Computational study of natural convection and entropy generation in 3-D cavity with active lateral walls

Alnaqi, Abdulwahab A.; Kadhim, Ahmed Hussein; Kolsi, Lioua; A.A.A., Abdullah Al-Rashed; Li, Dong; Ali, Hafız Muhammad

doi:10.2298/tsci180810346a

Cited by 18 publications

(10 citation statements)

References 29 publications

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“…Spizzichino et al [17] enclosure was cold including cold and hot vertically aligned cylinders. Alnaqi et al [18] cavity with lateral active walls, the vertical front and right walls kept cold. While the vertical back and left were hot.…”

Section: Introductionmentioning

confidence: 99%

The natural convection inside a 3D triangular cross section cavity filled with nanofluid and included cylinder with different arrangements

Ghoben¹,

Hussein²

2022

Diagnostyka

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In this paper the laminar unsteady natural convection heat transfer of (Al2O3-water) nanofluid inside 3D triangular cross section cavity was investigated. The cavity was heated differentially, the vertical walls were kept at different constant temperatures. The left hot and the right cold. The effect of the solid volume fraction was examined for two values and compared with the pure water results. The (Ra) range studied was (103 ≤ Ra ≤ 106). Inserting cylindrical body inside the cavity also investigated in three cases. One concentric cylinder has radius (15%) of the cavity side length. The other cases were of two cylinders having radius (7.5%) of the cavity side length, aligned vertically or nonaligned. The results show that the higher solid volume fraction gives the maximum enhancement of the average (Nu) and this enhancement increases with (Ra) increase. For the cases with inner cylinders, the average (Nu) enhanced for the case of double cylinders over single cylinder. On other hand, the nonaligned position of the cylinders giving more enhancement than other position. As like as, the location of maximum horizontal or vertical velocities were varied with the cylinders position while (Ra) has no effect.

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Section: Introductionmentioning

confidence: 99%

The natural convection inside a 3D triangular cross section cavity filled with nanofluid and included cylinder with different arrangements

Ghoben¹,

Hussein²

2022

Diagnostyka

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“…Systems can be optimized by reducing their entropy generation. Alnaqi et al (2020) studied the natural convection and entropy generation in a cubical cavity and observed that total entropy fairly increased with an increase in Rayleigh number until a certain value, when it then rose significantly. Similar studies have also been carried out (Bondareva et al, 2017;Hussein et al, 2016;Yang et al, 2021;Zhang et al, 2021;Ishak et al, 2021;Oztop et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Natural Convection Heat Transfer and Entropy Generation Analysis in Saltbox Roof under Summer Conditions

Ogwumike¹,

Olakoyejo²,

Oloruntoba³

et al. 2022

FUOYEJET

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This study investigates numerically the 2D laminar natural convection in a Saltbox roof type geometry under summer climate conditions as obtained in Africa, particularly Nigeria using ANSYS FLUENT to model the boundary conditions. The effects of Rayleigh number (Ra) within the range of 103-107 and pitch angles (top and base) on heat transfer, the flow structure, temperature distribution and entropy generation within the geometry were analysed. Results show that the flow is nearly symmetric at lower Ra, while for higher Ra, the flow becomes asymmetric. The Nusselt number (Nu) has a proportional relationship with the top pitch angle and an inverse relationship with the base pitch angle when the Rayleigh number is fixed. The effect of the Ra on the Nu is insignificant at lower Ra, but becomes noticeable at higher Ra. The total entropy generation increases with an increase in top pitch angle and a decrease in base pitch angles, at fixed Rayleigh numbers. The physical implication is that, for a Saltbox roof type geometry, at fixed Ra, the best convective heat transfer process is achieved by lowering the base pitch angle and increasing the top pitch angle.

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“…The authors reported that the angle of inclination has an insignificant effect with respect to low Rayleigh numbers. Alnaqi et al 26 examined numerically laminar natural convection and entropy generation in a 3D cubical cavity with active perpendicular walls. They revealed that with increasing the Rayleigh number until reaching a value of 10 5 , heat transfer and total entropy generation increased slightly.…”

Section: Introductionmentioning

confidence: 99%

CFD‐based analysis of entropy generation due to mean and fluctuating fields during turbulent natural convection in a square enclosure

2022

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The current study aims to numerically investigate the entropy generation during the natural convection flow of air in a square cavity. The governing equations for the conservation of mass, momentum, energy, and turbulence are solved using a control volume‐based technique employing the commercial code Fluent. Runs have been performed for both laminar and turbulent flow regimes by varying the Rayleigh number (Ra) from 103 to 1010. On the other hand, various viscous distribution coefficients (ϕ = 10−4, 10−3, and 10−2) and constant Prandtl number (Pr = 0.71) were considered. Given the conflicting perspectives in the literature regarding the entropy generation under turbulent regimes, more research is needed to better understand the impact that the fluctuating flow has on entropy production. The four terms of entropy generation inherent to turbulent natural convection (entropy generation due to dissipation in the mean and the fluctuating velocity fields in addition to the heat flux due to the mean and the fluctuating temperature) are computed in the present work and compared to calculations based on only mean values of temperature and velocity gradients. It was found that taking into account the fluctuating terms of temperatures and velocities augment the total entropy generation by 10.10%, 14.43%, and, 17.70%, up to 32.60%, respectively, for Ra = 5 × 108, Ra = 109, Ra = 1.58 × 109, and Ra = 1010. The gain shows the tendency to increase with the Rayleigh number. Thus, the fluctuating terms cannot be neglected particularly for high Rayleigh numbers. Furthermore, unlike entropy production due to the mean flow field, numerical outcomes reveal that the generated irreversibilities due to fluctuating flow are located around the upper hot and the lower cold corners of the heated walls. In addition, a numerical relationship between the first and the second laws of thermodynamics has been derived. A promising result that emerged from this study has shown that the Nusselt number and therefore the first law of thermodynamics is sufficient to estimate the heat part of entropy generation without the necessity of using the second law.

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Computational study of natural convection and entropy generation in 3-D cavity with active lateral walls

Cited by 18 publications

References 29 publications

The natural convection inside a 3D triangular cross section cavity filled with nanofluid and included cylinder with different arrangements

The natural convection inside a 3D triangular cross section cavity filled with nanofluid and included cylinder with different arrangements

Natural Convection Heat Transfer and Entropy Generation Analysis in Saltbox Roof under Summer Conditions

CFD‐based analysis of entropy generation due to mean and fluctuating fields during turbulent natural convection in a square enclosure

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