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ABSTRACT
In the present work, enhancement of convective heat transfer rate in three-dimensional U-shaped enclosures using nanofluids is numerically investigated. Two different types of nanoparticles, namely, Cu, and Al2O3, with pure water, are the considered single-phase nanofluids. Natural convection and geometric parameter effects on the averaged Nusselt numbers are investigated. Velocity vectors and isotherm fields for the Al2O3/H2O nanofluid are presented at various Rayleigh numbers. The governing dimensionless equations are solved using the commercial finite-volume-based computational fluid dynamics code, FLUENT. Our results are consistent with previously published predictions. In particular, heat transfer enhancement is found to increase with increasing nanoparticles volume fractions, Rayleigh numbers, as well as cooled wall length extensions.
Nomenclature
| Cp | = | Specific heat capacity, J·kg−1·K−1 |
| C1 | = | Left side concave surface, m2 |
| C2 | = | Bottom concave surface, m2 |
| C3 | = | Right side concave surface, m2 |
| CFD | = | Computational fluid dynamics |
| ds | = | Nanoparticle diameter, m2 |
| g | = | Gravitational acceleration, m·s−2 |
| H | = | Domain height, m |
| h | = | Heat transfer coefficient, W·m−2·K−1 |
| k | = | Thermal conductivity, W·m−1·K−1 |
| L1 | = | Width of the concave in the U-shaped cavity, m |
| L2 | = | Height of the concave in the U-shaped cavity, m |
| n | = | Normal vector |
| Nuloc | = | Local Nusselt number |
| Nuavg | = | Average Nusselt number |
| p | = | Pressure, Pa = kg·m−1·s−2 |
| p* | = | Dimensionless pressure |
| Pr | = | Prandtl number |
| q | = | Constant heat flux, W·m−2 |
| Ri | = | Richardson number |
| Ra | = | Rayleigh number ( = g βH3ΔT/να) |
| S1 | = | Left side surface, m2 |
| S2 | = | Bottom surface, m2 |
| S3 | = | Right side surface, m2 |
| T | = | Temperature, K |
| Th | = | Hot cube wall temperature, K |
| Tc | = | Cold cube wall temperature, K |
| u, v, w | = | Dimensional velocity components, m.s−1 |
| u*, v*,w* | = | Dimensionless velocity component |
| x, y, z | = | Cartesian coordinates, m |
| x*, y*, z* | = | Dimensionless Cartesian coordinates |
| Greek Symbols | ||
| α | = | Thermal diffusivity, m2·s−1 |
| β | = | Thermal expansion coefficient, K−1 |
| Θ* | = | Dimensionless temperature |
| μ | = | Dynamic viscosity, kg·m−1·s−1 |
| ν | = | Kinematic viscosity, m2·s−1 |
| ξ | = | Empirical shape factor |
| ρ | = | Density, kg·m−3 |
| ϕ | = | Volume fraction of nanofluids |
| ψ | = | Particle sphericity |
| Subscripts | ||
| avg | = | Average |
| f | = | Fluid |
| s | = | Solid particle |
| sr | = | Surface |
| h | = | Hot |
| c | = | Cold |
| nf | = | Nanofluid |
| Superscript | ||
| * | = | Dimensionless quantity |
Additional information
Notes on contributors
Lotfi Snoussi
Lotfi Snoussiis a Research Assistant Professor at the HIEST. Member of Thermal Processes Laboratory (LPT) within Research and Technology Center of Energy (CRTEn), Borj-Cedria, Tunisia. He received his M.Sc. and Ph.D. Diploma in fluid mechanics at the University of Tunisia. His research interests include nanofluids dynamics, heat and mass transfer simulation, CFD. He is a Civil Society Activist, Board Member of some Associations and Organizations, member of Tunisian Writers' Union, Poets & Writers. He has published a collection of poems and a book in the political analytical articles.
Noureddine Ouerfelli
Noureddine Ouerfelli has a Ph.D. and Habilitation Diploma in Physical Chemistry; he is a head of research project in the Laboratory of Biophysics and Medical Technologies. He has published about 50 papers in international journals on modeling and prediction of physicochemical and thermophysical properties of fluids in different types of liquid solutions.
Xavier Chesneau
Xavier Chesneau has a Ph.D. and Habilitation Diploma in fluid mechanics. Within the LAMPS laboratory, his research work concerns the understanding and the control of various phenomena implied in the fields of the mechanics and thermal sciences. His research work provided over 30 publications in international reviews and 60 oral presentations in international congresses.
Ali J. Chamkha
Ali J. Chamkha is the Dean of Research, Professor and former Chairman of the Mechanical Engineering Department and Prince Sultan Endowed Chair for Energy and Environment at Prince Mohammad Bin Fahd University in the Kingdom of Saudi Arabia. He earned his Ph.D. in Mechanical Engineering from Tennessee Technological University, USA, in 1989. His research interests include multiphase fluid-particle dynamics, nanofluids dynamics, fluid flow in porous media, heat and mass transfer, magnetohydrodynamics and fluid-particle separation. He has served as an editor, associate editor, or a member of the editorial board for many journals. He has authored and co-authored over 550 publications in archival international journals and conferences.
Fethi Bin Muhammad Belgacem
Fethi Bin Muhammad Belgacem earned all his undergraduate, and graduate degrees from the University of Miami, Florida, USA. He received his B.S. in Engineering Science/Math/Physics in 1985, his Dual M.S. in Mathematics and Biomedical Engineering in 1990/1991, and a Ph.D. in Mathematics in 1994. He then sequentially served as a Faculty in the University of Miami, Kuwait University, and Kuwait Arab Open University. Currently he is serving in the Department of Mathematics in the Public Authority for Applied Education and Training PAAET. His main interests span a variety of interdisciplinary fields in engineering, mathematics, physics and science. To date, he published over 80 scientific journal and conference papers and three mathematical books and served as plenary speakers in many specialized international scientific conferences.
Amenallah Guizani
AmenAllah Guizani is a Professor of Mechanical Engineering at University of Carthage. He received his Ph.D. from the University of Tunis and since 1988 he has been the head of the Thermal Process Laboratory of CRTEn. His research activities concern mainly renewable energies and heat transfer simulation. He has held the position of local team coordinator of 2 EU funded projects. He is a member of Tunisian Society of Physics and is National Contact Point in Energy