Thermal Science 2015 Volume 19, Issue 2, Pages: 591-608
https://doi.org/10.2298/TSCI120328111C
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Natural convection in square enclosures differentially heated at sides using alumina-water nanofluids with temperature-dependent physical properties
Cianfrini Marta (DIAEE Sezione Fisica Tecnica - Sapienza Università di Roma, Rome, Italy)
Corcione Massimo (DIAEE Sezione Fisica Tecnica - Sapienza Università di Roma, Rome, Italy)
Quintino Alessandro (DIAEE Sezione Fisica Tecnica - Sapienza Università di Roma, Rome, Italy)
Laminar natural convection of Al2O3 + H2O nanofluids inside square cavities
differentially heated at sides is studied numerically. A computational code
based on the SIMPLE-C algorithm is used for the solution of the system of the
mass, momentum and energy transfer governing equations. Assuming that the
nanofluid behaves like a single-phase fluid, these equations are the same as
those valid for a pure fluid, provided that the thermophysical properties
appearing in them are the nanofluid effective properties. The thermal
conductivity and dynamic viscosity of the nanofluid are calculated by means
of a couple of empirical equations based on a wide variety of experimental
data reported in the literature. The other effective properties are evaluated
by the conventional mixing theory. Simulations are performed for different
values of the nanoparticle volume fraction in the range 0-0.06, the diameter
of the suspended nanoparticles in the range 25-100 nm, the temperature of
the cooled sidewall in the range 293-313 K, the temperature of the heated
sidewall in the range 298-343 K, and the Rayleigh number of the base fluid in
the range 103-107. All computations are executed in the hypothesis of
temperature-dependent effective properties. The main result obtained is the
existence of an optimal particle loading for maximum heat transfer, that is
found to increase as the size of the suspended nanoparticles is decreased,
and the nanofluid average temperature is increased.
Keywords: nanofluid, temperature-dependent physical properties, natural convection, side-heated enclosure, numerical analysis