Sidi El Becaye Maïga
Bio: Sidi El Becaye Maïga is an academic researcher from Université de Moncton. The author has contributed to research in topic(s): Nanofluid & Heat transfer coefficient. The author has an hindex of 7, co-authored 7 publication(s) receiving 1770 citation(s).
Topics: Nanofluid, Heat transfer coefficient, Heat transfer enhancement, Heat transfer, Forced convection
01 Aug 2005-International Journal of Heat and Fluid Flow
Abstract: In the present paper, the problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water–γAl2O3 and Ethylene Glycol–γAl2O3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol–γAl2O3 nanofluid appears to offer a better heat transfer enhancement than water–γAl2O3; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered. For the case of radial flow, results have also shown that both the Reynolds number and the distance separating the disks do not seem to considerably affect in one way or another the heat transfer enhancement of the nanofluids (i.e. when compared to the base fluid at the same Reynolds number and distance).
01 Mar 2004-Superlattices and Microstructures
Abstract: In the present work, we consider the problem of the forced convection flow of water– γAl2O3 and ethylene glycol– γAl2O3 nanofluids inside a uniformly heated tube that is submitted to a constant and uniform heat flux at the wall. In general, it is observed that the inclusion of nanoparticles has increased considerably the heat transfer at the tube wall for both the laminar and turbulent regimes. Such improvement of heat transfer becomes more pronounced with the increase of the particle concentration. On the other hand, the presence of particles has produced adverse effects on the wall friction that also increases with the particle volume concentration. Results have also shown that the ethylene glycol– γAl2O3 mixture gives a far better heat transfer enhancement than the water– γAl2O3 mixture.
Abstract: Purpose – To study the hydrodynamic and thermal behaviors of a turbulent flow of nanofluids, which are composed of saturated water and Al2O3 nanoparticles at various concentrations, flowing inside a tube submitted to a uniform wall heat flux boundary condition.Design/methodology/approach – A numerical method based on the “control‐volume” approach was used to solve the system of non‐linear and coupled governing equations. The classical κ‐e model was employed in order to model the turbulence, together with staggered non‐uniform grid system. The computer model, satisfactorily validated, was used to perform an extended parametric study covering wide ranges of the governing parameters. Information regarding the hydrodynamic and thermal behaviors of nanofluid flow are presented.Findings – Numerical results show that the inclusion of nanoparticles into the base fluid has produced an augmentation of the heat transfer coefficient, which has been found to increase appreciably with an increase of particles volume co...
01 Aug 2004-International Journal of Thermal Sciences
Abstract: The problem of the transient laminar mixed convection flow of air in a vertical tube under buoyancy effect and high wall heat flux condition has been numerically investigated by using a full 3D-transient-model and Boussinesq's assumptions. The tube is submitted to a uniform but time-dependent wall heat flux. Results have clearly shown that the flow reversal was first initiated near the tube exit section, on the tube wall and at the level Gr=3×105 for opposed-buoyancy case, and on the tube centerline and at the level of Grashof number around 106 for assisted-buoyancy one. With further increase in time of the wall heat flux, such reversed flow region has considerably increased in size and intensity and it clearly spreads into the upstream region. The presence of such recirculation cells has drastically perturbed the flow and the thermal field as well as the heat transfer. Although the flow structure appears to conserve its axisymmetrical characters even for cases with very high Grashof numbers, results from this study have shown that the flow seems to remain stable and unique up to the level Gr=5×105 and 106, respectively, for opposed and assisted buoyancy cases. Beyond these critical Grashof numbers, an extremely slow and rather difficult and tedious convergence behaviors have been experienced, which are believed to be due to a possible flow transition.
01 Jan 2005-
Abstract: The problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water-γAl 2 O 3 and Ethylene Glycol-γAl 2 O 3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol -γAl 2 O 3 nanofluid appears to offer a better heat transfer enhancement than water- γ/Al 2 O 3 ; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered
Jacopo Buongiorno1•Institutions (1)
Abstract: Nanofluids are engineered colloids made of a base fluid and nanoparticles (1-100 nm) Nanofluids have higher thermal conductivity' and single-phase heat transfer coefficients than their base fluids In particular the heat transfer coefficient increases appear to go beyond the mere thermal-conductivity effect, and cannot be predicted by traditional pure-fluid correlations such as Dittus-Boelter's In the nanofluid literature this behavior is generally attributed to thermal dispersion and intensified turbulence, brought about by nanoparticle motion To test the validity of this assumption, we have considered seven slip mechanisms that can produce a relative velocity between the nanoparticles and the base fluid These are inertia, Brownian diffusion, thermophoresis, diffusioplwresis, Magnus effect, fluid drainage, and gravity We concluded that, of these seven, only Brownian diffusion and thermophoresis are important slip mechanisms in nanofluids Based on this finding, we developed a two-component four-equation nonhomogeneous equilibrium model for mass, momentum, and heat transport in nanofluids A nondimensional analysis of the equations suggests that energy transfer by nanoparticle dispersion is negligible, and thus cannot explain the abnormal heat transfer coefficient increases Furthermore, a comparison of the nanoparticle and turbulent eddy time and length scales clearly indicates that the nanoparticles move homogeneously with the fluid in the presence of turbulent eddies so an effect on turbulence intensity is also doubtful Thus, we propose an alternative explanation for the abnormal heat transfer coefficient increases: the nanofluid properties may vary significantly within the boundary layer because of the effect of the temperature gradient and thermophoresis For a heated fluid, these effects can result in a significant decrease of viscosity within the boundary layer, thus leading to heat transfer enhancement A correlation structure that captures these effects is proposed
01 Jan 2007-International Journal of Thermal Sciences
Abstract: Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension This review summarizes recent research on fluid flow and heat transfer characteristics of nanofluids in forced and free convection flows and identifies opportunities for future research
01 Jun 2009-International Journal of Heat and Mass Transfer
Abstract: Nanofluids are considered to offer important advantages over conventional heat transfer fluids. Over a decade ago, researchers focused on measuring and modeling the effective thermal conductivity and viscosity of nanofluids. Recently important theoretical and experimental research works on convective heat transfer appeared in the open literatures on the enhancement of heat transfer using suspensions of nanometer-sized solid particle materials, metallic or nonmetallic in base heat transfer fluids. The purpose of this review article is to summarize the important published articles on the enhancement of the forced convection heat transfer with nanofluids.
01 Oct 2008-International Journal of Heat and Fluid Flow
Abstract: Heat transfer and fluid flow due to buoyancy forces in a partially heated enclosure using nanofluids is carried out using different types of nanoparticles. The flush mounted heater is located to the left vertical wall with a finite length. The temperature of the right vertical wall is lower than that of heater while other walls are insulated. The finite volume technique is used to solve the governing equations. Calculations were performed for Rayleigh number (103 ⩽ Ra ⩽ 5 × 105), height of heater (0.1 ⩽ h ⩽ 0.75), location of heater (0.25 ⩽ yp ⩽ 0.75), aspect ratio (0.5 ⩽ A ⩽ 2) and volume fraction of nanoparticles (0 ⩽ φ ⩽ 0.2). Different types of nanoparticles were tested. An increase in mean Nusselt number was found with the volume fraction of nanoparticles for the whole range of Rayleigh number. Heat transfer also increases with increasing of height of heater. It was found that the heater location affects the flow and temperature fields when using nanofluids. It was found that the heat transfer enhancement, using nanofluids, is more pronounced at low aspect ratio than at high aspect ratio.
01 May 2007-International Journal of Heat and Mass Transfer
Abstract: The behaviour of nanofluids is investigated numerically inside a two-sided lid-driven differentially heated square cavity to gain insight into convective recirculation and flow processes induced by a nanofluid. A model is developed to analyze the behaviour of nanofluids taking into account the solid volume fraction χ. The transport equations are solved numerically with finite volume approach using SIMPLE algorithm. Comparisons with previously published work on the basis of special cases are performed and found to be in excellent agreement. The left and the right moving walls are maintained at different constant temperatures while the upper and the bottom walls are thermally insulated. Three case were considered depending on the direction of the moving walls. Governing parameters were 0.01 < Ri < 100 but due to space constraints only the results for 0.1 < Ri < 10 are presented. It is found that both the Richardson number and the direction of the moving walls affect the fluid flow and heat transfer in the cavity. Copper–Water nanofluid is used with Pr = 6.2 and solid volume fraction χ is varied as 0.0%, 8%, 16% and 20%. Detailed results are presented for flow pattern and heat transfer curves.