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_This research delves into the decomposition kinetics of propylene oxide within a novel reactor design characterized by a corrugated inner wall for enhanced cooling. By applying Computational Fluid Dynamics (CFD), this study aims to optimize the reactor's heat transfer capabilities to achieve precise control over the exothermic decomposition process. This approach addresses a previously unexplored area in CFD application, proposing a model that fine-tunes the decomposition efficiency of propylene oxide by considering the interplay of key parameters such as inlet mixture temperature, activation energy, flow rate, and the resulting thermal profile. The primary goal is to advance the development of more efficient and environmentally friendly chemical processing techniques in the propylene oxide industry. The study highlights the critical relationship between activation energy (74–76 kJ/mol), process temperature (29–37 °C), and cooling efficiency in optimizing the decomposition process. Significant findings indicate that higher inlet temperatures (37 °C) and lower activation energies (74 kJ/mol) lead to superior conversion rates. The study presents a clear correlation between temperature elevation, reduced activation energy, and enhanced conversion rates, demonstrating that optimizing these parameters can lead to significantly improved conversion efficiencies, potentially approaching 100 % under ideal conditions.

The prominent novelty of current review is to exhibit the fluctuating and oscillatory convective heat transfer properties along various geometries with magnetic force, variable density, Prandtl number, buoyancy force and magnetic Prandtl number effects. The significance of present work is to illustrate a comprehensive review on transient convective heat transfer. Transient convective heat transfer plays an essential role in various technological and environmental applications, including climate control, structure safety, engines, thermal control, computer heating and cooling, and energy safety. The literature primarily focuses on steady temperature and velocity domains, with few studies exploring time-varying fluid flow in forced, natural, or mixed convective mechanisms with different methods. In current review, justification of results was performed by using oscillating stokes conditions directly in partial differential models. The similarity variables and stream functions are used in literature but in current review, the primitive variable transformation is used with implicit form of finite difference method and Gaussian elimination technique through FORTRAN and Tecplot-360 programming tools. The governing model is reduced into steady, real and imaginary form to explore steady and oscillating convective heat transmission. Transient flows have gained significance due to their ability to achieve large oscillating convective heat transfer rates. Compared with steady movement, oscillating flows exhibit higher velocity variations along the heated surface. Periodic flow produces an improved transient surface heat transmission rate than steady flow. Predicting and controlling transients in thermal exchangers requires a concept of transient forced convection heat transport. Transient convective thermal transmission solutions are important for ensuring the effectiveness and reliability of electrical components, nuclear and thermal power stations, heat-generating engines, steam turbines, condensation systems, catalytic converters, heat shielding for spacecraft, electrical devices, internal combustion engines, air conditioning and refrigerator components, cooling networks for batteries, generators, and transformers. It is found that the frequency of convective heat transport enhances through periodic and oscillating stokes variables. It was depicted that the higher amplitude in convective heat transfer was displayed for each choice of magnetic force parameter around two angles π/4 and π of circular magnetized surface. It was depicted that the maximum transient convective heat transmission was reported along vertical angle π/2 with buoyancy force, Prandtl and magnetic Prandtl values.

This work investigates the dynamics of the hybrid nanofluidic convective heat transfer in a permeable thermal system under the influence of multifrequency heating and a magnetic field. The geometry comprises a wavy-walled cavity filled with a water-based hybrid nanoliquid (Al2O3–Cu–H2O) in a saturated porous medium. The finite volume approach is applied to scrutinize the hydro-thermal characteristics resulting from bottom heating and side cooling, considering various flow-controlling parameters. The analysis reveals that nonuniform multi-frequency heating can be a highly effective strategy for enhancing heat transfer in complex geometries involving porous systems, nanofluid flow, and magnetic fields. Significant heat transfer improvement is observed at higher frequencies, with an increase of approximately 261.49 % when offset temperatures are introduced. Additionally, an increase in the undulation height of the wavy sidewalls contributes to a partial heat transfer improvement of 13.41 % compared to the case without undulations. The influence of the Darcy number, Hartmann number, porosity index, and nanoparticle concentration on heat transfer performance is also investigated. Higher Darcy and Hartmann numbers result in reduced thermal convection, while increased porosity enhances thermal convection. Elevated nanoparticle concentrations weaken the flow strength due to higher viscosity. System engineers can optimize heat transfer systems in their respective applications by comprehending the interactions between these flow-controlling parameters. This work contributes to a deeper understanding of the hydro-thermal phenomena in a multiphysics problem and provides a foundation for the development of more efficient heat transfer systems.

Hyperthermia is one of the non-invasive therapy of an Abdominal Aortic Aneurysm (AAA), which is achieved by applying a heat source upon the AAA without surgical operation. This research paper considers laminar flow and heat transfer in a heated abdominal aortic aneurysm using an isothermal boundary condition. Heat is added to explicate the thermal treatment of a diseased artery. The blood is assumed as a non-Newtonian fluid based on the shear-thinning Carreau model. Two unequal aneurysms are assumed in the lower wall to simulate bulges or a disordered artery. Flexible wall segments are assumed in the upper wall and opposing to each aneurysm. The transient momentum and energy equations are solved based on the fluid–structure interaction (FSI) using the Arbitrary-Lagrangian–Eulerian (ALE) method. It is found that the shear stress is much higher for a higher index of the power-law fluid governing the blood viscosity and hence, it is strictly recommended to reduce the viscous nature of the blood in diseased vessels. It is found also that the thermal energy can be greatly transported across the blood at a higher Reynolds number, this means that the hyperthermia therapy becomes effective when blood flows violently through the aortic.

A new theoretical tri-hybrid nanofluid model for enhancing the heat transfer is presented in this article. This model explains the method to obtain a better heat conductor than the hybrid nanofluid. The tri-hybrid nanofluid is formed by suspending three types of nanoparticles with different physical and chemical bonds into a base fluid. In this study, the nanoparticles TiO2, Al2O3 and SiO2 are suspended into water thus forming the combination TiO2-SiO2-Al2O3-H2O. This combination helps in decomposing harmful substances, environmental purification and other appliances that requires cooling. The properties of tri-hybrid nanofluid such as Density, Viscosity, Thermal Conductivity, Electrical Conductivity and Specific Heat capacitance are defined mathematically in this article. The system of equations that governs the flow and temperature of the fluid are converted to ordinary differential equations and are solved using RKF-45 method. The results are discussed through graphs and it is observed that the tri-hybrid nanofluid has a better thermal conductivity than the hybrid nanofluid.

This analysis is framed to take care of the high heat transfer demand from various application prospects and in this context nanofluid may be in consideration because nanofluids are well-known liquids with higher heat transfer capabilities. Here, a mixed convection flow of Molybdenum disulfide-water (MoS2-H2O) nanofluid on a moving vertical plate is examined when there are chemical reactions. Nanofluid problem is investigated using Tiwari and Das model, and numerically solved by "bvp4c" method. For the considered effects in the study, overshoots in temperature profile of nanofluid are observed. Momentum and thermal layer thicknesses become thinner with suction and thicker with blowing. Temperature overshoot is higher for blowing cases. Enhanced homogeneous–heterogeneous reactions lead to rise of the concentration boundary layer's thickness. Also, magnitude of surface-drag force decays and cooling rate enhances with MoS2-H2O nanofluid mixed convection. For weaker suction and for blowing, cooling of nanofluid is faster with larger volume fraction of nanoparticles, but contrast results are obtained for greater suction. Importantly, compared to the homogeneous reaction, the heterogeneous reaction exhibits more impactful influences on flow and heat-mass transport characters. [ABSTRACT FROM AUTHOR]

Riga plate is known to create a crossing electric and magnetic field to generate a wall-parallel Lorentz force. The significance of Casson nanofluid flow past a Riga plate is observed in the sphere of engineering, such as polymer extrusion, food manufacturing, plastic films, oil reserves and geothermal manufacturing. Researchers are interested in this model because of its potential use in biological rheological models. As Casson nanofluid flows are of great interest, this study aims to investigate the three-dimensional magnetohydrodynamics (MHD) flow with heat and mass transport of Casson nanofluid over a flat Riga plate. As a novelty, this study also includes the effectiveness of wall velocity slip, activation energy, nonlinear radiation, and temperature and space-dependent heat source/sink. Suitable similarity transformations have been employed to generate the dimensionless ordinary differential equations (ODEs) from the partial differential equations (PDEs) regulating the fluid flow problem. The transformed nonlinear boundary value problem is then solved numerically using the in-built routine "bvp4c" in MATLAB. The visual demonstrations are provided for the effects of various significant physical factors on the flow, heat and mass distributions. On the other hand, wall shear stress and rates of heat and mass transport at the surface are measured and displayed numerically in tabular form. The findings indicate that the fluid velocity in both directions slows as the velocity slip parameter increases. However, the velocity profile is escalated with the boost of modified Hartmann number. An increase in heat source parameters leads to decrease the heat transmission rate at the wall. The higher values of the radiation parameter result in a better wall heat transmission rate. Further, the rate of mass transport drops when the activation energy parameter is hiked. [ABSTRACT FROM AUTHOR]

The present flow problem analyzes the impact of radiative heat and mass transfer with inclined magnetic field on thermal exchange and entropy production of two immiscible nature of electrically conducting couple stress fluid in a static porous saturated conduit. In this model, the lower and upper porous regions of the rectangular channel are occupied by two different types of couple stress fluids. The static horizontal parallel plates of the porous duct are completely isothermal and the flow of immiscible fluid through the porous duct develops because of a constant pressure gradient at the entry zone of the duct. The Brinkman model is utilized in the modeling of fluid flow through porous saturated domain and Rosseland's approximation is utilized to compute the radiative thermal exchange effect on nonmiscible couple stress fluid. In this work, authors have analyzed the effect of various thermo-physical parameters such as the Hartmann number (Ha), permeability parameter (Da), Schmidt number (Sc), Soret number (Sr) and couple stress parameter ( s i , i = 1 , 2) on the entropy generation characteristics, Bejan number distribution, thermal behavior, concentration distribution and flow characteristics of immiscible couple stress fluid which passes through the porous channel. The parameters Ha, Da, s i , Sc, Sr correspond to magnetic field effect, permeability of porous media, couple stress, mass diffusion and thermal diffusion, respectively. The most significant findings of this research work are as follows: • In a porous saturated channel, the immiscible couple stress fluid velocity, entropy production number and thermal profile get enhanced on increasing the couple stress parameter. • On increasing the Hartmann number and decreasing the permeability of porous region, the thermal properties and entropy production number both decrease. • The couple stress fluid's concentration field and Bejan number distribution get decreased on enhancing Soret number Sr and Schmidt number Sc. • The entropy generation near the wall of the channel rapidly increases on increasing the Schmidt number and Soret number. The emerging finding of this research work exhibits excellent agreement with previously published work. This research work can be utilized in food processing, petroleum products and chemical process. [ABSTRACT FROM AUTHOR]

This investigation deals with the flow of Al2O3–water nanofluid in a wavy porous channel embedded in porous rocks. Fluid exchange takes place uniformly between porous rocks and the wavy channel. In this analysis, cylindrical and parallel plate wavy porous channels are considered. Consequences of Brownian motion and thermophoresis on the flow inside a wavy porous channel are elucidated. The modeled equations are made dimensionless by using dimensionless quantities. Impacts of flow parameters on the velocity, temperature, Nusselt number and friction factor are depicted through graphs. The numerical results with respect to parallel plate wavy porous channel are validated by comparing with the published results. The effectiveness of the cylindrical wavy porous channel as a heat transfer enhancement device in comparison to the parallel plate wavy porous channel is confirmed in this study. Designing devices at microlevels and understanding the heat transfer enhancement mechanism in wavy channels using the nanoparticle addition are the major outcomes from the results of this numerical investigation. The heat and mass transfer rate enhancements in the wavy porous channels are due to the higher Brownian motion in the boundary layer region and accelerated thermophoresis through thermal and concentration boundary layer thicknesses. [ABSTRACT FROM AUTHOR]

This study examines how a chemical reaction and a nonuniform heat source effect the flow of an MHD Casson nanofluid over a nonlinear stretching sheet. By incorporating viscous dissipation, the energy equation is strengthened. Brownian diffusion, thermophoresis diffusion effects are taken place. By using the necessary similarity transformations, the governing equations for the current flow are converted into a nonlinear system. The RKF technique yields a numerical solution along with a shooting technique for the condensed system. Thereafter, to better understand the physical interpretation of flow and heat transfer, the flow-controlling parameters are shown graphically and in tabular form in the current work. Based on the present study's numerical results, a fair connection is found between this analysis and previous studies. Some of the observations are velocity profile is decreased for the effects of magnetics and stretching parameter variations and Eckert number plays a great role in the increase of temperature profile. [ABSTRACT FROM AUTHOR]

An analysis into the transient natural convective flow of a nanofluid in a vertical tube is made. The governing equations of momentum, heat transfer and nanoparticle volume fraction are deduced, and the influence of the thermophoresis parameter and Brownian motion is incorporated. By direct integration and variation of the parameter, analytical solutions are obtained for flow formation and heat/mass transfer at steady-state. On the other hand, due to the complexity of same problem at transient state, a numerical solution is used to solve the discretized equations of motion using the implicit finite difference technique. The influence of the thermophoresis parameter and Brownian motion is noted and well discussed. For accuracy check, a numerical comparison is made between the steady state and transient state solution at large time; this comparison gives an excellent agreement. The role of various principal parameters on velocity profile, temperature, concentration of nanoparticles, Sherwood and Nusselt numbers are presented graphically and well discussed. It is noted that the buoyancy ratio decreases the fluid velocity significantly.

In the present paper, recent advances in the application of nanofluids in heat transfer in porous materials are reviewed. Efforts have been made to take a positive step in this field by scrutinizing the top papers published between 2018 and 2020. For that purpose, the various analytical methods used to describe the flow and heat transfer in different types of porous media are first thoroughly reviewed. In addition, the various models used to model nanofluids are described in detail. After reviewing these analysis methods, papers concerned with the natural convection heat transfer of nanofluids in porous media are evaluated first, followed by papers on the subject of forced convection heat transfer. Finally, we discuss articles related to mixed convection. Statistical results from the reviewed research regarding the representation of various parameters, such as the nanofluid type and the flow domain geometry, are analyzed, and directions for future research are finally suggested. The results reveal some precious facts. For instance, a change in the height of the solid and porous medium results in a change in the flow regime within the chamber; as a dimensionless permeability, the effect of Darcy’s number on heat transfer is direct; and the effect of the porosity coefficient has a direct relationship with heat transfer: when the porosity coefficient is increased or decreased, the heat transfer will also increase or decrease. Additionally, a comprehensive review of nanofluid heat transfer in porous media and the relevant statical analysis are presented for the first time. The results show that Al2O3 nanoparticles in a base fluid of water with a proportion of 33.9% have the highest representation in the papers. Regarding the geometries studied, a square geometry accounted for 54% of the studies.

Nanofluids behave like non-Newtonian fluids in many cases and, therefore, studying their symmetrical behavior is of paramount importance in nanofluid heat transfer modeling. This article attempts to provide are flection on symmetry via thorough description of a variety of non-Newtonian models and further provides a comprehensive review of articles on non-Newtonian models that have applied symmetrical flow modeling and nanofluid heat transfer. This study reviews articles from recent years and provides a comprehensive analysis of them. Furthermore, a thorough statistical symmetrical analysis regarding the commonality of nanoparticles, base fluids and numerical solutions to equations is provided. This article also investigates the history of nanofluid use as a non-Newtonian fluid; that is, the base fluid is considered to be non-Newtonian fluid or the base fluid is Newtonian, such as water. However, the nanofluid in question is regarded as non-Newtonian in modeling. Results show that 25% of articles considered nanofluids with Newtonian base fluid as a non-Newtonian model. In this article, the following questions are answered for the first time: Which non-Newtonian model has been used to model nanofluids? What are the most common non-Newtonian base fluids? Which numerical method is most used to solve non-Newtonian equations?

The principal aim of this investigation is to examine the gold and magnesium oxide hybrid nanoparticles in different physical capacities on the water-based hybrid nanofluid and elaborate on an erratic squeezing flow among both infinite plates. Melting effect and thermal radiation depict heat transfer features. Production of the Bejan number and entropy is upward. The explains the governing equations, and the standard transformation is supplied. The numerical solutions are carried out using an efficient finite element method. To analyze difference between heat transfer and its implication in industrial zone, the Nusselt number was arranged in a horizontal pattern. The results showed that a thicker thermal boundary layer increased the Eckert number and the volume fraction of gold nanoparticles. Anyhow, the heat transfer rate by Au–MgO/water was necessarily greater than the Au–water. The obtained results are excellent and vigorously oppose those that are applicable to the literature by the attached position. It was established for hybrid nanofluids to display higher entropy generation rates. The outcomes of this analysis were the consequence of the appraisal of the impact on few required form parameters in heat transfer and consequently on the expansion for industrial use. [ABSTRACT FROM AUTHOR]

This paper was written to demonstrate the value of using nanofluids for cooling high power transformers while also providing current techniques for business and academia. A numerical analysis of the improvement caused by the cooling of a high voltage transformer using nanofluids has been done. A tank with a temperature source inside and a charge of mineral oil-barium titanate nanoparticles is used to study natural-convection. This study investigates the effects of variables on the thermal efficiency of the tank, including the thermal Rayleigh number and volume fraction. The results show that quenching varies with low and high Rayleigh thermal numbers and depends on the volume percentage of used nanoparticles. The effects were illustrated in thermal transfer rate representations as functions of the thermal Rayleigh number (Rat = 103 and 106) and the solid volume particle from the nanoparticles (0% = f < 10%). The findings showed that improving the solid volume particle of the nanoparticles by 10% causes the fluid being utilized to become more effectively conductive, which improves the rate of heat transfer by roughly 10% when compared to the case of the base fluid. [ABSTRACT FROM AUTHOR]

Abstract There is an intense worldwide activity in the development of instrumentation for medical diagnosis and bioscreening based on biological labeling and detection of nanoparticles. Based on this profound observation, Hall and ion slip effects on magnetohydrodynamic (MHD) free convective rotating flow of nanofluids in a porous medium past a moving vertical semi-infinite flat plate are investigated. The equations for governing flow are solved analytically by perturbation approximation. The effects of various parameters on the flow are discussed through graphs and tables. The velocity increases with Hall and ion slip parameters. An increase in the convective parameter led to amplify the thermal boundary layer thickness, but when the heat generation parameter is taken into consideration, an opposite effect occurs. The skin friction coefficient increases with an increase in nanoparticle volume fraction and it reduces with increase in Hall and ion slip parameters. Outcomes disclose that the impact of thermal convection of nanoparticles has increased the temperature distribution, which helps in destroying the cancer cells during the drug delivery process.

The main objective of this work is to investigate viscous dissipation with thermal radiation impact on hybrid nanofluid flow past an exponentially stretching/shrinking surface along with magnetic field, and heat source/sink, slip boundary conditions. Water ( H 2 O ) is taken into account as a host fluid with copper (Cu) and alumina ( Al 2 O 3 ) as nanoparticles to form a hybrid nano liquid (Cu- H 2 O - Al 2 O 3 ). The coupled nonlinear partial differential equations are transmuted into ordinary differential equations using similarity transformations with boundary conditions and these ODEs are simplified using numerical solver, bvp4c in MATLAB. The behavior of momentum profiles, thermal profiles, coefficient of heat transfer ( Nux 1 ) and skin friction ( C f ) are explored using the pertinent parameters such as Eckert Number ( Ec 1 ), Suction Parameter ( S 1 ), Magnetic Parameter ( M 1 ), Radiation Parameter ( Nr 1 ), Stretching/Shrinking Parameter (λ ), Velocity and thermal slip Parameters ( A 1 and B 1 ), Heat source/sink Parameter ( β 1 ), variable thermal Parameter (ϵ ), thermal conductivity (K) are depicted through tables and graphs. The present simulation is more stable and convergence when compared with the existing literature, which is portrayed in the tables. The presence of dual solution is noticed for Ec 1 = 0.1, 0.11,0.12 when the critical value of λ (= λ c ) are λ c 1 = - 1.60355799, λ c 2 = - 1.60322884 and λ c 3 = - 1.6031348, respectively. The existence of the dual solution is reported due to the presence of shrinking surface and suction, further, the first solution is found to be more stable. The novelty of the current simulation includes MHD hybrid nano liquid flow stability with the impact of viscous dissipation and thermal radiation past stretching/shrinking permeable plane to fill the research gap in the existing literature. The applications of transmission of heat by stretching/shrinking surface in boundary layers is used in various fields such as polymer and material processing, biomedical engineering, heat exchangers, etc. [ABSTRACT FROM AUTHOR]

In the current research, a thorough examination unfolds concerning the attributes of magnetohydrodynamic (MHD) boundary layer flow and heat transfer inherent to nanoliquids derived from Sisko Al2O3-Eg and TiO2- Eg compositions. Such nanoliquids are subjected to an extending surface. Consideration is duly given to slip boundary conditions, as well as the effects stemming from variable viscosity and variable thermal conductivity. The analytical approach applied involves the application of suitable similarity transformations. These conversions serve to transform the initial set of complex nonlinear partial differential equations into a more manageable assembly of ordinary differential equations. Through the utilization of the FEM, these reformulated equations are solved, considering the specified boundary conditions. The outcomes attained are graphically depicted by means of plots and tables. These visual aids facilitate a comprehensive exploration of how diverse parameters exert influence over the distributions of velocity, temperature, and concentration. Furthermore, detailed scrutiny is directed towards the fluctuations characterizing pivotal parameters, viz., Nusselt number, skin-friction coefficient, and Sherwood number. It is identified that the Nusselt number showcases a diminishing trend coinciding with increasing values of the volume fraction parameter (φ). This trend remains consistent regardless of whether the nanoliquid under consideration is Al2O3-Eg or TiO2-Eg based. In contrast, both the skin-friction coefficient and Sherwood number assume lower values as the volume fraction parameter (φ) escalates. This pattern remains congruent across both classifications of nanoliquids. The findings of the study impart valuable insights into the complex interplay governing the characteristics of HMT pertaining to Sisko Al2O3-Eg and TiO2-Eg nanoliquids along an extending surface. [ABSTRACT FROM AUTHOR]

This computational fluid dynamic analysis attempts to simulate the incompressible steady fluid flow and heat transfer in a solar air channel with wall-mounted baffles. Two ꞌSꞌ-shaped baffles, having different orientations, i.e., ꞌSꞌ-upstream and ꞌSꞌ-downstream, were inserted into the channel and fixed to the top and bottom walls of the channel in a periodically staggered manner to develop vortices to improve the mixing and consequently the heat transfer. The analyses are conducted with the Commercial CFD software FLUENT using the finite volume method for Reynolds number varying from 12,000 to 32,000. The numerical results are presented in terms of streamlines, velocity-magnitude, x-velocity, y-velocity, dynamic pressure coefficient, turbulent kinetic energy, turbulent viscosity, turbulent intensity, temperature field, coefficient and factor of normalized skin friction, local and average numbers of normalized Nusselt, and thermal performance factor. The insertion of the S-shaped baffles in the channel not only causes a much high friction loss, f/f0 = 3.319 - 32.336, but also provides a considerable augmentation in the thermal transfer rate in the channel, Nu/Nu0 = 1.939 - 4.582, depending on the S-baffle orientations and the Reynolds number. The S-upstream baffle provides higher friction loss and heat transfer rate than the S-Downstream around 56.443 %, 55.700 %, 54.972 %, 54.289 % and 53.660 %; and 25.011 %, 23.455 %, 21.977 %, 20.626 %, and 19.414 % for Re = 12,000, 17,000, 22,000, 27,000, and 32,000, respectively. In addition, the result analysis shows that the optimum thermal performance factor is around 1.513 at the highest Reynolds number and S-downstream.

The aim of this work is to examine numerically the effect of using a rotating cylinder and porous layers on the forced convection in a bifurcating grooved channel (BGC) filled with two types of nanofluids (MgO-water, SiO2-water). The semi-implicit finite volumes method was used to solve the governing equations. The effects of Reynolds number, nanoparticles volume fraction, and cylinder rotation speed on hydro-thermal performances have been investigated. According to the obtained results, the rotation direction plays a significant role in the formation of vortices at the branching channel, such that when the cylinder rotates clockwise, the vortex occurs in the vertical channel, and it decreases with increasing Reynolds number. Besides, using BGC with a porous medium enhances the heat transfer rate by 52% and 49% at the vertical and horizontal walls of the porous layer, respectively. On the other hand, the heat transfer rate is improved by 2.6% when using MgO nanoparticles compared to SiO2. Therefore, the use of bifurcating grooved channels can improve the thermal performance of various applications in thermal engineering, from fuel cells to electronic cooling. [ABSTRACT FROM AUTHOR]

Separation control and formation of boundary layer Newtonian flow in a diverging permeable channel in Darcy-Forchheimer porous material having suction/injection are discussed. Self-similar equations from governing equations are acquired and existence conditions for boundary layer structure are derived using nature of velocity gradient inside boundary layer. It reveals that if sum of Darcy permeability parameter and twice of Forchheimer parameter exceeds 2, then the boundary layer flow always exists with all type of mass suction/injection and even without suction/injection. Also, if mass suction parameter goes beyond 2/2, then there is no matter what are the values of Darcy permeability parameter and Forchheimer parameter, a boundary layer exists inside the divergent channel. In addition, obtained numerical solutions are exhibited graphically. It reveals that thicknesses of velocity and thermal boundary layers reduce with Darcy and non-Darcy resistances of porous medium and fluid temperature also diminishes. The velocity and temperature reduce with increment of mass suction and contrary results are found for mass injection. [ABSTRACT FROM AUTHOR]

The numerical simulation of a shell-and-tube heat exchanger (STHE) depends on a large number of computational cells. The number of computational cells increases dramatically with increasing heat transfer surfaces in heat exchangers, such as increasing the number of tubes or using dimples as modified surfaces. Computational cost is one of the critical parameters in many industrial applications for heat exchanger analysis. The present study uses the P-NTU thermal analysis method, proposes correlations to predict heat transfer inside and outside the tubes, and then analyzes the STHE with elliptical dimples. The analytical approach shows 0.8% and 9% errors for two STHEs with specified heat performance, which is entirely acceptable. Also, for the STHE with elliptical dimples, the results indicate a 40.6% increase in the heat capacity of STHE. Increasing the heat capacity of STHE by using modified surfaces such as dimples significantly reduces the dimensions and weight of STHE in industrial applications. Furthermore, the analytical method can be used for different types of dimples with different geometries and arrangements. [ABSTRACT FROM AUTHOR]

The heat transfer between ambient medium and moving material can be examined by the fluid flow past an impulsively started vertical plate (ISVP). In manufacturing processes such as wire/fiber drawing, hot rolling, continuous casting, and hot extrusion can be related to the hot moving material and heat transfer to the ambient medium. Also, a similar type of study addresses the understanding of aerospace engineering applications. This present study considers a mathematical model which describes the hybrid nanofluid past the ISVP by considering the transient term as a fractional derivative. The fractional order of flow governing equations is derived to enhance the heat transfer predictions with real-world problems by considering viscous dissipation, applied magnetic field, and radiation effects. Such a mathematical model is discretized by a finite difference technique and solved by a computational algorithm using FORTRAN. The findings of the study are illustrated using the velocity and temperature profiles. Also, the heat transfer and fluid friction against the boundary are interpreted using the Nusselt number and skin-friction coefficient, respectively. The results are examined under the variation of dimensionless parameters such as Eckert number, time-fractional order, Grashof number, the fraction of nanoparticles, suction, magnetic, and radiation parameters. It is observed that the heat transfer and fluid flows are affected by changing the time-fractional order. Also, a transition in the distribution of velocity and temperature is detected with varying time-fractional order. [ABSTRACT FROM AUTHOR]

The current study investigates the 2D entropy production and the mixed convection inside a wavy-walled chamber containing a rotating cylinder and a heat source. The heat source of finite-length h is placed in the middle of the left vertical surface in which its temperature is fixed at T h . The temperature of the right vertical surface, however, is maintained at lower temperature T c . The remaining parts of the left surface and the wavy horizontal surfaces are perfectly insulated. The governing equations and the complex boundary conditions are non-dimensionalized and solved using the weighted residual finite element method, in particular, the Galerkin method. Various active parameters are considered, i.e., Rayleigh number R a = 10 3 and 10 5 , number of oscillations: 1 ≤ N ≤ 4 , angular rotational velocity: − 1000 ≤ Ω ≤ 1000 , and heat source length: 0 . 2 ≤ H ≤ 0 . 8 . A mesh independence test is carried out and the result is validated against the benchmark solution. Results such as stream function, isotherms and entropy lines are plotted and we found that fluid flow can be controlled by manipulating the rotating velocity of the circular cylinder. For all the considered oscillation numbers, the Bejan number is the highest for the case involving a nearly stationary inner cylinder.

The current study focuses on the effect of obstacles and their positioning within the square cavity (L = H) on heat exchange. This work considers heating the cavity's bottom wall to a steady, high temperature. The top wall of the cavity is adiabatic, while the two vertical side walls are cooled. Four cases are explored under these conditions: the first case is a square‐shaped cavity holding a square‐shaped obstacle h = l = 0,15 L, while the other three cases, respectively, each include two, three, and four square obstacles. The cavity was filled with Cu–Al2O3/H2O hybrid nanofluid with a volume fraction φ = 0.03. Numerical results for laminar and stationary flow regimes with Rayleigh numbers 104 ≤ Ra ≤ 106. The finite volume approach solves the governing equations numerically. The findings show that the number of square obstacles within the square‐shaped cavity significantly impacts heat exchange and hybrid nanofluid flow. The second example, with two square obstacles, improves heat exchange more than other cases with one to four barriers. In the second example, the obstacle location at the plane Y = 0.25H is suitable and helps boost heat transmission of the hybrid nanofluid. The ideal obstacle position in the fourth scenario, which has four square barriers, is at the plane Y = 0.75H. [ABSTRACT FROM AUTHOR]

Modern thermal energy storage (TES) systems rely laboriously on finding a low-cost method to improve heat transfer. In the present analysis, adding CuO nanoparticles and tilting the enclosure simultaneously is compared with a novel approach that employed water as a supplemental fluid to improve the melting process using the density difference between PCM and supplemental fluid. Oleic acid is selected as an immiscible PCM in water, which causes PCM and auxiliary fluid utterly separate at the end of the melting process to be usable in more additional TES cycles. By placing water as a heavier material directly on top of oleic acid, the melted oleic acid is replaced by water at the bottom of the enclosure when it melts because water has a heavier density than oleic acid. At first, adding 1% and 2% of CuO nanoparticles in an enclosure with different inclinations of 0°, 45°, and 90° is studied to identify the energy storage rate. Continuity, momentum, and energy equations are used to formulate a mathematical model of the TES system. In the next step, the melting process of the combined system is analyzed to determine the energy storage rate of the combined system compared to the system, including CuO nanoparticles in the inclined enclosure. Comparing the combined system with the optimal case of nano-PCM in the inclined enclosure, it was found that the energy storage rate in the system using auxiliary fluid is 1.396 times higher. [ABSTRACT FROM AUTHOR]