Abstract
This numerical study considers the mixed convection and the inherent entropy generated in AlO–water nanofluid filling a cavity containing a rotating conductive cylinder. The vertical walls of the cavity are wavy and are cooled isothermally. The horizontal walls are thermally insulated, except for a heat source segment located at the bottom wall. The dimensionless governing equations subject to the selected boundary conditions are solved numerically using the Galerkin finite-element method. The study is accomplished by inspecting different ranges of the physical and geometrical parameters, namely, the Rayleigh number (), angular rotational velocity (), number of undulations (), volume fraction of AlO nanoparticles (), and the length of the heat source . The results show that the rotation of the cylinder boosts the rate of heat exchange when the Rayleigh number is less than . The number of undulations affects the average Nusselt number for a still cylinder. The rate of heat exchange increases with the volume fraction of the AlO nanoparticles and the length of the heater segment.
Highlights
Natural convection contributes vitally in releasing or adding energy from enclosures, mixed convection might be more appropriate in such a task
The values of the irreversibility distribution ratio, amplitude, thermal conductivity of the solid cylinder, dimensionless radius of rotating cylinder, dimensionless length of the surface of the cylinder and Prandtl number are fixed at Nμ = 10−3, A = 0.1, k s = 0.76 W/m·K, R = 0.2, Θ = 360 and Pr = 4.623, respectively
This paper presents a numerical study of entropy generation in mixed convection resulting from the rotation of a conductive cylinder inside a cavity with wavy walls under the assumption of laminar
Summary
Natural convection contributes vitally in releasing or adding energy from enclosures, mixed convection might be more appropriate in such a task. Mixed convection is often regarded for efficient heat transfer removal or control in cooling of electric and electronic systems, lubrication [1], emergency cooling systems of nuclear reactors, etc. Moving surfaces are considered a common mechanism to introduce the mixed convection in enclosures. Moving surfaces may be lid-driven walls or rotating bodies inside the enclosure. Other strategies can contribute in enhancing the process of heat removal such as the use of nanofluids and increasing the surface area. Increasing of the surface area can be carried out by corrugating some isothermal walls of the enclosures [3]. According to the second law of Entropy 2018, 20, 664; doi:10.3390/e20090664 www.mdpi.com/journal/entropy
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