Natural Convection of a Power-Law Nanofluid in a Square Cavity with a Vertical Fin
Amira M’hadbi1,2,*, Mohammed El Ganaoui1, Haïkel Ben Hamed3, Amenallah Guizani2, Khalid Chtaibi3
1 LERMAB, Department of Transition and Energy Efficiency Professions, IUT H Poincaré de Longwy, University of Lorraine, Longwy, 54400, France
2 LPT, Center for Energy Research and Technologies (Borj Cedria, 2084), University of Tunis El Manar, Tunis, 1068, Tunisia
3 LTI, Department of Mechanical Engineering and Production, IUT, University of Picardie Jules-Verne, Amiens, 80025, France
* Corresponding Author: Amira M’hadbi. Email: 
(This article belongs to the Special Issue: Materials and Energy an Updated Image for 2023)
Fluid Dynamics & Materials Processing https://doi.org/10.32604/fdmp.2024.050763
Received 17 February 2024; Accepted 17 May 2024; Published online 01 July 2024
Abstract
The behavior of non-Newtonian power-law nanofluids under free convection heat transfer conditions in a cooled square enclosure equipped with a heated fin is investigated numerically. In particular, the impact of nanofluids, composed of water and
Al₂O₃,
TiO₂, and
Cu nanoparticles, on heat transfer enhancement is examined. The aim of this research is also to analyze the influence of different parameters, including the Rayleigh number (
Ra = 10 − 10), nanoparticle volume fraction (
φ = 0% − 20%), non-Newtonian power-law indexes (
n = 0.6 − 1.4), and fin dimensions (
Ar = 0.3, 0.5, and 0.7). Streamlines and isotherms are used to depict flow and related heat transfer characteristics. Results indicate that thermal performance improves with increasing Rayleigh number, regardless of the nanoparticle type or nanofluid rheological behavior. This suggests that the buoyancy force has a significant impact on heat transfer, particularly near the heat source. The Nusselt number is more sensitive to variations in
Cu nanoparticle volume fractions compared to
Al₂O₃ and
TiO₂. Moreover, the average Nusselt numbers for power-law nanofluids with
n < 1 (
n > 1) are greater (smaller) than for Newtonian fluids due to the decrease (increase) in viscosity with increasing (decreasing) shear rate, at the same values of Rayleigh number Ra owing to the amplification (attenuation) of the convective transfer. Notably, the most substantial enhancement is observed with
Cu–water shear-thinning nanofluid, where the Nusselt number increases by 136% when changing from Newtonian to shear thinning behavior and by 154.9% when adding 16% nanoparticle volume fraction. Moreover, an even larger increase of 57% in the average Nusselt number is obtained on increasing the fin length from 0.3 to 0.7.
Keywords
Heat transfer; nanofluid; non-Newtonian fluid; natural convection
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