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Enhancing thermal performance and lowering heat loss in energy conversion systems are essential, especially for new and complicated products that make this requirement worse. In order to address this difficulty, this study looks at fluid flow and heat transmission using hybrid nanofluid and nanoporous materials in combination cavities. The numerical simulation of natural convection within a hollow two-dimensional cavity comprised of two connected tilted squares with a circular hollow at the center is investigated. The inner heated square is filled with a nanoporous material, whereas the rest of the cavity is filled with Cu-Al2O3 hybrid nanofluid. The COMSOL Multiphysics software is utilized to simulate the dimensionless governing equations. A comparison with previously published research showed a good agreement. Calculations are performed for different values of Ra number (Ra: 103, 104, 105, and 106), Darcy number (Da: 10–1, 10–2, 10–3, 10–4, and 10–5), volume fraction (φ: 0, 0.02, 0.04, and 0.06), width (W: 0, 0.1, 0.2, 0.3, and 0.4), and uniform porosity (ε: 0.2, 0.4, 0.6, and 0.8). The results demonstrated that the increase of the porosity leads to a decrease in the Nu number with the Rayleigh number increase. Darcy and Rayleigh numbers have a significant impact on the width (W) between the hybrid nanofluid and nanoporous layers. In addition to the above, the fluid flow slows down at Ra = 103, which causes S ˙ gen , T ⌣ and Be to increase. The rising of Ra from 104 to 105 causes no change in the S ˙ gen , T ⌣ because heat is primarily transported by conduction, but the maximum Be number is reduced. [ABSTRACT FROM AUTHOR]

The current work investigated numerically the natural convection within a square enclosure filled with nanofluid by examining four different types of attached fins (rigid fins, flexible oscillating in the same and opposing directions) and comparing it to the case without fins. The governing equations of heat and fluid flow (mass, energy and momentum) of fluid had been solved using the finite element scheme. The results are validated with the previous studies and presented in terms of streamlines, isotherm and Nusselt number. The influence of Rayleigh number (104 ≤ Ra ≤ 106), dimensionless time (10–4 ≤ τ ≤ 1), thermal conductivity ratios (1 ≤ ks ≤ 1000), the amplitude of the flexible fins (10–2 ≤ A ≤ 0.1) and frequency (0.05 ≤ λ ≤ 0.5) are studied. The governing parameters have been tested based upon their influence on fluid flow and heat transfer for the current study. The results are shown as contours of vortices, velocity, streamlines and isotherms as well as the local and average Nusselt number (Nuave). It is observed that the larger amounts of heat are transmitted by convection at higher thermal conductivity ratios, and the greater the magnitude of the Nusselt number demonstrates the pronounced effect of the fin oscillation. In addition, when the flexible fins oscillated in the same directions, the Nusselt number increased by 18.34% as compared to the case without fins. Furthermore, increasing the flexible fins' amplitude improves the oscillating motion of the fins inside the cavity, which improves fluid flow and heat transmission strength. [ABSTRACT FROM AUTHOR]

The current study focuses on the transient mixed convection within a vented square enclosure with differentially heated vertical walls and a flexible baffle coupled to a circular solid cylinder. In numerical analysis, the COMSOL Multiphysics tool is used to simulate and solve two-dimensional governing equations using the Galerkin finite element approach and the arbitrary Lagrange–Euler (ALE) method, as well as the coupling of structure deflection and fluid flow. This work considered the effects of changing locations of flexible baffles attached to a cylinder on thermal and flow structures. The effect of several parameters, such as Richardson number (10–1 ≤ Ri ≤ 102), Cauchy number (10–12 ≤ Ca ≤ 10–4), and Reynolds numbers, (50 ≤ Re ≤ 250) on convective heat transfer characteristics are investigated for time 0.01 to 10 s. It is observed that changing time steps leads to a continuous change in fluid flow intensity which reflects on the deformation direction of the flexible baffle. The results indicated that the cavity with flexible baffle has the best average Nusselt number compared to cavities with rigid baffle and without baffles, respectively. As Re is raised from 50 to 250, the percentage of the average Nusselt number increased to 40% at Ri = 0.1 and 59% at Ri = 200. [ABSTRACT FROM AUTHOR]

In the present paper, numerical investigations of the magnetohydrodynamics forced convection of CNT–water nanofluid inside a square enclosure with one inlet and one outlet were performed. The analysis was carried out for a wide range of Reynolds number ( 100 ≤ R e ≤ 1000 ), Hartmann number ( 0 ≤ H a ≤ 60 ), inclination angle of the magnetic field ( 0 ∘ ≤ γ ≤ 90 ∘ ), elasticity of the bottom and left walls of the enclosure ( 10 4 ≤ E ≤ 10 7 ), location of the center of the hexagonal body in horizontal directions ( 0.3 ≤ x 0 / L ≤ 0.7 ) and in normal directions ( 0.25 ≤ y 0 / L ≤ 0.75 ), size of the internal hexagonal body ( 0.1 ≤ a / L ≤ 0.3 ), and, finally, the volume fraction of the nanoparticles ( φ = 0 and 0.1). For the flexible walls of the enclosure, a series of coupled fluid–structure interaction (FSI) analyses were accomplished by utilizing the Arbitrary Lagrangian–Eulerian formulation. It has been revealed that the bottom wall of the enclosure is very sensitive to the elastic wall, while the Nusselt number on the top wall increases with Hartmann number no matter which wall is elastic. It is also the most contributor to the heat transfer at Reynolds numbers of R e = 100 and 500, while the contribution of other walls changes with Reynolds number. [ABSTRACT FROM AUTHOR]