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The aim of this work is to present a natural convective and squeezing flow model of two-dimensional couple stress nanofluid which is flowing on the sensory surface with variable fluid viscosity. The fluid flowing on a microcantilever sensory surface and squeezing is happening at free stream. The sensor is also useful to detect the movement of fluid and the variations in thermal and solutal rates. The Cattaneo–Christov model is adopted along with nanoparticle and chemical reaction to explore the transmission of heat and mass rates. The analysis of heat transmission in non-Newtonian couple stress fluid flowing on squeezed sensory surface by using the Cattaneo–Christov heat conduction model has various industrial and scientific applications including the polymer processing, wastewater treatment, chemical reactors, biomedical flows, cooling and heating processes in industries, heat exchangers, microfluidics, oil and gas industries. All the assumptions are applied in the basic governing laws laws and then we get the model of the partial differential equations. The governing model of equations is transmuted into ordinary differential equations form via the transformations and then the numerical results of these ODE's are examined with a well-defined numerical technique "Shooting Method". For higher inputs of couple stress, squeezing index and permeability velocity, the fluid's internal velocity decreases. Because of the Prandtl number and thermal relaxation coefficient, the heat transfer mechanism slows down. Mass transfer increases for greater inputs of the thermal diffusivity coefficient and decreases due to concentration relaxation. Further, the numerical dependency of emerging parameters on the skin friction is illustrated in tabular form. The parametric effects on the model (velocity, temperature and concentration) are introduced using numerical values shown in the table. [ABSTRACT FROM AUTHOR]

The analysis of non-Newtonian fluid flow over an oscillating surface often involves numerical simulations and experimental investigations. Computational fluid dynamics method including finite difference or finite element techniques can be used to crack the governing equations of the fluid flow. In this work, we used the Crank–Nicolson numerical technique to analyze the numerical behavior of unsteady boundary layer flow of Casson fluid with natural convection past an oscillating vertical plate. The temperature-dependent viscosity is assumed for the flow analysis. The impact of chemical reaction and heat generation coefficient is used to examine the mass and heat transferal rates. The investigation of non-Newtonian fluid flow over an oscillating surface is crucial for a wide range of industrial, biomedical, and scientific applications. The governing model of equations occurs in the form of nondimensional PDEs and then we use the dimensionless variables in order to achieve the dimensional PDEs. These equations are numerically solved by using the Crank–Nicolson technique. The Crank–Nicolson scheme is used because it has the ability to provide accurate and stable solutions and make it a valuable numerical technique in various scientific and engineering disciplines. The findings indicate the significance of numerous parameters on the mass, velocity and energy regions. The numerical outcomes of skin friction are observed due to fluid parameter, viscosity parameter, Grashof numbers of heat and solutal rates. [ABSTRACT FROM AUTHOR]

We present a comprehensive analytical model for laminar flow in a vertically heated rectangular convection loop, with applications to oil cooling in transformer systems. Starting from an integral equation, we apply a quasi-one-dimensional approach to derive equations for both loop velocities and temperature distributions. In this model, we account for temperature-dependent dynamic viscosity and introduce cooling at the loop top and in the fin. The analytical predictions are rigorously validated against finite volume method (FVM) simulations across different geometries and heat flux conditions, demonstrating strong agreement within a 2% discrepancy range for most parameters. This model provides a viable analytical alternative to computationally intensive simulations, offering insights into natural convection dynamics within closed-loop configurations. [ABSTRACT FROM AUTHOR]

This paper analyzed the effect of a flat tube with various aspect ratio (AR) and inclination angle (φ) inside a square enclosure on natural convection. The study covered the Rayleigh number (Ra) from 103 to 106 and a Prandtl number (Pr) of 0.7. The aspect ratio of the flat tube was changed from 0.5 to 2.5 in intervals of 0.5, while the inclination angle ranged from 0° to 90° in intervals of 15°. All simulated cases achieved a steady state, though the thermal and fluid flow characteristics exhibited slight variations depending on the simulation parameters. The value of AR and φ of the flat tube notably influenced heat transfer performance. Specifically, NY ¯ cy increased by up to 5.56 % and 6.96 %, respectively, across the entire range compared to the circular cylinder. Furthermore, correlation equations of the Nusselt number were developed to predict the heat transfer performance on both the flat tube and the enclosure. These equations provide a comprehensive understanding of how Ra, AR, and φ affect heat transfer performance in two-dimensional natural convection system. [ABSTRACT FROM AUTHOR]

This study investigates the convection phenomena of magnetohydrodynamic (MHD) nanofluids, focusing on the effects of thermal radiation and nanoparticle shape factors. Using the finite element method, we analyze various parameters, including radiation parameter, nanoparticle volume fractions, Hartmann number, and Rayleigh number. Our findings reveal that the presence of nanoparticles significantly enhances both average and local Nusselt numbers compared to other nanoparticle shapes. This research contributes to understanding heat transfer mechanisms in nanofluid systems, with implications for engineering applications. The novelty of this study is to analyze the impact of thermal radiation, MHD, and nanoparticles on natural convection in a cavity. It provides insights into the interplay of parameters and heat transfer processes. The control-volume finite element method allows detailed examination of flow and heat transfer characteristics. [ABSTRACT FROM AUTHOR]

Taguchi method is an experimental design methodology that uses a statistical technique to optimize process parameters while minimizing variability and improving output quality. In this article, Taguchi methodology has been utilized for parametric optimization of the design of a porous triangular enclosure, with an in-line rectangular finned array, to achieve maximum natural convection heat transfer. Three influencing parameters viz. fin spacing (S), percentage volume occupied (Vo) (measure of enclosure porosity), and fin tip to cooling plate distance (d), are optimized with consideration of maximizing the heat transfer (i.e. Nusselt number). The experimental design has been created using Taguchi's L9 (3^3) orthogonal array. An analysis of variance (ANOVA) table, regression equation, response surfaces, and contour plots have also been generated using Response surface methodology, and the optimum values of influencing parameters have been suggested. [ABSTRACT FROM AUTHOR]

This study conducts a comprehensive numerical investigation into enhancing thermal transfer within square enclosures filled with water-based oxide nanoparticle suspensions, subjected to central sinusoidal heating. Further flow configuration, influenced by an inclined magnetic field, is designed with a focus on enhancing thermal efficiency for engineering applications. Key innovations include the application of sinusoidal heating elements to enhance thermal performance significantly. Computational analysis supported by finite element analysis, quantifies the impact of these parameters on flow dynamics and thermal transmission, presenting a substantial advance in the understanding of nanofluid-filled enclosure thermal management. The study reveals that the undulation of the heating element plays a crucial role in the heat transfer rate, with improvements observed as undulation increases. The introduction of magnetic fields further controls flow distribution and buoyancy effects, as demonstrated by our findings that an increase in the Rayleigh number correlates with enhanced convection, dominating the cavity's thermal dynamics. Additionally, the report outlines the conditions under which the Nusselt number increases, indicating enhanced thermal performance. These insights are pivotal for designing optimized heat transfer systems and energy-efficient applications, setting a new benchmark for thermal management strategies in practical engineering contexts. [ABSTRACT FROM AUTHOR]

The present investigation deals with the natural convection (NC) of Al2O3-Cu-water hybrid nanofluid (HNF) within a " π "-shaped cavity under the influence of an externally applied magnetic field (MF). Also we studied the porous media with radiative effect as well as common heat transfer for better fitting to real industrial problems. The inverse U shaped-cavity design includes upper walls that are partially heated and wavy right and left walls designed for cooling purposes, while the remaining walls are maintained as adiabatic. A FORTRAN home code using finite difference method-based approach is adopted to solve the governing equations. A verification is performed by comparing with previous numerical investigations to substantiate the precision of the established numerical model. The findings are expressed in term of stream function, isotherms, and local and averaged Nusselt number. It was found that by increasing amplitude (A), location of the heater (D), thermal radiation parameter (Rd) and wavelength (λ) about 140%, 94%, 775%, and 28% Nuavg increases, respectively. In addition, by increasing Dimensionless of heat source/sink length (B), Ha, and heat generation/absorption coefficient (Q) about 20%, 1.1% and 28% Nuavg decreases, respectively. Also, Nuavg first decreases and then increases by increasing Ra. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of porous fin parameters on natural convection heat transfer performance in a closed cavity under sinusoidal periodic temperature boundary conditions. The study examines the impact of periodic boundary parameter variation on the Nusselt number, which represents the ratio of convective heat transfer to conduction heat transfer close to the wall region. The study results indicate that the average Nu number on the heat source surface fluctuates with different sinusoidal patterns, and the top surface of the heat source has a greater impact on convective heat transfer in the cavity. The analysis of the response surface method reveals that the interaction between the fin height Sa and the fin length La has the most significant influence on the average Nu of the heat source surface. The optimal combination of fin parameters coming from the response surface method is: Sa (0.35 ≤ Sa ≤ 0.65), La (0.06 ≤ La ≤ 0.3), ΔSab (0.05 ≤ ΔSab ≤ 0.25), A(0.5 ≤ A ≤ 1), B (0.004 ≤ B ≤ 0.016), θ (30° ≤ θ ≤ 150°). Under the combination of these parameters, the time-average Nu number on surface of heat source reaches the maximum value 11.63, which is 13.00% higher than that without fins. The convective heat transfer intensity in the cavity increases with the increasing dimensionless amplitude a. In addition, the time-averaged Nu number on the surface of the heat source has a negative correlation with the dimensionless period τp. [ABSTRACT FROM AUTHOR]

This numerical study provides a comprehensive examination of thermosolutal natural convection of Al2O3-Ag hybrid nanofluid inside a porous parallelepipedic cavity at three values of aspect ratios. It noticed that the phenomena of convection heat and mass transfer of nanofluid in three-dimensional porous cavities are important in applications for heat exchangers, heat storage in solar collectors, refrigeration equipment and many other heat transfer devices. Since present study continues novel physical approach of double diffusive convection of hybrid nanofluid contained in porous saturated three-dimensional enclosure, so this is the novelty of the current work. The numerical simulations are executed by using the finite volume method. Impacts of Rayleigh number, solid particle volume fraction, porosity, Darcy number and aspect ratio on the convective heat and mass transfer performance were studied. The Brinkman–Darcy model is involved to simulate for the fluid flow through the porous medium. Our results illustrate that when the aspect ratio enclosure increases, there is an important improvement in flow rate at any combination of Darcy number, Rayleigh number and nanoparticle volume concentration. In fact, a higher enhancement in the average Nusselt of 42.9% and Sherwood number of 44.11% is achieved with the increase in aspect ratio from Ar = 2 to Ar = 4. Furthermore, the increase in 3D character flow with aspect ratio is observed only at higher Rayleigh number. The results show also that increasing the volume fraction of solid nanoparticles reduces Nusselt and Sherwood amplitudes. Conversely, increasing the Darcy number induces increased impacts of heat and mass transfer by convection. An increment in the average Nusselt number is observed when the porosity number increases even though the average Sherwood number is reduced and the value is 3.75%. [ABSTRACT FROM AUTHOR]

This study innovatively developed a sinusoidal cavity heat transfer model and applied it to the natural convection heat transfer effect under magnetic field excitation through experimental exploration. The effects of heat input, mass concentration of nanofluids, magnetic density, magnetic field layout and other variables on heat transfer were studied. The consequence showed that for heat transfer, the horizontal magnetic field has a weakening effect, which can reduce the Nusselt number by 2.57% at most. The double lateral vertical staggered magnetic field has the best effect, and the Nusselt number can be increased by 5.37% at most. Under a vertical magnetic field, increasing the magnetic field strength will increase the corresponding entropy generation. The maximum increase is 9.11%. This will provide some guidance for design of cavity and the application of magnetic nanofluids in the field of thermal management of electronic components and also provides the possibility for designing more efficient thermal management systems in the future. [ABSTRACT FROM AUTHOR]

The present work examines numerically the natural convection along with the entropy generation within H-shaped enclosure with wavy walls filled by (Ag-MgO/water) hybrid nanofluid considering inner bodies and under the influence of horizontal magnetic field and thermal radiation using finite element scheme. The inner bodies of the circular shapes are kept at a hot temperature, while the two-sided wavy walls are kept at a cold temperature. The rest of the enclosure's walls are thermally insulated. The influence of many parameters had been examined such as Rayleigh number (10 3 ≤ Ra ≤ 10 5) , Hartmann number 0 ≤ Ha ≤ 60 vertical location of inners bodies 0.2 ≤ δ ≤ 0.8 , distance between inner bodies 0.3 ≤ E ≤ 0.9 , height of the enclosure walls 0.2 ≤ B ≤ 0.8 and width of the enclosure wall 0.1 ≤ A ≤ 0.9 in addition to the radiation parameter 0 ≤ Rd ≤ 3 on fluid flow, heat transfer and entropy generation. The results of this study had been presented in terms of streamlines, isotherms, entropy generation, Nusselt and Bejan number. The results showed that the Nusselt number will be at its lowest value when the vertical location of the inner bodies is δ = 0.8 and the influence of Hartmann number will be negligible at this value. Also, at high Rayleigh number Ra = 10 5 increasing the distance between the inner bodies from E = 0.3 into E = 0.9 leads to increasing Nu by 76 % . However, increasing the height of the enclosure's walls from B = 0.2 into B = 0.8 leads to enhancing Nu by 0.02 %. However, increasing width of the enclosure wall from A = 0.1 into A = 0.9 leads to an obvious reduction in Nusselt number by 20 % . Additionally, it had been obtained that increasing the vertical location of the inner bodies, the distance between them and the width of the enclosure and reduction of the height of the enclosure's wall lead to increasing Bejan number. Stronger magnetic fields enhance conductive heat transfer; increasing the Bejan number which represents irreversibility as noted at increasing Hartmann number from Ha = 0 into Ha = 60 leads to increasing Bejan number by 79 % . [ABSTRACT FROM AUTHOR]

In order to explore the heat transfer properties of natural convection in the cavity, this article uses the three-dimensional CFD inverse method and the temperature measurement points based on the experimental results. In addition, different flow modes and mesh divisions are used. For the applicability of different turbulence models, the least squares method is then used to calculate Q value of the heat source in the cavity and compare that with the experimental measurement results and consistent with the overall trend. Finally, the temperature distribution diagram and velocity streamline diagram of the simulation results are provided to visualize the flow field and analyze its heat transfer characteristics. The results show that the flow pattern and the number of grid points have a great influence on the results. In terms of experiments, with the change of the cavity size and the influence of the opening, the air flow will be different. To achieve the effect of enhancing natural convection, due to the inflow of a large amount of cold air, although the overall temperature of the cavity is greatly reduced, the upper cold wall is surrounded by cold air, which reduces the heat transfer coefficient. In order to verify the reliability and usability of the results of the inverse algorithm in this article, the obtained results of heat transfer coefficient and heat dissipation are compared with previous results or empirical formulas in other related literature. When the height drops from h = 0.1 m to h = 0.05 m, the average increase in heat transfer coefficient is 2.79%; while for the height drops from h = 0.05 m to h = 0.02 m, the average increase in heat transfer coefficient is 74.8%. When side fin length is reduced form W2 = 0.1 m to W2 = 0.08 m, the average increase in heat transfer coefficient is 14.33%; when side fin length is reduced form W2 = 0.08 m to W2 = 0.06 m, the average increase in heat transfer coefficient is 41.28%. [ABSTRACT FROM AUTHOR]

The present research utilizes an inverse 3D CFD technique, coupled with the least squares approach and laboratory temperature readings, to predict the suitable turbulence flow model and unknown heat transfer rates within a cubic hot box. This enclosure features four cylindrical horizontal tubes arranged in a diamond configuration, functioning as heaters to generate heat within the space. Furthermore, the heat dissipation from each tube, flow field and temperature contours are also established. The energy equation for tubes and the governing equations for air are solved by coupling. The present estimates are obtained assuming a constant heat transfer rate. The range of the Rayleigh number is from 60,294 to 76,824. Testing various turbulence models revealed that the zero-equation turbulence model reduces the root mean square discrepancy between the simulated thermal behavior and laboratory outcomes compared to other methodologies. To verify the chosen flow model's accuracy, the Nusselt numbers and flow field distributions aress compared with existing correlations and interferometer photographs. The maximum errors between the estimates of heat loss and heat transfer rate and the corresponding values from previous studies are 44 and 28% for St = 0.036, 34 and 3% for St = 0.045, and 37 and 18% for St = 0.054. To assess the impact of tube surface and spacing on the flow field model, calculation results are compared with those from four square-arranged tubes, revealing a lack of existing studies on this specific investigation. [ABSTRACT FROM AUTHOR]

The traditional approach of open-sun drying is facing contemporary challenges arising from the widespread adoption of energy-intensive methods and the quality of drying. In response, solar dryers have emerged as a sustainable alternative, utilizing solar thermal energy to effectively dehydrate vegetables. This study investigates the performance of a single-basin, double-slope solar dryer utilizing natural convection for drying bottle gourds and tomatoes, presenting a sustainable alternative to traditional open-sun drying. The solar dryer exhibited superior moisture removal efficiency, achieving a 94.42% reduction in tomatoes and 83.87% in bottle gourds, compared to open-sun drying. Drying rates were significantly enhanced, with maximum air and plate temperatures reaching 54.42 °C and 63.38 °C, respectively, accelerating the dehydration process. Moisture diffusivity analysis revealed a marked improvement in drying behavior under solar drying, with values ranging from 3.12 × 10−11 to 4.31 × 10−11 m2/s for bottle gourds, and 4.65 × 10−11 to 2.31 × 10−11 m2/s for tomatoes. Energy efficiency assessments highlighted the solar dryer's advantage, with exergy efficiency peaking at 61.78% for bottle gourds and 68.5% for tomatoes. Furthermore, the activation energy required for drying was significantly lower in the solar dryer (29.14–46.41 kJ/mol for bottle gourds and 27.16–55.42 kJ/mol for tomatoes) compared to open-sun drying, enhancing energy conservation. Visual inspections confirmed the superior quality of the solar-dried vegetables, free from dust and impurities. An economic analysis underscored the system's viability, with payback periods of 2 years for bottle gourds and 1.6 years for tomatoes. Overall, this study demonstrates the efficacy of solar dryers in optimizing vegetable preservation while promoting energy efficiency, aligning with global sustainability goals by reducing post-harvest losses and supporting eco-friendly practices. [ABSTRACT FROM AUTHOR]

Enhancing the energy efficiency of thermal systems reduces their consumption, lowers costs, and reduces undesired environmental impact, thus making these systems more sustainable. The current work introduces a passive method for heat transfer enhancement that is carried out using natural convection by nanofluid. This work introduces a computational study of the process of natural convection within a square cavity containing Cu/H2O nanofluid. The cavity wall on the left side undergoes partial isothermal heating, while the opposing side is fully cooled isothermally, with all other boundaries maintained adiabatic. A mathematical model formulated based on a 2-D model was used to provide the solution for the system of governing equations of mass, momentum, and energy conservation, employing the finite element technique. A commercial CFD package is utilized to perform the computational simulation. The present investigation delves into the impact of the Rayleigh number, nanoparticle concentration, heater length, and heater location on the flow field and heat transfer characteristics. The model outcomes were displayed for a wide range of the pertinent parameters as 103 ≤ Ra ≤ 106, 0.25 ≤ lh ≤ 1.0, 0.125 ≤ hc ≤ 0.875, and 0.02 ≤ ϕ ≤ 0.10. Also, correlation equations relating the average Nusselt number to these crucial parameters are derived. These equations are simple and can be applied in practice easily in many fields, such as electric and electronic equipment cooling and thermal management of heat sources. Also, these equations gather all the parameters that affect the heat transfer process. They are shedding light on the intricate interplay between these parameters in the natural convection heat transfer process. [ABSTRACT FROM AUTHOR]

The Al alloy melting behavior and interfacial reactions during the steelmaking process of high-Al automotive steel were investigated in this study. The total dissolution time of Al bars (20 × 20 × 80 mm) in molten steel was quite short, decreasing from 21.4 s to 10.0 s with an increase in bath temperature from 1580 to 1620 °C. The Al alloy melting process at the molten steel temperature of 1600 °C included the formation of a solidified steel layer, the latter's rapid melting, and Al alloy normal melting, while at 1600 °C, the process included a second increase in the thickness of the solidified layer. Because steel elements such as [Fe], [C], [O], and [N] could diffuse during the whole Al alloy melting process, an Fe (Al)-FeAl-FeAl2-Fe2Al5-Al diffusion layer along the direction of the Al-rich matrix could be found at the Fe–Al interface. Moreover, FexO, Al2O3, and unstable AlN inclusions could be observed in the FeAl layer. This study also investigated how to reduce the number of these easily formed inclusions. Decreasing the pre-heating process time and dissolved oxygen content could be useful in decreasing FexO and Al2O3 inclusion formation. Some small-sized AlN inclusions formed in the center of the Al bars where they could not come into contact with the molten steel directly during the melting process; even for the immersion time of only 1 second, these inclusions were not stable in molten steel at the refining temperature and disappeared during the melting process. [ABSTRACT FROM AUTHOR]

This paper explores the effects of egg orientation and yolk position during thermal processing using computational fluid dynamics simulation and experimentation. A carboxymethyl cellulose suspension was used to simulate the egg white, and a two‐dimensional model incorporated an air cell near the larger end. The simulation included four cases: two focused on vertical orientation with the yolk at the rear shell and the geometric center, and two on horizontal orientation with similar yolk positions. Repositioning the yolk in a horizontal orientation near the eggshell resulted in significant temperature variations. The findings show that a horizontal egg position, especially with the yolk near the eggshell, led to a significant 8%–16% reduction in heating times. This configuration also improved pasteurization efficiency, assessed by the F value, by about 13.8%. The study also revealed distinct flow patterns influenced by buoyancy forces, significantly related to temperature distribution inside the egg. [ABSTRACT FROM AUTHOR]

The current study explores the thermal performance and geometric optimization of radial heat sinks manufactured through selective laser melting process of AlSi10Mg material, primarily intended for cooling applications in light-emitting diodes (LEDs). Few studies have systematically approached the geometric optimization of radial heat sink designs, particularly considering variable fin heights (both fin outer and fin inner height), in conjunction with other geometric parameters like fin length, fin thickness, and the number of fins tested across a broad spectrum of heat flux values. Through comprehensive experimentation and numerical simulations, the independent and combined impact of these considered key geometric parameters was investigated on the heat sink performance. The experimental design, guided by Response Surface Methodology, encompasses a wide range of heat flux levels, varying from 300 to 1800 W/m2, to ensure the broad applicability of the findings. The results underscore the significance of fin thickness, which notably influences the base temperature of the heat sink, particularly at higher heat flux levels. The interaction between heat flux and fin length also plays a pivotal role in base temperature control, with additional fins contributing to lower temperatures. Furthermore, it was revealed that higher fin outer heights, combined with lower fin inner heights, lead to superior heat sink performance, aligning with practical LED cooling requirements. The optimization process results in configurations that consistently maintain base temperatures below the critical 70 °C threshold, thus contributing to effective thermal management in LED devices. [ABSTRACT FROM AUTHOR]

Non-Newtonian fluids within heterogeneous porous media may give rise to complex spatial energy and mass distributions owing to non-local mechanisms, the modeling of which remains unclear. This study investigates the natural convection heat and mass transfer of non-Newtonian fluids in porous media, considering the Soret and Dufour effects. A strongly coupled model is developed to quantify the coupled transport of energy and reactive pollutants with the non-Newtonian fluid. The constitutive equation for the non-Newtonian fluid is described by a two-sided Caputo type space fractional velocity gradient. The governing equation, with a symmetric diffusion term, is effectively solved using a stable and convergent shifted Grünwald–Letnikov formula. The influences of three important parameters, which are the average skin friction coefficient, the average Nusselt number, and the Sherwood number, on fluid heat and mass transfer are calculated and analyzed. Numerical results reveal a significant interaction between the fractional derivative and the buoyancy ratio number, both of which affect the average skin friction coefficient. Furthermore, the average Nusselt number increases with the Dufour number while decreasing with the average Sherwood number. These findings enhance our understandings of the dynamics of energy and mass co-transport in non-Newtonian fluids, particularly in relation to their constitutive equation featuring spatial non-local properties. [ABSTRACT FROM AUTHOR]

The Particle Image Velocity method was used to investigate the velocity fields when the liquid layer height changed from 0.6 to 5.1 mm. The loss of stability of the velocity field during local heating is realized at the Bond number (Bo) 0.01–0.02, which is 10–20 times lower than the critical value of Bo(cr) compared to heat exchange at a uniform wall temperature. The Marangoni flow depends both on the height and the layer diameter. The critical height of the layer 2–2.5 mm leads to a sharp change in the flow pattern. [ABSTRACT FROM AUTHOR]

Many designs for natural-convection heat sinks and semi-empirical correlations have been proposed in the recent years, but they are only valid in a limited range of Elenbaas numbers E l and were mostly tested for laminar flows. To alleviate those limits, parametric studies with 2D and quasi-3D models were carried out, in ranges of Grashof numbers up to 1.55 × 10 11 and Elenbaas numbers up to 3.42 × 10 7 . Ansys Fluent's laminar, transition-SST, SST k- ω and k- ϵ models were applied. In addition, when used in this valid range, i.e., mean Elenbaas numbers, with the simplified quasi-3D model, the transition-SST model could predict better results, overestimating the heat flux by 10 to 15 % compared to semi-empirical correlations. The 2D model was not deemed satisfying, regarding turbulence models. Consequently, a quasi-3D model was developed: it appeared to be an efficient trade-off between computational time and prediction accuracy, in particular for turbulence models. New grouping factors were also found, to ensure proper dimensioning of natural-convection heat sinks. They corresponded to non-dimensional parameters that dictated the physical behaviour of the heat sink with respect to the semi-empirical correlations. Typically, the ratio of the spacing to the optimal spacing predicted by Bar-Cohen's correlation turned out to be an appropriate grouping factor with a threshold of 1, above which the fins could safely be considered as isolated, thus greatly simplifying all further calculations. [ABSTRACT FROM AUTHOR]

The present investigation centers on the impact of viscous dissipation and ohmic heating on the plume generated by a line heat source under the impact of an aligned magnetic field. In this study, the flow model is adapted to incorporate ohmic heating and viscous dissipation by including the respective terms in the energy equation. A mathematical model is formulated as a system of coupled partial differential equations to analyze the flow problem. Subsequently, a numerical solution is derived with stream function formulation for the system of coupled partial differential equations, which transmutes it into ordinary differential equations. To achieve this, the numerical properties of the problem are established through the utilization of the Shooting method in tandem with the MATLAB tool bvp4c. The graphical representations of both missing and specified boundary conditions depict the effects of the magnetic parameter, viscous dissipation variable, magnetic force parameter, Prandtl number, and magnetic Prandtl number. These are accompanied by a discussion of their respective physical implications. The observed results claimed that the velocity, current density, and temperature distribution decrease for enhancing magnetic parameters. Meanwhile, the skin friction and magnetic flux drop while the heat transfer rate increases with an increment in magnetic parameters. These fluid flow and heat transfer characteristics were observed to decrease for increasing viscous dissipation. The current work is novel in incorporating ohmic heating viscous dissipation in energy equations coupled with Max-well and magnetic induction equations. [ABSTRACT FROM AUTHOR]

AbstractExamining the effects of varying transient magnetic fields and their orientations on boundary layers aids in understanding the flow in complex surface geometries, turbulence control, drag reduction, aircraft and ship design, groundwater management, and the study of construction and coastal engineering. The study introduces a novel dynamics of the boundary layer of a natural convective Jeffrey fluid flowing over an erect porous moving plate under the influence a non-uniform and transient magnetic field M˜ that grows exponentially over time with α as an accelerating parameter. The governing partial differential equations (PDEs) were non-dimensionalized using similarity variables and then solved analytically using the perturbation technique. The impact of various thermosphysical properties including chemical reactions, thermal source, Jeffrey fluid parameter and plate permeability on the fluid flow were presented graphically utilizing finite difference approximation(FDA) technique in MATLAB ODE15s solver. The study highlighted a notable decrease in shear stress (skin friction) by introducing M˜ to the vertical plate results in the reduction of momentum boundary layer, accompanied by an increment in thermal boundary layer. Also, the results shows that increasing the magnitude of α leads to decrease the velocity and increase the temperature distribution curve. Additionally, the concentration profile was also found to decrease with stronger chemical reactions. Furthermore, key parameters like heat and mass flux were estimated and discussed through comparison tables. Understanding the effects of unsteady and externally applied increasing magnetic field M˜ on viscous fluid flow have potential applications in biomedical engineering, such as the design of magnetic drug delivery systems and the analysis of blood flow in human body. [ABSTRACT FROM AUTHOR]

In order to improve convective flow, this study primarily used techniques including curved surfaces and a strong magnetic force. Cold temperatures and even flow are experienced by both the circular outer wall and the sinusoidal inner wall. FHD can have a bigger effect when combined with iron oxide in the base fluid. The electric current-carrying wire was positioned close to the interior wall in order to produce Kelvin force. A novel modeling approach was chosen to ascertain the number of scalars throughout the entire domain, and the process was validated using earlier numerical work. Gravity forces, ferrofluid concentrations, and the Kelvin force serve as the main pillars of current research. Conduction features increase and the Nu rises by 12.44% when nanopowders are used. Due to gravity and magnetic forces, the nanofluid can move more easily through the container. At Ra = 1 e 3 and 1e4, respectively, Nu increases by 93.04% and 35.43%; with an increase in MnF. Additionally, Nu rises with Ra at Mn F = 0 and Mn F = 4 0 0 0 by 43.55% and 0.71%, respectively. [ABSTRACT FROM AUTHOR]

An air-rock bed thermal storage system was designed for small-scale powered generation and analyzed with computational fluid dynamics (CFD) using ANSYS-Fluent simulation. An experimental system was constructed to compare and validate the simulation model results. The storage unit is a cylindrical steel container with granite rock pebbles as a storage medium. The CFD simulation used a porous flow model. Transient-state simulations were performed on a 2D axisymmetric model using a pressure-based solver. During charging, heat input that keeps the bottom temperature at 550 °C was applied to raise the storage temperature. Performance analysis was conducted under various porosities, considering natural and forced convection. The natural convection analysis showed insignificant convection contribution after 10 h of charging, as observed in both average air velocity and the temperature profile plots. The temperature distribution profiles at various positions for both convection modes showed good agreement between the simulation and experimental results. Additionally, both cases exhibited similar temperature growth trends, further validating the models. Forced convection reduced the charging time from 60 h to 5 h to store 70 MJ of energy at a porosity of 0.4, compared to natural convection, which stored only 50 MJ in the same time. This extended charging period was attributed to poor natural convective heat transfer, indicating that relying solely on natural convection for thermal energy storage under the given conditions is not practical. Using a small fan to enhance heat transfer, forced convection is a more practical method for charging the system, making it suitable for power generation applications. [ABSTRACT FROM AUTHOR]

The study of steady natural convection Couette flow is vital in designing as well as the optimization of microfluidic devices, geothermal energy systems, cooling of electronic devices and systems, etc., due to several recent applications. The present investigation aims to analyze radiative heat transfer and dissipative energy in the free convection of Couette flow within a vertically positioned channel. Incorporating carbon nanotubes (CNTs), specifically single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs), into the base fluid water enhances the flow phenomena. Additionally, the explanation of heat source/sink on the energy phenomenon encounters various properties. Further, suitable similarity variables are employed for the transformation of the governing equations. However, the homotopy perturbation method (HPM), an analytical approach, is used for the solution of the coupled ordinary differential equations. The thermophysical parameters and their impact are depicted through graphs, and the comparative analysis is presented via tables. Explore the combined effects of CNT nanoparticle concentrations on the Couette flow through a vertical channel. The inclusion of radiating heat on free convection of nanofluid enriches the flow phenomena. The adaptation of various thermophysical properties, i.e., in particular, the thermal conductivity, shows its effectiveness on the heat transport phenomenon. Clarify different contributing parameters by using the homotopy analysis method. [ABSTRACT FROM AUTHOR]

This work describes the natural convection and thermodynamic irreversibility of alumina-water nanofluid filled inside a layered cavity. The local thermal non-equilibrium (LTNE) approach is taken into consideration. The cavity bed is considered as a wavy hot plate of a very thin thickness, while its roof is thermally insulated. The heat is dissipated from the cold vertical walls. A porous layer fills the cavity's lower half and is assumed to obey the Darcy-Forchheimer model. The finite-element method is adopted to compile the numerical results. The relevant parameters assessed in this paper are the Darcy number, waviness of the hot bottom wall, porosity, volume fraction of alumina nanoparticles and the modified ratio of thermal conductivity. The obtained numerical results show that the LTNE condition expands as the Darcy number augments, while a quasi-local thermal equilibrium is attained with a higher modified ratio of thermal conductivity. The waviness of the hot wall raises the Nusselt number of both the fluid and the solid phases but produces more entropy. It is quoted that the augmentations in the fluid and solid phases of the Nusselt numbers and the increase in the maximum entropy production are 42.25%, 69% and 55.5%, respectively. [ABSTRACT FROM AUTHOR]

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Natural convection is a heat transfer mechanism driven by temperature or density differences, leading to fluid motion without external influence. It occurs in various natural and engineering phenomena, influencing heat transfer, climate, and fluid mixing in industrial processes. This work aims to use the Updated Lagrangian Particle Hydrodynamics (ULPH) theory to address natural convection problems. The Navier-Stokes equation is discretized using second-order nonlocal differential operators, allowing a direct solution of the Laplace operator for temperature in the energy equation. Various numerical simulations, including cases such as natural convection in square cavities and two concentric cylinders, were conducted to validate the reliability of the model. The results demonstrate that the proposed model exhibits excellent accuracy and performance, providing a promising and effective numerical approach for natural convection problems. [ABSTRACT FROM AUTHOR]

The Buongiorno nanofluid model serves as a foundational model for theoretical and experimental research in the field of nanofluids, and this model can be applied to various engineering problems, including heat exchangers, biomedical applications, solar collectors, nuclear reactors, and different cooling systems in the automotive and electronics industries. The use of nanofluids in the Eyring-Powell fluid over a squeezed sensing surfaces is a vital area of research for the design and improvement of microfluidic devices and sensors, which find widespread usage in industrial and medical applications. The main purpose of this work is to note the augmentation in thermal conductivity by using the Buongiorno nanofluid model along with the natural convective flow of non-Newtonian Eyring-Powell fluid that is moving on the squeezed sensory surface along with slip velocity. The viscosity of a fluid is assumed to be dependent on temperature. The Cattaneo-Christov heat and mass flux and chemical reaction are assumed to determine the combined effect of heat and mass transport. The governing model of equations is in the form of dimensional partial differential equations, and we have to convert these equations into ordinary differential equations; therefore, a set of similarity transformations is adopted for making the equations into dimensionless form. The numerical results were obtained by adopting the predictor and corrector multistep method, namely the ‘Adams-Bashforth’ technique, in Matlab software. The use of natural convective flow enhances the velocity region. The velocity slip parameter increases the velocity of the fluid, whereas the viscosity parameter drops the velocity profile. The thermophoresis and Brownian motion parameters are the sources of the increment in the temperature region. The thermal relaxation and solutal relaxation parameters are the sources of decline in the temperature region. The squeezing parameter is the source of reduction in the skin friction, whereas the result indicates that the fluid parameter, Grashof number, and viscosity coefficients increase the skin friction.

Abstract The traditional approach of open-sun drying is facing contemporary challenges arising from the widespread adoption of energy-intensive methods and the quality of drying. In response, solar dryers have emerged as a sustainable alternative, utilizing solar thermal energy to effectively dehydrate vegetables. This study investigates the performance of a single-basin, double-slope solar dryer utilizing natural convection for drying bottle gourds and tomatoes, presenting a sustainable alternative to traditional open-sun drying. The solar dryer exhibited superior moisture removal efficiency, achieving a 94.42% reduction in tomatoes and 83.87% in bottle gourds, compared to open-sun drying. Drying rates were significantly enhanced, with maximum air and plate temperatures reaching 54.42 °C and 63.38 °C, respectively, accelerating the dehydration process. Moisture diffusivity analysis revealed a marked improvement in drying behavior under solar drying, with values ranging from 3.12 × 10−11 to 4.31 × 10−11 m2/s for bottle gourds, and 4.65 × 10−11 to 2.31 × 10−11 m2/s for tomatoes. Energy efficiency assessments highlighted the solar dryer’s advantage, with exergy efficiency peaking at 61.78% for bottle gourds and 68.5% for tomatoes. Furthermore, the activation energy required for drying was significantly lower in the solar dryer (29.14–46.41 kJ/mol for bottle gourds and 27.16–55.42 kJ/mol for tomatoes) compared to open-sun drying, enhancing energy conservation. Visual inspections confirmed the superior quality of the solar-dried vegetables, free from dust and impurities. An economic analysis underscored the system’s viability, with payback periods of 2 years for bottle gourds and 1.6 years for tomatoes. Overall, this study demonstrates the efficacy of solar dryers in optimizing vegetable preservation while promoting energy efficiency, aligning with global sustainability goals by reducing post-harvest losses and supporting eco-friendly practices.

This study aims to explore the natural convection, magnetohydrodynamics and ternary nanofluids containing Fe3O4, Cu and TiO2 in water-ethylene glycol within a hexagonal cavity containing a square obstacle. The Finite element method is utilized through the COMSOL Multiphysics 6.1 software. By utilizing visual representations, the influence of key variables on flow patterns, temperature distribution, and local Nusselt number is effectively illustrated. Simulations were carried out with Rayleigh number ranging from 103 to 105, heat source and absorption coefficients ranging from -5 to 15, and Hartmann numbers of 0, 70 and 90. The Prandtl number for ethylene glycol is 29.86. The findings of this research confirm that the proper incorporation of nanoparticles significantly enhances the heat transfer properties of base fluids.

Laminar natural convection heat transfer from vertical hollow polygonal cylinders with a wide range of cross-sectional areas is investigated. The buoyancy-driven three-dimensional (3D) flow around hollow polygonal cylinders immersed in quiescent ambient air with equal outer and inner surface temperatures is analyzed. The governing equations are numerically solved in nondimensional variables using the finite volume method. The numerical solution is validated using available experimental and numerical data. Results of the mean Nusselt number for the outer and inner surfaces are obtained by varying a number of key parameters. These parameters are the Rayleigh number based on the cylinder height (Rah) in the range 10³ Rah 107, the nondimensional cross-sectional area (A) in the range 0.006 ≤ AC ≤ 0.5, and the number of sides of the polygon (N) in the range 6 ≤ n ≤ ∞ N. In all cases, a Prandtl number (Pr) of 0.7 has been assumed. The study shows that at a certain Rayleigh number and a certain number of sides, the heat transfer rate from the inner surface decreases (by as much as 79.8%) as the polygon area decreases (by as much as 83.32%), whereas the heat transfer rate on the outer surface increases (by as much as 133.3%) as the polygon area decreases (by as much as 83.32%). It has also been found that the behavior of the buoyancy-driven flow in the vicinity of the outer surface is fundamentally different than that near the inner surface. Additional details about this fundamental difference are presented in the Results and Discussion section of the paper. New correlations to calculate the average velocity at the exit surface of the cylinder inner core and the mean Nusselt number for both the outer and inner surfaces have also been developed. Also, correlations have been developed for selecting the optimal cross-sectional area for purposes of identifying the regions where the thermal and velocity boundary layers overlap within the inner core of the cylinder. [ABSTRACT FROM AUTHOR]

The decay heat removal in advanced nuclear power plants encourages the use of natural convection cooling as a precaution during power outages. The ongoing designs of micro nuclear reactors institute an ambient air-cooled system via natural convection, which points to a localized heat source cooling in an open loop. The analyses presented in this paper address the problem of natural convection heat transfer of a heat source placed in an open-ended annular channel. Numerical simulations were carried out for various heat source lengths, moved along the inner cylinder of the annulus. Using the transition SST turbulence model, the influence of the annular gap size on heat transfer rates was investigated by adjusting the radius ratios between 3 and 5, while heat transfer enhancement was achieved by way of longitudinal fins. Results of heat transfer rates, local heat transfer characteristics, and mass flow rates are presented. The change in elevation of the heat source at L c /b > 2.7 in the open system did not have a profound influence as indicated by the Rayleigh number buoyancy parameter and Nusselt numbers. However, the annular gap size was unequivocally the most influential geometrical parameter. Additionally, the average Nusselt numbers at any unfinned heated section length were adequately described by the correlation Nu L = 0.959Nu H (L/H)0.855, for 0 < L / H < 1. The number of fins and the fin height were the most important parameters for the finned system where case-specific gains of more than 50 % in average Nusselt number were obtained. The results of the present analyses provide invaluable information for the development of passively cooled systems utilizing ambient air. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive numerical computation of the natural convection of magnetized permeable nanoliquids contained within a composite wavy cabinet. The domain of interest includes two parts. One portion is filled with a nanofluid fluid saturated with a porous matrix, whereas the other region is filled solely with the nanofluid. The finite element approach is utilized to solve the coupled highly nonlinear partial differential equations numerically. A selected set of graphical results illustrating the effects of frequency, amplitude, Rayleigh number, Hartmann number, Darcy number, and different porous materials on the streamlines and isotherms are presented. The variations in these parameters enable us to examine the impact on Nusselt number, flow patterns, and thermal performance. The addition of a response surface technique based on sensitivity analysis is a major innovation in this study, and the findings reveal intricate interactions between magnetohydrodynamics (MHDs), Joule heating, and porous medium effects, providing valuable insights into optimizing thermal management and energy efficiency in advanced MHD systems. [ABSTRACT FROM AUTHOR]

The present study aims to enhance the natural convection in the heat sink inside an enclosure by perforating fins for power electronic applications. The enclosure is a cube that is manufactured in such a way that the upper and lower surfaces, as well as the front and back surfaces, are thermally insulated. The right surface is hot, while the left surface is cold at a temperature difference ∆T of (4°C, 8°C, 10°C). The heat sink used consists of five fins that are attached to the heated surface. The heat sink fins are perforated with perforation number NP (4, 8, 12, and 16) and perforation diameter DP (0.5 and 1 cm). Temperatures are measured using 13 thermocouples placed within the enclosure and the temperature distribution is determined using a FLIR E30BX IR thermal camera, while velocity contours are obtained using numerical software. The main results showed improvement in heat transfer with an increase in the number of perforations and (DP = 1 cm) was found to be more efficient than (DP =.5 cm), for instance, when (∆T = 10°C) for (NP = 16) and (DP =.5 cm). There is a 2.9% improvement in temperature reduction on the fins' tip, while at =(DP = 1 cm), the percentage of improvement was 3.5% and showed a greater expansion of the velocity lines between the fins at (∆T = 10°C), where the rate of increase in the velocity contours from (∆T = 4 and 8°C) reaches 20% and 7% respectively. In addition, heat sinks with perforated fins are both lighter and more cost‐effective in terms of metal usage during the manufacturing process. [ABSTRACT FROM AUTHOR]

Abstract The work numerically investigated laminar natural convection heat transfer from the single sphere with a constant heat flux surface in air over the wide range of Grashof number ( $$10 \le Gr \le 10^{7}$$ 10 ≤ G r ≤ 10 7 ). The more efficient and precise numerical method based on Bejan et al. was employed here, the accuracy of which has been confirmed through validation against a single sphere case. The heat transfer characteristics were systemically analyzed in terms of isothermal contours and streamlines around the sphere, dimensionless temperature and velocity profiles. Additionally, local Nusselt number as well as local pressure and friction drag coefficients were studied with different Grashof number. In comparison to the sphere with uniform heat flux surface, the heat transfer from the isothermal sphere was found to be enhanced attributable to a more robust buoyancy force and a steeper temperature gradient. Moreover, the average Nusselt number for the sphere with a constant heat flux between 60.4 and 98.6% of the isothermal sphere’s value, this range being contingent upon the specific Grashof number. What’s more, the proposed correlation addresses a notable void in the predictive understanding of heat transfer from the sphere with uniform heat flux, which is scenario prevalent in various engineering applications, particularly for the cooling of electrical and nuclear systems, and offer values for academic research.

The heat transfer by natural convection of a nanofluid, which is ethylene glycol−Al2O3 has been analyzed in an open cavity numerically using the multiple-relaxation-time - lattice Boltzmann method by the graphics processing unit high-performance parallel computing. The right side of the cavity is open, and different boundary conditions have been applied to all the walls. Besides, one adiabatic fin has been installed on each side of the enclosure’s top and bottom sides. Here, the Prandtl number is fixed at 16.6, and the Rayleigh number changes from 104−106 with the nanoparticle volume fraction from 0%−5% has been used for numerical simulations. Besides, in this work, the power-law index is an important parameter as well, and 0.7, 0.8, 1, 1.2, and 1.4 are the values of this parameter. Results are presented concerning both the average and local Nusselt numbers in the form of streamlines, isotherms, temperature distributions, velocity distributions, heat transfer rate, and entropy production. It is observed when increases, average Nusselt number increases 607.94%, and for this reason, the overall heat transfer rate rises because of buoyancy force. In addition, the average Nusselt number falls by 83.28% when the power-law index rises; as a result, the total heat transfer rate falls because fluid viscosity increases with the power-law index. It is also observed that for shear-thickening fluids, the temperature gradient is higher. On the contrary, the temperature started decreasing with the increase of the power-law index. Additionally, the local Nusselt number value rises as power-law index falls. Moreover, the heat transfer rate increases by 7.08% when volume fraction increases. The intensity of buoyancy force reduces with the increase of volume fraction. Besides, the overall entropy generation rises when the Rayleigh number and the volume fraction increase, but it decreases when the power-law index increases. So, when the Rayleigh number is 106, the power-law index is 0.7, and the volume fraction is 0.00 then the entropy generation is the highest. This current research has many applications for example heat exchangers, electronic cooling equipment, solar heating systems, aerospace applications, medical devices, and entropy generation-related systems.

The cellular automaton-lattice Boltzmann method-immersed moving boundary coupled model is established to study the microstructure evolution during the solidification process of 2009Al/SiCp. After several model benchmarks, the natural convection of liquid phase and its effect on particle settlement under different pulling velocities were studied firstly. The results showed that at higher pulling velocity, the particle decelerates downward before contacting with dendrite front due to intensified natural convection. At lower pulling velocity, the particle decelerates gradually until a change in direction and upward movement. As the particle approach the tip of the dendrite, the particle experiences a brief upward movement before contacting the dendritic front. Then the convection induced by particles has an impact on the distribution of solutes in the liquid phase. It has been observed that at lower pulling velocity, there is a significant difference in solute distribution at the solidification front. The primary reason for this phenomenon is the higher solute concentration near the solidification front at lower pulling velocity, rather than the higher liquid phase flowing rate. Finally, our model investigated the microstructure evolution process during the directional solidification process of 2009Al/SiCp at different pulling velocities. The results indicate a good agreement between the simulation results and experiment observations.

This paper presents a numerical study of natural convection in an annular cavity filled with a hybrid nanofluid under the influence of a magnetic field. This study is significant for applications requiring enhanced thermal management, such as in heat exchangers, electronics cooling, and energy systems. The inner cylinder, equipped with fins and subjected to uniform volumetric heat generation, contrasts with the adiabatic outer cylinder. This study aims to investigate how different nanoparticle combinations (Fe3O4 with Cu, Ag, and Al2O3) and varying Hartmann and Rayleigh numbers impact heat transfer efficiency. The finite volume method is employed to solve the governing equations, with simulations conducted using Fluent 6.3.26. Parameters such as volume fraction (ϕ2 = 0.001, 0.004, 0.006), Hartmann number (0 ≤ Ha ≤ 100), Rayleigh number (3 × 103 ≤ Ra ≤ 2.4 × 104), and fin number (N = 0, 2, 4, 6, 8) are analyzed. Streamlines, isotherms, and induced magnetic field contours are utilized to assess flow structure and heat transfer. The results reveal that increasing the Rayleigh number and magnetic field enhances heat transfer, while the presence of fins, especially at N = 2, may inhibit convection currents and reduce heat transfer efficiency. These findings provide valuable insights into optimizing nanofluid-based cooling systems and highlight the trade-offs in incorporating fins in thermal management designs. [ABSTRACT FROM AUTHOR]

In industrial applications, annular fins are commonly made of homogeneous materials such as aluminum, struggling to provide uniform temperature distribution along their length. Recognizing the potential of Functionally Graded Materials (FGMs) to enhance thermal performance by combining two different materials with a gradual variation, this study proposes their use as fin materials to achieve optimum performance. The study consists of three major components: (1) numerical analyses to determine the optimum volume composition of FG fins, (2) the fabrication process of aluminum and FG fins utilizing powder metallurgy and the hot-pressing technique, and (3) experiments to evaluate the thermal performance of FG and aluminum fin arrays attached to a horizontal cylinder of 250 mm length under natural convection. Heat ranging from 25 W to 150 W is applied to the cylinder during these experiments. Based on the experiments, the thermal performances of fins are evaluated in terms of net free convection heat transfer rate, the Nusselt number, and fin effectiveness. Overall, experimental results demonstrate that the net convection heat transfer rate depends on fin spacing, material, and the base-to-ambient temperature difference. Specifically, FG fin arrays enhance the net heat transfer rate by 59%, while aluminum fin arrays increase it by 33% compared to finless cylinders. Moreover, FG fins outperform aluminum fin arrays by 40% in convective heat transfer coefficient h. Due to being the first experimental study, this study sets itself apart. [ABSTRACT FROM AUTHOR]

• 3D ice storage spheres with different metal foam methods and proportions are designed. • Solidification performance of PCMs augmented by partially metal foam is studied. • The competitive mechanism of natural convection and heat conduction is analyzed. • Considering the economic benefit, the optimal filling radius 6/13 is obtained. The advancement of ice-ball thermal energy storage systems is limited by the poor thermal conductivity of phase change materials(PCM). This paper presents a numerical investigation into enhancing heat transfer in ice balls by partially filling them with metal foam. Dynamic temperature changes, solid phase fraction, and cold storage capacity are analyzed for various filling radius ratios (2/13, 4/13, 6/13, 8/13, and 13/13). We quantitatively assess the specific impact of metal foam filling on heat transfer by calculating changes in the comprehensive thermal conductivity coefficient. Our findings reveal that the comprehensive thermal conductivity coefficient increases nonlinearly with the growing metal foam filling radius ratio, indicating that full filling may not the most optimal configuration. Furthermore, the energy storage capacity per unit time, per unit weight and per unit cost of the ice ball filled with metal foam under different radius ratios was evaluated by comprehensive evaluation criteria, and the optimal filling radius ratio was determined to be 6/13. Contrary to prior findings, this research highlights the efficacy of partial filling strategies, offering valuable insights for optimizing ice ball performance in thermal energy storage applications. [ABSTRACT FROM AUTHOR]

Free convective heat transfer created from two aligned cylinders immersed inside a vented air duct is experimentally investigated. The experiments include the measurements of cylinders temperature and the air temperature inside the enclosure under steady, turbulent, and incompressible flow properties by using steady‐state heat equations. The studied parameters include Rayleigh number (105≤Ra≤3.4×106 ${10}^{5}\le {Ra}\le {3.4\times 10}^{6}$), opening sizes at lower and upper enclosure surfaces (0.146≤O≤1 $0.146\le O\le 1$), and space size between cylinders (0.35≤S≤0.532 $0.35\le S\le 0.532$) with the constant ratio of enclosure width to cylinder diameter equal to 6. The findings displayed that the average air temperature inside the enclosure for the low values of S and O is low, and it rises as S is raised. The behaviors of Nu differ with changing Ra values. An interaction between hot cylinder and cold cylinder inside the enclosure is observed that depends on O and S values, and hence, they have a large impact on fluid temperature. The data indicated that Nu ${Nu}$ rises with the Ra ${Ra}$ for all S $S$ and O $O$ values. The value of Nu ${Nu}$ for each cylinder depends on the values of S $S$ and O $O$. The maximum Nu ${Nu}$ value has been obtained when O=0.439 $O=0.439$ and S=0.35 $S=0.35$ with maximum enhancement between 30% and 50% depending on Ra values as compared with O=0.146 $O=0.146$ and S=0.523 $S=0.523$, whereas the minimum average Nu ${Nu}$ has been indicated when O=0.146 $O=0.146$ and S=0.35 $S=0.35$. The profiles of Nu ${Nu}$ reveal that O $O$, Ra ${Ra}$, and S $S$ have a considerable influence on heat transfer. [ABSTRACT FROM AUTHOR]

Analysis of various accident scenarios is vital for the safety assessment of nuclear fuel storage facilities. The accidents in the storage vault due to loss of cooling are generally considered highly uncertain since the accident progression is slow (in comparison to reactors) and allows time for remedial activities to the operator. In the present work, numerical simulations of different accident scenarios have been carried out for a short duration to understand the situation better. Thermal aspects of accident conditions such as failure of the suction blower, drying of cooling water at the chiller, and combined effect of both accidents were investigated. The airflow inside the ventilated enclosures due to the failure of the blower and the rise in inlet air temperature is analyzed numerically. The temperature distributions inside the vault and the rise in temperature of the sub-assemblies and magazines have been studied. The key mechanisms of heat transfer, which take part in nuclear fuel storage vault for post-accident conditions, were identified. The study will be helpful to classify various accident conditions based on their thermal implications and the model developed can be used to design passive cooling systems. [ABSTRACT FROM AUTHOR]

This research aims to enhance convective thermal transport in an inverted T-shaped porous enclosure filled with a water-based hybrid nanofluid, incorporating a circular cylinder at different vertical locations (Case C1-no cylinder, Case C1-cylinder at (0.5, 0.25), Case C2-cylinder at (0.5, 0.5), Case C3-cylinder at (0.5, 0.75)). The numerical investigation employs the penalty finite element technique to simulate the Darcy–Brinkmann–Forchheimer-based mathematical model. Moreover, the complete results of streamlines, isotherms, mean Nusselt number (Num), and thermal enhancement percentage ( En % ) are analyzed at the broad range of flow parameters, including Rayleigh number ( Ra = ( 10 3 − 10 6 ) ), Darcy number ( Da = ( 10 − 5 − 10 − 2 ) ), and porosity value ( ϵ = (0.1 − 0.9) ). Initial comparative investigations of different configurations (C0–C3) at selected Ra values reveal that case C1 exhibits significant potential for enhancing convective heat transport phenomena. Consequently, only case C1 physical domain has been explicitly analyzed for convective heat and fluid flow characteristics at the selected range of flow parameters. Further, it is analyzed that the increasing range of Ra, Da, and ϵ enhances the convective heat and fluid flow phenomena. Furthermore, the comparative study of Num and En % for case C1 against the simple case C0 reveals substantial improvements as Ra, Da, and ϵ increase. The En % for Da and Ra reaches up to 97%, while a maximum of 25% improvement is observed with varying values of ϵ. These findings highlight the promising opportunities to optimize convective thermal transport in the investigated system, mainly through adopting case C1. [ABSTRACT FROM AUTHOR]

The MHD finite element analysis naturally convective flow across an exponentially accelerating plate with viscous dissipation is investigated numerically. In this process dimensional partial differential equations are changed to dimensional less form. The Galerkin finite element method is emerged to solve non-dimensional partial differential equations. Obtained results are effectively depicted through the utilization of graphs, allowing for a comprehensive understanding of the impact that different physical parameters on primary velocity, transverse velocity, temperature, and concentration profiles. The study effectively differentiated between the present and prior findings, ultimately demonstrating a strong consensus of excellent agreement between the results. The key findings of this study are: The primary velocity increases on growing the values of Thermal Grashof number, Solutal Grashof number, Eckert number, and Dufour number and decreases on climb up the values of Magnetic parameter, Prandtl number, Schmidt number, and Hall parameter. The secondary velocity increases on raising the values of Thermal Grashof number and Solutal Grashof number and diminishes on enhancing the value of Hall parameter. The temperature increases on increasing the values Eckert number and Dufour number and decreases on improving the value of Prandtl number. The concentration decreases on increasing the value of Schmidt number. [ABSTRACT FROM AUTHOR]

This paper focuses on the emerging branch of the deep learning technique that is employed in the various simple and nonlinear mathematical models of one and two-dimension. This numerical technique takes advantage of the backpropagation algorithm and computational graph of deep learning. A computational ability of a feedforward neural network (FNN) has been further employed, which utilized the randomly or uniformly sampled collocation points over the physical domain and different boundary conditions. Furthermore, a loss function is formulated based on the mathematical model and boundary conditions which is further enforced to minimize the unlabeled sampled points. The minimization process of the loss function is achieved through the various optimizer during the backpropagation algorithm. Eventually, the training process of FNN completes after getting an admissible error for the solution. Multiple examples are tested and cross-validated with the exact solutions for the problem. Furthermore, the DL-based solutions have a good agreement with the solution obtained from finite element approach, indicating that the DL-based numerical techniques can be considered an alternate numerical technique for solving various mathematical models. [ABSTRACT FROM AUTHOR]