458 results on '"ALI, J."'
Search Results
2. Flow and heat transfer of nanofluids in a cylindrical permeable wavy channel embedded in porous medium using Buongiorno's model.
- Author
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Dash, D. N., Arjun, K. S., Thatoi, D. N., Ali, Rifaqat, Nayak, M. K., and Chamkha, Ali J.
- Subjects
HEAT transfer ,THERMAL boundary layer ,NUSSELT number ,MASS transfer ,NANOFLUIDS ,BOUNDARY layer (Aerodynamics) ,POROUS materials - Abstract
This investigation deals with the flow of Al
2 O3 –water nanofluid in a wavy porous channel embedded in porous rocks. Fluid exchange takes place uniformly between porous rocks and the wavy channel. In this analysis, cylindrical and parallel plate wavy porous channels are considered. Consequences of Brownian motion and thermophoresis on the flow inside a wavy porous channel are elucidated. The modeled equations are made dimensionless by using dimensionless quantities. Impacts of flow parameters on the velocity, temperature, Nusselt number and friction factor are depicted through graphs. The numerical results with respect to parallel plate wavy porous channel are validated by comparing with the published results. The effectiveness of the cylindrical wavy porous channel as a heat transfer enhancement device in comparison to the parallel plate wavy porous channel is confirmed in this study. Designing devices at microlevels and understanding the heat transfer enhancement mechanism in wavy channels using the nanoparticle addition are the major outcomes from the results of this numerical investigation. The heat and mass transfer rate enhancements in the wavy porous channels are due to the higher Brownian motion in the boundary layer region and accelerated thermophoresis through thermal and concentration boundary layer thicknesses. [ABSTRACT FROM AUTHOR]- Published
- 2024
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3. Effect of entropy minimization and melting heat on gold-magnesium oxide hybrid nanofluid in squeezing channel with magnetic field with radiation.
- Author
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Gangadhar, Kotha, Victoria, E. Mary, and Chamkha, Ali J.
- Subjects
NANOFLUIDS ,ENTROPY ,THERMAL boundary layer ,HEAT radiation & absorption ,MAGNETIC entropy ,MAGNETIC fields ,NUSSELT number ,HEAT transfer - Abstract
The principal aim of this investigation is to examine the gold and magnesium oxide hybrid nanoparticles in different physical capacities on the water-based hybrid nanofluid and elaborate on an erratic squeezing flow among both infinite plates. Melting effect and thermal radiation depict heat transfer features. Production of the Bejan number and entropy is upward. The explains the governing equations, and the standard transformation is supplied. The numerical solutions are carried out using an efficient finite element method. To analyze difference between heat transfer and its implication in industrial zone, the Nusselt number was arranged in a horizontal pattern. The results showed that a thicker thermal boundary layer increased the Eckert number and the volume fraction of gold nanoparticles. Anyhow, the heat transfer rate by Au–MgO/water was necessarily greater than the Au–water. The obtained results are excellent and vigorously oppose those that are applicable to the literature by the attached position. It was established for hybrid nanofluids to display higher entropy generation rates. The outcomes of this analysis were the consequence of the appraisal of the impact on few required form parameters in heat transfer and consequently on the expansion for industrial use. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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4. Two-phase modeling of nanofluid forced convection in different arrangements of elliptical tube banks
- Author
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Mousavi, Seyed Mohammad, Akbari, Omid Ali, Sheikhzadeh, Ghanbarali, Marzban, Ali, Toghraie, Davood, and Chamkha, Ali J.
- Published
- 2020
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5. Fluid Flow and Heat Transfer over Staggered ꞌ+ꞌ Shaped Obstacles
- Author
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Younes Menni, Ali J. Chamkha, and Ahmed Azzi
- Subjects
heat exchange ,friction ,fluid flow ,complex obstacle ,reynolds number ,nusselt number ,Mechanics of engineering. Applied mechanics ,TA349-359 - Abstract
The inclusion of complex obstacles within solar channels is the aim of this article. Two obstacles of the form ꞌ+ꞌ interlaced within a two-dimensional and rectangular channel are the subject of our study. The fluid is Newtonian, turbulent, incompressible and has constant properties. The Reynolds number varies from 12,000 to 32,000 with a constant temperature along the upper surface of the channel. The thermal and dynamic analysis of the channel's internal structure has been carefully processed. Different fields of speed and heat, with various profiles of frictions and heat exchange coefficients, have been included in this research. Future work will involve more complex geometries and using nanofluids to assess the optimum conditions for heat transfer enhancements.
- Published
- 2020
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6. Thermo-magneto-hydrodynamical effects on merging flow of TiO2–water nanofluid
- Author
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Siddiqui, Abuzar Abid and Chamkha, Ali J.
- Published
- 2020
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7. The optimum double diffusive natural convection heat transfer in H-Shaped cavity with a baffle inside and a corrugated wall
- Author
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Soroush Eshaghi, Farhad Izadpanah, A. Sattar Dogonchi, Ali J. Chamkha, Mohamed Bechir Ben Hamida, and Hesham Alhumade
- Subjects
Double diffusive hybrid nanofluid natural convection ,H-shaped cavity ,Nusselt number ,Sherwood number ,Corrugated wall ,Baffle ,Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
Double diffusive natural convection (DDNC) is caused by temperature and concentration gradients in buoyancy-driven flows which is applicable in printing, HVAC, and solar collectors. A numerical study is accomplished to investigate DDNC of a hybrid Cu–Al2O3-water nanoliquid inside an H-shaped cavity with a baffle at the top wall. The Finite Element technique and Boussinesq approximation with no slip wall condition are applied to solve the governing equations. The left and right walls are at the cold temperature, while the inner up and down ribs and baffle are at constant heat flux, and other walls are insulated. The effect of Rayleigh number (104-106), Lewis number (2–8), and Buoyancy ratio (1–3) on Nusselt, Sherwood numbers, and entropy generation is investigated. Besides, the effects of baffle inclination angle (−60°to 60°) and also the aspect ratio of the corrugated bottom rib (0.375, 0.75, 1.5) on the mean Sherwood and Nusselt numbers are investigated to find the optimum geometry with the highest heat transfer performance. The results depict that the geometry with baffle angle −60°and with no corrugation has the best Nuavg; however, the geometry with baffle angle +60° and with no corrugation has the best Shavg.
- Published
- 2021
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8. Natural convection and entropy generation of a nanoliquid in a crown wavy cavity: Effect of thermo-physical parameters and cavity shape
- Author
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A. Sattar Dogonchi, M.S. Sadeghi, M. Ghodrat, Ali J. Chamkha, Yasser Elmasry, and Radi Alsulami
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Nusselt number ,Entropy generation ,Rayleigh number ,Natural convection ,Radiation ,Crown cavity ,Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
Natural convection (NC) of nanoliquids specifically in enclosures is of use in diverse fields such as solar collectors, HVAC, and medical treatment. Recent research shows that suspension of nano-materials within the base fluid enhanced the heat transfer performance. NC heat transfer of Al2O3–H2O nanoliquid within a crown cavity with a circular cylinder inside it is studied in this paper. The flow is considered buoyancy-driven which is under thermal radiation (Rd) and constant magnetic field within the porous media. Dimensionless modes of Navier-Stokes equations are considered as governing equations, and FEM is used to discrete the equations. Two scenarios are considered in the present paper. In the first scenario, the effect of parameters namely; Rayleigh number (103-105), Darcy number (0.001–0.1), Hartmann number (0–20), Radiation parameter (0.1–0.3), angle of magnetic field (0∘−90∘), and nanoparticle concentration (0.01–0.04) on heat transfer performance and entropy generation (Sgen) is studied. In the second scenario, the effect of geometry on Nusselt number (Nu) and Sgen is investigated. Da, Rd, and nanoparticle concentration have a positive impact on Nuavg and enhance heat transfer. Besides, the geometry with the best heat transfer performance is the one with the base wavy wall and the cylinder at the left side.
- Published
- 2021
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9. Comparative Numerical Analysis of Heat and Mass Transfer Characteristics in Sisko Al2O3-Eg and TiO2-Eg Fluids on a Stretched Surface.
- Author
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Jyothi, K., Dasore, Abhishek, Ganapati, R., Shareef, Sk. Mohammad, Chamkha, Ali J., and Prasad, V. Raghavendra
- Subjects
MAGNETOHYDRODYNAMICS ,HEAT transfer ,FINITE element method ,VELOCITY distribution (Statistical mechanics) ,MATHEMATICAL models of velocity distribution - Abstract
In the current research, a thorough examination unfolds concerning the attributes of magnetohydrodynamic (MHD) boundary layer flow and heat transfer inherent to nanoliquids derived from Sisko Al
2 O3 -Eg and TiO2 - Eg compositions. Such nanoliquids are subjected to an extending surface. Consideration is duly given to slip boundary conditions, as well as the effects stemming from variable viscosity and variable thermal conductivity. The analytical approach applied involves the application of suitable similarity transformations. These conversions serve to transform the initial set of complex nonlinear partial differential equations into a more manageable assembly of ordinary differential equations. Through the utilization of the FEM, these reformulated equations are solved, considering the specified boundary conditions. The outcomes attained are graphically depicted by means of plots and tables. These visual aids facilitate a comprehensive exploration of how diverse parameters exert influence over the distributions of velocity, temperature, and concentration. Furthermore, detailed scrutiny is directed towards the fluctuations characterizing pivotal parameters, viz., Nusselt number, skin-friction coefficient, and Sherwood number. It is identified that the Nusselt number showcases a diminishing trend coinciding with increasing values of the volume fraction parameter (φ). This trend remains consistent regardless of whether the nanoliquid under consideration is Al2 O3 -Eg or TiO2 -Eg based. In contrast, both the skin-friction coefficient and Sherwood number assume lower values as the volume fraction parameter (φ) escalates. This pattern remains congruent across both classifications of nanoliquids. The findings of the study impart valuable insights into the complex interplay governing the characteristics of HMT pertaining to Sisko Al2 O3 -Eg and TiO2 -Eg nanoliquids along an extending surface. [ABSTRACT FROM AUTHOR]- Published
- 2024
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10. Viscous Dissipation Impact on Free Convection Flow of Cu-water Nanofluid in a Circular Enclosure with Porosity Considering Internal Heat Source
- Author
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Abdul Sattar Dogonchi, Ali J. Chamkha, Seyyed Masoud Seyyedi, Mehdi Hashemi-Tilehnoee, and Davood Domiri Ganji
- Subjects
Free convection of nanofluid ,Porous circular enclosure ,Viscous dissipation ,CVFEM ,Nusselt number ,Mechanics of engineering. Applied mechanics ,TA349-359 - Abstract
In this work, free convection of Cu-water nanofluid in an enclosure by considering internally heat generated in the porous circular cavity and the impacts of viscous dissipation are numerically evaluated by control volume finite element method (CVFEM). The outer and inner sides of the circular porous enclosure are maintained at a fixed temperature while insulating the other two walls. The impacts of diverse effective parameters including the Rayleigh number, viscous dissipation, and nanofluid concentration on features of heat transfer and fluid flow are examined. Moreover, a new correlation for the average Nusselt number is developed according to the study’s active parameters. It can be deduced by the results that the maximum value of the temperature is proportional to the viscous dissipation parameter.
- Published
- 2019
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11. Numerical analysis of natural convection of Cu–water nanofluid filling triangular cavity with semicircular bottom wall
- Author
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Dogonchi, A. S., Ismael, Muneer A., Chamkha, Ali J., and Ganji, D. D.
- Published
- 2019
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12. Effects of baffles and vortex generators on cooling performance of a gas turbine combustion chamber: Numerical assessment
- Author
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Ali J. Chamkha, Hamed Arjmandi, Reza Amini, Hamid Rahmani, and Ali Ghaffari
- Subjects
Materials science ,Turbulence ,General Engineering ,Reynolds number ,Baffle ,Mechanics ,Vortex generator ,Computational fluid dynamics ,Performance evaluation criteria ,Engineering (General). Civil engineering (General) ,Nusselt number ,Vortex ,Physics::Fluid Dynamics ,symbols.namesake ,Gas turbine cooling methods ,symbols ,Hydraulic diameter ,Baffles and vortex generators ,Combustion chamber ,TA1-2040 - Abstract
In this work, the effect of using baffles and vortex generators on the cooling performance of a gas turbine combustion chamber is numerically investigated. The RNG k-ɛ model is utilized in order to simulate the flow turbulence. The effects of baffles and vortex generator pitch, hydraulic diameter and bypass ratio on the Nusselt number and friction coefficient at different Reynolds number are studied. The cooling performance of applying baffles and vortex generators are also evaluated and compared based on the Performance Evaluation Criterion (PEC). The numerical results are verified with available experimental data. The results show that the pitch increment results in the decrement of the Nusselt number and the wall friction coefficient due to the lower vortices generation and the turbulence kinetic energy dissipation. Also, the Nusselt number is increased by increasing both the bypass ratio and the hydraulic diameter. It is also found that vortex generators and baffles improve the cooling performance of the gas turbine combustion chamber by 18.8% and 26% respectively through decreasing the external wall temperature.
- Published
- 2022
13. Numerical and statistical explorations on the dynamics of water conveying Cu-Al2O3 hybrid nanofluid flow over an exponentially stretchable sheet with Navier's partial slip and thermal jump conditions
- Author
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Rohit Sharma, Ali J. Chamkha, and S. M. Hussain
- Subjects
Physics::Fluid Dynamics ,Nonlinear system ,Nanofluid ,Partial differential equation ,Materials science ,Flow (mathematics) ,Parasitic drag ,Thermal radiation ,Heat transfer ,General Physics and Astronomy ,Mechanics ,Nusselt number - Abstract
This research study aims to illustrate the dynamics of water conveying hybrid nanofluid flow over an exponentially stretchable sheet in the presence of Navier's partial slip and thermal jump conditions. The nanoparticles of Cu, TiO2 and Al2O3 are suspended into water (H2O) to prepare three forms of hybrid nanofluids. Also, the influences of Joule dissipation and thermal radiation are considered in the study. The mathematical model embodies the system of highly coupled nonlinear partial differential equations. The set of similarity equations are derived from these partial differential equations by utilizing appropriate similarity variables. Further, these similarity equations together with allied conditions are numerically solved by making use of a finite difference scheme based Lobatto IIIa-bvp4c solver in MATLAB. The significance of emerging dimensionless flow parameters on the water conveying Cu-Al2O3 hybrid nanofluid temperature and velocity are quantified by depicting various graphs. Besides, temperature and velocity profiles are compared for three different water-driven hybrid nanofluids comprising a colloidal mixture of Cu-Al2O3, TiO2-Al2O3 and Cu-TiO2 nanoparticles respectively. The local Nusselt numbers and wall velocity gradients are obtained in numerical form for various emerging physical parameters. Also, to comprehend the linking between heat transfer rate and emergent flow parameters, a statistical method is executed for the investigation of regression (quadratic) approximation on the skin friction coefficients and Nusselt numbers. Finally, the computed numerical results are compared with earlier reported paper and excellent conformity is noticed. The findings infer that the heat transport rate can be improved by the inspirations of suction and thermal radiation while viscous dissipation, magnetic field, injection and thermal slip factor are significant to reduce the heat transport rate of hybrid nanofluid
- Published
- 2022
14. Impacts of uniform and sinusoidal heating in a nanofluid saturated porous chamber influenced by the thermal radiation and the magnetic field.
- Author
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Muthukumar, S., Sureshkumar, S., El-Sapa, Shreen, and Chamkha, Ali J.
- Subjects
HEAT radiation & absorption ,FREE convection ,NUSSELT number ,FINITE volume method ,MAGNETIC fields ,HEATING - Abstract
A numerical investigation on the impacts of heater length increased from left corner along with the bottom wall in a Cu-water nanofluid-filled porous cavity in the existence of MHD and thermal radiation is performed out. The bottom wall is heated with two different types of heater (both uniform and nonuniform) separately. Three various lengths of heater are considered. Constant cold upper horizontal wall moves in the positive direction. The other sidewalls and excluding the heating portion of the bottom wall are considered to be adiabatic. The system of dimensionless form of governing equations is solved by finite volume method (FVM) with appropriate boundary and initial conditions and SIMPLE algorithm has been employed for the pressure term. For both types of heating, the highest heat transfer is attained with the length of heater L H = 1 / 4 for all taken Richardson number. The effect of magnetic field is very low on heat transfer with the thermal source length L H = 1 / 2 and nonuniform heating in free convection regime. On increasing the heater length in nonuniform heating, overall heat transfer rate is decreased first and then raised. The percentage of increasing of average Nusselt number with an increase of thermal radiation parameter in nonuniform heating is higher than uniform heating. The effect of magnetic field is significant for all taken solid volume fraction in uniform heating than the nonuniform heating with heater length L H = 1 / 2. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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15. Numerical study of heat transfer between hot moving material and ambient medium using various hybrid nanofluids under MHD radiative-convection, viscous dissipation effects, and time-fractional condition.
- Author
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Doley, Swapnali, Alagarsamy, Vanav Kumar, Chamkha, Ali J., Lawrence, Jino, and Jacob, Ashwin
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HEAT transfer ,MAGNETOHYDRODYNAMICS ,HEAT transfer fluids ,FLUID friction ,NUSSELT number ,NANOFLUIDS ,HOT rolling - Abstract
The heat transfer between ambient medium and moving material can be examined by the fluid flow past an impulsively started vertical plate (ISVP). In manufacturing processes such as wire/fiber drawing, hot rolling, continuous casting, and hot extrusion can be related to the hot moving material and heat transfer to the ambient medium. Also, a similar type of study addresses the understanding of aerospace engineering applications. This present study considers a mathematical model which describes the hybrid nanofluid past the ISVP by considering the transient term as a fractional derivative. The fractional order of flow governing equations is derived to enhance the heat transfer predictions with real-world problems by considering viscous dissipation, applied magnetic field, and radiation effects. Such a mathematical model is discretized by a finite difference technique and solved by a computational algorithm using FORTRAN. The findings of the study are illustrated using the velocity and temperature profiles. Also, the heat transfer and fluid friction against the boundary are interpreted using the Nusselt number and skin-friction coefficient, respectively. The results are examined under the variation of dimensionless parameters such as Eckert number, time-fractional order, Grashof number, the fraction of nanoparticles, suction, magnetic, and radiation parameters. It is observed that the heat transfer and fluid flows are affected by changing the time-fractional order. Also, a transition in the distribution of velocity and temperature is detected with varying time-fractional order. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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16. Flow of aqueous Fe2O3–CuO hybrid nanofluid over a permeable stretching/shrinking wedge: A development on Falkner–Skan problem
- Author
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Ali J. Chamkha, Mohammad Izady, Ioan Pop, and Saeed Dinarvand
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Physics::Fluid Dynamics ,Boundary layer ,Partial differential equation ,Materials science ,Nanofluid ,Ordinary differential equation ,Numerical analysis ,General Physics and Astronomy ,Mechanics ,Boundary layer thickness ,Wedge (geometry) ,Nusselt number - Abstract
Here, continuous two-dimensional boundary layer flow of a Fe2O3 CuO/water hybrid nanofluid over a porous stretching/shrinking wedge with radiation and MHD effects has been investigated semi–analytically. The dual solutions of the problem and also its stability analysis are taken into account. Moreover, the mass-based procedure for hybrid nanofluid modeling has been used. According to this procedure, the volume fraction of first and second nanoparticles is written in terms of both nanoparticles as well as base fluid masses. The Tiwari-Das model joined with mass-based hybrid nanofluid procedure is applied to find the governing partial differential equations which are then transferred to a set of dimensionless ordinary differential equations with help of the similarity transform method. The numerical method of solution has been chosen based on a famous finite difference scheme (bvp4c) from MATLAB software. The results demonstrate that dual solutions exist for a certain domain of the wedge stretching/shrinking parameter. Also it is observed that always the first solutions have thinner boundary layer thickness than the second ones. Moreover, the critical value in which the solution is in existence increase with the enhancement of magnetic parameter and suction parameter. The magnetic parameter and the mass suction at the wedge's surface also leads to the increase in the local Nusselt number. Further, it is inferred that the second nanoparticle's mass enhancement results in the amplification of the skin friction coefficient and the local Nusselt number for the first solutions. In addition, the rise in radiation parameter tends to enhance the thermal boundary layer thickness.
- Published
- 2021
17. Dissection of entropy production for the free convection of NEPCMs-filled porous wavy enclosure subject to volumetric heat source/sink
- Author
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A. Sattar Dogonchi, Hani Abulkhair, Ali J. Chamkha, Satyaranjan Mishra, Nader Karimi, and S.R. Afshar
- Subjects
Physics::Fluid Dynamics ,Materials science ,Nanofluid ,Natural convection ,Thermal conductivity ,Convective heat transfer ,Heat flux ,Entropy production ,General Chemical Engineering ,General Chemistry ,Rayleigh number ,Mechanics ,Nusselt number - Abstract
Background The exploration of natural convection which is one the substantial types of convective heat transmission in various applications for instance heat exchangers and geothermal systems along with nanofluids (Nanofluids have greater thermal conductivity in comparison to the conventional fluids) engrossed all researchers’ attention. Methods This study is dedicated to the inspection of the free convection of nanofluid as well as entropy generation inside a porous cavity loaded with nano-encapsulated phase change materials (NEPCMs). The wavy bottom section of the enclosure may be subject to a constant heat flux due to the transmitted sunlight comes from a parabolic trough solar collector. The volumetric heat source/sink is comprised in the governing equation. The robust finite element method (FEM) is deployed to handle the transformed governing equations. Findings The numerical simulation of the streamlines and isotherms associated with velocity distribution for diverse factors are displayed. Further, the significant behavior of the contributing parameters on the Nusselt and Bejan numbers are represented. The results demonstrate that the various profiles of wavy bottom section could affect the heat transmission features as well as fluid flow remarkably. Furthermore, it is noteworthy that all the profiles of entropy enhance with increasing the amplitude with respect to the increasing undulation number for the existence of various Rayleigh number.
- Published
- 2021
18. Thermal entropy generation and exergy efficiency analyses of coiled wire inserted nanodiamond + Fe3O4/water hybrid nanofluid in a tube
- Author
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L. Syam Sundar, Solomon Mesfin, Antonio C.M. Sousa, V. Punnaiah, Ali J. Chamkha, and E. Venkata Raman
- Subjects
Pressure drop ,Materials science ,Turbulence ,Reynolds number ,Heat transfer coefficient ,Condensed Matter Physics ,Nusselt number ,symbols.namesake ,Nanofluid ,Heat flux ,symbols ,Exergy efficiency ,Physical and Theoretical Chemistry ,Composite material - Abstract
Exergy efficiency, Nusselt number, friction factor, pressure drop, thermal and frictional entropy generation of water-based nanodiamond + Fe3O4 nanofluid flow in a tube and with various coiled wire inserts have been studied experimentally under turbulent and constant heat flux boundary conditions. The experiments were conducted in the Reynolds number range from 2000 to 22,000, particle concentrations of 0.05%, 0.1% and 0.2% and coiled wire inserts of different $$p/d$$ values of 3.67, 2.34 and 1.00, respectively. Results indicate that at 0.2% vol. and Reynolds number of 20,095, without coiled wire inserts, the heat transfer coefficient, Nusselt number, friction factor, pressure drop and pumping power are enhanced to 44.36%, 29.55%, 11.1%, 29.58% and 39.49% over the base fluid data. Similarly, at 0.2% vol. and Reynolds number of 20,095, with coiled wire inserts of $$p/d$$ = 1, the heat transfer coefficient, Nusselt number, friction factor, pressure drop and pumping power are further enhanced to 107.19%, 66.36%, 38.84, 64.44% and 76.54% over the base fluid data without inserts. The thermal entropy generation is decreased to 30.80% and it is further decreased to 46.34% at 0.2% vol. and Reynolds number of 20,095 with coiled wire inserts of $$p/d$$ = 1. The exergy efficiency of water is 18.95%, and it is increased to 24.06% for 0.2% vol. and it is further increased to 51.85% for 0.2% vol. and Reynolds number of 20,095 with coiled wire inserts of $$p/d$$ = 1. The study indicates that the hybrid nanofluids with coiled wire inserts are guaranteed choice for augmenting the exergy efficiency of flow through tube.
- Published
- 2021
19. Non-Newtonian phase change study of nano-enhanced n-octadecane comprising mesoporous silica in a porous medium
- Author
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Obai Younis, Hani Abulkhair, Seyed Mohsen Hashem Zadeh, Mohammad Vaezi, Nima Sedaghatizadeh, Ali J. Chamkha, S.A.M. Mehryan, and Mohammad Ghalambaz
- Subjects
Materials science ,Applied Mathematics ,Thermal resistance ,02 engineering and technology ,Metal foam ,01 natural sciences ,Nusselt number ,Non-Newtonian fluid ,symbols.namesake ,020303 mechanical engineering & transports ,Fourier number ,0203 mechanical engineering ,Modeling and Simulation ,0103 physical sciences ,Heat transfer ,symbols ,Composite material ,Porous medium ,Porosity ,010301 acoustics - Abstract
Poor thermal conductivity of phase change materials (PCMs) is the principal barrier to their widespread application. As such, numerous single or hybrid techniques have been proposed to lower the thermal resistance of PCMs. In the present paper, a hybrid approach, including the dispersing of nano-sized particles and embedding in a porous medium, was employed to augment the rate of heat transfer and melting process of the resulting nano-enhanced PCM (NePCM). Aluminum foam was used as the solid matrix, and phase-change heat transfer of a NePCM comprising n-octadecane as the phase change substance and nano-sized particles of mesoporous silica (MPSiO2) was studied. Previous experimental studies have shown that, although n-octadecane behaves as a Newtonian fluid, the mentioned NePCM behavior deviates from that of Newtonian fluids. Hence, the thermal and hydrodynamic behaviors of the non-Newtonian suspension of the NePCM in porous media were investigated numerically. Governing equations, including mass and momentum conservation for the liquid NePCM and energy equations for both solid and liquid phases, were solved using the Galerkin finite element method. The deformed mesh technique was employed to address the movement of the melting front. The finite element code was validated against several experimental and numerical works and was sufficiently accurate. Results showed that owing to the alteration of the rheological and thermophysical characteristics of the NePCM, increasing concentration of nanoparticles reduced the average Nusselt number and the normalized melt volume fraction (NMVF). It was also found that porosity played an important role in the phase-change rate. Although the steady-state condition was achieved faster in the case of lowest porosity, the maximum NMVF was achieved in the case of the highest porosity after Fourier number = 0.02.
- Published
- 2021
20. Transient nanofluid flow and energy dissipation from wavy surface using magnetic field and two rotating cylinders
- Author
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Ammar I. Alsabery, Engin Gedik, Ishak Hashim, Ali J. Chamkha, and Muneer A. Ismael
- Subjects
Convection ,Rotational speed ,Mechanics ,Dissipation ,Hartmann number ,Nusselt number ,Physics::Fluid Dynamics ,Computational Mathematics ,Nanofluid ,Computational Theory and Mathematics ,Modeling and Simulation ,Heat transfer ,Magnetohydrodynamic drive ,Mathematics - Abstract
The problem of transient Magnetohydrodynamic (MHD) combined convection within a wavy-heated rectangular cavity having two inner cylinders is investigated using the non-homogeneous nanofluid scheme. The lower wavy surface of the cavity is kept at a constant hot temperature ( T h ) while the upper flat surface is kept at a constant cold temperature ( T c ). The remaining surfaces (vertical surfaces) are maintained adiabatic. An Al 2 O 3 /water nanofluid is filled inside the cavity and a non-homogeneous approach is adopted to solve governing equations by using the Galerkin method. The effect of some parameters such as the angular rotational speed, the volume fraction of nanoparticles, Hartmann number on the flow and heat transfer characteristics are examined. The results indicate that the waving of the hot base of the cavity enhances the Nusselt number. The maximal Nusselt numbers are obtained when the number of undulations N is 2, where the Nusselt number augments by 18% when N is boosted from 0 to 2 and by 16% from 0 to and 5. Also, the outcomes reveal that the enhancement of the Nusselt number as a result of raising the rotational speed of the two cylinders from 0 to ± 500 is about 315%.
- Published
- 2021
21. Radiation absorption on MHD convective flow of nanofluids through vertically travelling absorbent plate
- Author
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M. Veera Krishna, N. Ameer Ahamad, and Ali J. Chamkha
- Subjects
Materials science ,020209 energy ,020208 electrical & electronic engineering ,Flow (psychology) ,Porous media ,General Engineering ,02 engineering and technology ,Mechanics ,Nanofluid ,Engineering (General). Civil engineering (General) ,Nusselt number ,Physics::Fluid Dynamics ,Radiation-absorption ,Boundary layer ,Thermal radiation ,MHD flows ,Vertical plate ,0202 electrical engineering, electronic engineering, information engineering ,Shear stress ,TA1-2040 ,Magnetohydrodynamics ,Absorption (electromagnetic radiation) - Abstract
An exploration of the unsteady MHD boundary layer flow over a moving vertical porous surface with nanofluids under the influence of a uniform transverse magnetic field and heat radiation absorption effects has been brought out. Two different kinds of water-based nanofluids comprising of Al2O3 and TiO2 are adopted into deliberation. The governing equations for the flow are solved by making use of the Laplace transform method, and the solutions are displayed in closed form. The velocity, temperature, concentration, the shear stress, the rate of heat and mass transportations near the surface has been described graphically for numerous values of the relevant parameters. The velocity and temperature enhances with increasing radiation absorption parameter. It is also observed that an increase of volume fraction of nanoparticles leads to the enhancement of the temperature on central line of the flow. Nusselt number might be tracked down to be elevated for alumina than titanium dioxide nanofluid. The present investigation originated applications in aerospace engineering as well as industrial many mechanisms.
- Published
- 2021
22. Natural convection of CuO-water nanofluid in a conventional oil/water separator cavity: Application to combined-cycle power plants
- Author
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Nader Karimi, Hesham Alhumade, Mohamad Sadegh Sadeghi, Ali J. Chamkha, Maryam Ghodrat, and Abdul Sattar Dogonchi
- Subjects
Materials science ,Natural convection ,Fin ,General Chemical Engineering ,Darcy number ,02 engineering and technology ,General Chemistry ,Mechanics ,Rayleigh number ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Hartmann number ,01 natural sciences ,Nusselt number ,0104 chemical sciences ,Physics::Fluid Dynamics ,Nanofluid ,Heat transfer ,0210 nano-technology - Abstract
The oily water from various sources in combined cycle power plants is collected in oil/water separator in which the oil separates from water due to the density difference. The idea of the presented geometry is taken from conventional oil/water separators. This paper studies the natural convection of the CuO-water nanoliquid in a rectangular cavity with fins attached to the insulated wall and porous media. Discretion of Navier-Stokes equations is done by Finite Element Method and assumptions are laminar, steady and incompressible flow. Heat transfer performance and entropy generation are investigated for distinct Rayleigh numbers (103–105), Darcy numbers (10−2–10−4), and Hartmann numbers (0, 10, 20). Different sizes of the fins are also studied to show consequences of fin size on heat transfer in cavity. This is the first time that these parameters and their impacts on Nusselt number and entropy generation are studied for a conventional oil/water separator cavity. Corollaries demonstrate that increasing Rayleigh number and Darcy number improves heat transfer performance and average Nusselt number. Nevertheless, Hartmann number has a reverse effect with average Nusselt number. Finally, a new equation for average Nusselt number is developed with regard to Rayleigh number, Hartmann number, and Darcy number.
- Published
- 2021
23. Interaction of fusion temperature on the magnetic free convection of nano-encapsulated phase change materials within two rectangular fins-equipped porous enclosure
- Author
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Satyaranjan Mishra, Nader Karimi, Hesham Alhumade, A. Sattar Dogonchi, and Ali J. Chamkha
- Subjects
Materials science ,Natural convection ,General Chemical Engineering ,Enclosure ,02 engineering and technology ,General Chemistry ,Rayleigh number ,Mechanics ,Heat transfer coefficient ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Hartmann number ,01 natural sciences ,Bejan number ,Nusselt number ,0104 chemical sciences ,Physics::Fluid Dynamics ,Streamlines, streaklines, and pathlines ,0210 nano-technology - Abstract
The present study encountered the impact of non-dimensional fusion temperature on the free convection of conducting nanofluid within a porous enclosure filled with nano-encapsulated phase change materials (NEPCMs). The enclosure is equipped with two parallel fins that have ability to move in both directions such as vertically as well as horizontally. In particular the particles are structured as core-shell with phase change materials. The phase change of the materials is obtained from the solid to liquid and absorbs the surrounding temperature in the hot region and releases in the cold region. The governing transformed equations are tackled by using the Finite Element Method (FEM). The numerical simulation of the isotherms, streamlines and heat transfer coefficient ratio along with velocity distribution for various parameters are presented. These are affecting a key role on the average and local Nusselt number as well as on the local Bejan number. However, the measure outcomes are; both the longitudinal and transverse velocity profiles boost up with an augmented Rayleigh number; however, the weaker flow field is generated for the increasing Hartmann number.
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- 2021
24. MHD mixed convection of localized heat source/sink in an Al2O3-Cu/water hybrid nanofluid in L-shaped cavity
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M. A. Mansour, Taher Armaghani, Ali J. Chamkha, Mohamad Sadegh Sadeghi, Ahmed Rashad, Hossam A. Nabwey, and Abdul Sattar Dogonchi
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Materials science ,020209 energy ,Enclosure ,Hybrid nanofluid ,02 engineering and technology ,Entropy generation ,Hartmann number ,01 natural sciences ,Sink (geography) ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Nanofluid ,Magneto-hydrodynamics ,Combined forced and natural convection ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Mixed convection ,geography ,geography.geographical_feature_category ,General Engineering ,Mechanics ,Engineering (General). Civil engineering (General) ,Nusselt number ,Heat generation ,Heat transfer ,TA1-2040 - Abstract
The effect of source/sink heat location and size on Magneto-hydrodynamic mixed convection in hybrid nanofluid of Al2O3-Cu/Water within the L-shaped cavity is studied in this paper. Two uniform heat sources are put at the corners of the bottom walls of enclosure and the beginning and the end of L-shape enclosure set to be at the cold temperature. The other parts of enclosure’s walls are supposed to be insulated. The finite difference method and Boussinesq approximation is utilized to discrete the governing equations. The fundamental flow physics and thermal behavior are explored in terms of pertinent parameters such as the effects of sink/source heat generation, magnetic field and angle, Hartmann number, cavity length ratio, and hybrid volume fraction on average and surface Nusselt number, streamlines, isotherms, and entropy generation are studied. The results demonstrate that maximum amount of the sink power causes the best heat transfer performance.
- Published
- 2021
25. Numerical investigation on unsteady MHD convective rotating flow past an infinite vertical moving porous surface
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M. Veera Krishna, Ali J. Chamkha, and N. Ameer Ahamad
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Physics ,Partial differential equation ,Buoyancy ,Radiation ,MHD ,Porous surface ,020209 energy ,020208 electrical & electronic engineering ,Schmidt number ,General Engineering ,02 engineering and technology ,Slip (materials science) ,Mechanics ,engineering.material ,Engineering (General). Civil engineering (General) ,Nusselt number ,Sherwood number ,Cubic B-splines method ,Collocation method ,0202 electrical engineering, electronic engineering, information engineering ,engineering ,Mass transfer ,Magnetohydrodynamics ,TA1-2040 - Abstract
Magnetic field plays an important role in numerous fields such as biological, chemical, mechanical and medical research. In clinical and medical research the magnets are extremely important to create three dimensional images of anatomical and diagnostic importance from nuclear magnetic resonance signals. In view of these applications, the purpose of present research is to the effects of thermal radiation and rotation on the unsteady MHD convective flow past an infinite vertical moving absorbent plate. The similarity transformations are employed to migrate the governing partial differential equations in a system of non-linear ordinary differential equations and elucidated computationally by making use of cubic B-splines collocation method. The consequences of physical variables on fundamental segmentations are commented through visual aids. Even if the digital estimates of frictional force, Nusselt number and Sherwood number with respect to different parameters are delivered in matrix template and exchange of views proportionally. From the results, the resultant velocity magnifies with an increasing in rotation parameter, the thermal and solutal buoyancy forces. Reversal performance is adhered with expanding in the slip parameter. An enlargement in the radiation parameter, rise in the fluid speed and temperature profiles. The concentration profiles augments with increasing in suction parameter. The rate of mass transport is influenced on strengthening in Schmidt number and slip parameter.
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- 2021
26. Impact of moving walls on combined convection flow and thermal performance in a wavy chamber
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Ali J. Chamkha, Hemanta Karmakar, Anirban Chattopadhyay, and Swapan K. Pandit
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Richardson number ,Flow (psychology) ,02 engineering and technology ,Mechanics ,Vorticity ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Physics::Fluid Dynamics ,Combined forced and natural convection ,Heat transfer ,Stream function ,Fluid dynamics ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The impact of wall movements in different directions on mixed convection flow and thermal performance in a wavy chamber is reported. The wavy wall of the chamber is heated non-uniformly, and the upper wall is kept at a constant cold temperature, while the vertical walls of the chamber are adiabatic. Four different cases, namely Case-1, Case-2, Case-3 and Case-4, are considered on the basis of multi-directional movements of the walls of the chamber. Mathematical model of the flow physics consists of the Navier–Stokes (N-S) equations in streamfunction ( $$\psi$$ ) —vorticity ( $$\zeta$$ ) formulation including the energy transport equations which are solved by higher-order compact (HOC) scheme on curvilinear grids Pandit SK, Chattopadhyay A.(Comput Math Appl 74(6):1414–34 2017) [45]. It is found that the fluid flow and thermal performance are both influenced by the direction of moving lids and the undulations of the wavy bottom surface of the chamber. Optimum thermal performance is noticed when the wavy bottom surface of the chamber is employed with one undulation at low Richardson number (Ri). Moreover, for $$Ri=0.01$$ , Case-2, in which the upper lid is moving in left direction and the left lid is moving in upward direction, gives better heat transfer rate with maximum value of average Nusselt number for one undulation. Furthermore, it is noticed that among all the cases, the cases (Case-2 and Case-4) in which upper lid is moving in left direction produce minimum entropy generation for every undulations of the wavy surface with each of the Ri values. So, on the basis of better heat transfer rate and the minimum entropy generation, Case-2 and Case-4 may be recommended as optimum configurations.
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- 2021
27. A Spectral Relaxation Approach for Boundary Layer Flow of Nanofluid Past an Exponentially Stretching Surface with Variable Suction in the Presence of Heat Source/Sink with Viscous Dissipation
- Author
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M. Venkata Subba Rao, Gangadhar Kotha, A. Srinivasa Rao, Ali J. Chamkha, and K. Dasaradha Ramaiah
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Physics ,Multidisciplinary ,Differential equation ,010102 general mathematics ,Mechanics ,01 natural sciences ,Nusselt number ,Thermophoresis ,Boundary layer ,Nanofluid ,Flow (mathematics) ,Parasitic drag ,Mass transfer ,0101 mathematics - Abstract
The present examination is considered to discuss the steady, two-dimensional flow of heat and mass transfer of nanofluid flow along with the variable suction under the influence of heat source/sink alongside the viscous dissipation. Because of the stretchable surface, flow is generated. Spectral relaxation technique is used to acquire the numerical solution for the altered nonlinear group of differential equations. Thereafter, outcomes which were obtained from the above numerical technique are validated by comparing with the available outcomes in the existing literature and also with MATLAB inbuilt solver bvp4c. All the acquired results from the above numerical system are shown through graphs and tables to discuss different resulting parameters related to the present analysis. The range of the physical parameters is taken as $$- \;0.1 \le f_{w} \le 0.5, \;0.1 \le Nt \le 0.7, \;0.1 \le Nb \le 0.7, \;0 \le Ec \le 1.2, \; - 0.5 \le Q \le 0.5, 1 \le Pr \le 10,\; 1 \le Le \le 5.$$ The main findings are as follows: For the effect of suction parameter, the profiles of velocity, temperature and mass friction are decreased, and the coefficient of skin friction and Nusselt number is declined for the impact of thermophoresis parameter.
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- 2021
28. Hall and ion slip impacts on unsteady MHD convective rotating flow of heat generating/absorbing second grade fluid
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Ali J. Chamkha, N. Ameer Ahamad, and M. Veera Krishna
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Convection ,Materials science ,Buoyancy ,Rotation ,MHD ,020209 energy ,02 engineering and technology ,Slip (materials science) ,engineering.material ,01 natural sciences ,Sherwood number ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Parasitic drag ,Mass transfer ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Hall and ion slip effects ,General Engineering ,Porous medium ,Second grade fluids ,Laminar flow ,Mechanics ,Engineering (General). Civil engineering (General) ,Nusselt number ,engineering ,TA1-2040 - Abstract
We have explored theoretically the Hall and ion slip impacts on an unsteady laminar MHD convective rotating flow of heat generating or absorbing second grade fluid over a semi-infinite vertical moving permeable surface. The non-dimensional equations for the governing flow are solved to the most excellent possible investigative solution using perturbation methodology. The effects of parameters on velocity, temperature and concentration are demonstrated graphically and described in detail. For engineering curiosity, the shear stresses, Nusselt number and Sherwood number are obtained analytically, represented computationally in a tabular format as well as explained with respect to foremost parameters. It is concluded that, the resultant velocity is increased with an increasing in Hall and ion slip parameters throughout fluid region. The thermal and solutal buoyancy forces contribute to the resultant velocity ever-increasing to high. The temperature distribution is trim downs through an increasing in heat source parameter. The concentration is reduced with an increase in the chemical reaction parameter in the entire fluid region. Rotation parameter is to diminish the skin friction, whereas it is augmented through an increase of the Hall and ion slip effects. The rate of mass transfer is increased with increasing chemical reaction parameter.
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- 2021
29. Transportation of magnetite nanofluid flow and heat transfer over a rotating porous disk with Arrhenius activation energy: Fourth order Noumerov’s method
- Author
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R. Kumar, Ali J. Chamkha, A. Bhattacharyya, and Gauri Shanker Seth
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Materials science ,General Physics and Astronomy ,Laminar flow ,Mechanics ,01 natural sciences ,Nusselt number ,Thermophoresis ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Boundary layer ,Nanofluid ,Incompressible flow ,0103 physical sciences ,Heat transfer ,Fluid dynamics ,010306 general physics - Abstract
This article explains the effect of magnetite nanofluid taking into account water as the base fluid, over a rotating disk in the presence of external magnetic field. The governing boundary layer equations of laminar and incompressible flow over rotating disk have been formulated under the simultaneous influence of thermophoresis and Brownian motion. Additionally, influence of chemical reaction between species, prompted by Arrhenius activation energy is considered into the model. The Von Karman’s transformations of the Navier-Stokes equations are used to obtain the non-dimensional forms of the governing equations, and then fourth order finite difference scheme is used to find the numerical solutions using Noumerov’s discretization. This technique has strong impact on the accuracy of finite difference scheme. The physical descriptions of fluid velocity, temperature, concentration profiles and quantities of practical interest such as skin friction coefficient, Nusselt number and Sherwood number are presented with the help of graphs. One of the significant findings of this analysis include that an intensification in the thermophoresis parameter causes a downfall in the rate of heat transfer at the surface of the disk whereas another significant outcomes of the present investigation is that there is a downfall in the behaviours of the species concentration with the strengthening of Arrhenius activation energy. The fluid flow due to rotating disks has application in mechanisms of thermal transformations for nuclear propulsion devices.
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- 2021
30. Effects of magnetic field inclination and internal heat sources on nanofluid heat transfer and entropy generation in a double lid driven L-shaped cavity
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Ali J. Chamkha, Z. M. A. Abdelrahman, Ahmed Rashad, M. A. Mansour, and Taher Armaghani
- Subjects
Materials science ,lid driven l-shaped enclosure ,Renewable Energy, Sustainability and the Environment ,lcsh:Mechanical engineering and machinery ,020209 energy ,entropy generation ,Enclosure ,magnetic field ,02 engineering and technology ,Mechanics ,heat source size/location ,Nusselt number ,Forced convection ,Physics::Fluid Dynamics ,Nanofluid ,Combined forced and natural convection ,Thermal ,Heat transfer ,0202 electrical engineering, electronic engineering, information engineering ,nanofluid ,lcsh:TJ1-1570 ,heat generation/absorption ,Internal heating - Abstract
Mixed convection has been one of the most interesting subjects of study in the area of heat transfer for many years. The entropy generation due to MHD mixed convection heat transfer in L-shaped enclosure being filled with Cu-water nanofluid and having an internal heating generation is explored in this investigation by the finite volume technique. Lid-motion is presented by both right and top parts of walls to induce forced convection and the cavity is under an inclined uniform magnetic field along the positive horizontal direction. The statistics concentrated specifically on the impacts of several key parameters like as the aspect ratio of the enclosure, Hartmann number, nanoparticle volume fraction, and heat source length/location on the heat transfer inside the L-shaped enclosure. Outcomes have been manifested in terms of isotherm lines, streamlines, local and average Nusselt numbers. The obtained results show that addition of nanoparticles into pure fluid leads to increase of heat transfer. The maximum value of local Nusselt pertaining to the heat source occurs when L = 0.1. Impacts of heat source size and location, internal heat generation absorption, angle of magnetic field on heat transfer and entropy generation are completely analyzed and discussed. The best configuration and values of important parameters are also presented using thermal performance criteria.
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- 2021
31. Lattice Boltzmann simulation of natural convection in a square enclosure with discrete heating
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Sina Hassanzadeh Saraei, Ali J. Chamkha, Abdolrahman Dadvand, and Soheila Ghoreishi
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Numerical Analysis ,Materials science ,Natural convection ,General Computer Science ,Applied Mathematics ,Lattice Boltzmann methods ,Enclosure ,010103 numerical & computational mathematics ,02 engineering and technology ,Mechanics ,01 natural sciences ,Nusselt number ,Theoretical Computer Science ,Vortex ,Physics::Fluid Dynamics ,Modeling and Simulation ,Heat transfer ,Thermal ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Streamlines, streaklines, and pathlines ,0101 mathematics - Abstract
In the present work, natural convection heat transfer in a differentially heated cavity is considered, in which, source–sink pairs are located on vertical walls with a constant temperature while other wall parts of the enclosure are insulated. The effects of different arrangements, sizes, and number of heat source–sink pairs on the flow and thermal fields are investigated by using the Lattice Boltzmann Method to solve the flow and thermal field equations. In this paper, streamlines, isotherms, the average Nusselt number, and the entropy generation are presented to get a better insight into the nature of the problem. Results of this study showed that the arrangement of the heat source–sink pairs could strongly affect the flow and thermal fields in the cavity due to the formation of the vortices. It was also found that the highest amount of heat transfer with the lowest entropy generation was achieved by splitting the discrete heat source–sink pairs into the smaller segments and putting them alternately on one sidewall.
- Published
- 2021
32. Magnetohydrodynamic Nanofluid Natural Convection in a Cavity under Thermal Radiation and Shape Factor of Nanoparticles Impacts: A Numerical Study Using CVFEM
- Author
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Ali J. Chamkha, A.S. Dogonchi, and D.D. Ganji
- Subjects
nanofluid ,CVFEM ,natural convection ,shape factor of nanoparticles ,thermal radiation ,Nusselt number ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
In this study, the natural convection of a magnetohydrodynamic nanofluid in an enclosure under the effects of thermal radiation and the shape factor of nanoparticles was analyzed numerically using the control-volume-based finite element method (CVFEM). Columns, spheres, and lamina are examples of the nanoparticle shapes used in the investigation. The study of nanofluid flow and heat transfer was accomplished with an extensive range of nanofluid volume fractions, radiation parameters, Hartmann numbers, Rayleigh numbers, and nanoparticle shape factors. Also, the correlation between the average Nusselt number and the influencing parameters of the current study was determined. The findings demonstrate that laminar nanoparticles have a more notable impact on the average and local Nusselt numbers than the other nanoparticle shapes.
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- 2018
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33. Study of graphene Maxwell nanofluid flow past a linearly stretched sheet: A numerical and statistical approach
- Author
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Chakravarthula S.K. Raju, Rohit Sharma, S. M. Hussain, Gauri Shanker Seth, and Ali J. Chamkha
- Subjects
Materials science ,Velocity gradient ,General Physics and Astronomy ,Mechanics ,01 natural sciences ,Nusselt number ,010305 fluids & plasmas ,Magnetic field ,Physics::Fluid Dynamics ,Momentum ,Nonlinear system ,Nanofluid ,Thermal radiation ,0103 physical sciences ,Heat transfer ,010306 general physics - Abstract
This study aims to unfold the significance of numerous physical parameters such as magnetic field, heat absorption, thermal radiation, viscous and Joule dissipations, etc. on the flow of graphene Maxwell nanofluid over a linearly stretched sheet with considerations of momentum and thermal slip conditions. The prevailing mathematical equations are reformed into extremely nonlinear coupled ordinary differential equations (ODE) utilizing similarity variables and then the equations are solved numerically by the scheme of Runge-Kutta Fehlberg method along with the shooting technique. The variations in graphene Maxwell nanofluid velocity and temperature owing to different physical parameters are shown via numerous graphs whereas numerical values of skin friction coefficients and Nusselt numbers are illustrated and reported in different tables. In addition, statistical approach is followed for the multiple regression estimation analysis on the numerical findings of wall velocity gradient and local Nusselt number and are reported in tabular form to demonstrate the relationship among the heat transfer rate and physical parameters. Our results reveal that the graphene Maxwell nanofluid velocity gets reduced owing to enhancement in magnetic field, angle of inclination of magnetic field, porosity and unsteadiness parameters whereas behavior of nanofluid velocity is reversed due to Maxwell parameter. Further, it is noticed that the heat transfer rate of nanofluid is augmented owing to heat absorption, radiation and thermal slip parameters while it is reduced due to increase in viscous dissipation and unsteadiness parameters. The numerical results of the paper are validated by making comparisons with the earlier published paper under the restricted conditions and we found an excellent agreement with those results. A careful review of research papers reported in literature reveals that none of the authors has attempted this problem earlier although the thoughts and methodology explained in this paper can be anticipated to lead to enormously prolific connections across disciplines.
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- 2020
34. Free convective melting-solidification heat transfer of nano-encapsulated phase change particles suspensions inside a coaxial pipe
- Author
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Nemat Mashoofi, Obai Younis, Mikhail A. Sheremet, Ali J. Chamkha, S.A.M. Mehryan, Ahmad Hajjar, and Mohammad Ghalambaz
- Subjects
Work (thermodynamics) ,Materials science ,business.industry ,General Chemical Engineering ,02 engineering and technology ,Mechanics ,Rayleigh number ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Phase-change material ,Nusselt number ,0104 chemical sciences ,Mechanics of Materials ,Heat transfer ,Stefan number ,Particle ,0210 nano-technology ,business ,Thermal energy - Abstract
The nano encapsulated phase change materials are of the great energy storage potential in various engineering applications. Since they are new nanomaterials, new models for understanding their thermal behavior and capability are essential. This work aims to investigate the unsteady thermal behavior of Nano-Encapsulated Phase Change Material (NEPCM) suspensions in a cylindrical cavity. The particles contain a Phase Change Material (PCM) core, which can absorb/release a substantial amount of thermal energy upon phase change. The phase change particles are well dispersed in a liquid fluid and freely move along with the fluid. The flow, heat transfer, and the particle phase change were modeled using partial differential equations. A non-dimensional approach was employed to generalize the study. The unsteady charging and discharging behavior of the NEPCM suspension are investigated for the volume fraction of the NEPCM particles, fusion temperature of nanoparticles, Stefan number, and the Rayleigh number. Numerical results show that an increment in the Stefan number, i.e., Ste, can significantly reduce the Nusselt number, i.e., Nua, at the charging mode of the system. However, the dependency of the Nua at the discharging mode on the Ste is negligible. Also, it was found that the effect of the fusion temperature of the particle’s core (θf) on heat transfer depends on the working mode of the system. In the charging mode, using a higher value of θf decreases the heat transfer rate. Reversibly, a higher value of θf inhibits the Nua during discharging state. Furthermore, the results show that for Ra = 106, Ste = 0.2, and θf = 0.1, a rise of ϕ from 0 to 0.05 leads in about 1.73 and 1.55 times of improvement in the value of Nua for the cases of the melting and solidification of the core of NEPCM particles.
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- 2020
35. Heat and mass transfer of two immiscible flows of Jeffrey fluid in a vertical channel.
- Author
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Kalyan, Shreedevi, Sharan, Ashwini, and Chamkha, Ali J.
- Subjects
HEAT transfer ,FLUID flow ,NUSSELT number ,GRASHOF number ,ORDINARY differential equations ,MASS transfer - Abstract
In this article, we examined the effect of heat and mass transfer flow of two immiscible Jeffrey fluids in a vertical channel. The highly nonlinear coupled ordinary differential equations are evaluated using regular perturbation parameters, for small values of perturbation parameter. The effect of Jeffrey's parameter on the flow and the effects of various physical parameters entering into the problem on dimensionless velocity, temperature, and concentration distribution is illustrated graphically. We observe that the Jeffrey parameter, thermal, and mass Grashof number enhance the fluid flow, while the chemical reaction parameter suppresses the fluid flow, also it is established that the Nusselt number is boosted by enhancing the thermal and mass Grashof number. We observed that the results are in very good agreement with the results obtained for a viscous fluid. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
36. Magneto-hydrodynamic thermal convection of Cu–Al2O3/water hybrid nanofluid saturated with porous media subjected to half-sinusoidal nonuniform heating
- Author
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Nirmal K. Manna, Ali J. Chamkha, U. K. Sarkar, and Nirmalendu Biswas
- Subjects
Materials science ,Natural convection ,Convective heat transfer ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Hartmann number ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Nanofluid ,Heat transfer ,Streamlines, streaklines, and pathlines ,Physical and Theoretical Chemistry ,0210 nano-technology ,Porous medium - Abstract
The present work aims to examine the thermal efficacy of half-sinusoidal nonuniform heating at different spatial frequencies for a porous natural convection system using Cu–Al2O3/water hybrid nanofluid and magnetic field. The system is presented utilizing a classical square enclosure heated nonuniformly at the bottom wall, and the sidewalls are allowed to exchange heat with the surroundings. The Brinkman–Forchheimer–Darcy model is adopted catering other additional terms for buoyant force and magnetic field. The governing equations are transformed into nondimensional forms and then solved numerically using a finite volume-based computing code. The importance and fundamental flow physics are explored in terms of the pertinent parameters such as the amplitude (I) and spatial frequency (f) of half-sinusoidal heating, Darcy–Rayleigh number (Ram), volume fraction of hybrid nanoparticles ( $$ \phi $$ ), and Hartmann number (Ha). The flow structure and heat transfer characteristics are analyzed and presented utilizing heatlines, streamlines and isotherms and average Nusselt number. The results show that the use of half-sinusoidal nonuniform heating along with hybrid nanofluid can be a viable method for enhancement and control of the overall thermal performance. The study indicates that half-sinusoidal heating could be a promising technique for better heat transfer even in the presence of flow dampening effects like porous media and magnetic fields.
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- 2020
37. Hybrid (ND-Co3O4/EG) nanoliquid through a permeable cylinder under homogeneous-heterogeneous reactions and slip effects
- Author
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S. Manjunatha, Ali J. Chamkha, G. S. Roopa, and G. K. Ramesh
- Subjects
Drag coefficient ,Materials science ,Complex differential equation ,Energy transfer ,02 engineering and technology ,Mechanics ,Slip (materials science) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Physics::Fluid Dynamics ,Nanofluid ,Homogeneous ,Boundary value problem ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Modeling and computations are performed to study the ND-Co3O4/EG hybrid nanoliquid mixed convective flow past a vertical porous cylinder. The flow analysis and formulation are given accounting for slip effects and homogeneous-heterogeneous reaction impacts. The governing complex equations formed with prescribed boundary conditions are simplified into self-similar equations through the use of suitable transformations. The numerical solutions of the drag coefficient, Nusselt number, liquid velocity, liquid temperature, and the liquid concentration are explored through graphs with the setting of pertaining parameter values. From the results, it is noticed that an ND-Co3O4/EG nanofluid plays a more impressive role in the process of energy transfer than a Co3O4/EG nanofluid. Further, it is found that the heterogeneous reaction parameter decreases the concentration whereas multiple slips enhance the temperature.
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- 2020
38. Numerical analysis of rarefied gaseous flows in a square partially heated two-sided wavy cavity with internal heat generation
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Ali J. Chamkha, Khalid Saleem, and Wael Al-Kouz
- Subjects
Materials science ,Natural convection ,Prandtl number ,Laminar flow ,Rayleigh number ,Mechanics ,Condensed Matter Physics ,Nusselt number ,symbols.namesake ,Heat generation ,symbols ,Knudsen number ,Physical and Theoretical Chemistry ,Internal heating - Abstract
The problem of steady-state laminar two-dimensional rarefied gaseous flow by natural convection heat transmission in a partly heated square two-sided wavy cavity with an internal heat generation is numerically studied employing the finite volume procedure. The Boussinesq approximation is adopted to account for buoyancy effects. A favorable comparison for validation purposes with previously published work is obtained. The study is performed with distinct values of the external Rayleigh number (104 ≤ RaE ≤ 106), Knudsen number (0.01 ≤ Kn ≤ 0.1), inclination angle (ϕ = 0°, 30°, 60°, and 90°), three non-dimensional heater lengths (L/H = 0.175, 0.35, and 0.52), while the Prandtl number (Pr) is fixed at 0.7. The outcomes of this research yield that the average Nusselt number (Nuavg) relies inversely on Kn and directly on RaE. Moreover, it is revealed that increasing L/H value decreases Nuavg values at the lower partially heated cavity wall. Additionally, the study reveals that as the heat generation term (Qgen) increases, the Nuavg increases as well. Finally, a correlation between Nuavg and the parameters inspected in this research is suggested.
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- 2020
39. Heatline visualization of mixed convection inside double lid-driven cavity having heated wavy wall
- Author
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Ammar I. Alsabery, Ali J. Chamkha, Fatin M. Azizul, and Ishak Hashim
- Subjects
Convection ,Physics ,Richardson number ,Prandtl number ,Reynolds number ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Thermal conduction ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Physics::Fluid Dynamics ,symbols.namesake ,Combined forced and natural convection ,Heat transfer ,symbols ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The current problem is performed to analyze the heatline visualization of the mixed convection mechanism and heat transfer in a double lid-driven square cavity having a heated wavy bottom surface. The moving vertical surfaces are under adiabatic conditions, and the top surface is at a cold temperature. The finite element method is employed to determine the dimensionless governing equations controlled by specific boundary conditions. The implications of the Reynolds number ( $$10 \le {\mathrm{Re}} \le 500$$ ), the directions of the constant moving wall ( $$\lambda _{\mathrm{l}}= \pm 1, \lambda _{\mathrm{r}}= \pm 1$$ ), Richardson number ( $$0.01 \le {\mathrm{Ri}} \le 100$$ ), Prandtl number ( $$0.015 \le \Pr \le 10$$ ) and the number of oscillations ( $$1 \le {\mathrm{N}} \le 4$$ ) are visualized by the streamlines, isotherms and the heatlines. The same direction of lid-driven cases leads to two primary circulation cells. The Richardson number increases as it imposes the increment of the vertical temperature gradient. At a high Prandtl number, the convection mode of heat transfer is fully established, and heat conduction occurs at a low Prandtl number. Moreover, the number of oscillations has the most significant direct impact on the streamlines and the temperature distributions compared to the flat surface. Higher Reynolds and Prandtl numbers result in an increment in the local and average Nusselt numbers. The result shows that one oscillation of the wavy surface with a low Richardson number yields to have an optimum heat transfer in the cavity.
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- 2020
40. Turbulent Heat Transfer Characteristics of a W-Baffled Channel Flow - Heat Transfer Aspect
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Ali J. Chamkha, Younes Menni, and Oluwole Daniel Makinde
- Subjects
Radiation ,Materials science ,020209 energy ,Turbulent heat transfer ,02 engineering and technology ,Mechanics ,Condensed Matter Physics ,Nusselt number ,Open-channel flow ,Forced convection ,Physics::Fluid Dynamics ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Heat transfer ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science - Abstract
In this work, the thermal behavior of a turbulent forced-convection flow of air in a rectangular cross section channel with attached W-shaped obstacles is investigated. The continuity, momentum and energy equations employed to control the heat and velocity in the computational domain. The turbulence model of k-ε is employed to simulate the turbulence effects. The finite volume method with SIMPLE algorithm is employed as the solution method. The results are reported temperature, local and average Nusselt numbers, and mean velocity contours. The subject is relevant and important for industrial applications.
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- 2020
41. Thermo-magneto-hydrodynamical effects on merging flow of TiO2–water nanofluid
- Author
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Abuzar Abid Siddiqui and Ali J. Chamkha
- Subjects
Materials science ,Splitter plate ,Reynolds number ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Stagnation point ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Open-channel flow ,symbols.namesake ,Nanofluid ,symbols ,Trailing edge ,Streamlines, streaklines, and pathlines ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The steady flow of a nanofluid (mixture of titanium dioxide and water) in a rectangular channel under the influence of an inclined magnetic field is studied. The channel contains an upstream hot splitter plate in alignment with the upper and lower plates of the channel. It may be said that two incoming channel flows merge to form a single channel flow. This setup may apply to the heating chamber in which titanium dioxide can be used to enhance the thermal transfer rate. It is observed that the position of the splitter plate (that may act as an electric heater) affects the velocity and temperature of the fluid. Therefore, in order to ensure these facts, the examination of the flow behavior and the temperature distributions in the channel if the splitter is placed at different positions in the upstream have been probed. In addition, the effect of nanoparticles on the convection process has been probed. The streamlines are almost similar for a clear fluid as well as for a nanofluid (for low values of solid volume fraction of nanoparticles (i.e. $$\varphi < 0.05$$ )) for all values of the Reynolds number. However, the rise in the temperature is noted for the nanofluid if the concentration of nanoparticles is increased. The increase in the Reynolds number also supports the enhancement of the Nusselt number and, hence, the thermal transfer rate of the nanofluid. The Nusselt number is dominant in the vicinity of the trailing edge of the splitter because the trailing edge exhibits as a stagnation point. In addition, the maximum Nusselt number for nanofluid at moderate Reynolds number (e.g., Re = 100) is enhanced to 0.3% with respect to the clear fluid. Moreover, obtained results for this particular case are compared with the existing literature, and the results compare well.
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- 2020
42. Hall and ion slip effects on unsteady MHD free convective rotating flow through a saturated porous medium over an exponential accelerated plate
- Author
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Ali J. Chamkha, N. Ameer Ahamad, and M. Veera Krishna
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Convection ,Materials science ,Rotation ,020209 energy ,02 engineering and technology ,Slip (materials science) ,01 natural sciences ,Sherwood number ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Shear stress ,Hall and ion slip effects ,Magnetohydrodynamic drive ,Inclined plate ,Radiation ,General Engineering ,Porous medium ,Mechanics ,Engineering (General). Civil engineering (General) ,Nusselt number ,Flow velocity ,Drag ,TA1-2040 ,Chemical reaction - Abstract
In this paper, we have investigated the Hall and ion slip effects on the unsteady magnetohydrodynamic (MHD) free convective rotating flow over an exponentially accelerated inclined plate entrenched in a saturated porous medium with the effect of angle of inclination, variable temperature and concentration. The flow induced by the presence of heat source/sink and destructive reaction. The Laplace transform technique has been used to solve the governing equations. The effects of the non-dimensional parameters on the governing flow velocity, temperature and concentration are examined with graphical profiles. Also for engineering interest the shear stress, Nusselt number and Sherwood number are obtained analytically and discussed computationally with reference to foremost flow parameters. It is reported that the presence of magnetic field prevents the flow reversal. Angle of inclination sustains a retarding effect on velocity distribution. The present study has an immediate application in understanding the drag experienced at the heated and inclined surfaces in a seepage flow.
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- 2020
43. Periodically fully developed nanofluid transport through a wavy module
- Author
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Ammar Alkhalidi, Aiman Alshare, Ali J. Chamkha, Suhil Kiwan, and Wael Al-Kouz
- Subjects
Work (thermodynamics) ,Materials science ,Finite volume method ,Reynolds number ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Physics::Fluid Dynamics ,symbols.namesake ,Nanofluid ,Amplitude ,Heat transfer ,symbols ,Boundary value problem ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The present work is a computational investigation of a periodically fully developed nanofluid transport through a wavy module. The governing equations for this investigation are formulated along with the appropriate boundary conditions and then solved using the finite volume method. Comparisons with previously reported results show excellent agreement. The simulations are carried out using five wavy amplitudes for a range of Reynolds number from 102 to 103. It is found that increasing the amplitude and increasing the nanoparticle volume fraction achieve enhancement of the heat transfer at the cost of increased pumping power. Correlations for the friction factor and the Nusselt number as functions of the amplitude and the Reynolds number are provided.
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- 2020
44. MHD mixed convection of Ag–MgO/water nanofluid in a triangular shape partitioned lid-driven square cavity involving a porous compound
- Author
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Ali J. Chamkha, Fatih Selimefendigil, Department of Mechanical Engineering, Celal Bayar University, Manisa, 45140, Turkey, and Department of Mechanical Engineering, Prince Sultan Endowment for Energy and Environment, Prince Mohammad Bin Fahd University, Al-Khobar, 31952, Saudi Arabia
- Subjects
Physics::Fluid Dynamics ,Nanofluid ,Materials science ,Richardson number ,Convective heat transfer ,Darcy number ,Heat transfer ,Mechanics ,Physical and Theoretical Chemistry ,Condensed Matter Physics ,Hartmann number ,Porous medium ,Nusselt number - Abstract
In the current study, magnetohydrodynamics mixed convective flow of Ag–MgO/water hybrid nanofluid in a triangular shaped partitioned cavity involving a porous layer is numerically investigated by using the finite element method. In the numerical simulation, various effects of pertinent parameters such as Richardson number (between 0.01 and 100), Hartmann number (between 0 and 60), magnetic field inclination angle (between 0 and 90), Darcy number (between $$10^{-4}$$ and $$5 \times 10^{-2}$$ ), location of the vertex of triangular porous region (between 0.2 and 0.8 H) and hybrid nanoparticle solid volume fraction ( $$\phi _1$$ between 0 and 0.01, $$\phi _2$$ between 0 and 0.01) on the fluid flow and convective heat transfer features are examined. It was observed that a large vortex is established below the main vortex near the upper wall for the lowest value Ri number. At the highest magnetic field strength, multi-recirculation flow pattern is seen in the right bottom corner. The average heat transfer enhances with higher values of permeability of the porous medium, magnetic field inclination angle, distance of the porous layer vertex from the hot wall and solid nanoparticle volume fraction of each particles in the hybrid nanofluid. The impact is reverse for higher values of Richardson number and Hartmann number. In the current work, significant changes in the average Nusselt number are obtained by varying the location of the porous medium. The triangular shaped porous compound can be used as an excellent tool for convective heat transfer control.
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- 2020
45. Inclined magneto: convection, internal heat, and entropy generation of nanofluid in an I-shaped cavity saturated with porous media
- Author
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Taher Armaghani, M. A. Mansour, Ali J. Chamkha, and Ahmed Rashad
- Subjects
Physics::Fluid Dynamics ,Convection ,Nanofluid ,Darcy's law ,Materials science ,Heat flux ,Heat transfer ,Streamlines, streaklines, and pathlines ,Mechanics ,Physical and Theoretical Chemistry ,Condensed Matter Physics ,Internal heating ,Nusselt number - Abstract
A numerical investigation of entropy generation due to MHD-free convective of Cu–water nanofluid in a porous I-shaped cavity is reported. The cavity is under Darcy law with inclined uniform magnetic field. The cavity is cooled from the top and a part of bottom wall subjected to uniform heat flux, while the other parts of walls of the cavity are adiabatic. Mathematical pattern formulated employing the single-phase nanofluid approach in governing equations the problem has been solved by finite difference technique. Prime efforts have been concentrated on the impacts of the pertinent parameters on the fluid flow and heat transfer inside the cavity. Numerical data have been plotted in the form of streamlines, isotherms, and average Nusselt numbers. The results show that the Nu number decreases via increasing the Ha number. It increases when the Ra number is increased. The maximum and minimum values of Nusselt occur at B = 0.2 and B = 0.8, respectively. Exerting an angle for magnetic flux leads to the improvement in thermal performance for all amount of B. The effects of Ha, nanofluid volume fraction, heat source size, location and angle of magnetic field on heat transfer, entropy generation, and thermal performance are completely studied and discussed.
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- 2020
46. Second law analysis of magneto-natural convection in a nanofluid filled wavy-hexagonal porous enclosure
- Author
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Abdul Sattar Dogonchi, D.D. Ganji, Mehdi Hashemi-Tilehnoee, Ali J. Chamkha, and Seyyed Masoud Seyyedi
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Physics ,0209 industrial biotechnology ,Natural convection ,Applied Mathematics ,Mechanical Engineering ,Enclosure ,02 engineering and technology ,Mechanics ,Coefficient of performance ,021001 nanoscience & nanotechnology ,Hartmann number ,Nusselt number ,Computer Science Applications ,Entropy (classical thermodynamics) ,020901 industrial engineering & automation ,Nanofluid ,Mechanics of Materials ,Heat transfer ,0210 nano-technology - Abstract
Purpose Natural convection heat transfer analysis can be completed using entropy generation analysis. This study aims to accomplish both the natural convection heat transfer and entropy generation analyses for a hexagonal cavity loaded with Cu-H2O nanoliquid subjected to an oriented magnetic field. Design/methodology/approach Control volume-based finite element method is applied to solve the non-dimensional forms of governing equations and then, the entropy generation number is computed. Findings The results portray that both the average Nusselt and entropy generation numbers boost with increasing aspect ratio for each value of the undulation number, while both of them decrease with increasing the undulation number for each amplitude parameter. There is a maximum value for the entropy generation number at a specified value of Hartmann number. Also, there is a minimum value for the entropy generation number at a specified value of angle of the magnetic field. When the volume fraction of nanoparticles grows, the average Nusselt number increases and the entropy generation number declines. The entropy generation number attains to a maximum value at Ha = 14 for each value of aspect ratio. The average Nusselt number ascends 2.9 per cent and entropy generation number decreases 1.3 per cent for Ha = 0 when ϕ increases from 0 to 4 per cent. Originality/value A hexagonal enclosure (complex geometry), which has many industrial applications, is chosen in this study. Not only the characteristics of heat transfer are investigated but also entropy generation analysis is performed in this study. The ecological coefficient of performance for enclosures is calculated, too.
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- 2020
47. Impact of finite wavy wall thickness on entropy generation and natural convection of nanofluid in cavity partially filled with non-Darcy porous layer
- Author
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Ishak Hashim, Ali J. Chamkha, Muneer A. Ismael, and Ammar I. Alsabery
- Subjects
0209 industrial biotechnology ,Materials science ,Natural convection ,Waviness ,Darcy number ,Laminar flow ,02 engineering and technology ,Mechanics ,Nusselt number ,Physics::Fluid Dynamics ,020901 industrial engineering & automation ,Nanofluid ,Artificial Intelligence ,Heat transfer ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,Porosity ,Software - Abstract
This paper investigates the natural convection inside a partially layered porous cavity with a heated wavy solid wall; the geometry is encountered in compact heat exchangers. Alumina nanoparticles are included in the water to enhance the heat exchange process. The incidental entropy generation is also studied to evaluate the thermodynamic irreversibility. The nanofluid flow is taken as laminar and incompressible while the advection inertia effect in the porous layer is taken into account by adopting the Darcy–Forchheimer model. The problem is explained in the dimensionless form of the governing equations and solved by the finite element method. The Darcy number (Da), porosity of the porous layer ( $$\varepsilon$$ ), number of undulations (N), and the nanoparticles volume fraction ( $$\phi$$ ) are varied to assess the heat transfer and the incidental entropy generation. It is found that the waviness of the solid wall augments the average Nusselt number and minimizes the generation of entropy. The results show for some circumstances that the Nusselt number is augmented by 43.8% when N is raised from 0 (flat solid wall) to 4. It is also found that the porosity of the porous layer is a more crucial parameter than its permeability, where a 37.4% enhancement in the Nusselt number is achieved when the porosity is raised from 0.2 to 0.8.
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- 2020
48. Numerical simulation of hydrothermal features of Cu–H2O nanofluid natural convection within a porous annulus considering diverse configurations of heater
- Author
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Nader Karimi, Abdul Sattar Dogonchi, M. K. Nayak, Davood Domiri Ganji, and Ali J. Chamkha
- Subjects
Natural convection ,Materials science ,02 engineering and technology ,Mechanics ,Rayleigh number ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Nusselt number ,Control volume ,Finite element method ,010406 physical chemistry ,0104 chemical sciences ,Physics::Fluid Dynamics ,Nanofluid ,Heat transfer ,Annulus (firestop) ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The purpose of the current study is to numerically investigate the effects of shape factors of nanoparticles on natural convection in a fluid-saturated porous annulus developed between the elliptical cylinder and square enclosure. A numerical method called the control volume-based finite element method is implemented for solving the governing equations. The modified flow and thermal structures and corresponding heat transfer features are investigated. Numerical outcomes reveal very good grid independency and excellent agreement with the existing studies. The obtained results convey that at a certain aspect ratio, an increment in Rayleigh and Darcy numbers significantly augments the heat transfer and average Nusselt number. Further, enhancement of Rayleigh number increases the velocity of nanofluid, while that of aspect ratio of the elliptical cylinder shows the opposite trend.
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- 2020
49. Magnetohydrodynamic natural convection and entropy generation analyses inside a nanofluid-filled incinerator-shaped porous cavity with wavy heater block
- Author
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D.D. Ganji, Ali J. Chamkha, Abdul Sattar Dogonchi, Seyyed Masoud Seyyedi, and Mehdi Hashemi-Tilehnoee
- Subjects
Physics ,Natural convection ,Turbulence ,Darcy number ,Laminar flow ,02 engineering and technology ,Rayleigh number ,Mechanics ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Hartmann number ,01 natural sciences ,Nusselt number ,010406 physical chemistry ,0104 chemical sciences ,Physics::Fluid Dynamics ,Nanofluid ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The aim of the current study is natural convection analysis conjugated with entropy generation analysis in an incinerator shaped permeable enclosure loaded with Al2O3–H2O nanofluid subjected to the magnetic field with a rectangular wavy heater block positioned on the bottom of the cavity wall. The bottom and top horizontal walls are adiabatic; the inclined and vertical walls are thought to be cooled. Firstly, the governing expressions and standard k–e turbulence model are rewritten from dimensional form to non-dimensional form using dimensionless parameters such as vorticity and stream function. In the next step, the equation of entropy generation is written in dimensionless form. Then, the system of non-dimensional governing equations is solved by the finite volume method (FVM) conjugated with a non-dimensionalization scheme using ANSYS Fluent. Fine grids (wall y+
- Published
- 2020
50. Hydrodynamic and thermal analysis of water, ethylene glycol and water-ethylene glycol as base fluids dispersed by aluminum oxide nano-sized solid particles
- Author
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Younes Menni, Noureddine Kaid, Mohammed Bensafi, Nicola Massarotti, Houari Ameur, and Ali J. Chamkha
- Subjects
Materials science ,Turbulence ,Applied Mathematics ,Mechanical Engineering ,Reynolds number ,02 engineering and technology ,Mechanics ,021001 nanoscience & nanotechnology ,Nusselt number ,Computer Science Applications ,Open-channel flow ,symbols.namesake ,020303 mechanical engineering & transports ,Nanofluid ,0203 mechanical engineering ,Mechanics of Materials ,Turbulence kinetic energy ,symbols ,Fluid dynamics ,0210 nano-technology ,Reynolds-averaged Navier–Stokes equations - Abstract
Purpose The purpose of this paper is to carry out a hydrodynamic and thermal analysis of turbulent forced-convection flows of pure water, pure ethylene glycol and water-ethylene glycol mixture, as base fluids dispersed by Al2O3 nano-sized solid particles, through a constant temperature-surfaced rectangular cross-section channel with detached and attached obstacles, using a computational fluid dynamics (CFD) technique. Effects of various base fluids and different Al2O3 nano-sized solid particle solid volume fractions with Reynolds numbers ranging from 5,000 to 50,000 were analyzed. The contour plots of dynamic pressure, stream-function, velocity-magnitude, axial velocity, transverse velocity, turbulent intensity, turbulent kinetic energy, turbulent viscosity and temperature fields, the axial velocity profiles, the local and average Nusselt numbers, as well as the local and average coefficients of skin friction, were obtained and investigated numerically. Design/methodology/approach The fluid flow and temperature fields were simulated using the Commercial CFD Software FLUENT. The same package included a preprocessor GAMBIT which was used to create the mesh needed for the solver. The RANS equations, along with the standard k-epsilon turbulence model and the energy equation were used to control the channel flow model. All the equations were discretized by the finite volume method using a two-dimensional formulation, using the semi-implicit method for pressure-linked equations pressure-velocity coupling algorithm. With regard to the flow characteristics, the interpolation QUICK scheme was applied, and a second-order upwind scheme was used for the pressure terms. The under-relaxation was changed between the values 0.3 and 1.0 to control the update of the computed variables at each iteration. Moreover, various grid systems were tested to analyze the effect of the grid size on the numerical solution. Then, the solutions are said to be converging when the normalized residuals are smaller than 10-12 and 10-9 for the energy equation and the other variables, respectively. The equations were iterated by the solver till it reached the needed residuals or when it stabilized at a fixed value. Findings The result analysis showed that the pure ethylene glycol with Al2O3 nanoparticles showed a significant heat transfer enhancement, in terms of local and average Nusselt numbers, compared with other pure or mixed fluid-based nanofluids, with low-pressure losses in terms of local and average skin friction coefficients. Originality/value The present research ended up at interesting results which constitute a valuable contribution to the improvement of the knowledge basis of professional work through research related to turbulent flow forced-convection within channels supplied with obstacles, and especially inside heat exchangers and solar flat plate collectors.
- Published
- 2020
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