Sofiane Touahri

Bio: Sofiane Touahri is an academic researcher. The author has contributed to research in topics: Nusselt number & Grashof number. The author has an hindex of 3, co-authored 7 publications receiving 41 citations.

Laminar mixed convective heat transfer enhancement by using Ag-TiO 2 -water hybrid Nanofluid in a heated horizontal annulus

Abstract: In the present paper, laminar mixed convection in horizontal annulus filled with a TiO2/water nanofluid and Ag-TiO2/water hybrid nanofluid has been numerically studied. The outer cylinder is uniformly heated while the inner cylinder is adiabatic. The governing equations with the appropriate boundary conditions are discretized by the finite volume method with second order precision, and solved by using the SIMPLER and Thomas algorithms. The numerical simulations are performed for various nanoparticles volume fractions, between 0 and 8% and Grashof numbers between 105 and 106. The results shows that for all studied Grashof numbers, the local and average Nusselt numbers, and the bulk temperature increase with the increasing of the volume fraction and the Grashof number. The heat transfer is very enhancement when using a Ag-TiO2/water hybrid nanofluid compared to the similar TiO2/water nanofluid. Moreover, the exploitation of the numerical results that we obtained enabled us to develop two new correlations, which allow the estimation of the average Nusselt number. The results reveal that the numerical data are in a good agreement with the correlation data. The maximum error for nanofluid and hybrid nanofluid was around 2.5% and 4.7% respectively. Hence, among the multitude of the obtained results in this work, it remains that the new correlations developed, especially for the hybrid nanofluid Ag-TiO2 / water, constitute for their originality, the most significant result of this research.

Numerical study of the conjugate heat transfer in a horizontal pipe heated by joulean effect

Abstract: The 3-D mixed convection heat transfer in a electrically heated horizontal pipe conjugated to a thermal conduction through the entire solid thickness is investigated by taking into account the thermal dependence of the physical properties of the fluid and the outer heat losses. The model equations of continuity, momentum, and energy are numerically solved by the finite volume method. The pipe thickness, the Prandtl and the Reynolds numbers are fixed while the Grashof number is varied from 10 4 to 10 7 The results obtained show that the dynamic and thermal fields for mixed convection are qualitatively and quantitatively different from those of forced convection, and the local Nusselt number at the interface solid-fluid is not uniform: it has considerable axial and azimuthally variations. The effect of physical variables of the fluid depending on temperature is significant, which justifies its inclusion. The heat transfer is quantified by the local and average Nusselt numbers. We found that the average Nusselt number of solid-fluid interface of the duct increases with the increase of Grashof number. We have equally found out that the heat transfer is improved thanks to the consideration of the thermo dependence of the physical properties. We have tried modelling the average Nusselt number as a function of Richardson number. With the parameters used, the heat transfer is quantified by the correlation: NuA = 12.753 Ri 0.156 .

Prediction of Nanofluid Forced and Mixed Convection Heat Transfer through an Annular Pipe

Abstract: This work is a numerical simulation of the 3D forced and mixed convection heat transfer of Al2O3water nanofluid flow through an annular pipe. The interest of this research is in enhancing heat transfer by using a nanofluid instead a usual fluid without solid particles. The external pipe is uniformly heated while the inner cylinder is insulated. Based on the single approach, the conservation equations are solved by a second order precision finite volume method. Extensive results are obtained for different values of the Reynolds (5002000) and Grashof (0, 10, 10) numbers and the nanoparticle concentration (1, 4, 8%). Our results show that the mixed convection Nusselt number becomes more superior to that of the forced convection when the Grashof number is increased. Furthermore, when the Reynolds number is fixed, the temperatures undergo a circumstantial variation under the influence of the Grashof number with significant azimuthally variation. Also, for the same concentration of nanoparticles, temperatures within the nanofluid are strongly influenced by the Reynolds number. They decrease with increasing Reynolds number.

Numerical study of developing laminar mixed convection in a heated annular duct with temperature dependent properties

Abstract: This study presents a numerical simulation of the 3-D laminar mixed convection between two concentric horizontal cylinders with physical properties which depend on temperature. The outer cylinder is subjected to an internal energy generated by the Joule effect whereas the inner cylinder is adiabatic. The flow and thermal fields are modeled by the continuity, momentum, and energy equations with appropriate initial and boundary conditions using a cylindrical co-ordinate system. The model equations are numerically solved by a finite volume method with a second order accurate spatiotemporal discretization. For the considered geometric, dynamic and thermal controlling parameters, it is found that the transverse flow is always the cause of the circumferential variation of the temperature and the physical properties of the fluid. The phenomenon of the temperature stratification is highlighted and the vortices obtained lead to an improvement in the heat transfer quantified by the increase in the number of Nusselt. The obtained axial Nusselt number increases with the increased of Grashof number which is proportional to the heat flux imposed at the surface of the outer cylinder.

Numerical Heat Transfer And Fluid Flow

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Heat and Mass Transfer

Abstract: Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

Utilization of hybrid nanofluids in solar energy applications: A review

Abstract: Hybrid nanofluids have several advantages compared with the conventional types due to their modified properties. Their enhanced thermophysical and rheological properties make them more appropriate for solar energy systems. In this review paper, an overview of solar energy systems is represented, and afterwards, applications of hybrid nanofluids in various solar technologies, especially solar thermal, are reviewed. Comparison between the nanofluidic systems, and the conventional ones is performed in order to gain a deeper insight into the advantages of using nanofluids. According to the results of the reviewed studies, the most important reason for performance enhancement of nanofluidic solar energy systems can be attributed to the improved thermal properties of the convective fluid. In addition, it can be concluded that the nanofluids’ specifications such as concentration of the nanostructures, type of the solid phase, etc., have significant impact on the behavior of the considered systems.

Magnetohydrodynamic Natural Convection Heat Transfer of Hybrid Nanofluid in a Square Enclosure in the Presence of a Wavy Circular Conductive Cylinder

Abstract: In this paper, steady natural convective heat transfer and flow characteristics of Al2O3-Cu/water hybrid nanofluid filled square enclosure in the presence of magnetic field has been investigated numerically. The enclosure is equipped with a wavy circular conductive cylinder. The natural convection in the cavity is induced by a temperature difference between the vertical left hot wall and the other right cold wall. The steady 2-D equations of laminar natural convection problem for Newtonian and incompressible mixture are discretized using the finite volume method. The effective thermal conductivity and viscosity of the hybrid nanofluid are calculated using Corcione correlations taking into consideration the Brownian motion of the nanoparticles. A numerical parametric investigation is carried out for different values of the nanoparticles volumic concentration, Hartmann number, Rayleigh number, and the ratio of fluid to solid thermal conductivities. According to the results, the corrugated conductive block plays an important role in controlling the convective flow characteristic and the heat transfer rate within the system.