Computational fluid dynamics study of heat transfer and entropy generation in a hybrid nanofluid‐filled three‐dimensional cavity crossed by a linearly heated finned pipe

This study investigates three‐dimensional (3D) natural convection and entropy generation within a cubic cavity containing a finned pipe subjected to a linearly decreasing temperature profile in the transversal direction. The cavity is filled with Carbon Nanotube (CNT)‐Al 2 O3/water hybrid nanofluid, and its boundaries are insulated except for cold‐maintained walls. External and internal Rayleigh numbers (10 3 ≤ Ra E ≤ 10 5 , 10 3 ≤ Ra I ≤ 10 6 ), fins’ lengths (0.1≤ 𝐿 𝑓 ≤ 0.3), and nanoparticle volume fractions (0 ≤ ϕ ≤ 0.045) are the main examined key parameters. Numerical simulations using the 3D Finite element method (FEM) reveal the interplay between buoyancy‐driven convection, fin geometry, and nanoparticle‐enhanced heat transfer. It was shown that raising the nanoparticles concentration and the internal Rayleigh number increases the entropy generation and significantly improves heat transfer. Furthermore, the convective circulations and heat removal are intensified when using longer fins whose influence on irreversibilities depends on the strength of buoyant forces. This work is a contribution in the advancement of thermal systems design that enhances excess heat dissipation and minimizes the entropy generation in order to boost the overall thermal performance.