretching sheet with internal heat ge...eSAT Journals
Abstract This paper pertains to investigate the heat transfer characteristics of two dimensional two phase flow in a porous medium over a stretching sheet with internal heat generation. The novelty of the present study is to consider the permeability parameter, space and temperature dependent internal heat generation along with various parameters like Froud number ,heat source/sink parameter, Grashof number, Prandtl number, Eckert number, Volume fraction, fluid interaction parameter etc. The method of solution involves similarity transformation which reduces the partial differential equations into non linear ordinary differential equations. These non linear ordinary differential equations have been solved by applying Runge-Kutta 4-th order method with help of shooting technique. The temperature profiles for different values of flow parameters are presented in figures. It is observed from all the figures that the boundary conditions are satisfied asymptotically in all the cases which supporting the accuracy of the numerical results. All the figures shows that increasing values of any parameter increase the thermal boundary layer except the prandtl number and permeability parameter. AMS classification 76T10, 76T15 Keywords: Heat source/sink, Volume fraction, Fluid – particle interaction parameter, Dusty fluid, Boundary layer flow, Stretching sheet, Eckert number, Grashof number, Prandtle number, Shooting techniques, Froud number, permeability parameter.
Boundary layer flow and heat transfer of a dusty fluid over a vertical permea...eSAT Journals
Abstract
The steady boundary layer free convective flow of a dusty fluid past a vertical permeable stretching surface is studied .The governing equations are converted into first order ordinary differential equations using similarity transformations. These equations are solved numerically by using Runge kutta forth order method. The effects of physical parameters like fluid-particle interaction parameter, local Grashof number, suction parameters, Prandtl number, radiation parameter and Eckert number on the flow and heat transfer characteristics are computed and presented graphically. Also the rate of heat transfer at the surface is discussed. The present results are compared with the previous study and there is a good agreement.
AMS classification 76T10, 76T15
Keywords: Volume fraction, Interaction parameter, Dusty fluid, Thermal radiation, suction parameter, steady flow and heat transfer, Boundary layer flow, Numerical solution.
Computational Analysis of Natural Convection in Spherical Annulus Using FEVIJMER
HEAT transfer by natural convection from a body to its finite enclosure is of importance
in nuclear reactor technology, electronic instrumentation packaging, aircraft cabin design, the
analysis of fluid suspension gyrocompasses, and numerous other practical situations. The steady
natural convection heat transfer of fluids between two concentric isothermal spheres is investigated
computationally with the help of FEV in ANSYS 14.5. The inner wall is subjected to a higher
temperature and outer is at room temperature. The steady behavior of the flow field and its
subsequent effect on the temperature distribution for different Rayleigh numbers and radius ratios
are analyzed.
Bossious boundary condition is taken for natural convection and which is solved in fluent
module. Steady solutions of the entire flow field is obtained for Rayleigh number (5x101<ra><105),><rr><3). The result shows that the Rayleigh number and
radius ratio have a profound influence on the temperature and flow fields and Prandlt number has
very negligible effect. The results of average Nusselt numbers are also compared with those of
previous numerical investigations. Excellent agreement is obtained.
Effect of Radiation on Mixed Convection Flow of a Non-Newtonian Nan fluid ove...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
Thermal Energy on Water and Oil placed Squeezed Carreau Nanofluids FlowMOHAMMED FAYYADH
this research work is focused on the numerical study regarding Carreau nanofluids’ squeezed flow via a permeable sensor surface. The nanofluids’ thermal conductivity is considered to be dependent on temperature. A convenient transformation is employed to reorganize governing equations into ordinary differential equations. The Runge–Kutta method and shooting technique are employed to accurately solve the boundary layer momentum as well as heat equations. Graphical and tabular aids are used to evaluate the solutions of applicable parameter with regards to temperature as well as the rate of heat transfer. In this work, a comparison is done from three nanofluids, i.e. copper, oxide aluminum and SWCNTs (nanoparticles) based fluids (water, crude oil and ethylene glycol) to improve heat transfer. It is found that the temperature dimensionless was dropped and dominated with the squeezed flow parameter and nanoparticle volume fraction parameter. That is for all nanomaterials. When compared with water and ethylene glycol, crude oil is cooler and a thinner thermal boundary layer is presented. For the rate of heat transfer (Nusselt number) was higher in: Ethylene glycol- SWCNT with high permeable velocity parameter 0.2, Ethylene glycol- SWCNT with low squeeze flow parameter 0.1 and Ethylene glycol- oxide aluminum with low nanoparticle volume fraction 0.05
Heat transefer of a dusty fluid over a stretching sheet with internal heat ge...eSAT Journals
Abstract This paper pertains to investigate the heat transfer characteristics of two dimensional two phase flow in a porous medium over a stretching sheet with internal heat generation. The novelty of the present study is to consider the permeability parameter, space and temperature dependent internal heat generation along with various parameters like Froud number ,heat source/sink parameter, Grashof number, Prandtl number, Eckert number, Volume fraction, fluid interaction parameter etc. The method of solution involves similarity transformation which reduces the partial differential equations into non linear ordinary differential equations. These non linear ordinary differential equations have been solved by applying Runge-Kutta 4-th order method with help of shooting technique. The temperature profiles for different values of flow parameters are presented in figures. It is observed from all the figures that the boundary conditions are satisfied asymptotically in all the cases which supporting the accuracy of the numerical results. All the figures shows that increasing values of any parameter increase the thermal boundary layer except the prandtl number and permeability parameter. AMS classification 76T10, 76T15 Keywords: Heat source/sink, Volume fraction, Fluid – particle interaction parameter, Dusty fluid, Boundary layer flow, Stretching sheet, Eckert number, Grashof number, Prandtle number, Shooting techniques, Froud number, permeability parameter.
Boundary layer flow and heat transfer of a dusty fluid over a vertical permea...eSAT Journals
Abstract
The steady boundary layer free convective flow of a dusty fluid past a vertical permeable stretching surface is studied .The governing equations are converted into first order ordinary differential equations using similarity transformations. These equations are solved numerically by using Runge kutta forth order method. The effects of physical parameters like fluid-particle interaction parameter, local Grashof number, suction parameters, Prandtl number, radiation parameter and Eckert number on the flow and heat transfer characteristics are computed and presented graphically. Also the rate of heat transfer at the surface is discussed. The present results are compared with the previous study and there is a good agreement.
AMS classification 76T10, 76T15
Keywords: Volume fraction, Interaction parameter, Dusty fluid, Thermal radiation, suction parameter, steady flow and heat transfer, Boundary layer flow, Numerical solution.
Moving Lids Direction Effects on MHD Mixed Convection in a Two-Sided Lid-Driv...A Behzadmehr
Magnetohydrodynamic (MHD) mixed convection flow of Cu–water nanofluid inside a two-sided lid-driven square enclosure with adiabatic horizontal walls and differentially heated sidewalls has been investigated numerically. The effects of moving lids direction, variations of Richardson number, Hartmann number, and volume fraction of nanoparticles on flow and temperature fields have been studied. The obtained results show that for a constant Grashof number (), the rate of heat transfer increases with a decrease in the Richardson and Hartmann numbers. Furthermore, an increase of the volume fraction of nanoparticles may result in enhancement or deterioration of the heat transfer performance depending on the value of the Hartmann and Richardson numbers and the configuration of the moving lids. Also, it is found that in the presence of magnetic field, the nanoparticles have their maximum positive effect when the top lid moves rightward and the bottom one moves leftward.
CFD Analysis for Heat Transfer Enhancement of a Corrugated Plate Heat Exchang...ijtsrd
The flow properties of heat transfer across such corrugated channels are very distinct from parallel plate channels. The primary flow direction is parallel to the waviness of the channel of the corrugated channel, although the local flow direction is still changed due to the waviness of the channel. By flow recirculation, separation and re attachment, the thermal boundary layer formed on its walls is regularly disrupted and the convective heat transfer coefficient is thus increased. In this work, in corrugated channels, the convective heat transfer and pressure drop characteristics of flow have been tested numerically. On channels of uniform heat flux and fixed corrugation over a Reynolds number spectrum, 10000 = Re = 30000, numerical research was conducted. The impacts of channel configuration, variation in Reynold’s number, and concentration variations of nanoparticles in base fluid on heat transfer are discussed. As opposed to the traditional corrugated channel, a major heat transfer gain was associated with the proposed corrugated channel. Based on the nanofluid concentration, Reynold number and channel configuration of the corrugated channel, the average Nusselt number increased by a factor of 2.2 up to 2.8 compared to that of the semi circular corrugated channel. Compared with the effect of channel configuration variation, triangular corrugated channel was the best Nusselt numbers, followed by the shape Semi circular Triangular , and Semi circular corrugated channel with the lowest results. Prof. Pushparaj Singh | Rishi Kesh Jha "CFD Analysis for Heat Transfer Enhancement of a Corrugated Plate Heat Exchanger using Different Corrugated Channel Configurations" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd35706.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/35706/cfd-analysis-for-heat-transfer-enhancement-of-a-corrugated-plate-heat-exchanger-using-different-corrugated-channel-configurations/prof-pushparaj-singh
Non-Newtonian Visco-elastic Heat Transfer Flow Past a Stretching Sheet with C...IJERA Editor
In this paper two dimensional flow of a viscoelastic fluid due to stretching surface is considered. Flow analysis is carried out by using closed form solution of fourth order differential equation of motion of viscoelastic fluid. Further (Walters’ liquid B’ model) heat transfer analysis is carried out using convective surface condition. The governing equations of flow and heat transfer are non-linear partial differential equations which are unable to solve analytically hence are solved using Runge-Kutta Numerical Method with efficient shooting technique. The flow and heat transfer characteristics are studied through plots drawn. Numerical values of Wall temperature are calculated and presented in the table and compared with earlier published results which are in good agreement
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...IJERA Editor
In the present paper a numerical attempt is made to study the combined effects of heat source and sink on unsteady laminar boundary layer flow of a viscous, incompressible, electrically conducting fluid along a semiinfinite vertical plate. A magnetic field of uniform strength is applied normal to the flow. The governing boundary layer equations are solved numerically, using Crank-Nicolson method. Graphical results of velocity and temperature fields, tabular values of Skin-friction and Nusselt are presented and discussed at various parametric conditions. From this study, it is found that the velocity and temperature of the fluid increase in the presence of heat source but they decrease in the presence of heat absorption parameter.
The results show that, with proper selection of physical parameters, significant heat transfer
enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and
the overall heat transfer performances in porous pin fin channels are much better than those in
traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the
pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer
efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI 20.
Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the
overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they
are the lowest in the short elliptic porous pin fin channels
Investigation of the Effect of Nanoparticles Mean Diameter on Turbulent Mixed...A Behzadmehr
Abstract
Turbulent mixed convection of a nanofluid (water/Al2O3, Φ=.02) has been studied numerically. Two-phase
mixture model has been used to investigate the effects of nanoparticles mean diameter on the flow parameters. Nanoparticles distribution at the tube cross section shows that the particles are uniformly dispersed. The non-uniformity of the particles distribution occurs in the case of large nanoparticles and/or high value of the Grashof numbers. The study of particle size effect showed that the effective Nusselt number and turbulent intensity increases with the decreased of particle size.
Study on Thermal and Hydrodynamic Indexes of a Nanofluid Flow in a Micro Heat...A Behzadmehr
The paper numerically presents laminar forced convection of a nanofluid flowing in a duct at microscale.
Results were compared with both analytical and experimental data and observed good concordance with
previous studies available in the literature. Influences of Brinkman and Reynolds number on thermal and
hydrodynamic indexes have been investigated. For a given nanofluid, no change in efficiency (heat dissipation
to pumping power) was observed with an increasing in Reynolds number. It was shown that the pressure was
decrease with an increase in Brinkman number. Dependency of Nu increment changes with substrate material.
International journal of engineering and mathematical modelling vol2 no3_2015_1IJEMM
A weak nonlinear stability analysis has been performed for an oscillatory mode of convection, heat and mass transports in terms of
Nusselt, Sherwood numbers are derived and evaluated by a non$-$autonomous complex Ginzburg-Landau equation. The porous layer boundaries are heated sinusoidally with time. The basic state temperature is defined in terms of study and oscillatory parts, where study part show nonlinear throughflow effect on the system and time dependant part show modulation effect. The generalized Darcy model is employed for the momentum equation. The disturbances of the flow are expanded in power series of amplitude of modulation, which is assumed to be small and employed using normal mode technics. The effect of vertical throughflow is found to stabilize or destabilize the system depending on its direction. The time relaxation parameter $\lambda_1$ has destabilizing effect, while time retardation parameter $\lambda_2$ has stabilizing effect on the system. Three types of modulations have been analyzed, and found that, OPM, LBMO cases are effective on heat and mass transfer than IPM case. The effects of amplitude and frequency of modulation on heat and mass transports have been analyzed and depicted graphically. The study establishes that the heat and mass transports can be controlled effectively by a mechanism that is external to the system.
In this paper, the unsteady motion of a spherical particle rolling down an inclined tube in a
Newtonian fluid for a range of Reynolds numbers was solved using a simulation method called
the Differential Transformation Method (DTM). The concept of differential transformation is
briefly introduced, and then we employed it to derive solution of nonlinear equation. The
obtained results for displacement, velocity and acceleration of the motion from DTM are
compared with those from numerical solution to verify the accuracy of the proposed method.
The effects of particle diameter (size), continues phase viscosity and inclination angles was
studied. As an important result it was found that the inclination angle does not affect the
acceleration duration. The results reveal that the Differential Transformation Method can achieve suitable results in predicting the solution of such problems.
International Journal of Mathematics and Statistics Invention (IJMSI)inventionjournals
International Journal of Mathematics and Statistics Invention (IJMSI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJMSI publishes research articles and reviews within the whole field Mathematics and Statistics, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Porous media has two specifications: First its dissipation area is greater than the conventional fins that enhance heat convection. Second the irregular motion of the fluid flow around the individual beads mixes the fluid more effectively. Nanofluids are mixtures of base fluid with a very small amount of nanoparticles having dimensions from 1 to 100 nm, with very high thermal conductivities, so it would be the best convection heat transfer by using porous media and nanofluids. Thus studies need to be conducted involving nanofluids in porous media. For that, the purpose of this article is to summarize the published subjects respect to the enhancement of convective heat transfer using porous media and nanofluids and identifies opportunities for future research.
OSCILLATORY FLOW OF MHD POLAR FLUID WITH HEAT AND MASS TRANSFER PAST A VERTIC...IAEME Publication
The study of unsteady two-dimensional laminar boundary layer flow of a viscous incompressible fluid (polar fluid) through porous medium past a semi-infinite vertical porous stretching plate in the presence of transverse magnetic field is investigated.
The sheet makes with a constant velocity in the longitudinal direction and the free stream velocity follows an exponentially increasing or decreasing small perturbation law. A uniform magnetic field acts perpendicularly to the porous sheet which absorbs the polar fluid with a suction velocity varying with time component. The effects of all parameters encountering in the problem are investigated for velocity and temperature fields across the boundary layer.
Influence of Interface Thermal Resistance on Relaxation Dynamics of Metal-Die...A Behzadmehr
Nanocomposite materials, including noble metal nanoparticles embedded in a dielectric host medium, are interesting because of their optical properties linked to surface plasmon resonance phenomena. For studding of nonlinear optical properties and/or energy transfer process, these materials may be excited by ultrashort pulse laser with a temporal width varying from some femtoseconds to some hundreds of picoseconds. Following of absorption of light energy by metal-dielectric nanocomposite material, metal nanoparticles are heated. Then, the thermal energy is transferred to the host medium through particle-dielectric interface. On the one hand, nonlinear optical properties of such materials depend on their thermal responses to laser pulse, and on the other hand different parameters, such as pulse laser and medium thermodynamic characterizes, govern on the thermal responses of medium to laser pulse. Here, influence of thermal resistance at particle-surrounding medium interface on thermal response of such material under ultrashort pulse laser excitation is investigated. For this, we used three temperature model based on energy exchange between different bodies of medium. The results show that the interface thermal resistance plays a crucial role on nanoparticle cooling dynamics, so that the relaxation characterized time increases by increasing of interface thermal resistance.
Moving Lids Direction Effects on MHD Mixed Convection in a Two-Sided Lid-Driv...A Behzadmehr
Magnetohydrodynamic (MHD) mixed convection flow of Cu–water nanofluid inside a two-sided lid-driven square enclosure with adiabatic horizontal walls and differentially heated sidewalls has been investigated numerically. The effects of moving lids direction, variations of Richardson number, Hartmann number, and volume fraction of nanoparticles on flow and temperature fields have been studied. The obtained results show that for a constant Grashof number (), the rate of heat transfer increases with a decrease in the Richardson and Hartmann numbers. Furthermore, an increase of the volume fraction of nanoparticles may result in enhancement or deterioration of the heat transfer performance depending on the value of the Hartmann and Richardson numbers and the configuration of the moving lids. Also, it is found that in the presence of magnetic field, the nanoparticles have their maximum positive effect when the top lid moves rightward and the bottom one moves leftward.
CFD Analysis for Heat Transfer Enhancement of a Corrugated Plate Heat Exchang...ijtsrd
The flow properties of heat transfer across such corrugated channels are very distinct from parallel plate channels. The primary flow direction is parallel to the waviness of the channel of the corrugated channel, although the local flow direction is still changed due to the waviness of the channel. By flow recirculation, separation and re attachment, the thermal boundary layer formed on its walls is regularly disrupted and the convective heat transfer coefficient is thus increased. In this work, in corrugated channels, the convective heat transfer and pressure drop characteristics of flow have been tested numerically. On channels of uniform heat flux and fixed corrugation over a Reynolds number spectrum, 10000 = Re = 30000, numerical research was conducted. The impacts of channel configuration, variation in Reynold’s number, and concentration variations of nanoparticles in base fluid on heat transfer are discussed. As opposed to the traditional corrugated channel, a major heat transfer gain was associated with the proposed corrugated channel. Based on the nanofluid concentration, Reynold number and channel configuration of the corrugated channel, the average Nusselt number increased by a factor of 2.2 up to 2.8 compared to that of the semi circular corrugated channel. Compared with the effect of channel configuration variation, triangular corrugated channel was the best Nusselt numbers, followed by the shape Semi circular Triangular , and Semi circular corrugated channel with the lowest results. Prof. Pushparaj Singh | Rishi Kesh Jha "CFD Analysis for Heat Transfer Enhancement of a Corrugated Plate Heat Exchanger using Different Corrugated Channel Configurations" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd35706.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/35706/cfd-analysis-for-heat-transfer-enhancement-of-a-corrugated-plate-heat-exchanger-using-different-corrugated-channel-configurations/prof-pushparaj-singh
Non-Newtonian Visco-elastic Heat Transfer Flow Past a Stretching Sheet with C...IJERA Editor
In this paper two dimensional flow of a viscoelastic fluid due to stretching surface is considered. Flow analysis is carried out by using closed form solution of fourth order differential equation of motion of viscoelastic fluid. Further (Walters’ liquid B’ model) heat transfer analysis is carried out using convective surface condition. The governing equations of flow and heat transfer are non-linear partial differential equations which are unable to solve analytically hence are solved using Runge-Kutta Numerical Method with efficient shooting technique. The flow and heat transfer characteristics are studied through plots drawn. Numerical values of Wall temperature are calculated and presented in the table and compared with earlier published results which are in good agreement
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...IJERA Editor
In the present paper a numerical attempt is made to study the combined effects of heat source and sink on unsteady laminar boundary layer flow of a viscous, incompressible, electrically conducting fluid along a semiinfinite vertical plate. A magnetic field of uniform strength is applied normal to the flow. The governing boundary layer equations are solved numerically, using Crank-Nicolson method. Graphical results of velocity and temperature fields, tabular values of Skin-friction and Nusselt are presented and discussed at various parametric conditions. From this study, it is found that the velocity and temperature of the fluid increase in the presence of heat source but they decrease in the presence of heat absorption parameter.
The results show that, with proper selection of physical parameters, significant heat transfer
enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and
the overall heat transfer performances in porous pin fin channels are much better than those in
traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the
pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer
efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI 20.
Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the
overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they
are the lowest in the short elliptic porous pin fin channels
Investigation of the Effect of Nanoparticles Mean Diameter on Turbulent Mixed...A Behzadmehr
Abstract
Turbulent mixed convection of a nanofluid (water/Al2O3, Φ=.02) has been studied numerically. Two-phase
mixture model has been used to investigate the effects of nanoparticles mean diameter on the flow parameters. Nanoparticles distribution at the tube cross section shows that the particles are uniformly dispersed. The non-uniformity of the particles distribution occurs in the case of large nanoparticles and/or high value of the Grashof numbers. The study of particle size effect showed that the effective Nusselt number and turbulent intensity increases with the decreased of particle size.
Study on Thermal and Hydrodynamic Indexes of a Nanofluid Flow in a Micro Heat...A Behzadmehr
The paper numerically presents laminar forced convection of a nanofluid flowing in a duct at microscale.
Results were compared with both analytical and experimental data and observed good concordance with
previous studies available in the literature. Influences of Brinkman and Reynolds number on thermal and
hydrodynamic indexes have been investigated. For a given nanofluid, no change in efficiency (heat dissipation
to pumping power) was observed with an increasing in Reynolds number. It was shown that the pressure was
decrease with an increase in Brinkman number. Dependency of Nu increment changes with substrate material.
International journal of engineering and mathematical modelling vol2 no3_2015_1IJEMM
A weak nonlinear stability analysis has been performed for an oscillatory mode of convection, heat and mass transports in terms of
Nusselt, Sherwood numbers are derived and evaluated by a non$-$autonomous complex Ginzburg-Landau equation. The porous layer boundaries are heated sinusoidally with time. The basic state temperature is defined in terms of study and oscillatory parts, where study part show nonlinear throughflow effect on the system and time dependant part show modulation effect. The generalized Darcy model is employed for the momentum equation. The disturbances of the flow are expanded in power series of amplitude of modulation, which is assumed to be small and employed using normal mode technics. The effect of vertical throughflow is found to stabilize or destabilize the system depending on its direction. The time relaxation parameter $\lambda_1$ has destabilizing effect, while time retardation parameter $\lambda_2$ has stabilizing effect on the system. Three types of modulations have been analyzed, and found that, OPM, LBMO cases are effective on heat and mass transfer than IPM case. The effects of amplitude and frequency of modulation on heat and mass transports have been analyzed and depicted graphically. The study establishes that the heat and mass transports can be controlled effectively by a mechanism that is external to the system.
In this paper, the unsteady motion of a spherical particle rolling down an inclined tube in a
Newtonian fluid for a range of Reynolds numbers was solved using a simulation method called
the Differential Transformation Method (DTM). The concept of differential transformation is
briefly introduced, and then we employed it to derive solution of nonlinear equation. The
obtained results for displacement, velocity and acceleration of the motion from DTM are
compared with those from numerical solution to verify the accuracy of the proposed method.
The effects of particle diameter (size), continues phase viscosity and inclination angles was
studied. As an important result it was found that the inclination angle does not affect the
acceleration duration. The results reveal that the Differential Transformation Method can achieve suitable results in predicting the solution of such problems.
International Journal of Mathematics and Statistics Invention (IJMSI)inventionjournals
International Journal of Mathematics and Statistics Invention (IJMSI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJMSI publishes research articles and reviews within the whole field Mathematics and Statistics, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Porous media has two specifications: First its dissipation area is greater than the conventional fins that enhance heat convection. Second the irregular motion of the fluid flow around the individual beads mixes the fluid more effectively. Nanofluids are mixtures of base fluid with a very small amount of nanoparticles having dimensions from 1 to 100 nm, with very high thermal conductivities, so it would be the best convection heat transfer by using porous media and nanofluids. Thus studies need to be conducted involving nanofluids in porous media. For that, the purpose of this article is to summarize the published subjects respect to the enhancement of convective heat transfer using porous media and nanofluids and identifies opportunities for future research.
OSCILLATORY FLOW OF MHD POLAR FLUID WITH HEAT AND MASS TRANSFER PAST A VERTIC...IAEME Publication
The study of unsteady two-dimensional laminar boundary layer flow of a viscous incompressible fluid (polar fluid) through porous medium past a semi-infinite vertical porous stretching plate in the presence of transverse magnetic field is investigated.
The sheet makes with a constant velocity in the longitudinal direction and the free stream velocity follows an exponentially increasing or decreasing small perturbation law. A uniform magnetic field acts perpendicularly to the porous sheet which absorbs the polar fluid with a suction velocity varying with time component. The effects of all parameters encountering in the problem are investigated for velocity and temperature fields across the boundary layer.
Influence of Interface Thermal Resistance on Relaxation Dynamics of Metal-Die...A Behzadmehr
Nanocomposite materials, including noble metal nanoparticles embedded in a dielectric host medium, are interesting because of their optical properties linked to surface plasmon resonance phenomena. For studding of nonlinear optical properties and/or energy transfer process, these materials may be excited by ultrashort pulse laser with a temporal width varying from some femtoseconds to some hundreds of picoseconds. Following of absorption of light energy by metal-dielectric nanocomposite material, metal nanoparticles are heated. Then, the thermal energy is transferred to the host medium through particle-dielectric interface. On the one hand, nonlinear optical properties of such materials depend on their thermal responses to laser pulse, and on the other hand different parameters, such as pulse laser and medium thermodynamic characterizes, govern on the thermal responses of medium to laser pulse. Here, influence of thermal resistance at particle-surrounding medium interface on thermal response of such material under ultrashort pulse laser excitation is investigated. For this, we used three temperature model based on energy exchange between different bodies of medium. The results show that the interface thermal resistance plays a crucial role on nanoparticle cooling dynamics, so that the relaxation characterized time increases by increasing of interface thermal resistance.
Modeling of Activated Carbon Preparation from Spanish Anthracite Based on ANF...A Behzadmehr
Carbon nanostructures are famous structures which are used in several industries such as separation, treatment, energy storage (i.e. methane and hydrogen storage), etc. A successful modeling of activated carbon preparation is very important in saving time and money. There are some attempts to achieve the appropriate theoretical modeling of activated carbon preparation but most of them were almost unsuccessful due to the complexity between the input and output variables. In this paper the empirical modeling of activated carbon preparation from Spanish anthracite based on adaptive neuro-fuzzy inference system (ANFIS) is investigated. ANFIS model is established to delineate the relationship between the BET surface area of the prepared activated carbon with initial and operational conditions; agent type, agent ratio, activation temperature, activation time and nitrogen flow. The results show that the selected model have a good accuracy with a coefficient of determination values (R2) of 0.9885 and average relative error (ARE) of 0.00268.
Ecos de sociedad, la importancia de la familia en la vida de las personas. El nuevo papel de la mujer en relación a la fertilidad. El proyecto ético de igualdad entre hombres y mujeres.
Bloque 02. tema 03. LOS FACTORES BIOLÓGICOS DE LOS ESPACIOS NATURALES.Ceper Cehel de Albuñol
LOS FACTORES BIOLÓGICOS DE LOS ESPACIOS NATURALES: Los climas cálidos.Los climas templados. Los climas fríos.
Los espacios naturales en Europa, España y Andalucía: Los espacios naturales de Europa. Los espacios naturales en España. Los espacios naturales de Andalucía
NUMERICAL INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER FROM CIRCULAR CYL...IAEME Publication
In the present work, the enhancement of natural convection heat transfer utilizing nanofluids as working fluid from horizontal circular cylinder situated in a square enclosure is investigated numerically. The type of the nanofluid is the water-based copper Cu. A model is developed to analyze heat transfer performance of nanofluids inside an enclosure taking into account the solid particle dispersionrs on the flow and heat transfer characteristics. The study uses different Raylieh
numbers (104 , 105 , and 106 ), different enclosure width to cylinder diameter ratios W/D (1.667, 2.5 and 5) and volume fraction of nanoparticles between 0 to 0.2. The work included the solution of the governing equations in the vorticity-stream function formulation which were transformed into body fitted coordinate system
NUMERICAL INVESTIGATION OF NATURAL CONVECTION HEAT TRANSFER FROM CIRCULAR CYL...IAEME Publication
In the present work, the enhancement of natural convection heat transfer utilizing nano fluids as working fluid from horizontal circular cylinder situated in a square enclosure is investigated numerically. Different types of nano particles were tested. The types of the nano fluids are Cu, Al2O3 and TiO3 with water as base fluid. A model is developed to analyze heat transfer performance of nano fluids inside an enclosure taking into account the solid particle dispersionrs on the flow and heat
transfer characteristics.
Effect of nanofluid on heat transfer characteristics of double pipe heat exch...eSAT Journals
Abstract A nanofluid is a mixture of nano sized particles of size up to 100 nm and a base fluid. Typical nanoparticles are made of metals, oxides or carbides, while base fluids may be water, ethylene glycol or oil. The effect of nanofluid to enhance the heat transfer rate in various heat exchangers is experimentally evaluated recently. The heat transfer enhancement using nanofluid mainly depends on type of nanoparticles, size of nanoparticles and concentration of nanoparticles in base fluid. In the present paper, an experimental investigation is carried out to determine the effect of various concentration of Al2O3 nano-dispersion mixed in water as base fluid on heat transfer characteristics of double pipe heat exchanger for parallel flow and counter flow arrangement. The volume concentrations of Al2O3 nanofluid prepared are 0.001 % to 0.01 %. The conclusion derived for the study is that overall heat transfer coefficient increases with increase in volume concentration of Al2O3 nano-dispersion compared to water up to volume concentration of 0.008 % and then decreases. Keywords: Nanofluid, Heat Transfer Characteristics, Double Pipe Heat Exchagner, Al2O3 Nano-dispersion
Double Diffusive Convection and the Improvement of Flow in Square Porous AnnulusIJERA Editor
There has been increased interest shown in recent years to investigate the behavior of heat and mass transfer in a square annulus with a porous medium fixed between the inner and outer walls. This paper aims to evaluate the Soret effect arising in the case of heat and mass transfer in a porous medium bounded by a square annulus and subjected to isothermal heating of the inner surfaces as well as the outer horizontal surfaces. The phenomenon is governed by 3 partial differential equations, the momentum, energy and concentration equations, that are coupled together and result in a situation where change in one variable affects the other equations and vice versa. The partial differential equations are converted into finite element equations with the help of the Galerkin method and then solved to predict solution variables such as temperature, stream function and concentration in the porous medium. It is found that the heat transfer rate at the hot wall decreases with increasing viscous dissipation effect in the porous medium.
Heat Transfer Enhancement Using Aluminium Oxide Nanofluid: Effect of the Base...CSCJournals
The flow and heat transfer is an important phenomenon in engineering systems due to its wide application in electronic cooling, heat exchangers, double pane windows etc.. The enhancement of heat transfer in these systems is an essential topic from an energy saving perspective. The lower heat transfer performance when conventional fluids, such as water, engine oil and ethylene glycol are used hinders improvements in performance and a consequent reduction in the size of such systems. The use of solid particles as an additive suspended into the base fluid is a technique for heat transfer enhancement. Therefore, the heat transfer enhancement in a horizontal circular tube that is maintained at a constant temperature under laminar regime has been investigated numerically. A computational code applied to the problem by use of the finite volume method was developed. Nanofluid was made by dispersion of Al2O3 nanoparticles in pur water and ethylene glycol. Results illustrate that the suspended nanoparticles increase the heat transfer with an increase in the nanoparticles volume fraction and for a considered range of Reynolds numbers. And in other hand, the heat transfer is very sensitive to the base fluid.
Numerical Investigation of Heat Transfer from Two Different Cylinders in Tand...IJERA Editor
A two dimensional technique has been studied numerically to predict the heat transfer from two different cylinders
in tandem arrangement (one is circular and the other is elliptical) using finite element technique with RNG k-ε turbulent
model, taking into consideration the effect of gap ratio (L/Deq ) and Reynolds number , where the distance between
the centers of cylinders is L (L=30 mm and 37 mm), the equivalent diameter of cylinder is Deq=22.5mm and
the range of Reynolds number is 2x103
< Reeq < 21x103 .The commercial CFD software FLUENT was used to get
the thermofluid characteristics (temperature, velocity, kinetic energy and pressure contours ,coefficient of friction ,
heat transfer coefficient , Stanton number …… etc) of the flow around cylinders. The dependency of the heat transfer
coefficient, Stanton number (Sta), pressure drop, and friction factor for circular and elliptical cylinders on the gap
ratio is clear from the results. Results show that, for circular cross section, the heat transfer coefficient is increased as
velocity, and gap ratio increase. On the other hand Sta decreased as velocity increase. The pressure drop and hence
the friction factor increase for circular cylinder as gap ratio increases. For elliptical tube the heat transfer and Sta are
relatively equal to that for circular one at the same gap ratio, but the overall power consumption and friction factor
for elliptical tube is lower than that of circular one. As the elliptical cylinder fixed on the second position the heat
transfer and Sta
increase, on the other hand the pressure drop and hence the friction factor decreases. For all studied
arrangements the highest heat transfer is observed for the arrangement of circular-first and elliptical-second cylinder
and the minimum pressure drop and hence the friction factor are for the elliptical one
Mixed Convection of Variable Properties Al2O3-EG-Water Nanofluid in a Two-Dim...A Behzadmehr
In this paper, mixed convection of Al2O3-EG-Water nanofluid in a square lid-driven enclosure is investigated numerically. The focus of this study is on the effects of variable thermophysical properties of the nanofluid on the heat transfer characteristics. The top moving and the bottom stationary horizontal walls are insulated, while the vertical walls are kept at different constant temperatures. The study is carried out for Richardson numbers of 0.01–1000, the solid volume fractions of 0–0.05 and the Grashof number of 104. The transport equations are solved numerically with a finite volume approach using the SIMPLER algorithm. The results show that the Nusselt number is mainly affected by the viscosity, density and conductivity variations. For low Richardson numbers, although viscosity increases by increasing the nanoparticles volume fraction, due to high intensity convection of enhanced conductivity nanofluid, the average Nusselt number increases for both constant and variable cases. However, for high Richardson numbers, as the volume fraction of nanoparticles increases heat transfer enhancement occurs for the constant properties cases but deterioration in heat transfer occurs for the variable properties cases. The distinction is due to underestimation of viscosity of the nanofluid by the constant viscosity model in the constant properties cases and states important effects of temperature dependency of thermophysical properties, in particular the viscosity distribution in the domain.
Experimental Investigation on Heat Transfer By Natural Convection Over A Cyli...Ijripublishers Ijri
Experiments were carried out to investigate natural convection heat transfer over uniformly heated hollow cylinder models
made of aluminium alloy and pure copper. The effect of surface temperature, heat transfer coefficient and Nusselt’s
number with respect to different heat fluxes and different orientations of two hollow cylinders. In the current study the
heat fluxes range covers from 124w/m2 to 621 w/m2 . Whereas, the different orientations consider for the present investigation
are 00(vertical), 300, 450, 600, 900(horizontal) respectively for conducting experiments on both hollow cylinders.
Based on the experimental result (surface temperature) the following parameters such as theoretical heat transfer
coefficient, experimental heat transfer coefficient and Nusselt number are evaluated and depicted graphically for both
hollow cylinders made of aluminium alloy and pure copper.
Helically Coiled Tube with Different Geometry and Curvature Ratio on Convecti...AM Publications
A helically coil-tube heat exchanger is generally applied in industry applications due to its compact structure, larger heat transfer area and higher heat transfer capability. Several studies from literature have also indicated that heat transfer rate in helically coiled tube are superior to straight tube due to complex flow pattern exist inside helical pipe. The concept behind compact heat exchanger is to decrease size and increase heat load which is the typical feature of modern helical tube heat exchanger. While the heat transfer characteristics of helical coil heat exchangers are available in the literature, This paper elaborates a brief review on different curvature ratio and geometry of tubes in heat transfer through heat exchangers.
Similar to Numerical Analysis of Inlet Gas-Mixture Flow Rate Effects on Carbon Nanotube Growth Rate (20)
Using Lattice Boltzmann Method to Investigate the Effects of Porous Media on ...A Behzadmehr
A numerical investigation of forced convection in a channel with hot solid block inside a square porous block mounted on a bottom wall was carried out. The lattice Boltzmann method was applied for numerical simulations. The fluid flow in the porous media was simulated by Brinkman-Forchheimer model. The effects of parameters such as porosity and thermal conductivity ratio over flow pattern and thermal field were investigated. In this paper the effects of mentioned parameters were discussed in detail. The result show with increasing the thermal conductivity ratio and porosity the fluid temperature will reduce.
Effect of Nanoporous Anodic Aluminum Oxide (AAO) Characteristics On Solar Abs...A Behzadmehr
Nanoporous anodic aluminum oxide (AAO) has been used in many different fields of science and technology, due to its great structural characteristics. Solar selective surface is an important application of this type porous material. This paper investigates the effect of nanoporous AAO properties, including; film thickness, pore area percentage and pore diameter, on absorption spectra in the range of solar radiation. The parameters were verified individually depending on anodization condition, and the absorption spectra were characterized using spectrophotometer analysis. The results showed that the absorptivity was increased with growth of the film thickness. Furthermore, increasing the pore diameter shifted the absorption spectra to the right range, and vice versa. The investigation revealed the presence of an optimum pore area percentage around 14% in which the absorptivity was at its maximum value.
MHD Nanofluid Flow Analysis in a Semi-Porous Channel by a Combined Series Sol...A Behzadmehr
In this paper, Least Square Method (LSM) and Differential Transformation Method (DTM) are used to solve the problem of laminar nanofluid flow in a semi-porous channel in the presence of transverse magnetic field. Due to existence some shortcomings in each method, a novel and efficient method named LS-DTM is introduced which omitted those defects and has an excellent agreement with numerical solution. In the present study, the effective thermal conductivity and viscosity of nanofluid are calculated by Maxwell–Garnetts (MG) and Brinkman models, respectively. The influence of the three dimensionless numbers: the nanofluid volume friction, Hartmann number and Reynolds number on non-dimensional velocity profile are considered. The results show that velocity boundary layer thickness decrease with increase of Reynolds number and nanoparticle volume friction and it increases as Hartmann number increases.
Numerical Study of Mixed Convection of Nanofluid in a Concentric Annulus with...A Behzadmehr
In this work, the steady and laminar mixed convection of nanofluid in horizontal concentric annulus with
rotating inner cylinder is investigated numerically. The inner and outer cylinders are kept at constant
temperature Ti and To respectively, where Ti>To. The annular space is filled with Alumina-water nanofluid.
The governing equations with the corresponded boundary conditions in the polar coordinate are discretized
using the finite volume method where pressure-velocity coupling is done by the SIMPLER algorithm.
Numerical results have been obtained for Rayleigh number ranging from 102 to 105, Reynolds number from 1 to 300 and nanoparticles volume fraction from 0.01 to 0.06. The effects of the Reynolds and Rayleigh numbers, average diameter of nanoparticles and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the annuli are investigated. According to the results, the average Nusselt number decreases with increasing the Reynolds number. However, the average Nusselt number increases by increasing the Rayleigh number. Moreover, the maximum average Nusselt number occurs for an optimal nanoparticle volume fraction except situations that heat conduction predominates over the heat convection. In these conditions the average Nusselt number is close to unity.
Natural Convection and Entropy Generation in Γ-Shaped Enclosure Using Lattice...A Behzadmehr
This work presents a numerical analysis of entropy generation in Γ-Shaped enclosure that was submitted to the natural convection process using a simple thermal lattice Boltzmann method (TLBM) with the Boussinesq approximation. A 2D thermal lattice Boltzmann method with 9 velocities, D2Q9, is used to solve the thermal flow problem. The simulations are performed at a constant Prandtl number (Pr = 0.71) and Rayleigh numbers ranging from 103 to 106 at the macroscopic scale (Kn = 10-4). In every case, an appropriate value of the characteristic velocity is chosen using a simple model based on the kinetic theory. By considering the obtained dimensionless velocity and temperature values, the distributions of entropy generation due to heat transfer and fluid friction are determined. It is found that for an enclosure with high value of Rayleigh number (i.e., Ra=105), the total entropy generation due to fluid friction and total Nu number increases with decreasing the aspect ratio.
Numerical Analysis of Inlet Gas-Mixture Flow Rate Effects on Carbon Nanotube ...A Behzadmehr
The growth rate and uniformity of Carbon Nano Tubes (CNTs) based on Chemical Vapor Deposition (CVD)
technique is investigated by using a numerical model. In this reactor, inlet gas mixture, including xylene as
carbon source and mixture of argon and hydrogen as carrier gas enters into a horizontal CVD reactor at
atmospheric pressure. Based on the gas phase and surface reactions, released carbon atoms are grown as CNTs on the iron catalysts at the reactor hot walls. The effect of inlet gas-mixture flow rate, on CNTs growth rate and its uniformity is discussed. In addition the velocity and temperature profile and also species concentrations throughout the reactor are presented.
Preparation of γ-Al2O3 and Prioritization of Affecting Factors on the Crystal...A Behzadmehr
In this work, boehmite sol was prepared by a previously applied and validated method; hydrolysis of aluminum chloride hexa-hydrate. In order to obtain precise results, the effect of pH after adding precipitating agent, aging time, peptizing temperature and ultrasonic vibration time on the crystallite size of final precipitate were investigated in a narrow range. The preparation conditions applied in the production step of nanocrystalline boehmite affected on the desired alumina phase. Experiments were set based on the statistical design of experiments (Taguchi method). Furthermore the influence of calcination on crystallization and phase transformation of the precipitate was investigated using X-ray diffractometry (XRD) and simultaneous thermal analysis (STA) techniques. To evaluate the results, the obtained data were statistically analyzed. Considering the statisti cal analysis of experiments, the pH after adding precipitating agent is the major parameter affecting crystallite size. In contrast, aging time has the smallest effect on the crystallite size. In addition, Transmission electron microscopy (TEM) of the samples revealed that the particle size of the powders was well distributed in the nano-size range. Taguchi prediction on the crystallite size was 2.096±0.139 nm (with confidence interval of 95%) which confirmed by a verification experiment (2.064 nm).
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
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• Remote control system for accessing CCR and allied system over serial or TCP.
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Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
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Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...
Numerical Analysis of Inlet Gas-Mixture Flow Rate Effects on Carbon Nanotube Growth Rate
1. 26
Trans. Phenom. Nano Micro Scales, 1(1): 26-36, Winter - Spring 2013
DOI: 10.7508/tpnms.2013.01.003
ORIGINAL RESEARCH PAPER .
Numerical Study of Mixed Convection of Nanofluid in a Concentric
Annulus with Rotating Inner Cylinder
G. A. Sheikhzadeh 1
, H. Teimouri 1,*
, M. Mahmoodi 1, 2
1
Department of Mechanical Engineering, University of Kashan, Kashan, Iran
2
Department of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran
Abstract
In this work, the steady and laminar mixed convection of nanofluid in horizontal concentric annulus with
rotating inner cylinder is investigated numerically. The inner and outer cylinders are kept at constant
temperature Ti and To respectively, where Ti>To. The annular space is filled with Alumina-water nanofluid.
The governing equations with the corresponded boundary conditions in the polar coordinate are discretized
using the finite volume method where pressure-velocity coupling is done by the SIMPLER algorithm.
Numerical results have been obtained for Rayleigh number ranging from 102
to 105
, Reynolds number from 1
to 300 and nanoparticles volume fraction from 0.01 to 0.06. The effects of the Reynolds and Rayleigh numbers,
average diameter of nanoparticles and the volume fraction of the nanoparticles on the fluid flow and heat
transfer inside the annuli are investigated. According to the results, the average Nusselt number decreases with
increasing the Reynolds number. However, the average Nusselt number increases by increasing the Rayleigh
number. Moreover, the maximum average Nusselt number occurs for an optimal nanoparticle volume fraction
except situations that heat conduction predominates over the heat convection. In these conditions the average
Nusselt number is close to unity.
Keywords: Concentric Annulus;Mixed Convection; Nanofluid; Finite Volume Method; Rotating Inner Cylinder
1. Introduction
The problem of mixed convection in annulus
between two rotating cylinders is noteworthy because
of its wide applications. Some applications are
methods for improvement of crystal formation in
technological applications [1,2] food processing [3,
4], and journal bearing. The increase of generation of
heat in industrial devices with decrease of their size
increases need for higher heat transfer rate in
minimum space. In spite of all of the advances in
enhancement of heat transfer, the low thermal
__________
*
Corresponding author
Email Address: hamidtmr@gmail.com
conductivity of the traditional coolants is a great
limitation in this way. One of the methods for
increase the heat transfer is use of nanoparticles in
the base fluid. The existence of the nanoparticles
increases the viscosity which is an undesirable effect
and reduces the rate of heat transfer. Based on these
effects of nanoparticles, they can reduces or increases
the rate of heat transfer based on the geometry and
boundary conditions of the problem, type, size,
shape, and volume fraction of the nanoparticles.
Therefore when the nanofluid is used its effect on
heat transfer must be investigated firstly.
In continue some of works done on mixed
convection in annuluses with rotating inner cylinder
2. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
27
Nomenclature
p PressureሺN mିଶ
ሻ ߠ Angle
P Dimensionless pressure ߆ Dimensionless temperature
Pr Prandtl number ߤ Dynamic viscosity ሺܰ ݏ ݉ିଶ
ሻ
r Radial coordinateሺmሻ ߥ Kinematic viscosity (݉ଶ
sିଵ
ሻ
R Dimensionless radial distance ߩ Density ሺ݇݃ ݉ିଷ
ሻ
RR Radius ratio ߮ Nanoparticle volume fraction
ܴ′ Dimensionless position
୰ି୰
୰ି୰
߰ Stream function ሺ݉ଶ
sିଵ
ሻ
Ra Rayleigh number ߖ Dimensionless stream function
Re Reynolds number ߱ Angular velocityሺrad sିଵ
ሻ
T Temperature (Kሻ
u, v Velocity componentsሺm sିଵ
ሻ Subscripts
U, V Dimensionless velocity components eff. Effective
݂ Fluid
Greek symbols i Inner
α Thermal diffusivity ሺmଶ
sିଵ
ሻ ݂݊ Nanofluid
β Thermal expansion coefficient ሺKିଵ
ሻ o Outer
are reviewed. These works have been done for
rotating Reynolds number lower than 2000 which the
flow becomes two dimensional and laminar. As early
as 1992, Lee [5] studied numerically laminar natural
convection of air in eccentric annulus with rotating
inner cylinders. He observed that in a constant
Rayleigh number the average Nusselt number
decreases with increase in rotation velocity of inner
cylinder. Natural convection of nanofluids in a
concentric annulus was firstly studied numerically by
Abu-Nada et al. [6]. They used Brinkman [7] and
Hamilton-Crosser [8] models for viscosity and
thermal conductivity of the nanofluid, respectively.
They observed enhanced heat transfer using nanofluid
at low Rayleigh numbers. Abu-Nada [9,10]
investigated effects of different viscosity and thermal
conductivity models for nanofluid on natural
convection in concentric annuluses. Izadi et al. [11]
conducted a numerical study on developing laminar
forced convection of Al2O3-water nanofluid in an
annulus. They used Masoumi et al. [12] and Chon et
al. [13] correlations for prediction of viscosity and
thermal conductivity of the nanofluid, respectively.
Their results showed that, in general, convective
heat transfer coefficient increases with nanoparticle
concentration.
Base on the knowledge of the authors effect of
nanoparticles on flow pattern and mixed convection in
annulus between two concentric cylinders with
rotating inner cylinder has not been investigated in
literature. In the present work this problem is
investigated.
2. Problem definition
Figure 1 shows the geometry of present problem.
Inner cylinder with radius of ri and the outer cylinder
with radius of ro are kept at temperatures of Ti and To,
respectively. The inner warmer cylinder rotates with
the angular velocity of ω in counterclockwise
direction. The annulus has infinite length. The annulus
is filled with Al2O3-water nanofluid. According to ref.
[14] for the Reynolds number lower than 2000 that the
Taylor vortices are not formed the flow is two
dimensional. In the present problem the natural
convection is due to the temperature difference and
gravity, while the forced convection is due to the
rotation of inner cylinder. In the present work the
effects of nanoparticles with different average
diameters and volume fraction on the flow pattern and
heat transfer are investigated. Also the effects of
boundary conditions such as angular velocity of inner
cylinder (Reynolds number) and temperature
difference of two cylinders (Rayleigh number) are
considered.
3. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
28
Fig. 1. Geometry of the problem and the boundary
conditions
3. Mathematical modeling
The thermophysical properties of the nanofluid are
considered to be constant with the exception of
density in the buoyancy term in the momentum
equation which varies according to the Boussinesq
approximation. The nanoparticles are assumed to be
uniform in shape and size. Moreover, the base fluid
and the nanoparticles are assumed to be in thermal
equilibrium. There is not any slip between the water
and the nanoparticles. With the assumption of
Newtonian fluid, steady state and incompressible
flow, the governing equations in polar system
coordinates are as follows:
Continuity:
(1)
߲ݒ
߲ݎ
ݒ
ݎ
1
ݎ
߲ݑ
߲ߠ
ൌ 0
Momentum equation in r direction:
(2)
ߩ ቆݒ
߲ݒ
߲ݎ
ݑ
ݎ
߲ݒ
߲ߠ
െ
ݑଶ
ݎ
ቇ ൌ െ
߲
߲ݎ
ߤ ቆ
߲ଶ
ݒ
߲ݎଶ
1
ݎ
߲ݒ
߲ݎ
െ
ݒ
ݎଶ
1
ݎଶ
߲ଶ
ݒ
߲ߠଶ
െ
2
ݎଶ
߲ݑ
߲ߠ
൰ ݂
Momentum equation in θ direction:
(3)
ߩ ൬ݒ
߲ݑ
߲ݎ
ݑ
ݎ
߲ݑ
߲ߠ
ݒݑ
ݎ
൰
ൌ െ
1
ݎ
߲
߲ߠ
ߤ ቆ
߲ଶ
ݑ
߲ݎଶ
1
ݎ
߲ݑ
߲ݎ
െ
ݑ
ݎଶ
1
ݎଶ
߲ଶ
ݑ
߲ߠଶ
2
ݎଶ
߲ݒ
߲ߠ
൰ ݂ఏ
Energy equation:
(4)ݒ
߲ܶ
߲ݎ
ݑ
ݎ
߲ܶ
߲ߠ
ൌ ߙሺ
߲ଶ
ܶ
߲ݎଶ
1
ݎ
߲ܶ
߲ݎ
1
ݎଶ
߲ଶ
ܶ
߲ߠଶ
ሻ
Where u and v are velocity components in radial
and tangential direction, g is gravitational
acceleration, µ, ρ, β, and α are viscosity, density,
thermal expansion coefficient and thermal diffusivity
coefficient, respectively. fr and fθ are components of
volumetric forces in radial and tangential directions as
follows:
(5)
݂ ൌ ሺߩߚሻ݃ሺܶ െ ܶሻ ܿݏ ߠ
݂ఏ ൌ െሺߩߚሻ݃ሺܶ െ ܶሻ ݊݅ݏ ߠ
The boundary conditions are:
(6)
ݒ ൌ 0, ݑ ൌ ݎ߱, ܶ ൌ ܶ ܽݐ ݎ ൌ ݎ
ݒ ൌ 0, ݑ ൌ 0, ܶ ൌ ܶ ܽݐ ݎ ൌ ݎ
The following dimensionless parameters are
considered in the problem [15, 16]:
(7)
ܸ ൌ
ݒ
ݎ߱
߆ ൌ
ܶ െ ܶ
ܶ െ ܶ
ܴ ൌ
ݎ
݈
ܲ ൌ
ߩݎ
ଶ߱ଶ
ܷ ൌ
ݑ
ݎ߱
(8)ܧ ൌ
݁
݈
ߖ ൌ
߰
ݎ݈߱
where l is radius differences of inner and outer
cylinders and is equal to (ro – ri). With the above
parameters the governing equations are converted in
non-dimensional form:
Continuity:
(9)
߲ܸ
߲ܴ
ܸ
ܴ
1
ܴ
߲ܷ
߲ߠ
ൌ 0
ω
Ti
X
r0
r
ri
θ
g
To
Y
4. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
29
Momentum equation in r direction:
(10)
ܸ
߲ܸ
߲ܴ
ܷ
ܴ
߲ܸ
߲ߠ
െ
ܷଶ
ܴ
ൌ െ
ߩ
ߩ
߲ܲ
߲ܴ
ߥ
ߥ
1
ܴ݁
ቆ
߲ଶ
ܸ
߲ܴଶ
1
ܴ
߲ܸ
߲ܴ
െ
ܸ
ܴଶ
1
ܴଶ
߲ଶ
ܸ
߲ߠଶ
െ
2
ܴଶ
߲ܷ
߲ߠ
൰
ߚ
ߚ
ܴܽ
ܴܲ݁ݎଶ
߆ ܿݏ ߠ
Momentum equation in θ direction:
(11)
ܸ
߲ܷ
߲ܴ
ܷ
ܴ
߲ܷ
߲ߠ
ܷܸ
ܴ
ൌ െ
ߩ
ߩ
1
ܴ
߲ܲ
߲ߠ
ߥ
ߥ
1
ܴ݁
ቆ
߲ଶ
ܷ
߲ܴଶ
1
ܴ
߲ܷ
߲ܴ
െ
ܷ
ܴଶ
1
ܴଶ
߲ଶ
ܷ
߲ߠଶ
2
ܴଶ
߲ܸ
߲ߠ
൰
െ
ߚ
ߚ
ܴܽ
ܴܲ݁ݎଶ
߆ ݊݅ݏ ߠ
Energy equation:
(12)
ܸ
߲߆
߲ܴ
ܷ
ܴ
߲߆
߲ߠ
ൌ
ߙ
ߙ
1
ܴ݁ܲݎ
ቆ
߲ଶ
߆
߲ܴଶ
1
ܴ
߲߆
߲ܴ
1
ܴଶ
߲ଶ
߆
߲ߠଶ
൰
where Ra, Pr, and Re are Rayleigh, Prandtl, and
Reynolds number and are defined as follows:
(13)
ܴܽ ൌ
݃ߚሺܶ െ ܶሻ݈ଷ
ߙߥ
,
ܲݎ ൌ
ߥ
ߙ
, ܴ݁ ൌ
ݎ݈߱
ߥ
Also the boundary conditions in dimensionless
form are:
(14)
ܸ ൌ 0, ܷ ൌ 1, ߆ ൌ 1 ܽݐ ܴ ൌ ܴ
ܸ ൌ 0, ܷ ൌ 0, ߆ ൌ 0 ܽݐ ܴ ൌ ܴ
The density, heat capacity, and thermal expansion
coefficient of the nanofluid are:
(15)ߩ ൌ ൫1 െ ߮൯ߩ ߮ߩ
(16)ܿ ൌ
൫1 െ ߮൯ߩܿ ߮ߩܿ
ߩ
(17)ߚ ൌ
൫1 െ ߮൯ሺߩߚሻ ߮ሺߩߚሻ
ߩ
Viscosity and thermal conductivity of nanofluid is
calculated with the assumption of thermal equilibrium
between base fluid and nanoparticles and uniform
shape of the nanoparticles. The viscosity of Al2O3-
water nanofluid with average diameters of 13, 28, and
36 mm is calculated by [17-19]:
(18)
ߤ ൌ ൫1 39.11߮ 533.9߮
ଶ
൯ߤ
݀ ൌ 13 ݊݉.
(19)
ߤ ൌ ൫1 7.3߮ 123߮
ଶ
൯ߤ
݀ ൌ 28 ݊݉.
(20)
ߤ ൌ ൫1 0.025߮ 0.015߮
ଶ
൯ߤ
݀ ൌ 36 ݊݉.
In (20) ߮ is in percentage. Thermal conductivity
of Al2O3-water nanofluid is calculated according to
the model proposed by Khanafer and Vafai [20]:
(21)
ቆ
݇
݇
ቇ
మைయ
ൌ 0.9843
0.398߮
.ଷ଼ଷ
ቆ
1
݀ሺ݊݉ሻ
ቇ
.ଶଶସ
ቆ
ߤሺܶሻ
ߤሺܶሻ
ቇ
.ଶଷହ
െ3.9517
߮
ܶ
34.034
߮
ଶ
ܶଷ
32.509
߮
ܶଶ
0 ߮ 10%;
11݊݉ ݀ 150݊݉;
20°ܥ ܶ 70°ܥ
Where ߮ is in percentage, T is in Celsius, and dp
is in nm. The viscosity of water in different
temperatures is obtained by:
(22)ߤሺܶሻ ൌ 2.414 ൈ 10ିହ
ൈ 10
ଶସ.଼
ሺ்ିଵସሻൗ
Where T is in Kelvin. The thermophysical
properties of water and Al2O3 at 293 K are presented
in Table 1.
5. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
30
Table 1
Thermophysical properties of water and Al2O3
Pr
T
(K)
ρ
(kg/m3
)
cp
(J/kg
K)
k
(W/m
K)
β×105
(1/K)
7.07293998.241820.5921
Water
[21]
–29339707650.8525
Al2O3
[9]
The local Nusselt numbers on the inner and outer
cylinders are calculated by the following equations
[15, 22, 23]:
(23)
ܰݑ ൌ െݎ݈݊ ൬
ݎ
ݎ
൰
݇
݇
1
ܶ െ ܶ
߲ܶ
߲ݎ
ቤ
ୀ
(24)
ܰݑ ൌ െݎ݈݊ ൬
ݎ
ݎ
൰
݇
݇
1
ܶ െ ܶ
߲ܶ
߲ݎ
ቤ
ୀ
The average Nusselt number on the inner cylinder
is calculated by:
(25)ܰݑതതതത ൌ
1
2ߨ
න ܰݑሺߠሻ݀ߠ
ଶగ
Also the Nusselt number based on the
dimensionless parameters is:
(26)ܰݑ ൌ െܴ݈݊ ൬
ܴ
ܴ
൰
݇
݇
߲߆
߲ܴ
ቤ
ோୀோ
The streamfunction in polar coordinates is as
follows:
(27)ݒ ൌ
1
ݎ
߲߰
߲ߠ
, ݑ ൌ െ
߲߰
߲ݎ
4. Numerical implementation
The governing equations with the respective
boundary conditions are discretized using the finite
volume method. As shown in Fig. 2 a non-uniform
grid is generated, then the governing equations are
discretized on the grid points. The diffusion terms are
discretized using a central difference scheme, while a
hybrid scheme, which is a combination of central
difference and upwind schemes, is used to discretize
the convective terms. The velocity and pressure fields
are coupled according to the SIMPLER algorithm
based on a staggered grid. The set of algebraic
equations are solved iteratively using TDMA method.
Fig. 2. Non-uniform grid for the computational domain
Different grid sizes are examined to ensure grid
independence results. The tested grids and the
obtained average Nusselt numbers are shown in Table
2. The results are obtained for air with Pr = 0.7, Re =
257 and Ra = 105
. The outer cylinder to inner cylinder
diameter ratio is 2.6. Figure 3 shows variation of
tangential velocity at θ = 90 for different grid sizes.
According to the Fig. 3 and Table 2, an 81×41 grid is
sufficiently fine. It should be noted that 81 points are
in tangential direction while 41 grid points are in
radial direction.
Table 2
average Nusselt number for different grid sizes
41×2161×3181×41101×51
3.4873.5053.5143.518ܰݑതതതത
Fig. 3. variation of tangential velocity at θ = 90 for different
grid sizes
R'
U
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
41-21
61-31
81-41
101-51
6. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
31
For validation of the results, the obtained results in
the present study are compared with results of other
researchers. At the first step natural convection of air
in a cylindrical annulus with constant temperature
walls at Ra = 5×104
and diameter ratio of 2.6 is
considered. The obtained results are compared with
those of Kuehn and Goldstein [22] in Figs. 4 and 5.
Fig. 4. Comparison of the local Nusselt number for two
concentric cylinders obtained in the present study with
those of Kuehn and Goldstein [22]
Fig. 5. Comparison of the tangential velocity for two
concentric cylinders obtained in the present study with
those of Kuehn and Goldstein [22]
Another test case is mixed convection in
concentric annulus with rotating inner cylinder. The
results are compared with those of Char and Hsu [16]
and Lee [5] in Figs. 6 and 7. In Fig. 6 the Pr, Ra, and
Re are 0.7, 105
and 119, respectively. In Fig. 7 the Pr
and Ra are 0.7 and 105
respectively. As can be seen in
the figures a good agreement exists between the
results. The minor difference is due to difference in
used numerical techniques and accuracy of
discretization.
Fig. 6. Comparison of the local Nusselt number for two
concentric cylinders with rotating inner cylinder obtained in
the present study with those of Char and Hsu [16]
Fig. 7. Comparison of the average Nusselt number for two
concentric cylinders with rotating inner cylinder obtained in
the present study with those of Lee [5]
5. Results and discussions
5.1. Effect of Reynolds number on flow pattern and
temperature distribution
In this section effect of Reynolds number on fluid
flow and heat transfer of Al2O3-water nanofluid in the
annulus is considered. The diameter ratio of annulus is
2.6, the Rayleigh number is 104
, the average
temperature of the walls is 293 K and the volume
fraction of the nanoparticles is varying from 0 to 0.06.
The results are obtained for Re = 1, 25, 100, and 300.
Therefore the Richardson number which evaluate the
θ(deg)
Nu
0 20 40 60 80 100 120 140 160 180
0
1
2
3
4
5
6
7
8
9
10
11
Inner cylinder: present work
Outer cylinder: present work
Inner cylinder: experimental results of [22]
Outer cylinder: experimental results of [22]
R'
U
0 0.2 0.4 0.6 0.8 1
-100
-80
-60
-40
-20
0
20
40
60
80
100
0o
present work
90
o
present work
0
o
numerical results of [22]
90
o
numerical results of [22] θ=90o
θ=0ο
θ
Nu
-180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180
0
2
4
6
8
10
12
14
Inner cylinder: present work
Outer cylinder: present work
Inner cylinder; numerical results of [16]
Outer cylinder; numerical results of [16]
Re
0 50 100 150 200 250 300
3
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
E=0; present work
E=(0.667,π); present work
E=0; Numerical results of [5]
E=(0.667,π); Numerical results of [5]
ܰݑതതത
7. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
32
strength of natural convection compared to the forced
convection is Ri = 1414.42, 2.26, 0.14, and 0.016.
IsothermsStreamlines
Re=1Re=25Re=100Re=300
Fig. 8. Streamlines and isotherms at Ra = 104 and different
Reynolds numbers for nanofluid with ߮ = 0.06 (solid line)
and pure fluid (dashed line)
Figure 8 shows the streamlines and isotherms for
nanofluid and base fluid. As can be seen from the
streamlines at Re = 1 the rotation of the inner cylinder
has a minor effect and two vortices are formed in side
of the inner cylinder. These vortices are
approximately symmetric. The fluid is heated at the
vicinity of the inner cylinder and moves upward. Then
blocked by the upper region of the outer cylinder and
is cooled when moves downward along it. At this
conditions the Richardson number is equal to 1414.14
and the natural convection is dominated the heat
transfer. Also it is observed from Table 3 that the
maximum value of stream function decreases with
increase in ߮.
Table 3
Minimum and maximum values of stream function for
different values of Reynolds number
߮ ൌ 0߮ ൌ 0.06
Re
߰߰௫߰߰௫
-1.6331.891-1.1151.4141
00.22600.26625
00.34300.340100
00.35900.328300
With increase in the Reynolds number the right
and left hand side vortices increases and decreases in
size, respectively. Also the isotherms are condensed at
the vicinity of the inner cylinder. The thermal plume
is shifted to the left in the direction of rotation of the
cylinder. With further increase in the Reynolds
number the weak vortex formed by natural convection
effect disappears. At Re = 100 and 300 the heat
transfer occurs mainly through conduction and the
average Nusselt number is close to unity and therefore
the Nusselt number increases by increase in ߮. In
contrast with Re = 100 that for ߮ = 0.06 the
streamfunction has a little increase compared to the
base fluid, at Re = 300 for ߮ = 0.06 stream function
decreases compared to the base fluid.
The local Nusselt numbers along the inner and
outer cylinders at different Reynolds numbers are
presented in Fig. 9 and Fig. 10, respectively. At Re =
1 the Nusselt number is approximately symmetric.
Minimum heat transfer on the inner cylinder occurs on
the location of separation of the plume, while its
maximum value is on the lower portion of the
cylinder. A reverse Nusselt number distribution is
observed along the outer cylinder. With increase in Re
minimum value of Nusselt number shifts the left side
and variation of the Nusselt number decreases. At Re
= 100 and 300 that heat transfer occurs mainly
through conduction the Nusselt number is close to
unity.
0.1
0.9
0.2
0.6
1
1.4
-1
-0.6
-0.2
0.1
0.9
0.2
0.16
0.22
0.12
0.26
0.1
0.9
0.26
0.34
0
0.1
0.9
0.32
0
0.24
8. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
33
Fig. 9. Nusselt number distribution along the inner cylinder
for different Reynolds numbers
Fig. 10. Nusselt number distribution along the outer
cylinder for different Reynolds numbers
Figure 11 shows variations of average Nusselt
number with volume fraction of the nanoparticles at
different Reynolds numbers. It is observed that by
increase in Reynolds number the Nusselt number
decreases and reaches to unity. This behaviour is
according to the results of ref.[16]. At Re = 1 and 25
with increase in ߮ from 0 to 0.01 the Nusselt number
increases while with further increase in ߮ it
decreases. At Re = 100 and 300 with increase in ߮
the Nusselt number show an increasing trend.
5.2. Effect of Rayleigh number on fluid flow and
heat transfer in the annulus
In this section effects of variation of Rayleigh
number on fluid flow and heat transfer in the
concentric annulus are investigated. The results are
obtained for diameter ratio of 2.6, Re = 25 and
average temperature of 293 K. the Rayleigh number is
varying from 102
to 105
.
Fig. 11. Average Nusselt number versus ߮ at
Ra = 104
and different values of Re
The streamlines and isotherms are shown in Fig.
12. As can be seen from the figure at Ra = 102
and 103
there is no vortices in the annulus. At these Rayleigh
number the heat transfer occurs through conduction
and therefore the increase in ߮ motivates the Nusselt
number to increases. At Ra = 104
a thermal plume is
formed. By increase in Rayleigh number the plume
moves to the upper region of the outer cylinder and
the strength of the vortices increases. At Ra = 105
the
isotherms are condensed which is characteristics of
temperature gradient and motivates the Nusselt
number to increase. At this Rayleigh number the
existence of the nanoparticles reduces the strength of
the vortices.
In Fig. 13 the average Nusselt numbers versus the
volume fraction of the nanoparticles are illustrated. At
Ra = 102
and 103
, which is conduction dominated
regime, the Nusselt number is close to unity. At these
Rayleigh numbers with increase in ߮ an increasing
trend in Nusselt number is observed. At Ra = 104
a
significant increase in Nusselt number in comparison
with lower Rayleigh numbers is observed. It is
because of formation of thermal plume at this
Rayleigh number. At Ra = 104
and 105
the Nusselt
number increases with increase in ߮ from 0 to 0.01.
Further increase in ߮ motivates the Nusselt number
to decrease.
θ
Nu
0 50 100 150 200 250 300 350
0
0.5
1
1.5
2
2.5
3
3.5
4
Re=1
Re=25
Re=100
Re=300
Inner cylinder
θ
Nu
0 50 100 150 200 250 300 350
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Re=1
Re=25
Re=100
Re=300
Outer cylinder
ϕ
0 0.01 0.02 0.03 0.04 0.05 0.06
0.8
1
1.2
1.4
1.6
1.8
2
2.2
Re=1
Re=25
Re=100
Re=300
ܰݑതതത
9. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
34
IsothermsStreamlinesRa=102
Ra=103
Ra=104
Ra=105
Fig. 12. Streamlines and isotherms at Re = 25 and
different Rayleigh numbers for nanofluid with ߮ = 0.06
(solid line) and pure fluid (dashed line)
5.3. Effect of average diameter of nanoparticles
on the average Nusselt number:
The average diameter of the nanoparticles due to
their effect on effective viscosity and thermal
conductivity of the nanofluid has a great effect on
average Nusselt number. Figure 14 depicted average
Nusselt number versus volume fraction of the
nanoparticles for different values of nanoparticles
diameter at Re = 25 and Ra = 104
.
As can be seen from the figure the average Nusselt
number increases with increase in nanoparticles
diameter. For dp = 13 nm the increase in ߮motivates
the Nusselt number to decreases. The nanofluid with
dp=36 nm has the highest effect on heat transfer
enhancement.
Fig. 13. Average Nusselt numbers versus volume
fraction of the nanoparticles at Re = 25 and different
Rayleigh numbers
Fig. 14. Average Nusselt number versus volume
fraction of the nanoparticles for different values of
nanoparticles diameter at Re = 25 and Ra = 104
6. Conclusion
Mixed convection of Al2O3-water nanofluid in a
concentric cylindrical annulus with rotating inner
cylinder was investigated numerically. Effects of
some pertinent parameters such as Reynolds number,
Rayleigh number, volume fraction of the
nanoparticles, and average diameter of the
nanoparticles on fluid flow and heat transfer were
considered. The main findings of the paper are stated
below:
0.9
0.1
0.32
0.28
0.04
0.9
0.1
0.32
0.24
0.04
0.1
0.9
0.2
0.16
0.22
0.12
0.26
0.9
0.7
0.1
-0.04
0
0.04
0.08
0.12
0.16
0.2
0.24
ϕ
0 0.01 0.02 0.03 0.04 0.05 0.06
1
1.5
2
2.5
3
3.5
Ra=102
Ra=103
Ra=104
Ra=105
ϕ
0 0.01 0.02 0.03 0.04 0.05 0.06
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
dp=13 nm.
dp=28 nm.
dp=36 nm.
T=293 K
ܰݑതതത
ܰݑതതത
10. G.A. Sheikhzadeh et al./ TPNMS 1 (2013) 26-36
35
1- The increase in Reynolds number reduces the
Nusselt number. At high Reynolds numbers and low
Richardson numbers the heat transfer occurs mainly
through conduction and the Nusselt number closes to
unity.
2- At all Rayleigh numbers with increase in
Reynolds number the local Nusselt number decreases
and closes to unity.
3- At low Reynolds number and high Richardson
numbers, which is a convection dominated regime,
with increase in volume fraction of the nanoparticles
the Nusselt number firstly increases and then
decreases. Therefore an optimum value of ߮ exists in
which maximum heat transfer occurs. At high
Reynolds numbers and low Richardson numbers
(conduction dominated regime) with increase in
volume fraction of the nanoparticles the Nusselt
number increases.
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