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Ali J. Chamkha - One of the best experts on this subject based on the ideXlab platform.
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Effects of various configuRations of an inserted corrugated conductive cylinder on MHD natural convection in a hybrid nanofluid-filled square domain
2020Co-Authors: Tahar Tayebi, Ali J. ChamkhaAbstract:This paper aims to understand the characteristics of heat transfer and flow by natural convection of Al_2O_3–Cu/water-based hybrid nanofluid-filled square domain containing various configuRations of a corrugated conducting solid under a horizontal magnetic field. The basic equations in their non-dimensional form are numerically solved using the finite volume discretization technique. The Corcione correlations are utilized to estimate the overall heat Conductivity and overall viscosity of the hybrid nanoliquid when the nanoparticle’s Brownian motion is taken into account. The dependency of different governing factors of the investigation, namely volume fraction of the combined nanoparticles, Rayleigh and Hartmann numbers, undulation number, undulation amplitude and the fluid/solid heat Conductivity Ratio, on thermohydrodynamic characteristics are delineated. Results stated that the maximum heat transmission rate was obtained for weak values of Hartmann, undulation number, undulation amplitude and high values of Rayleigh and nanoparticles volumic fraction. In addition, the fluid/solid heat Conductivity Ratio parameter was found to boost the heat transfer at weak Rayleigh while reducing it at high Rayleigh.
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entropy geneRation analysis during mhd natural convection flow of hybrid nanofluid in a square cavity containing a corrugated conducting block
2019Co-Authors: Tahar Tayebi, Ali J. ChamkhaAbstract:The purpose of this paper is to study the influence of magnetic field on entropy geneRation and natural convection inside an enclosure filled with a hybrid nanofluid and having a conducting wavy solid block. Also, the effect of fluid–solid thermal Conductivity Ratio is investigated.,The governing equations that are formulated in the dimensionless form are discretized via finite volume method. The velocity–pressure coupling is assured by the SIMPLE algorithm. Heat transfer balance is used to verify the convergence. The validation of the numerical results was performed by comparing qualitatively and quantitatively the results with previously published investigations.,The results indicate that the magnetic field and the Conductivity Ratio of the wavy solid block can significantly affect the dynamic and thermal field and, consequently, the heat transfer rate and entropy geneRation because of heat transfer, fluid friction and magnetic force.,To the best of the authors’ knowledge, the present numerical study is the first attempt to use hybrid nanofluid for studying the entropy geneRation because of magnetohydrodynamic natural convective flow in a square cavity with the presence of a wavy circular conductive cylinder. Irreversibilities due to magnetic effect are taken into account. The effect of fluid–solid thermal Conductivity Ratio is considered.
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natural convection in a cuo water nanofluid filled cavity under the effect of an inclined magnetic field and phase change material pcm attached to its vertical wall
2019Co-Authors: Fatih Selimefendigil, Ali J. Chamkha, Hakan F OztopAbstract:In this study, natural convection of CuO–water nanofluid in a square cavity with a conductive partition and a phase change material (PCM) attached to its vertical wall is numerically analyzed under the effect of an uniform inclined magnetic field by using finite element method. Effects of various pertinent parameters such as Rayleigh number (between \(10^5\) and \(10^6\)), Hartmann number (between 0 and 100), magnetic inclination angle (between \(0^{\circ}\) and \(90^{\circ}\)), PCM height (between 0.2H and 0.8H), PCM length (between 0.1H and 0.8H), thermal Conductivity Ratio (between 0.1 and 100) and solid nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and thermal characteristics were numerically analyzed. It was observed that when magnetic field is imposed, more reduction in average Nusselt number for water is obtained as compared to nanofluid which is \(31.81\%\) for the nanofluid at the highest particle volume fraction. The average heat transfer augments with magnetic inclination angle, but it is less than \(5\%\). When the height of the PCM is increased which is from 0.2H to 0.8H, local and average Nusselt number reduced which is \(42.14\%\) . However, the length of the PCM is not significant on the heat transfer enhancement. When the Conductivity Ratio of the PCM to the base fluid within the cavity is increased from 0.1 to 10, \(29.5\%\) of the average Nusselt number enhancement is achieved.
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mhd convective heat transfer in a discretely heated square cavity with conductive inner block using two phase nanofluid model
2018Co-Authors: Ammar I. Alsabery, Mikhail A Sheremet, Ali J. Chamkha, Ishak HashimAbstract:The problem of steady, laminar natural convection in a discretely heated and cooled square cavity filled by an alumina/water nanofluid with a centered heat-conducting solid block under the effects of inclined uniform magnetic field, Brownian diffusion and thermophoresis is studied numerically by using the finite difference method. Isothermal heaters and coolers are placed along the vertical walls and the bottom horizontal wall, while the upper horizontal wall is kept adiabatic. Water-based nanofluids with alumina nanoparticles are chosen for investigation. The governing parameters of this study are the Rayleigh number (103 ≤ Ra ≤ 106), the Hartmann number (0 ≤ Ha ≤ 50), thermal Conductivity Ratio (0.28 ≤ k w ≤ 16), centered solid block size (0.1 ≤ D ≤ 0.7) and the nanoparticles volume fraction (0 ≤ ϕ ≤ 0.04). The developed computational code is validated comprehensively using the grid independency test and numerical and experimental data of other authors. The obtained results reveal that the effects of the thermal Conductivity Ratio, centered solid block size and the nanoparticles volume fraction are non-linear for the heat transfer rate. Therefore, it is possible to find optimal parameters for the heat transfer enhancement in dependence on the considered system. Moreover, high values of the Rayleigh number and nanoparticles volume fraction characterize homogeneous distributions of nanoparticles inside the cavity. High concentRation of nanoparticles can be found near the centered solid block where thermal plumes from the local heaters interact.
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effects of finite wall thickness and sinusoidal heating on convection in nanofluid saturated local thermal non equilibrium porous cavity
2017Co-Authors: Ammar I. Alsabery, Ishak Hashim, Ali J. Chamkha, Habibis Saleh, B ChananeAbstract:The effects of finite wall thickness and sinusoidal heating on convection in a nanofluid-saturated local thermal non-equilibrium (LTNE) porous cavity are studied numerically using the finite difference method. The finite thickness vertical wall of the cavity is maintained at a constant temperature and the right wall is heated sinusoidally. The horizontal insulated walls allow no heat transfer to the surrounding. The Darcy law is used along with the Boussinesq approximation for the flow. Water-based nanofluids with Cu nanoparticles are chosen for investigation. The results of this study are obtained for various parameters such as the Rayleigh number, periodicity parameter, nanoparticles volume fraction, thermal Conductivity Ratio, Ratio of wall thickness to its height and the modified Conductivity Ratio. Explanation for the influence of the various above-mentioned parameters on the streamlines, isotherms, local Nusselt number and the weighted average heat transfer is provided with regards to the thermal conductivities of nanoparticles suspended in the pure fluid and the porous medium. It is shown that the overall heat transfer is significantly increased with the relative non-uniform heating. Further, the convection heat transfer is shown to be inhibited by the presence of the solid wall. The results have possible applications in the heat-storage fluid-saturated porous systems and the applications of the high power heat transfer.
Hakan F Oztop - One of the best experts on this subject based on the ideXlab platform.
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natural convection in a cuo water nanofluid filled cavity under the effect of an inclined magnetic field and phase change material pcm attached to its vertical wall
2019Co-Authors: Fatih Selimefendigil, Ali J. Chamkha, Hakan F OztopAbstract:In this study, natural convection of CuO–water nanofluid in a square cavity with a conductive partition and a phase change material (PCM) attached to its vertical wall is numerically analyzed under the effect of an uniform inclined magnetic field by using finite element method. Effects of various pertinent parameters such as Rayleigh number (between \(10^5\) and \(10^6\)), Hartmann number (between 0 and 100), magnetic inclination angle (between \(0^{\circ}\) and \(90^{\circ}\)), PCM height (between 0.2H and 0.8H), PCM length (between 0.1H and 0.8H), thermal Conductivity Ratio (between 0.1 and 100) and solid nanoparticle volume fraction (between 0 and 0.04) on the fluid flow and thermal characteristics were numerically analyzed. It was observed that when magnetic field is imposed, more reduction in average Nusselt number for water is obtained as compared to nanofluid which is \(31.81\%\) for the nanofluid at the highest particle volume fraction. The average heat transfer augments with magnetic inclination angle, but it is less than \(5\%\). When the height of the PCM is increased which is from 0.2H to 0.8H, local and average Nusselt number reduced which is \(42.14\%\) . However, the length of the PCM is not significant on the heat transfer enhancement. When the Conductivity Ratio of the PCM to the base fluid within the cavity is increased from 0.1 to 10, \(29.5\%\) of the average Nusselt number enhancement is achieved.
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conjugate natural convection in a cavity with a conductive partition and filled with different nanofluids on different sides of the partition
2016Co-Authors: Fatih Selimefendigil, Hakan F OztopAbstract:Abstract In this study, conjugate natural convection–conduction heat transfer in an inclined partitioned cavity filled with different nanofluids (Al 2 O 3 –water and CuO–water) on different sides of the partition is numerically investigated by using finite element method. The left and right vertical walls of the square enclosure are maintained at constant hot and cold temperatures while other wall enclosures are assumed adiabatic. Different combinations of solid nanoparticle volume fractions are imposed in the left and right half cavities. Numerical simulations are performed for different values of Grashof numbers (between 10 3 and 10 6 ), inclination angles of the cavity (between 0 o and 275 o ), partition locations (between 0.15 and 0.75), thermal Conductivity Ratio (between 0.01 and 10) and solid volume fraction of the nanofluids of the two cavities (between 0 and 0.04). The averaged heat transfer enhances with Grashof number and solid particle volume fraction. It is also observed that adding nanoparticles with low thermal Conductivity on the right cavity is effective for the heat transfer enhancement as compared to adding nanoparticles with high thermal Conductivity. As the thermal Conductivity Ratio of the partition increases, the averaged heat transfer rate enhances and the highest value of the thermal Conductivity Ratio of 10, 14.11% of averaged heat transfer enhancement is obtained when both cavities are filled with nanofluids at the highest value of nanoparticle volume fractions.
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conduction combined forced and natural convection in lid driven enclosures divided by a vertical solid partition
2009Co-Authors: Hakan F Oztop, Zepu Zhao, Bo YuAbstract:Numerical simulations of the conduction-combined forced and natural convection (mixed convection) heat transfer and fluid flow have been performed for 2-D lid-driven square enclosure divided by a partition with a finite thickness and finite Conductivity. Left vertical wall of enclosure has two different orientations in positive or negative vertical coordinate. Buoyancy forces are taken into account in the system. Horizontal walls are adiabatic while two vertical walls are maintained isothermal temperature but the temperature of the left moving wall is higher than that of the right stationary wall. Thus, heat transfer regime between moving lid and partition is mixed convection. Conduction occurs along the partition. And, pure natural convection is formed between the partition and the right vertical wall. This investigation covers a wide range of Richardson number which is changed from 0.1 to 10, thermal Conductivity Ratio varies from 0.001 to 10. It is observed that higher heat transfer was formed for higher Richardson number for upward moving wall for all values of thermal Conductivity Ratio. When forced convection becomes effective, the orientation of moving lid becomes insignificant. Heat transfer is a decreasing function of increasing thermal Conductivity Ratio for all cases and Richardson numbers.
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entropy analysis due to conjugate buoyant flow in a right angle trapezoidal enclosure filled with a porous medium bounded by a solid vertical wall
2009Co-Authors: Yasin Varol, Hakan F Oztop, Ioan PopAbstract:Abstract Entropy geneRation due to buoyancy induced convection and conduction in a right angle trapezoidal enclosure filled with fluid saturated porous medium has been performed numerically. Left vertical solid wall of the trapezoidal enclosure has a finite thickness and Conductivity. The outside temperature of the solid wall is higher than that of inclined wall, while horizontal walls are adiabatic. The governing Darcy and energy equations are solved numerically using a finite difference method. The study is performed for different governing parameters including the Rayleigh number ( 50 ⩽ Ra ⩽ 1000 ), inclination angle of the inclined wall of the enclosure ( γ = 35 ° , 45° and 60°), dimensionless thickness of the solid vertical wall ( S = 0.05 , 0.1 and 0.2), and thermal Conductivity Ratio ( k = 0.1 , 1.0 and 10). Entropy geneRation is calculated by using the obtained velocities and temperature distributions from the computer code. Results are presented for the Bejan number, local and mean Nusselt numbers, streamlines, isotherms, iso-Bejan lines and entropy geneRation contours. It is found that the most important parameters on heat transfer and fluid flow are thermal Conductivity Ratio and dimensionless thickness of the solid wall of the enclosure. Thus, these parameters also generate entropy for the whole system. It is also found that increasing the Rayleigh number decreases the Bejan number; however, heat transfer is an increasing function of Rayleigh number.
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entropy geneRation due to conjugate natural convection in enclosures bounded by vertical solid walls with different thicknesses
2008Co-Authors: Yasin Varol, Hakan F Oztop, Ahmet KocaAbstract:Abstract Entropy geneRation due to conjugate natural convection heat transfer and fluid flow has been studied inside an enclosure with bounded by two solid massive walls from vertical sides at different thicknesses. Enclosure is differentially heated from vertical walls and horizontal walls are adiabatic. Governing equations which are written in streamfunction-vorticity form solved by finite difference technique for the governing parameters as Rayleigh number, 103 ≤ Ra ≤ 106, length Ratio of solid walls as ɛ1 (for left vertical wall) and ɛ2 (for right vertical wall) and thermal Conductivity Ratio of solid to fluid (k), 1 ≤ k ≤ 10. Entropy geneRation contours due to fluid friction and heat transfer irreversibility, isotherms, streamlines, Nusselt numbers and velocity profiles were obtained. It is found that entropy geneRation increases with increasing of thermal Conductivity Ratio and thicknesses of the walls. Entropy geneRation due to heat transfer is more significant than that of fluid flow irreversibility for all values of thickness of the solid vertical walls.
Omid Mahian - One of the best experts on this subject based on the ideXlab platform.
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natural convection of hybrid nanofluids inside a partitioned porous cavity for application in solar power plants
2019Co-Authors: Rasul Mohebbi, Omid Mahian, S A M Mehryan, Mohsen IzadiAbstract:The present article deals with the CFD simulation of natural convection heat transfer of a hybrid nanofluid in an inverted T-shaped cavity partitioned and saturated by two different types of porous media. Suspensions of organic and inorganic nanoparticles, i.e., MWCNTs and Fe3O4, in water were selected as the working fluid. The macroscopic conservation equations for the flow field and heat transfer were modeled via volume averaging the microscopic equations inside porous media over a representative elementary volume. The effects of many parameters were investigated. The parameters included the Rayleigh number (Ra = 103–106), porosity coefficient Ratio of two porous media (er = 0.5–1.8), volume fraction of the dispersed nanoparticles ( $$\varphi$$ = 0–0.003), Richardson number (Ri = 0.1–20), Darcy number Ratio of two porous media (Dar = 0.01, 1, 100) and thermal Conductivity Ratio of two porous media (kr = 0.2, 0.4, 1, 5). The results showed that, with an increase in the Rayleigh number, porosity Ratio and Darcy number Ratio and decrease in the thermal Conductivity Ratio, the averaged Nusselt number increased.
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A proposed model to predict thermal Conductivity Ratio of Al_2O_3/EG nanofluid by applying least squares support vector machine (LSSVM) and genetic algorithm as a connectionist approach
2019Co-Authors: Mohammad Hossein Ahmadi, Mohammad Alhuyi Nazari, Mohammad Ali Ahmadi, Omid Mahian, Roghayeh GhasempourAbstract:In this study, a model is proposed by applying the least squares support vector machine (LSSVM). In addition, genetic algorithm is used for selection and optimization of hyperparameters that are embedded in the LSSVM model. In addition to temperature and concentRation of nanoparticles, the parameters which are used in most of the modeling procedures for thermal Conductivity, the effect of particle size is considered. By considering the size of nanoparticles as one of the input variables, a more comprehensive model is obtained which is applicable for wider ranges of influential factor on the thermal Conductivity of the nanofluid. The coefficient of determination ( R ^2) for the introduced model is equal to 0.9902, and the mean squared error is 8.64 × 10^−4 for the thermal Conductivity Ratio of Al_2O_3/EG.
Masoud Afrand - One of the best experts on this subject based on the ideXlab platform.
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an experimental study on the thermal Conductivity of cerium oxide ethylene glycol nanofluid developing a new correlation
2018Co-Authors: Mehdi Keyvani, Masoud Afrand, Davood Toghraie, Mahdi ReiszadehAbstract:Abstract The main aim of this experimental study is to examine the effect of cerium oxide nanoparticles on the thermal Conductivity of ethylene glycol. In this way, cerium oxide nanoparticles with the particle diameter of 10–30 nm have been used for making nanofluid samples. The samples were made in volume concentRation range of 0.25–2.5% using a two-step method. Visual observation of nanofluid samples showed that they have acceptable stability. Transient hot wire method was used for measuring the thermal Conductivity of the samples. Measurements were done for all samples at temperatures ranging from 25to 50°C. Measurements showed that the thermal Conductivity of nanofluid enhanced with increasing temperature and solid volume fraction. The results also showed that the thermal Conductivity of ethylene glycol could enhance by about 22% when the nanoparticles volume fraction reaches 2.5%. This enhancement occurred at 50°C. Finally, a mathematical correlation was presented to predict the thermal Conductivity Ratio of CeO2/EG using curve-fitting. This correlation, a two-variable function of temperature and volume fraction, showed a linear relationship between thermal Conductivity Ratio and these variables.
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thermal Conductivity enhancement of cooh functionalized mwcnts ethylene glycol water nanofluid for application in heating and cooling systems
2016Co-Authors: Mehdi Soltanimeh, Masoud AfrandAbstract:Abstract In this paper, an experimental investigation on the effects of temperature and nanotubes concentRation on the thermal Conductivity of MWCNTs/EG–water (40:60 vol.%) nanofluids is presented. The experiments were performed at temperatures ranging from 25 °C to 50 °C and solid volume fraction range of 0–1.0%. They showed that the thermal Conductivity Ratio enhances with increasing the solid volume fraction and temperature. Moreover, at higher concentRation of MWCNTs, the effect of temperature on the thermal Conductivity Ratio was more tangible. The thermal Conductivity measurements also indicated that the maximum enhancement of thermal Conductivity of nanofluid was 34.7%, which occurred at solid volume fraction of 1.0% and temperature of 50 °C. The experimental results were compared with data obtained from Maxwell model. Since, this model failed to predict the thermal Conductivity of the nanofluid, for engineering applications, using experimental findings, an accurate correlation was presented to predict the thermal Conductivity of MWCNTs/EG–water (40:60 vol.%) nanofluids. The maximum value of the deviation was obtained ±1.8% for the proposed correlation.
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experimental study on thermal Conductivity of water based fe3o4 nanofluid development of a new correlation and modeled by artificial neural network
2016Co-Authors: Masoud Afrand, Davood Toghraie, Nima SinaAbstract:Abstract In this paper, the thermal Conductivity of Fe 3 O 4 magnetic nanofluids has been investigated experimentally. The nanofluid samples were prepared using a two-step method by dispersing Fe 3 O 4 nanoparticles into the water with the solid volume fractions of 0.1%, 0.2%, 0.4%, 1%, 2% and 3%. Thermal Conductivity measurements were performed by employing a KD2 Pro thermal properties analyser under temperatures ranging from 20 °C to 55 °C. Then, using experimental data, a new correlation was proposed to predict the thermal Conductivity Ratio of the magnetic nanofluid. Finally, an optimal artificial neural network was designed to predict the thermal Conductivity Ratio of the magnetic nanofluid. The experimental results indicated that the maximum enhancement of thermal Conductivity of nanofluid was about 90%, which occurred at solid volume fraction of 3.0% and temperature of 55 °C. The comparative results showed that there are deviations of 5% and 1.5%, respectively, for correlation and ANN from the experimental data. It was found from comparisons that the optimal artificial neural network model is more accurate compared to empirical correlation.
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measurement of thermal Conductivity of zno tio2 eg hybrid nanofluid
2016Co-Authors: Davood Toghraie, Vahid Avalin Chaharsoghi, Masoud AfrandAbstract:The hybrid nanofluids are novel nanofluids and can be prepared by suspending various kinds of nanoparticles in base fluid. In this paper, an experimental investigation on the effects of temperature and nanoparticles concentRation on the thermal Conductivity of ZnO–TiO2/EG hybrid nanofluids is presented. The experiments were implemented at temperature ranging from 25 to 50 °C and solid volume fraction range of 0–3.5 %. Experiments indicate that the thermal Conductivity enhances with increasing the solid volume fraction and temperature. It was found that the variation of thermal Conductivity enhancement of nanofluids with solid volume fraction at higher temperatures is greater than that at lower temperature. Moreover, it can be also seen that the variation of thermal Conductivity enhancement of nanofluids with temperature at higher solid volume fraction is more than that at lower solid volume fraction. Finally, based on experimental data, in order to predict the thermal Conductivity Ratio of ZnO–TiO2/EG hybrid nanofluids, a correlation was proposed. Deviation analysis of the thermal Conductivity Ratio was also performed. Comparison between experimental data and the proposed correlation outputs revealed that this correlation has a good accuracy.
Ammar I. Alsabery - One of the best experts on this subject based on the ideXlab platform.
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mhd convective heat transfer in a discretely heated square cavity with conductive inner block using two phase nanofluid model
2018Co-Authors: Ammar I. Alsabery, Mikhail A Sheremet, Ali J. Chamkha, Ishak HashimAbstract:The problem of steady, laminar natural convection in a discretely heated and cooled square cavity filled by an alumina/water nanofluid with a centered heat-conducting solid block under the effects of inclined uniform magnetic field, Brownian diffusion and thermophoresis is studied numerically by using the finite difference method. Isothermal heaters and coolers are placed along the vertical walls and the bottom horizontal wall, while the upper horizontal wall is kept adiabatic. Water-based nanofluids with alumina nanoparticles are chosen for investigation. The governing parameters of this study are the Rayleigh number (103 ≤ Ra ≤ 106), the Hartmann number (0 ≤ Ha ≤ 50), thermal Conductivity Ratio (0.28 ≤ k w ≤ 16), centered solid block size (0.1 ≤ D ≤ 0.7) and the nanoparticles volume fraction (0 ≤ ϕ ≤ 0.04). The developed computational code is validated comprehensively using the grid independency test and numerical and experimental data of other authors. The obtained results reveal that the effects of the thermal Conductivity Ratio, centered solid block size and the nanoparticles volume fraction are non-linear for the heat transfer rate. Therefore, it is possible to find optimal parameters for the heat transfer enhancement in dependence on the considered system. Moreover, high values of the Rayleigh number and nanoparticles volume fraction characterize homogeneous distributions of nanoparticles inside the cavity. High concentRation of nanoparticles can be found near the centered solid block where thermal plumes from the local heaters interact.
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effects of finite wall thickness and sinusoidal heating on convection in nanofluid saturated local thermal non equilibrium porous cavity
2017Co-Authors: Ammar I. Alsabery, Ishak Hashim, Ali J. Chamkha, Habibis Saleh, B ChananeAbstract:The effects of finite wall thickness and sinusoidal heating on convection in a nanofluid-saturated local thermal non-equilibrium (LTNE) porous cavity are studied numerically using the finite difference method. The finite thickness vertical wall of the cavity is maintained at a constant temperature and the right wall is heated sinusoidally. The horizontal insulated walls allow no heat transfer to the surrounding. The Darcy law is used along with the Boussinesq approximation for the flow. Water-based nanofluids with Cu nanoparticles are chosen for investigation. The results of this study are obtained for various parameters such as the Rayleigh number, periodicity parameter, nanoparticles volume fraction, thermal Conductivity Ratio, Ratio of wall thickness to its height and the modified Conductivity Ratio. Explanation for the influence of the various above-mentioned parameters on the streamlines, isotherms, local Nusselt number and the weighted average heat transfer is provided with regards to the thermal conductivities of nanoparticles suspended in the pure fluid and the porous medium. It is shown that the overall heat transfer is significantly increased with the relative non-uniform heating. Further, the convection heat transfer is shown to be inhibited by the presence of the solid wall. The results have possible applications in the heat-storage fluid-saturated porous systems and the applications of the high power heat transfer.