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The optimization of heat transfer in various engineering applications, such as thermal management systems and energy storage devices, remains a crucial challenge. This study aims to investigate the potential of Casson-based Cu-H2O nanofluids in enhancing free convection heat transfer within complex geometries. The research examines the free convection heat transfer and fluid flow characteristics of a Casson-based Cu-H2O nanofluid within a semi-parabolic enclosure that includes a wavy corrugated cylinder. Utilizing numerical simulations based on the Galerkin Finite Element Method, the study investigates the impact of different factors, including the Rayleigh number (103 ≤ Ra ≤ 106), Casson fluid parameter (0.1 ≤ γ ≤ 1), corrugation number (3 ≤ N ≤ 10), nanoparticle volume fraction (0 ≤ ϕ ≤ 0.15), and enclosure inclination angle (0° ≤ ζ ≤ 60°), on both heat transfer efficiency and flow patterns. The results reveal that increasing the Rayleigh number and Casson fluid parameter enhances heat transfer performance, with the average Nusselt number increasing by up to 165 % as Ra increases from 103 to 106. An optimal range of corrugation numbers is identified for maximizing heat transfer at higher Rayleigh numbers. The addition of nanoparticles significantly improves heat transfer, with a 20 % increase in the average Nusselt number observed at Ra = 105 when the nanoparticle volume fraction increases from 0 to 0.15. These findings provide valuable insights for designing more efficient thermal management systems in applications such as electronics cooling, solar thermal collectors, and heat exchangers, potentially leading to improved energy efficiency and performance in various industrial and technological sectors.

Until now, there has been a lack of two-phase velocity and vapor investigations under the evaporation condition. Therefore, this work addresses this title in order to be additive to this subject. The spray droplets are modelled using the moments method, and the gas phase is modelled using the Eulerian approach. The spray drag, breakup, and evaporation sub-models are taken into account. Based on the RANS turbulence model for the carrier gas phase and a calibrated atomisation model for the dispersed droplets, turbulence closure is accomplished. The spray tip penetration is evaluated and compared with experimental data. The fuel vapour mass fraction is calculated by using a transport equation for the droplet-gas interaction. The distribution of the fuel vapour mass fraction is compared with the KIVA code. Fortunately, there are no experimental results for the spray or gas velocity to be compared with. All presented results are investigated by their variation with positions and time to give the total behaviour. The fuel vapour mass fraction distribution exhibits a bell-shaped behaviour. In close proximity to the injector, the evaporation rate is significantly higher. There was no significant increase in the evaporation rate of the pressure swirl nozzle as the distance from the injector increased. During the evaporation of spray droplets, higher fuel vapour concentrations are present at the core spray than at the peripheral edge. The droplet velocities in the outer edge’s axial and radial directions display a reduced magnitude. The droplet’s diameter is greater at the inner edge than at the outer edge. The comparisons showed that there was good agreement with both the experimental and numerical results.

This study investigates the effects of Nano-Encapsulated Phase Change Materials (NEPCMs) on double diffusive free convection in a partially porous cavity, considering Soret-Dufour effects and magnetohydrodynamics. The problem is modeled using non-dimensional governing equations, solved numerically through a Galerkin finite element method. The research examines the influence of key parameters including Rayleigh number (Ra: 103–105), Darcy number (Da: 10–4 -10–1), Hartmann number (Ha:0−80), NEPCM volume fraction (ϕ:0−0.04), Lewis number (Le:0.1−10), fusion temperature (θf:0.1−0.9), and Stefan number (Ste:0.1−0.9) on heat and mass transfer characteristics and entropy generation. Results show that increasing Ra significantly enhances heat and mass transfer, with Nusselt and Sherwood numbers rising by 424.8 % and 547.3 % respectively as Ra increases from 103 to 105. Higher Da and ϕ improve heat transfer, while stronger magnetic fields suppress both heat and mass transfer. An optimal fusion temperature (θf=0.5) is identified for maximum heat transfer enhancement. Total entropy generation, considering thermal diffusion, nanofluid friction, magnetic effects, porous medium, and mass diffusion contributions, increases by 15,957 % with Ra and decreases by 42.5 % with increasing Ha. The Bejan number analysis reveals that non-thermal irreversibilities become increasingly dominant at higher Ra and Ha values. The study concludes that NEPCMs can effectively enhance heat transfer in partially porous cavities, with their performance strongly influenced by Ra, Da, and Ha. The findings provide valuable insights for optimizing thermal management systems incorporating NEPCMs, particularly in applications involving porous media and magnetic fields.

This study presents a novel investigation into the thermal behavior of a hybrid nanofluid (MgO − Ag − H2O) in natural convection around a porous fin in a triangular enclosure under the influence of radiation and magnetohydrodynamic effects. The research uniquely combines these complex phenomena, addressing a significant gap in the literature. This configuration has potential applications in advanced solar thermal collectors, electronic cooling systems for high-power devices, and compact heat exchangers in various industries. The main objectives are to understand how various parameters influence heat transfer and fluid flow behavior and to optimize the design for enhanced thermal performance. The study considers a range of variables including Rayleigh number (103 − − 106), Hartmann number (0 – 50), Aspect ratio (0.3 – 0.6), radiation parameters (Rd = 1 − − 5, λ = 1 − 5), and volume concentration (0- 0.05), which have been numerically analyzed using the finite element method (FEM). The findings reveal that increasing the Darcy number (Da) enhances heat transfer at low Rayleigh numbers (Ra = 103,104). However, at higher Ra (Ra = 106), the impact of Da becomes more complex, with a critical Da beyond which heat transfer efficiency decreases due to an increase in flow resistance. The nanoparticle volume concentration plays a vital role, as higher concentrations lead to improved heat transfer efficiency, especially at higher Ra, through enhanced thermal conductivity and thermal dispersion. The length of the porous fin greatly impacts fluid flow patterns and heat transfer rates, with longer fins creating more complex flow patterns, promoting enhanced heat transfer and stronger thermal plumes. Thermal radiation, represented by the radiation parameters (Rd and λ), significantly influences both the heat transfer rate and the convective flow patterns within the enclosure. This study also incorporates a comprehensive entropy generation analysis, providing novel insights into system irreversibilities and optimization potential. The entropy analysis reveals the complex interplay between various parameters and their impact on system efficiency, offering valuable guidance for designing high-performance thermal management systems.

Mixed convection convection is a vital subject and it is beneficial in many engineering applications. The current paper addresses this subject with a novel geometry and very vital variables including magnetohydrodynamic influences on the forced/free convection as well as the reproduction of irreversibilities in an enclosure filled with water/carbon nanotubes (CNT) and a nonadiabatic cylinder. The top wall is split from the middle and moves in different directions to drive the isotherms which are generated from the bottom wall and cold from the vertical surfaces. The numerical analysis was carried out using finite element method; the variables are Reynolds number (40–200), Richardson number (0.01–10), Hartmann number (0–62), inclined magnetohydrodynamic angle (0–60), volume concentration (0–0.08) while Prandtl number has kept constant at 6.2. The results show that the transformation of heat, as well as the fluid flow, are largely influenced by the change of variables, where increasing Reynolds number, Richardson number enhances heat and increases the flow circulation. Furthermore, heat transfer enhances by 57 % when increasing Ri from 0.1 to 10 at Re=41 and this enhancement increases to 62.5 % at Re = 200. Furthermore, increasing the concentration of the carbon nanotube can cause heat transfer but decrease the circulation of the fluid. In contrast, the transfer of heat as well as the flow streams are remarkably decreased with the increase of the Hartmann at zero inclination angle; however, the value of the Nusselt average increases with the increase of the inclination angle. Moreover, the value of Nusselt average decreses by 34.7 % when increasing Ha from 0 to 62 at Re = 200. Furthermore, the total entropy generation increases as Richardson number, Reynolds number, and volume concentration increase; in contrast, detraction with the rise of the MHD.

This paper delves into the numerical investigation of aluminum oxide–water nanofluid thermal and dynamic performances under the influences of magnetic field application and chemical reaction, utilizing the Finite Element Method within a circular enclosure containing three inner tubes, as an application to the heat exchanging phenomenon between the reactive shell of the cavity and the surface of the triple tubes. Various governing parameters were studied for their interaction on the nanofluid flow and heat transmission rate within the proposed geometry, including the Rayleigh parameter (103≤Ra≤105), Hartmann parameter (0≤Ha≤61), nanoparticles concentration (0≤∅≤6×10-2), magnetic rotational angle (0o≤γ≤90o), and Frank-Kamenetskii parameter (0≤Fk≤3). The results indicated that raising Ra from 103 to 105 results in expediting the nanofluid velocity by 10.62 % and 100 % respectively as well as raising the total heat transfer efficiency. The nanofluid speed was also increased by 28.57 % when Fk has to further increase to a value of 3. When there was no exothermic activity present, the rate of heat transmission was at its lowest, and it was greater when the Fk value was 3. Similarly, there were discernible impacts in various areas of the geometry as the Ha number intensified and the Nuavg decreased. Improvements in local and mean Nusselt parameters are observed when the concentration of nanoparticles is increased, suggesting better heat transfer, achieving an increase by 7 % in the average Nusselt number. This research emphasizes the importance of nanoparticle concentration in raising the medium’s rates of heat transmission, contributing to advancements in energy storage development.

Magnetohydrodynamic and entropy generation of double-diffusive mixed convection in a curvilinear cavity filled with nano-enhanced phase change material and a rotating cylinder has been studied in this paper. Three heat sources have been considered and a range of different variables such as Reynolds number (10 ≤ Re ≤ 100), Richardson number (0.1≤ Ri ≤ 10), Hartmann number (0≤ Ha ≤50) Lewis number (0.1≤ Le ≤ 0.9), bouncy ratio (1≤ Nz ≤ 5), fusion temperature (0.1≤ θf ≤0.9) and Stephan number (0.1≤ Ste ≤0.9). These variables have been numerically solved by applying the Finite Element Method. The main results indicated that heat transfer, mass transfer and heat capacity are hugely increased with the increase of the Re, Ri and volume concentration while decreasing with the increase of the Ha number and entropy generation. Furthermore, the melting/solidification region is hugely influenced by the fusion temperature while this variable has a negligible influence on streams, heat transfer and mass transfer. Furthermore, the value of the average Nusselt number and average Sherwood number has increased by 328 % and 258 % respectively by increasing the Reynolds number from 10 to 100. Also, these two numbers have decreased by 61 % and 54 % respectively by increasing the Hartmann number from 0 to 20.

Using porous media is an efficient technique aimed at enhancing heat transfer in engineering systems. Replacing conventional fluids by ferrofluids and applying external magnetic fields through magnets is another method for heat transfer control. In this regard, understanding the behavior of ferrofluids through porous media in the presence of magnets is important. The present study aims at providing a thorough analysis of the properties of heat transfer resulting from the combination of buoyancy driven convection and thermomagnetic convection in a porous enclosure. The equations governing the two types of convection in the fluid as well as the conduction in the solid matrix are presented in the dimensionless form and solved numerically. The control volume finite element method has been used to solve the governing equations. The influence of various parameters such as the magnetic Rayleigh number, the porosity, Darcy number, and the interfacial heat transfer coefficient on the flow and temperature contours and on the Nusselt number is then investigated. For low interface coefficient, the heat transfer in the fluid is enhanced when the overall porosity in the cavity is raised, while for high coefficients, the porosity of the bottom porous layer is the main parameter affecting the heat transfer.

Unsteady study of the natural convection of aluminum oxide-water nanofluid within a trapezoidal geometry containing a circular cylinder located at its center. Finite Element method has been considered for the numerical analysis. The proposed investigation handled the impact of Rayleigh number (103–105), chemical reaction parameter (0–4), aluminum oxide nanoparticles volume fraction (0–0.06), magnetic field (0–63) and its inclination angle (0°–90°), and circular obstacle diameter (0.3–0.7) effects on time-dependent natural convection of Al2O3–H2O nanofluid. On the other hand, the value of Prandtl number has kept constant at (Pr = 6.2). Since the nanofluid mobility at φ = 0.02, Ha = 3, and Fk = 1 significantly improved, the heat transfer rate achieved its maximum intensity at Ra = 105. Research also reveals a little effect on heat transfer by increasing the fraction of nanoparticles. Additionally, as Ha intensifies from 0 to 63, a final change in the mean Nusselt number of 28.65 % is displayed. Finally, as the magnetic field angle of rotation is diminished, more enhancement in heat transmission is achieved. This research provides insights into the intricate relationship between natural convection and exothermic reaction under the influences of various conditions. This can illustrate the flow and thermal behaviors of nanofluid in such non-uniform shapes in many engineering applications.

In this study, numerical analysis of a porous block influence on the mixed convection in a cavity filled with nanfluid has been investigated. The cavity is curvilinear shaped, in which the cold side is the top which is split to move in two directions on the same plane. The base is partially heated and connected to a block of porous media, while other walls are adiabatic. The complex governingequations are solved numerically using the finite element technique. For the assessment of the thermal performance, the considered variables which are Richardson number (from 0.15 to 10), Reynolds number (from 25 to 200), Darcy number (from 10−5 to 10−1), Hartmann number (from 0 to 62), ma magnetohydrodynamic's inclination angle (from 0° to 90º) and nanoparticles concentration (from 0 to 0.08). The height of the porous block is also investigated. The results’ main finding stated that the heat transfer could be enhanced due to the rise in Reynolds number, Richardson number, and the volume concentration while decreasing with the rise of Hartmann number. Also, value of Nuavg and the streams’ strength increase with the increase in Darcy number.

From some decades, the world has a deep problem which called energy crisis. Therefore, a considerable effort has introduced in the field of renewable energy to cove and solve this problem especially wind energy. Some attempts succeeded to improve the wind turbine to convert the wind energy into mechanical energy. However, rare designs are available to convert the low-speed wind energy. Savonius turbine is one of promising converters for low wind speed energy. In the present work, an important improvement in the power output coefficient has been achieved as well as an interesting increase in the static torque coefficient which shows the self-starting capability. A modification has been performed on the conventional design by adding a couple of frontal guiding plated to reduce the negative torque increase the positive torque. An optimization technique based on in-house optimization library called OPAL coupled with CFD is utilized in the current work. The main objective of this optimization study is to maximize the turbine power coefficient. An interesting increase in the Savonius turbine performance has been gained (typically 39.8% relative increase of the power coefficient).

In this work, the performance of a new wind turbine design derived from a conventional Savonius turbine is investigated by numerical simulations. The new design consists of three blades without passage between them (closed center). All unsteady computations (which mean computational fluid dynamics as well in the next sections) presented in the current work depend on a commercial software ANSYS Fluent 19. In particular, the blade geometry, the influence of a deflecting plate, and the influence of mobile parts on the returning plate have been investigated in detail. Since first results were partly disappointing for the turbine with a deflector but very interesting for the turbine with an opening blade, these same properties have also been investigated for the classical Savonius turbine. By comparison between both, an optimal solution can emerge from this first study for these designs. The results indicated that the opening blade design improved the performance by 25.9% at λ = 0.7; however, the deflecting plate reduces the performance along the operating range.

In this study, the performance of a new wind turbine design derived from a conventional Savonius turbine is optimized by numerical simulation. The new design consists of three blades without passage between them (closed center). The coupling between the CFD codes (ANSYS Fluent) and the optimizer (OPAL) is used through an automatic procedure in-house codes, as documented, for example, in Thévenin et al.’s Optimization and Computational Fluid Dynamics (2008). A single-objective function (output power coefficient, Cp) is considered as the target of the optimization technique and the shape of the blade as an optimization parameter and relies on evolutionary algorithms. An optimal solution can emerge from this optimization study. By comparison between regular design (semi-cylindrical shape blades) and the optimal configuration, a considerable improvement (up to 7.13% at λ = 0.7) of the optimal configuration performance can be obtained in this manner.

This research article proposes a novel design of solar still; furthermore, it investigates, experimentally, its thermal and productivity performances, as well as its efficiency, under the realistic meteorological conditions of the city of Gafsa, Tunisia (34.4311° N, 8.7757° E), in terms of ambient temperature and solar irradiance. The novel proposed design presents a cylindrical solar still with a rotating transparent plastic (Plexiglass) cover, wiped continuously on the inner surface. A specific technological configuration of the evaporation and condensation compartments is elaborated. A real prototype is manufactured in order to carry out the performance experimental investigation. A performance comparison is carried out between the cylindrical transparent plastic cover rotating and it being fixed, for two experimentation days presenting slightly different meteorological conditions. The experimental water and plastic cover temperatures, the hourly and the cumulative water production, as well as the hourly efficiency are deeply quantified and interpreted.

This work deals with controlling the solar radiation reception rate (SRRR) (ratio of the incident solar radiation on tilted panel to the global incident solar radiation). Controlling the SRRR will permit the amount of the received solar energy on solar panels to be adjusted. This SRRR control is very useful for several technological applications such as solar thermal and photovoltaic technologies in extremely sunny regions around the world, such as the case of Makkah, Saudi Arabia. Thus, the sustainability of the cities and villages, located in such regions, is promoted. A novel design proposing a poly-tilted segmented panel (PTSP) is proposed as an original techno-logical solution enabling the control of the SRRR. Design technical details are clearly explained. The proposed design presents a cheap, simple and effective alternative to conventional sun tracking systems. The SRRR on the proposed PTSP is mathematically modeled. The influence of the combinations “number of segment/tilt angles” on the SRRR is assessed for the most significant days in the year: equinox, summer solstice and winter solstice. A specific “document-aided design”, showing the SRRR level reached by each specific combination “num-ber of segment/tilt angles”, is provided. Based on these documents, the adequate combination “number of segment/tilt angles” is easily determined by knowing the desired SRRR level. The SRRR level is determined based on the global incident solar radiation and the desired level of the incident so-lar radiation on the tilted panel. Results are properly presented, discussed and interpreted for each segment/tilt angles combination.

Darrieus wind rotor is a vertical axis wind turbine that is a very promising kind of wind converters at remote and domestic locations that have soft and weak wind potential and speed, but from the quantitative comparison with horizontal axis wind turbines, this type of turbines has a weak performance. Additional researches are still needed to develop its efficiency to identify all the requirements of the generated power in low power demands. The aim of the current investigation is to analyze all the acting forces on the main parts of Darrieus rotor over the rotations as well as in maintenance and stationary conditions. Aerodynamic forces assessment will be executed for 3 different blade shapes (nonsymmetric and symmetric airfoils) like the airfoil section shapes of the Darrieus rotor blades. NACA 0021, LS413, and S1046 are selected as cross-sectional profile in this work. CFD simulations have been used in this work to get the different aerodynamic forces on the rotor blades of the Darrieus turbines. The present results indicated that the symmetric S1046 blade has higher forces during the rotation and stagnant (static) conditions. Moreover, the self-starting capability of NACA 0021 is better than S1046 due to low aerodynamic torsion on the S1046 blades.