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Computational Thermal Sciences: An International Journal
ESCI SJR: 0.249 SNIP: 0.434 CiteScore™: 1.4

ISSN 印刷: 1940-2503
ISSN オンライン: 1940-2554

Computational Thermal Sciences: An International Journal

DOI: 10.1615/.2014010754
pages 199-217

NUMERICAL STUDY OF NATURAL CONVECTION HEAT TRANSFER OF NANOFLUIDS IN PARTIALLY HEATED SEMI-ANNULI

Sonia Bezi
Laboratory of Mechanic of Fluids, Physics Department, Faculty of Sciences of Tunis, University of Tunis El-Manar, 2092 El-Manar II, Tunis, Tunisia
Antonio Campo
Department of Mechanical Engineering, The University of Texas at San Antonio, San Antonio, Texas 78249, USA
Nader Ben-Cheikh
Laboratory of Mechanic of Fluids, Physics Department, Faculty of Sciences of Tunis, University of Tunis El-Manar, 2092 El-Manar II, Tunis, Tunisia
Brahim Ben-Beya
Laboratory of Physics of Fluids, Physics Department, Faculty of Science of Tunis, University of Tunis El-Manar, 2092 El-Manar 2, Tunis, Tunisia

要約

This study addresses a numerical analysis of heat transfer and fluid flow in a partially heated horizontal annulus filled with nanofluids. The conservation equations in cylindrical coordinates are solved using an in-house FORTRAN code based on the finite-volume method coupled with multigrid acceleration. A heat source owing constant temperature is placed along the outer cylinder of the annular region. The temperature of the inner cylinder is lower than that of the outer cylinder, while the remaining parts are kept insulated. The numerical investigation is carried out for a Rayleigh number in the range of 102 ≤ Ra ≤ 106 and for solid volume fraction of nanoparticles limited to 0 ≤ φ ≤ 0.08. Four nanoparticles (Au, Cu, CuO, Al2O3) and three base fluids (water, ethylene glycol, oil) are selected to examine potential heat transfer enhancement in the annulus. In order to investigate the effects of the size and/or location of the heat source on the fluid flow and heat transfer, different configurations are considered. Results are presented in terms of streamline and isotherms plots, as well as the local and average Nusselt numbers at the heat source surface under different conditions. It is found that the average Nusselt number exhibits an increasing trend as dual functions of the Rayleigh number and the solid volume fraction of the nanoparticles. Furthermore, the results reveal that one type of nanoparticle or base fluid is a key factor for improving the heat transfer. In particular, the highest values of enhancement are obtained when using Au nanoparticles or an oil base fluid. Moreover, it is observed that the size, γ, and location, θp, of the heat source significantly affect the resulting convective flow. An optimum size of the heat source is manifested in which the average Nusselt number attains a minimum for a given Rayleigh number. Reliable correlations formulae expressing the average Nusselt number in terms of Ra, φ, γ, and θp are established.


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