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This paper aims to numerically investigate the natural convection heat transfer of multi-wall carbon nanotubes (MWCNTs)-water nanofluid in U-shaped enclosure equipped with a hot obstacle by using the lattice Boltzmann method.

The combination of the three topics (U-shaped enclosure, different positions of the hot obstacle and MWCNTs-water nanofluid) is innovative in the present study. In total, 15 different positions of the hot obstacle have been arranged, and the effects of pertinent parameters such as Rayleigh numbers, the solid volume fraction of the MWCNTs nanoparticles on the flow field, temperature distribution and the rate of heat transfer inside the enclosure are also investigated.

It is found that the average Nusselt number increased by raising the Rayleigh number, and so did the nanoparticle solid volume fraction regardless the position of the hot obstacle. Moreover, enclosures where the hot obstacle is located at the bottom region proved to provide a better rate of heat transfer at high Rayleigh number (106). It is concluded that at a low Ra number (103-105), the higher heat transfer rate and Nu number will be obtained when the hot obstacle is located in the left or right channel.

In the literature, no trace of studying the natural convection of nanofluids in U-shaped enclosures with heating obstacles was found. Also, MWCNTs were less used as nanoparticles. As the natural convection of nanofluids in thermal engineering applications would expand the existing knowledge, the current researchers conducted a numerical study of the natural convection of Maxwell nanofluid with MWCNTs in U-shaped enclosure equipped with a hot obstacle by using lattice Boltzmann method.

In recent times, there has been a growing interest in buoyancy-induced heat transfer within confined enclosures due to its frequent occurrence in heat transfer processes across diverse engineering disciplines, including electronic cooling, solar technologies, nuclear reactor systems, heat exchangers and energy storage systems. Moreover, the reduction of entropy generation holds significant importance in engineering applications, as it contributes to enhancing thermal system performance. This study, a numerical investigation, aims to analyze entropy generation and natural convection flow in an inclined square enclosure filled with Ag–MgO/water and Ag–TiO2/water hybrid nanofluids under the influence of a magnetic field. The enclosure features heated slits along its bottom and left walls. Following the Boussinesq approximation, the convective flow arises from a horizontal temperature difference between the partially heated walls and the cold right wall.

The governing equations for laminar unsteady natural convection flow in a Newtonian, incompressible mixture is solved using a Marker-and-Cell-based finite difference method within a customized MATLAB code. The hybrid nanofluid’s effective thermal conductivity and viscosity are determined using spherical nanoparticle correlations.

The numerical investigations cover various parameters, including nanoparticle volume concentration, Hartmann number, Rayleigh number, heat source/sink effects and inclination angle. As the Hartmann and Rayleigh numbers increase, there is a significant enhancement in entropy generation. The average Nusselt number experiences a substantial increase at extremely high values of the Rayleigh number and inclination.

This numerical investigation explores advanced applications involving various combinations of influential parameters, different nanoparticles, enclosure inclinations and improved designs. The goal is to control fluid flow and enhance heat transfer rates to meet the demands of the Fourth Industrial Revolution.

In a 90° tilted enclosure, the addition of 5% hybrid nanoparticles to the base fluid resulted in a 17.139% increase in the heat transfer rate for Ag–MgO nanoparticles and a 16.4185% increase for Ag–TiO2 nanoparticles compared to the base fluid. It is observed that a 5% nanoparticle volume fraction results in an increased heat transfer rate, influenced by variations in both the Darcy and Rayleigh numbers. The study demonstrates that the Ag–MgO hybrid nanofluid exhibits superior heat transfer and fluid transport performance compared to the Ag–TiO2 hybrid nanofluid. The simulations pertain to the use of hybrid magnetic nanofluids in fuel cells, solar cavity receivers and the processing of electromagnetic nanomaterials in enclosed environments.

The nanofluid natural convection heat transfer in a hollow complex enclosure, which is named as Shamse knot shape, is studied numerically. This paper aims to present how the Rayleigh number, nanoparticle volume fraction, Hartmann number and hollow side length affect the fluid flow and heat transfer characteristics.

The continuity, momentum and energy equations have been solved using lattice Boltzmann method (LBM). Numerical simulation has been obtained for a wide range of Rayleigh number (10³ ≤ Ra ≤ 10⁶), nanoparticle volume fraction (0 ≤ ϕ 0.05) and Hartmann number (0 ≤ Ha ≤ 60) to analyze the fluid flow pattern and heat transfer characteristics. Moreover, the effect of hollow side length (D) on flow field and thermal performance is studied.

The results showed that the magnetic field has a negative effect on the thermal performance and the average Nusselt number decreases by increasing the Hartmann number. Because of the high conduction heat transfer coefficient of nanoparticles, the average Nusselt number increases by rising the nanoparticle volume fraction. The effect of adding nanoparticles on heat transfer is more effective at low nanoparticle volume fraction (0 ≤ ϕ ≤ 0.01). It was also found that at Ra = 10⁶, when the hollow side length increases to 3, the flow pattern becomes different due to the small gap. The averaged Nu is an increasing function of D at low Ra and an opposite trend occurs at high Rayleigh number.

For the first time, the effects of magnetic field, Rayleigh number, nanoparticle volume fraction and hollow side length on natural convection heat transfer of hybrid nanofluid (Ag-TiO₂/water) is investigated in a complicated cavity.

This study aims to numerically study the buoyant convective flow of two different nanofluids in a porous annular domain. A uniformly heated inner cylinder, cooled outer cylindrical boundary and adiabatic horizontal surfaces are considered because of many industrial applications of this geometry. The analysis also addresses the comparative study of different porous media models governing fluid flow and heat transport.

The finite difference method has been used in the current simulation work to obtain the numerical solution of coupled partial differential equations. In particular, the alternating direction implicit method is used for solving transient equations, and the successive line over relaxation iterative method is used to solve time-independent equation by choosing an optimum value for relaxation parameter. Simpson’s rule is adopted to estimate average Nusselt number involving numerical integration. Various grid sensitivity checks have been performed to assess the sufficiency of grid size to obtain accurate results. In this analysis, a general porous media model has been considered, and a comparative study between three different models has been investigated.

Numerical simulations are performed for different combinations of the control parameters and interesting results are obtained. It has been found that the an increase in Darcy and Rayleigh numbers enhances the thermal transport rate and strengthens the nanofluid movement in porous annulus. Also, higher flow circulation rate and thermal transport has been detected for Darcy model as compared to non-Darcy models. Thermal mixing could be enhanced by considering a non-Darcy model.

The present results could be effectively used in many practical applications under the limiting conditions of two-dimensionality and axi-symmetry conditions. The only drawback of the current study is it does not include the three-dimensional effects.

The results could be used as a first-hand information for the design of any thermal systems. This will help the design engineer to have fewer trial-and-run cases for the new design.

A pioneering numerical investigation on the buoyant convective flow of two different nanofluids in an annular porous domain has been carried out by using a general Darcy–Brinkman–Forchheimer model to govern fluid flow in porous matrix. The results obtained from current investigation are novel and original, with numerous practical applications of nanofluid saturated porous annular enclosure in the modern industry.

The purpose of this paper is to investigate the effects of Ha and the Nanoparticles (NP) volume fraction over the irreversibility and heat transport in Darcy–Forchheimer nanofluid saturated lid-driven porous medium.

The present paper highlights entropy generation because of mixed convection for a lid-driven porous enclosure filled through a nanoliquid and submitted to a uniform magnetic field. The analysis is achieved using Darcy–Brinkman–Forchheimer technique. The set of partial differential equations governing the considered system was numerically solved using the finite element method.

The main observations are as follows. The results indicate that the movement of horizontal wall is an important factor for the entropy generation inside the porous cavity filled through Cu–water nanoliquid. The variation of the thermal entropy generation is linear through NPs volume fraction. The total entropy generation reduces when the Darcy, Hartmann and the nanoparticle volume fraction increase. The porous media and magnetic field effects reduce the total entropy generation.

Interest in studying thermal interactions by convective flow within a saturating porous medium has many fundamental considerations and has received extensive consideration in the literature because of its usefulness in a large variety of engineering applications, such as the energy storage and solar collectors, crystal growth, food processing, nuclear reactors and cooling of electronic devices, etc.

By examining the literature, the authors found that little attention has been paid to entropy generation encountered during convection of nanofluids. Hence, this work aims to numerically study entropy generation and heat transport in a lid-driven porous enclosure filled with a nanoliquid.

The purpose of this study is to simulate the thermo-solutal convection resulting from a circular cylinder hanging in a rod inside a ∧-shaped cavity.

The two dimensional ∧-shaped cavity is filled by Al₂O₃-water nanofluid and saturated by three different levels of heterogeneous porous media. An incompressible smoothed particle hydrodynamics (ISPH) method is adopted to solve the governing equations of the present problem. The present simulations have been performed for the alteration of buoyancy ratio (−2≤N≤2), radius of a circular cylinder (0.05≤Rc≤0.3), a height of a rod (0.1≤Lh≤0.4), Darcy parameter (10−3≤Da≤10−5), Lewis number (1≤Le≤40), solid volume fraction (0≤ϕ≤0.06), porous levels (0≤η1=η2≤1.5)and various boundary-wall conditions.

The performed numerical simulations indicated the importance of embedded shapes on the distributions of temperature, concentration and velocity fields inside ∧-shaped cavity. Increasing buoyancy ratio parameter enhances thermo-solutal convection and nanofluid velocity. Adiabatic conditions of the vertical-walls of ∧-shaped cavity augment the distributions of the temperature and concentration. Regardless the Darcy parameter, a homogeneous porous medium gives the lowest values of a nanofluid velocity.

ISPH method is used to simulate thermo-solutal convection of a nanofluid inside a novel ∧-shaped cavity containing a novel embedded shape and heterogeneous porous media.

Natural convection in finite enclosures is a common phenomenon in various thermal applications. To provide the thermal design guidelines, this study aims to numerically explore the potential of using internal baffles and nanofluids to either enhance or suppress heat transport in a vertical annulus. Furthermore, the annular-shaped enclosure is filled with aqueous-silver nanofluid and the effects of five distinct nanoparticle shapes are examined. In addition, the influence of baffle design parameters, including baffle position, thickness and length, is thoroughly analyzed.

The finite difference method is used in conjunction with the alternating direction implicit and successive line over relaxation techniques to solve nonlinear and coupled partial differential equations. The single phase model is used for nanofluid which is considered as a homogeneous fluid with improved thermal properties. The independence tests are carried out for assessing the sufficiency of grid size and time step for obtaining results accurately.

The baffle dimension parameters and nanoparticle shape exhibit significant impact on the convective flow and heat transfer characteristics, leading to the following results: sphere- and blade-shaped nanoparticles demonstrate around 30% enhancement in the heat transport capability compared with platelet-shaped nanoparticles, which exhibit the least. When considering the baffle design parameter, either a decrease in the baffle length and thickness or an increase in baffle height leads to an improvement in heat transport rate. Consequently, a threefold increase in baffle height yields a 40% improvement in thermal performance.

Understanding the impact of nanoparticle shapes and baffle design parameters on flow and thermal behavior will enable engineers to provide valuable insight on thermal management and overall system efficiency. Therefore, the current work focuses on exploring buoyant nanofluid flow and thermal mechanism in a baffled annular-shaped enclosure. Specifically, an internal baffle that exhibits conductive heat transfer through it is considered, and the impact of baffle dimensions (thickness, length and position) on the fluid flow behavior and thermal characteristics is investigated. In addition, the current study also addresses the influence of five distinct nanoparticle shapes (e.g. spherical, cylindrical, platelet, blade and brick) on the flow and thermal behavior in the baffled annular geometry. In addition to deepening the understanding of nanofluid behavior in a baffled vertical annulus, the current study contributes to the ongoing advancements in thermal applications by providing certain guidelines to design application-specific enclosures.

The purpose of this study is to investigate the impact of varying baffle height and spacing distance on heat transfer and cooling performance of electronic components in a baffled horizontal channel, using a Cu-H₂O nanofluid under mixed convection and laminar flow.

The mathematical model is two-dimensional and comprises a system of four governing equations, such as the conservation of continuity, momentum and energy. To obtain numerical solutions for these equations, the finite volume method was used for discretization. A validation process was performed by comparing this study’s results with those of previously published studies. The comparison revealed a close agreement. The numerical study was performed for a wide range of key parameters: The baffle height (0 ≤ h ≤ 0.7), the spacing distance between baffle and blocks (0.25 ≤ w ≤ 3), the Grashof and Reynolds numbers are kept equal to 10⁴ and 75, respectively, the channel aspect ratio is L/H = 10, and the volume fraction of Cu nanoparticles is fixed at φ = 5%.

The results of the study reveal a significant improvement in heat transfer in terms of total Nusselt number of the top and bottom hot components, which exhibited an improvement of 16.89% and 17.23% when the baffle height increases from h = 0 to h = 0.7. Additionally, the study found that reducing the distance between the baffle and the electronic components up to a certain limit can improve the heat transfer rate. Therefore, the optimal height of the baffle was found to be no lower than 0.6, and the recommended distance between the heaters and the baffle was 0.5.

This study provides valuable insights into the optimization of the design of baffled channels for improved heat transfer performance. The findings of study can be used to improve heat exchangers and cooling systems in various applications. The use of Cu-H₂O nanofluid under mixed convection and laminar flow conditions in channel with baffle and electronic components is also unique, making this study an original contribution to the field.

This study aims to investigate numerically the problem of conjugate conduction and mixed convection heat transfer of a nanofluid in a rotational/stationary circular enclosure using a two-phase mixture model.

Hot and cold surfaces on the wall or inside the enclosure (heater and cooler) are maintained at constant temperature of T_h and T_c, respectively, whereas other parts are thermally insulated. To examine the effects of various parameters such as Richardson number (0.01 = Ri =100), thermal conductivity ratio of solid to base fluid (1 = K_r = 100), volume fraction of nanoparticle (0 = φ = 0.05), insertion of conductive covers (C.Cs) around the heater in a different shape (triangular, circular or square), segmentation and arrangement of the conductive blocks (C.Bs) and rotation direction of the enclosure on the flow structure and heat transfer rate, two-dimensional equations of mass, momentum and energy conservation, as well as volume fraction, are solved using finite volume method and Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm.

The results show that inserting C.C around heater can increase or decrease heat transfer rate, and it depends on thermal conductivity ratio of solid to pure fluid. Also, it is found that by the division of C.B and location of its portions in a horizontal configuration, heat transfer rate reduces. Moreover, it is observed that external heating and cooling of the enclosure causes enhancement of heat transfer relative to that of internal heating and cooling. Finally, results illustrate that under the condition that cylinders rotate in the same direction, the heat transfer rate increases as compared to those that rotate in the opposite direction. Hence rotation direction of cylinders can be used as a desired parameter for controlling heat transfer rate.

A comprehensive report of results for the problem of conjugate conduction and mixed convection heat transfer in a circular cylinder containing different shapes of C.C, conducting obstacle and heater and cooler has been presented. An efficient numerical technique has been developed to solve this problem. The achievements of this paper are purely original, and the numerical results were never published by any researcher.

The purpose of this paper is to analyse the relationship between Olympic stadiums and the urban environment. This relationship is considered as key to understanding the cultural significance of these exceptional event‐based buildings. It helps to explain present challenges faced by their conservation and raises the issue of considering likely heritage values at the design stage of stadiums.

The analysis is based on a periodization of the relationship between Olympic stadiums and the urban environment. This periodization proposes a six stage typology, starting from the stadium of Olympia at the Hellenistic period. It combines an analysis of the stadium architecture itself and the integration of Olympic facilities within their urban setting and the city at large.

The article highlights that Olympic stadiums have progressively been isolated from the city environment they are located in. This isolation can both be observed at the scale of the building, through the progressive adoption of arena‐shaped envelopes, and at the scale of the city through the clustering of Olympic facilities in campus‐like sites. Although it can be explained by functional and city‐marketing requirements, it is argued that this isolation will hamper an adaptive reuse of these facilities once the Olympic event is over. It is further suggested that the conservation of Olympic stadiums should be considered at the design stage of these buildings, considering their potential outstanding socio‐cultural values.

This research is based on the analysis of Olympic stadiums solely. It may have been completed and refined by a comparison with other stadiums, especially those dedicated to football competitions. It means that the research results are closely related to a very specific type of stadium, which is designed for a once in lifetime a time event, repeated throughout the world every four years.

The main originality of the work consists in the combination of a building‐ and a settlement‐oriented typology within the periodization. It has been further considered that considering the stadium of Olympia at the Hellenistic period within the typology would help to better describe a general movement from opened‐ to closed‐stadium environments that definitively finds its roots in the Greek Antiquity.