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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]

The prismatic gas-cooled micro reactor core is composed of graphite prismatic blocks with gaps between them. The coolant passes through the gap to form flows that affect the flow and temperature distribution of the core. Conventionally, computational fluid dynamics methods have been used for prismatic gas-cooled reactor core analysis. However, they require considerable computational time and cost. For rapid and accurate calculation, in this study, a flow and heat transfer network analysis method is developed for evaluation of the core flow and temperature distribution. Finally, the calculated results of the flow heat transfer network analysis method are compared with the calculated results of computational fluid dynamics. The results show that the results of the flow heat transfer network analysis method are in good agreement with the results of computational fluid dynamics. [ABSTRACT FROM AUTHOR]

A numerical model based on the enthalpy method for solidification/melting that incorporates liquid-phase convection was established for a shell-and-tube phase-change thermal energy storage device with dispersed heat sources. This model optimized the heat source structure and simulated the phase change process, thermal storage performance, and evolution and effects of convection-induced vortices. To overcome the limitations of melting blind spots in traditional inner-tube heat sources, a dispersed heating approach was introduced to optimize the heat source distribution on the inner and outer tubes without changing the heat exchange area. The optimal heat source model demonstrated superior heat transfer performance, featuring an inner-tube top heat source and three uniformly distributed outer-tube bottom heat sources at a dispersion angle of 60°. It reduced the complete melting time by 70.88% compared to the inner-tube heat source alone and by 51.99% compared to the outer-tube bottom heat source. The dispersed heat sources effectively utilized the natural convection benefits at the upper inner side and enhanced the heat transfer at the lower sections to address the melting blind spots of the central heat source, thereby improving the uniformity of the process. The enhancement in heat transfer within the dispersed heat source model is primarily due to the optimized heat source distribution, which facilitates a more dispersed and uniform vortex evolution during the phase change. This promotes the development of the liquid-solid interface and reduces the mutual interference in convection vortex expansion. Hence, the internal heat transfer rate and thermal storage capacity of the system are improved. [ABSTRACT FROM AUTHOR]

In this work, a numerical study is conducted to analyze the spreading dynamics of an insoluble and non-diffusive surfactant through the Marangoni convection mechanism on the surface of a deep layer of a shear thickening fluid, whose behavior follows the power-law fluid rheological model. The momentum and convective–diffusion equations are non-dimensionalized and solved numerically by an implicit finite-difference scheme. The dynamic of the physical problem depends on dimensionless parameters that control the decay of the temporal variations in the surfactant concentration: the Reynolds number R e , the power index n , and ɛ is the ratio between the wave amplitude and the mean surfactant concentration. The main findings show that opposite to shear-thinning fluids, shear-thickening fluids require less time to reach the uniform condition in the surfactant distribution due to a lower response to the inertia of the fluid; this time is even less than that needed for Newtonian fluids. Besides, both types, pseudoplastic and dilatant fluids, showed a similar response when varying the Reynolds number; as this parameter increases, the temporal decay of the surfactant concentration on the fluid surface increases while the distance over which the fluid motion is diffused towards the bottom of the fluid layer decreases. [ABSTRACT FROM AUTHOR]

This study examines the impact of the transfer of mass and heat characteristics on the magnetohydrodynamic natural convection travel over a slanted surface in an impermeable, electrically conductive fluid. The equations that govern can be transformed into standard differential equations through the use of nondimensional quantities, which can subsequently be solved through the ordinary perturbation method. Equations for temperature, concentration, and velocity were produced by using this method. Furthermore, MATLAB-generated graphics were used to analyse and illustrate the effects of several parameters on acceleration, concentration and temperature, including the Schmidt number, thermal Grashof, singular Grashof number and angle of inclination. [ABSTRACT FROM AUTHOR]

The integration of thermal and electromagnetic interference (EMI) insulation is of great significance for fields such as aerospace that face extreme environments. The challenge lies in ensuring that the protective layer is lightweight while simultaneously possessing the ability to suppress heat conduction, heat convection, thermal radiation, and electromagnetic radiation. To address these challenges, we propose a novel ultralight all‐fiber‐structure composite sponge, yttria‐stabilized zirconia/polyvinyl butyral‐supported silver (YAP) nanofiber sponge, with ultralight mass (∼65 mg/cm3), exceptionally low thermal conductivity (21 mW/m K at 25°C, and 329 mW/m K at 500°C), and remarkable EMI shielding effectiveness (∼62.6 dB). Moreover, benefiting from its all‐fiber‐structure, the YAP nanofiber sponge can endure 100 cycles of compression up to 50% of its original volume while retaining its mechanical properties with minimal degradation. These characteristics render YAP nanofiber sponge an ideal material for integrated thermal and EMI insulation, offering a promising solution to the rigorous demands of extreme environment protection such as space exploration. [ABSTRACT FROM AUTHOR]

In recent times, bioconvection has numerous uses, like, biological and biotechnological problems. The present study describes the magnetic bioconvective Buongiorno's flow model with microorganisms in a stretchable area with convective heat transfer and second‐order velocity slip in a non‐Darcian porous regime. Here, the influence of variable viscosity, viscous dissipation, Joule heating, and heat source/sink are considered in the occurrence of higher‐order chemical reactions. Employing proper similarity transformations leading equations are transformed to dimension‐free form. The transformed equations are solved via MATLAB bvp4c problem solver. This study's main objective is to graphically analyze the effects of different pertinent factors on the density of motile microorganisms, velocity, concentration, temperature, number of motile microorganisms' density, skin friction, mass transport rate, and heat transport rate. The main findings drawn from this study are viscosity (−5≤θr≤−1) $(-5\le {\theta }_{r}\le -1)$ and magnetic parameter (0.5≤M≤3) $(0.5\le M\le 3)$ lowers the fluid velocity. Biot number (0.4≤Bi≤0.6) $(0.4\le {B}_{i}\le 0.6)$ increases fluid temperature, but reduces heat transport rates and skin friction. Schmidt (0.5≤Sc≤1) $(0.5\le Sc\le 1)$ and Eckert numbers (0.1≤Ec≤3) $(0.1\le {E}_{c}\le 3)$ reduce the fluid concentration. A rise of 0.3 in bioconvective Rayleigh number (0.3≤Rab≤0.9) $(0.3\le R{a}_{b}\le 0.9)$ and 0.2 in buoyancy ratio number (0.1≤Nr≤0.5) $(0.1\le {N}_{r}\le 0.5)$ causes a percentage drop in velocities of 8.79% and 3.91% (approximately), respectively, in the neighborhood of the sheet. Furthermore, the increase in Peclet number (0.8≤Pe≤1.5) $(0.8\le {P}_{e}\le 1.5)$ by 0.2 lowers the density number of microorganisms by 28%. Additionally, the profile of motile microorganisms is improved by thermophoresis impact, while it is diminished by chemical reaction. [ABSTRACT FROM AUTHOR]

A numerical investigation of the Nusselt number, heat transfer augmentation efficiency, and friction factor in a laminar flow tube with triangular perforated nail head twisted tape (TPNHTT) is reported using ANSYS 19.2 Fluent. The effects of triangular cut (each side 3 mm) in the middle pitch of the tape along the height, diameter, and top diameter of the nail head (10, 2, and 2.5 mm, respectively) have been explored for (300 ≤ Re ≤ 1800) in a tube of 22 mm diameter. In this paper, implementation has been done with a TPNHTT varying width (14 ≤ b ≤ 20) twist ratio (TR) ranging from (3 ≤ TR ≤ 6), inserts in a tube for laminar flow. Twisted tape (TT) produces a swirl flow associated with fluid resulting in heat transfer enhancement and pressure drop characteristics other than that for the plain tube (PT). The performance of the Nusselt number and friction factor increased up to 123.62% and 495.30%, respectively, on the application of TPNHTT as compared with PT. A maximum thermal performance efficiency of 2.98 has been achieved using the twisted‐tape ratio of the current tube in laminar flow at a Reynolds number of 1700. In addition, correlation equations (11) and (12) have been developed for the friction factor and Nusselt number valid for 300 ≤ Re ≤ 1800, 14 ≤ b ≤ 20, and 3 ≤ TR ≤ 6. The study has proved that applying TT is an upgraded approach for laminar convection heat transfer. This novel work finding will be supportive for researchers to design the latest heat exchangers. [ABSTRACT FROM AUTHOR]

The present study aims to quantify the flow field, flow velocity, and heat transfer features over a horizontal flat plate under the influence of an applied magnetic field, with a particular emphasis on low Prandtl number fluids. Nonlinear partial differential expressions can be incorporated into the ordinary differential framework with the use of appropriate transformations. This research utilizes the variational iteration method (VIM) to approximate solutions for the system of nonlinear differential equations that define the problem. The objective is to demonstrate superior flexibility and broader application of the VIM in addressing heat transfer issues, compared to alternative approaches. The results obtained from the VIM are compared with numerical solutions, revealing a significant level of accuracy in the approximation. The numerical findings strongly suggest that the VIM is effective in providing precise numerical solutions for nonlinear differential equations. The analysis includes an examination of the flow field, velocity, and temperature distribution across various parameters. The study found that improving temperature patterns, velocity distribution, and flow dynamics were all positively impacted by increasing the Prandtl numbers. As a result, this leads to the thickness of the boundary layer to decrease and improves heat transfer at the moving surface. Thus, the convection process becomes more efficient. When the strength of the magnetic field is increased, the velocity of the fluid decreases. This observation aligns with expectations since the magnetic field hampers the natural flow of convection. Notably, the convection process can be precisely controlled by carefully applying magnetic force. [ABSTRACT FROM AUTHOR]

The quest for augmenting dropwise condensation heat transfer performance has been the driving force behind the exploration of innovative techniques and approaches to fulfill the desired objective. Mostly, earlier research on dropwise condensation was devoted to study condensation from horizontal tubes and plates but, rarely, addressed dropwise condensation from vertical tubes. An interesting topic of current research in dropwise condensation is to explore the application of Slippery Liquid Infused Porous Surfaces (SLIPSs) to improve the condensation performance. The aforesaid facts are the motivation behind the topics of interest in the present study. In this study, we explore the applicability of semisolid lubricant‐impregnated porous surfaces in enhancing dropwise condensation performance of a vertical condenser tube. The experiments conducted over a wide range of subcooling (5°C ≤ ΔT ≤ 65°C) in saturated steam environment showed significant improvement in condensation heat transfer coefficient of a vertical condenser tube impregnated with semisolid lubricants when compared to bare vertical condenser tube. The highest enhancement is found to be 280% at a subcooling of 40°C. Furthermore, these surfaces proficiently sustain dropwise condensation over a period of 72 hours without compromising heat transfer performance. The devised fabrication method is simpler, more cost‐effective, and less time‐consuming than earlier techniques used for creating SLIPSs. Additionally, an approach based on numerical optimization by a stochastic global optimization technique, namely, Genetic Algorithm, is proposed to retrieve the coefficients and the exponent in the mathematical expression of overall resistance, that is being used to compute the tube‐side dropwise convection heat transfer coefficient. [ABSTRACT FROM AUTHOR]

This study explores the effectiveness of periodically placed rotating blades in enhancing heat transfer in a channel. The channel consists of a cold top plate moving at a constant speed and a fixed hot plate at the bottom. Thin rotating blades are placed periodically along the channel's centerline, with the spacing between their axes equal to the channel's height. This paper analyzes a transient, two‐dimensional, laminar flow problem using energy, momentum, and continuity equations. To address the challenges posed by moving blades, the Galerkin finite element method is implemented within an arbitrary Lagrangian–Eulerian framework, employing a triangular mesh discretization scheme. This study comprehensively explores thermal and hydrodynamic characteristics, including overall heat transfer, thermal frequency, and power consumption of the rotating blade for heat transfer in mixed convection scenarios with Richardson numbers (Ri) ranging from 0.1 to 10 at varying rotational frequency of the blade. Outcomes demonstrate that the inclusion of a rotating blade increases heat transfer up to 50% at lower Ri, after which the impact of the rotating blade diminishes and heat transfer reduces up to 20% at higher Ri. In addition, heat transfer enhances with increasing blade frequency up to Ri = 6.5, beyond which the effect of the frequency overturns. Examining thermal and hydrodynamic characteristics reveals that the blade achieves optimal performance when operating at f = 1 and Ri = 3. The study's insights into mixed convection heat transfer offer versatile applications, benefiting industries and equipment such as electronic cooling, chemical reactors, food processing, material fabrication, solar collectors, and nuclear reactor systems. Moreover, the findings are instrumental in the thermal ventilation of buildings and the development of micro‐electromechanical systems. [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]

During the Stelmor air‐cooling process, the temperature distribution has a significant impact on the wire loops' final mechanical properties. The temperature distribution during the air‐cooling process is accurately solved by establishing three‐dimensional model and numerical simulations. The heat transfer coefficient at the highly dense region is much smaller than that of wire loops at the low dense region, and changes periodically over time, according to a computational fluid dynamics simulation method. It is also found that the heat transfer coefficient on the cross‐section of the wire loop is very different, with a difference of 70–100 W/m2 K. Finally, the finite difference method is used to calculate the mathematical model of the temperature distribution during the Stelmor air‐cooling process. Comparing the results with the measurement data, the simulation results and measurement data match up well. [ABSTRACT FROM AUTHOR]

The current work is interested on investigating the impacts of thermal radiation, chemical reaction, and absorption radiation of a hydromagnetic convection‐free mass and heat transfer flow in case of an electrically conducting fluid that passes through a vertical plate moving impulsively. The analytical solutions of the governing momentum, energy, and species concentration equations with the initial and boundary conditions are obtained by the Laplace transformation technique. Graphs for fluid characteristics are used to analyze the impact of changing parametric quantities such as M, N, Sc, Kc, Q, Gr, Gm, and t on the temperature, velocity, concentration, and Sherwood number. We derive the engineering curiosity expressions for the Nusselt number and stress, and at the end, we tabulate and discuss the consequences of new parameters. The magnetic field effect and the chemical reaction are seen to diminish the fluid velocity and concentration, respectively, but in contrast, the absorption radiation effect is seen to accelerate both velocity and temperature. It is closely studied that the Nusselt number and skin friction values for hydrogen consistently exceed those for carbon monoxide. [ABSTRACT FROM AUTHOR]

Two new cold plates manufactured via metal 3D printing were experimentally investigated for thermal performance analysis in indirect liquid cooling operations; then they were compared to the traditional cold plates. Experiments were performed with different coolant inlet temperatures (15.7 °C and 24.5 °C) and ambient air velocities (0.5 m/s and 3 m/s) at tropical conditions; hereby, the impact of high dew point temperatures at tropics was also investigated. Body-centered cubic (BCC) and pillar elements were applied in the cooling cavity of the cold plates. The results showed that the target surface temperature in both BCC- and pillar-filled plate designs was maintained below the limits at the lower inlet temperature. However, at the higher inlet temperature, the temperature was only maintained below the limit when the ambient air velocity was 3 m/s. The convective heat transfer coefficient at the inlet temperature of 15.7 °C was found 1.5 and 2.5 times higher than the convective heat transfer coefficient value at the inlet temperature of 24.5 °C for the pillar- and BCC-filled plates, respectively. The performance evaluation criterion values were found in the range of 1.2 − 2.4, which depended on the operating conditions and were already higher than the referenced studies in the literature. [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]

In today's world, research on cooling systems that can effectively reduce the cooling time of heat sinks and enhance heat transfer efficiency in a shorter duration is extremely crucial. This experimental study analyzed the cooling time by simultaneously utilizing two cooling techniques. This involved the passage of ferrofluid (Fe3O4/water) through three channels of a heat sink under the influence of a magnetic field, as well as the application of an air impingement jet on the heat sink's surface. A novel plate-fin heat sink with dimensions of 40 mm (L) × 31.32 mm (W) × 23.5 mm (H) consists of three channels with a diameter of 3 mm for crossing ferrofluid flow and 24 channels on the top of the heat sink for crossing the air was designed and built for the study. The heat sink was exposed to an air impingement jet and an external magnetic field simultaneously. Multiple tests were conducted to determine the convective heat transfer coefficients of the heat sink over time under specific conditions, including a magnetic field of 800 G, a volume fraction of 3%, a Reynolds number of 600 for the ferrofluid, and a mass flow rate of 0.1 kg/s. It was discovered that using the combined method of magnetic field and impingement jet (MF-IJ) compared to cooling by air impingement jet with the simultaneous passage of pure water through the ferrofluid channels (Water-IJ), as well as the ferrofluid flow under a magnetic field without the impingement jet (MF) methods for the designed heat sink, can increase the maximum heat transfer coefficient by 27.4% and 46.4%, respectively. The findings of this study suggest that using the MF-IJ cooling method as a flow control mechanism, along with this innovative geometry, can reduce the cooling time of the heat sinks. [ABSTRACT FROM AUTHOR]

This study has investigated a Darcy‐Forchheimer thin film flow over an extended horizontal surface with thermal radiation and chemical reaction effects. The governing time‐dependent equations have been non‐dimensionalized using similarity transformations and solved numerically using the fourth‐order Runge‐Kutta method and the shooting technique. The influence of magnetohydrodynamics, non‐uniform heat sourcing, viscous heat radiation, and chemical reactions on temperature, velocity, skin friction, Nusselt, and Sherwood numbers has been examined. Results have shown that porous media, magnetic field, and transient effects decrease the velocity profile, while thermal radiation and variable thermal properties enhance temperature distributions. Findings have indicated that the magnetic field and porosity enhance the skin friction coefficient whereas the heat transfer rate increases with Eckert number and Prandtl number. Rising the chemical reaction parameter from 0.2 to 0.5 rises the mass transfer rate by approximately 9.85%. The thermal analysis of MHD Darcy‐Forchheimer thin film flow in a porous system has been crucial for understanding heat transfer and fluid dynamics in complex environments. It helped in optimizing various engineering processes, such as cooling systems, filtration, and energy conversion, by providing insights into temperature distribution, convective heat transfer, and fluid behavior. This analysis has aided in designing efficient and reliable systems with improved performance and reduced energy consumption. [ABSTRACT FROM AUTHOR]

AbstractTo optimize the drying process of bamboo bundles, this study investigates the heat and mass transfer behavior during the drying process by using temperature sensors to measure the temperature field at different positions and track the overall moisture content over time. Additionally, a heat transfer model is used to simulate and predict the drying process. The analysis of the experimental results indicates that the diameter of the bamboo bundles has a greater impact on the drying rate than the drying temperature. At the same temperature, the drying time significantly decreases as the temperature increases. Under drying conditions at 80 °C, the average drying rate constant is 0.072 for bamboo bundles with a diameter of 40 mm, whereas it is only 0.015 for bundles with a diameter of 100 mm. Using Newton’s law of cooling, the convective heat transfer coefficient calculation method was derived. The average convective heat transfer coefficients at 40, 60, and 80 °C were calculated to be 6.16 W/(m2 K), 7.14 W/(m2 K), and 7.22 W/(m2 K), respectively. A mathematical model was established for the temperature at the center of the bamboo bundles, the temperature of the drying medium, the diameter of the bamboo bundles, and the drying time. This model effectively simulates the temperature variation inside the bamboo bundles, and the temperature simulation data fits well with the measured values, with a standard error of less than 2.8 °C and a prediction error of less than 6.1%. This coupled model and method provide a theoretical basis for predicting and controlling the bamboo bundle drying process, reducing energy and time consumption in actual production. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive three-dimensional Computational Fluid Dynamics (CFD) analysis of the pre-cooling process of a Type B LNG tank using various refrigerants, including liquid nitrogen (LN), nitrogen gas (NG), liquefied natural gas (LNG), boil-off gas (BOG), and their combinations. The simulation model accounts for phase change (through the mixture multiphase model), convective heat transfer, and conjugate heat exchange between the fluid and the tank structure. The results indicate that liquid nitrogen is the most efficient refrigerant, achieving the highest cooling rate through both latent and sensible heat. LNG also demonstrated a relatively high cooling rate, 79% of that of liquid nitrogen. Gas-only pre-cooling schemes relying solely on sensible heat exhibited slower cooling rates, with BOG achieved 79.4% of the cooling rate of NG. Mixed refrigerants such as NG + LN and BOG + LNG can achieve comparable, while slightly slower, cooling than the pure liquid refrigerants, outperforming gas-only strategies. A further assessment of the heat transfer coefficient suggests the mixed cooling schemes have almost identical heat transfer coefficient on the inner tank surface to the liquid cooling scheme, over 5% higher than the gas refrigerants. The study also highlighted the uneven temperature distribution within the tank due to the bulkhead's blockage effect, which can induce significant thermal stress and potentially compromise structural integrity. Mixed schemes exhibit thermal gradients higher than those of gas schemes but lower than those of liquid schemes, while achieving cooling speeds comparable to liquid schemes if the inlet velocity of the refrigerants is properly configured. These findings offer valuable insights for developing safer and more efficient pre-cooling procedures for Type B LNG tanks and similar cryogenic storage tanks. [ABSTRACT FROM AUTHOR]

This research work highlights the relationship between heat transport in nanofluids and wall velocity ratios in the context of mixed convection heat transport in porous cavities. The research scrutinizes the inspiration of numerous flow variables such as Richardson number, porosity, Hartmann number, Darcy number, wall velocity ratio, nanomaterials volume fraction and Eckert number on fluid flow and heat transport performance. The governing flow expressions are tackled using the SIMPLE algorithm, and the outcomes are authenticated against prior research. The findings designate that heat transfer rates upsurge with higher values of Richardson number, Darcy number, nanomaterials volume fraction, and absolute value of wall velocity ratio, while decreasing with increasing porosity and Hartmann number. [ABSTRACT FROM AUTHOR]

This study developed a one-step chemical reaction model for hydrogen combustion and investigated the effect of heat loss on premixed hydrogen/air deflagration in closed pipelines using numerical simulations with the CFD code GASFLOW-MPI. The simulation results were compared and verified with experimental data. The numerical simulations accurately predicted the flame front structure, pressure, and flame tip position during the deflagration of premixed hydrogen/air. Furthermore, a comparison of adiabatic simulation and heat transfer simulation results revealed that large-scale vortices within the turbulent flow were closely linked to heat loss during the tulip flame stage. Simultaneously, heat loss reduced pressure and flame tip position by diminishing the flame wrinkling factor caused by thermodiffusive instability. Finally, convective heat transfer identified as the most critical factor contributing to heat loss during the deflagration of premixed hydrogen/air in closed pipelines. Specifically, during the tulip flame stage, heat loss was mainly due to convective heat transfer (73.8%∼76.3%), with radiation playing a minor role (23.7%∼26.2%). Therefore, accurate prediction of characteristic parameters during the deflagration of premixed hydrogen/air requires numerical simulations that account for both convective and radiative heat transfer. • Heat transfer simulation can better predict the evolution of hydrogen deflagration. • Heat loss can cause a reduction in pressure and flame tip position. • Large-scale vortices within the turbulent flow are closely linked to heat loss. • Thermodiffusive instability is closely related to heat loss. • Convection heat transfer plays a crucial role in the heat loss. [ABSTRACT FROM AUTHOR]

Utilizing phase change materials (PCMs) in passive energy-saving wall panels to regulate indoor temperatures during hot seasons can improve people's thermal comfort and reduce the energy consumption of air conditioning systems. This study is based on the hot summer and warm winter climatic characteristics of Hainan. According to local meteorological data and residents' living habits, a suitable phase change temperature of approximately 28 °C was determined. A composite PCM of paraffin and stearic acid n-butyl ester was prepared and tested for thermal performance. Encased in an aluminum box with non-penetrating aluminum rods to enhance heat transfer, the phase change panel was applied to the inner side of exterior walls. Thermal tests demonstrated that increasing the mass ratio of stearic acid n-butyl ester to paraffin lowers the melting point and latent heat. At a 3:7 mass ratio, the melting point of the composite PCM was 28.30 °C, and the latent heat was 128.26 J/g. The 20 mm thick panel maintained a stable phase change process, with unheated surface temperatures between 28 °C and 29 °C for up to 180 min. Compared to panels without aluminum rods, those with rods exhibited a 20% longer phase change time, extended heat transfer paths, and reduced liquid-phase convective heat transfer rates, demonstrating improved PCM utilization. Therefore, the phase change panel with non-penetrating aluminum rods exhibits excellent insulation and temperature control properties. [ABSTRACT FROM AUTHOR]

This paper investigates the stagnation point flow of a second-grade nanomaterial, considering nanofluid effects via thermophoresis and Brownian motion. The study addresses convective heat and mass transfer conditions within the flow induced by a stretching cylinder. The transformed systems are solved using the optimal homotopy solutions (OHAM) method, revealing the impact of various parameters on the quantities of interest. The results indicate that an increase in curvature, viscoelasticity, velocity ratio and injection parameters leads to an enhancement in velocity, while the opposite trend is observed due to suction. The viscoelasticity and curvature parameters also increase skin friction. Additionally, thermophoresis enhances the temperature and concentration fields, while Brownian motion reduces mass diffusion. [ABSTRACT FROM AUTHOR]

This research presents an analytical study of magnetohydrodynamics (MHD)‐free convective heat and mass transfer flow of a nanofluid bounded by a semi‐infinite flat plate. A magnetic field of strength (B0)$( {{B}_0} )$ is applied throughout the fluid region. The plate is moving with a constant velocity (U0)$( {{U}_0} )$, temperature, and the concentration are assumed to be fluctuating with time harmonically from a constant mean at the plate. The frontier equations are assumed to be of an oscillatory nature and cracked analytically using the perturbation technique. The novelty of the present work is to examine the heat and mass transfer MHD flow for Cu‐water and TiO2‐water nanofluids in the presence of thermal radiation. The influence of physical parameters on the flow domain is described in the discussions by graphically and in tabular form. It was found that the fluid temperature and skin friction were reduced with the increased values of the radiation parameters for Cu‐water and TiO2‐water nanofluids. Also, it is noticed that the concentration boundary layer thickness decreases with an increase in chemical reaction parameters. [ABSTRACT FROM AUTHOR]

This article discusses a study on the relationship between flower traits and pollination in the campo rupestre ecosystem in Brazil. The study found that flower longevity is linked to petal mass per area and petal thickness, indicating that longer-lived flowers require more resources. Larger flowers have lower rates of water loss and longer water residence times. The document also provides references to scientific articles on various topics related to flower physiology and plant reproduction, which can be valuable for researchers in this field. [Extracted from the article]

Heat sinks are used as heat exchangers to dissipate heat from electronic equipment due to their high functionality and viability. However, heat dispersion is the main obstacle to improving the heat sinks thermal efficiency. This paper has two main parts. The first part of this study focuses on the thermal design of the heat sink, encompassing several factors such as heat dissipation devices using natural convection, heat sinks with various geometries, locations of intake and outlet, materials of the core, flat fins (especially FPFHS and PFHS fins), and porosity fins. Heat sinks that are single-layered or multi-layered and heat sinks that use different cooling liquids. The second part examines interior heat transmission by investigating various indoor geometries, including cylindrical, circular, rectangular, and hexagonal shapes, and assessing their effect on the transport of heat. Additionally, interior structures influence various fin arrangements for any type of heat convection, including actual trials conducted on enclosures using diverse fin designs, are considered. The current study aims to collect research literature that studies the heat sink and various enclosures. The research has been divided into groups to simplify the research process for activities that use cavitation-based technology to improve heat transfer for heat sinks, especially heat exchangers used to cool electrical equipment. These advantages can be attributed to their outstanding features, which include ease of production, cost-effectiveness, and effective heat dissipation. [ABSTRACT FROM AUTHOR]

Nanofluids are emerging as a revolutionary replacement for traditional cooling agents. In addition to this, the motile microorganism helps to stabilize the nanofluid. In this direction, the present investigation addressed Casson fluid flow immersed with gyrotactic microorganisms due to an inclined surface. This flow is controlled by incorporating magnetic forces and restricted to passing through porous media. The influence of the chemical activities and heat convection is examined to complete the mathematical description of the flow situation. The total energy involvement is obtained by the addition of resistive heating and viscous dissipation terms in the energy equation. The current flow situation of equations of said physical condition is renovated into the ordinary differential equations (ODEs) with the implementation of proper similarity variables. The numerical solution is developed with the Runge-Kutta scheme. Graphical illustration for respective physical parameters is obtained via MATLAB. The numerical discussion of the present work is validated with previously published literature. The flow motion is controlled by strengthening the magnetic strength. Boost in the Schmidt number and bioconvection Schmidt number reduces the boundary layer thickness. [ABSTRACT FROM AUTHOR]

Microwave ablation has become a viable alternative for cancer treatment for patients who cannot undergo surgery. During this procedure, a single‐slot coaxial antenna is employed to effectively deliver microwave energy to the targeted tissue. The success of the treatment was measured by the amount of ablation zone created during the ablation procedure. The significantly large blood vessel placed near the antenna causes heat dissipation by convection around the blood vessel. The heat sink effect could result in insufficient ablation, raising the risk of local tumor recurrence. In this study, we investigated the heat loss due to large blood vessels and the relationship between blood velocity and temperature distribution. The hepatic artery, with a diameter of 4 mm and a height of 50 mm and two branches, is considered in the computational domain. The temperature profile, localized tissue contraction, and ablation zones were simulated for initial blood velocities 0.05, 0.1, and 0.16 m/s using the 3D Pennes bio‐heat equation, temperature–time dependent model, and cell death model, respectively. Temperature‐dependent blood velocity is modeled using the Navier–Stokes equation, and the fluid–solid interaction boundary is treated as a convective boundary. For discretization, we utilized HcurlΩ elements for the wave propagation model, H1Ω elements for the Pennes bio‐heat model, and H1Ω3×L02Ω elements for the Navier–Stokes equation, where Ω represents the computational domain. The simulated results show that blood vessels and blood velocity have a significant impact on temperature distribution, tissue contraction, and the volume of the ablation zone. [ABSTRACT FROM AUTHOR]

As electronic device performance is enhanced, the amount of heat generation is also increased. Electrohydrodynamic (EHD) technology presents a promising alternative solution to address the cooling demands. The EHD flow is generated by a corona discharge, directly converting the electrical energy into kinetic energy, and offers unique advantages over traditional cooling methods. The use of a magnetic field can improve the efficiency of the EHD flow by enhancing the local energy conversion. Experimental results showed that a magnetic field deflected the local velocity distribution, and improved the ionic wind velocity. At a magnetic flux density of 78.1 mT, the energy conversion efficiency was improved by 66.8 %. The convective heat transfer on the surface of high-power light emitting diode (LED) was analyzed. The heat transfer coefficient also increased under the effect of the electromagnetic field. The potential of alternative cooling systems for electronic devices using EHD technology was confirmed. [ABSTRACT FROM AUTHOR]

Nuclear reactors are very complex units in which many physical processes occur simultaneously. Efficient heat removal from the reactor core is the most important of these processes. Heat is removed from the reactor core via heat conduction, radiation, and convection. Thus, convective heat transfer and its conditions play a crucial role in the operation and safety of nuclear reactors. Convective heat transfer in nuclear reactors is a very complex process, which is dependent on many conditions and is usually described by different correlations which combine together the most important criteria numbers, such as the Nusselt, Reynolds, and Prandtl numbers. The applicability of different correlations is limited by the conditions of heat transfer in nuclear reactors. The selection of the proper correlation is very important from the reactor design accuracy and safety points of view. The objective of this novel review is to conduct a comprehensive analysis of the models and correlations which may be applied for convective heat transfer description and modeling in various types of nuclear reactors. The authors review the most important research papers related to convective heat transfer correlations which were obtained by experimental or numerical research and applied calculations and heat transfer modeling in nuclear reactors. Special focus is placed on pressurized water reactors (PWRs), boiling water reactors (BWRs), CANDU reactors, small modular reactors (SMRs), and molten salt reactors (MSRs). For each type of studied reactor, the correlations are grouped and presented in tables with their application ranges and limitations. The review results give insights into the main research directions related to convective heat transfer in nuclear reactors and set a compendium of the correlations that can be applied by engineers and scientists focused on heat transfer in nuclear reactors. Prospective research directions are also identified and suggested to address the ongoing challenges in the heat transfer modeling of present and next-generation nuclear reactors. [ABSTRACT FROM AUTHOR]

This paper presents exact, analytical, and numerical solutions to the two‐dimensional Casson fluid boundary layer flow over a moving wedge with varying wall temperature. The boundary layer flow of the Casson fluid with varying wall temperature is governed by a system of partial differential equations called Prandtl boundary layer equations modified by Casson fluid. By applying similarity transformations the governing system of partial differential equations is reduced to a system of nonlinear ordinary differential equations called as the Falkner–Skan equation modified by Casson fluid flow with heat transfer (C‐FSEHT). In the beginning, an exact solution of the C‐FSEHT is obtained for the particular values of physical parameters (i.e., β=−1$\beta = -1$, Pr=cc+1$\text{Pr} = \frac{c}{c+1}$, N=0$N = 0$, see nomenclature) in terms of two standard functions, namely error function and exponential function. Thus, obtained exact solution is then modified to obtain the analytical solution of C‐FSEHT for general values of physical parameters, in terms of power series. The analysis of the asymptotic behavior of the problem, when the wedge velocity is very large (λ→∞$\lambda \rightarrow \infty$), is performed using the Dirichlet series. A comparative analysis is performed using the Chebyshev collocation technique (CCT) to validate the obtained results in all the scenarios. The effect of governing parameters, which are the Casson parameter c$c$, Hartree pressure gradient parameter β$\beta$, moving wedge parameter λ$\lambda$, Prandtl number Pr$Pr$, and wedge temperature parameter N$N$ on the skin friction coefficient, temperature coefficient, velocity profiles, and temperature profiles is discussed in detail. Multiple solutions are found analytically for fixed values of governing parameters. The fact that an increase in the value of the Casson parameter (c$c$) reduces the thickness of both velocity and temperature boundary layers, is also validated during the study. [ABSTRACT FROM AUTHOR]

The thermoelastic time-dependent creep progress of a rotating annular plate with nonuniform thickness made of functionally graded piezoelectric material considering convection heat transfer and solar radiation was investigated. The nonlinear differential equation of heat transfer considering conduction, convection, and solar radiation was solved using the differential transformation method. Then, the differential equation of equilibrium for the annular plate containing creep strains was derived. Firstly, the differential equation was solved analytically for the zero time. Then, the stress and strain rates were achieved using Norton's law with Prandtl–Reuss equations. Finally, the time-dependent creep stresses and deformation redistributions were obtained employing an iterative method. [ABSTRACT FROM AUTHOR]

In arteries blood flow is the usual example for a Casson fluid flow among the other vital utilizations of this fluid model. Thus, it would be helpful to study the Brownian motion diffusion and thermophoresis diffusion in Casson fluid for biomedical applications. In this analysis, the electrically conducting Casson nanofluid, with suction and convective boundary condition, has been addressed in a shrinking surface. The mechanism of convective heat transfer has been elaborated with Ohmic heating and viscous dissipation effects. The numerical solutions to the governing equations have been obtained by applying the similarity transformation to the nonlinear partial differential equations. The present model is employed to examine the viscoplastic characteristics in the porous regime. This dimensionless ruling problem, along with physical boundary conditions, is handled numerically by using a Runge–Kutta Fehlberg scheme. The outcomes of the present study show that the rate of heat and mass transfer at the surface of the shrinking sheet enhances with the growth in Casson fluid parameter and magnetic parameter. Furthermore, it is observed that the shear stress at the wall rises with the increment in magnetic parameter. Moreover, unsteadiness parameter is the decreasing function of heat and mass transfer rates. [ABSTRACT FROM AUTHOR]

This article recognizes the time-dependent axisymmetric flow of a non-Newtonian Williamson fluid caused by a radially stretching surface in the presence of nanoparticles in the porous medium. The combined impacts of Joule heating and viscous dissipation on the flow profiles are also discussed. Chemical reaction at the surface is implemented. The convective heat transfer model and Brownian motion are also studied for the electrically conducting nanofluid flow. The Williamson nanofluid flow has been modeled using a set of partial differential equations based on the fundamental conservation laws of mechanics. By using nondimensional quantities, these equations are first transformed into ordinary differential equations. The Galerkin weighted residual method is performed to resolve these equations numerically. Visual displays and detailed descriptions of the impacts of relevant variables on the thermal performance, concentration field, and velocity field are provided. It is noticed that the thermal profile enhances as the values of the Brownian motion parameter and temperature ratio parameter increase while declining when the values of the velocity slip parameter increase. The Biot number, activation energy, and unsteadiness parameters have proportional effects on the concentration profile, but the reaction parameter has inversely proportional effects on the concentration profile. Heat transfer rate increases with increasing the Weissenberg number and velocity slip parameter, drops with increasing the thermophoresis and unsteadiness parameters, and the Arrhenius activation energy. Finally, a comparison of the obtained numerical solution for the porous and nonporous medium are also done graphically and discussed in details. [ABSTRACT FROM AUTHOR]

Based on the differential idea, this article establishes two segmented algorithms which are the linear equations method and iterative method for solving the one-dimensional digital twin of the temperature field and pressure field of plate heat exchanger (PHE). The segmented algorithms are to consider the change of the physical properties of the fluid along the flow direction, which makes the solution of the temperature field and pressure field more accurate than that without segmentation. It can still get other important parameters besides temperature and is easy to converge with a few iterative steps. When the boundary conditions are known, it can accurately solve the heat transfer, wall temperature, convective heat transfer coefficient, temperature field and pressure field of fluid. Under six groups of test conditions, the heat exchange, temperature and pressure calculated by the two algorithms are compared with the commercial software Flownex, when the number of segments is 100, the average maximum error of each segment is not more than −0.39%, −0.97%, and 0.18%, respectively. To balance accuracy and calculation speed, this article also explores the impact of the number of segments on accuracy. It is found that when the number of segments increases to 10, the impact on the calculation accuracy can be ignored. Compared with Flownex, these two algorithms have smaller errors, and the solution speed of solving linear equations method is faster than that of iteration. It provides application value for emerging digital twin technology, data center chilled water system and other projects and industries that need to accurately control the outlet temperature and wall temperature of PHE. [ABSTRACT FROM AUTHOR]

Molten salt is popularly applied in solar thermal power generation as high-temperature heat transfer medium. The thermophysical properties of nitrate molten salt nanofluids can be improved compared with that of pure molten salt. In order to improve the heat transfer performance of molten salt nanofluids, a new heat transfer enhanced tube with converging–diverging bulge is proposed. In this study, the convective heat transfer characteristics of molten salt nanofluids in the enhanced tube with converging–diverging bulge are studied numerically. The effects of the height-width ratio (J) and length–width ratio (K) on heat transfer and flow resistance are investigated. The results show that Nussel number (Nu) increases with the increase of J value, and Nu decreases with the increase of K value. The range of Reynolds number (Re) is 8000–24,000, the range of PEC in enhanced tube is 1.15–1.48. When J = 0.27, K = 2.08, and Re = 8000, the PEC of the enhanced tube is the largest 1.48. The mechanism of heat transfer enhancement is analyzed based on the field synergy principle, and the simulation results are analyzed based on the improved entropy theory. The change trend of heat transfer efficiency and heat transfer entropy production is opposite. With the increase of J, the heat transfer exergy loss number (NHT) decrease, the heat transfer effectiveness (ε), flow resistance entropy number (Np) and pressure drop (Δp) increase. With the increase of K, the heat transfer exergy loss number (NHT) increase, the heat transfer effectiveness (ε), flow resistance entropy number (Np) and pressure drop (Δp) decrease. The new enhanced tube could be used to promote the further development of molten salt heat exchanger. [ABSTRACT FROM AUTHOR]

This study investigates combined heat transfer by convection and radiation of magnetohydrodynamics hybrid nanofluid within an open rectangular enclosure using numerical simulations. The Roseland approximation serves as the basis for incorporating the thermal radiation term into the energy equation. The chosen nanofluid is a hybrid mixture of Al2O3 and MgO nanoparticles suspended in H2O. Thermal behavior within an enclosure is investigated by analyzing temperature distributions and Nusselt number variations on the bottom hot wall under different conditions. The effects of three factors are explored, including values of parameter radiation (Rk), magnetic field strengths, and nanoparticles volume fractions. The key finding is that the highest full heat transfer ratio on the lowest warm fence occurs when there is no magnetic field (Ha = 0), the radiative parameter is the highest (R = 1), and the hybrid nanoparticle concentration is at its highest level (φ = 0.02 Al2O3 + 0.02 MgO). [ABSTRACT FROM AUTHOR]

This research stands out due to its utilization of a Casson ternary hybrid nanofluid (THNF) consisting of SiC, SWCNTs and MWCNTs , and H 2 O as the base fluid. Additionally, the introduction of slip flow, convective heat transfer boundary, and applied magnetic field are the objectives to elucidate the heat transfer behavior on fluid flow and energy profile. The article emphasizes the analysis of heat transfer properties in a 2D flow of magnetohydrodynamic Casson ternary nanofluid past a stretching sheet. The effect of non-uniform heat absorption/generation is considered in the study to better understand the heat transfer phenomena. By operating suitable similarity variables, the governing equations are transmuted into a dimensionless form. The numerical outcomes are obtained through the Runge–Kutta-based shooting scheme. The uniqueness of this paper stems from employing a Casson THNF with partial velocity jump and convective boundary. The highlight of the study is that an increment in the Casson parameter enhances fluid yield stress, reducing momentum and thermal boundary layer thickness. Elevated suction reduces boundary layer thickness, while magnetic fields influence fluid thermal conductivity, leading to higher Nusselt numbers and enhanced convective heat transfer. The findings derived from this study offer valuable insights applicable to a range of engineering and industrial processes. [ABSTRACT FROM AUTHOR]

This computational study looks at the dynamics of free convection in a differentially heated square chamber occupied by ionized propane and saturated permeable partition. The modified Navier–Stokes equations and temperature equations are used to describe fluid and porous domain flow and heat transport phenomena. To solve these equations, the Galerkin finite element technique is used. Parametric adjustments are made for various heat source and sink lengths, Rayleigh number, Hartman number, and Darcy number. The results are quantitatively described in terms of the mean Nusselt number along the heated wall as the Rayleigh number increases (104 ≤ Ra ≤ 106). Streamlines and isotherms are used to visualize qualitative insights on these parametric changes. A comparative study is also performed without the porous media. Conclusive data demonstrate that using a permeable partition over a solid partition improves the mean Nusselt value by 26.28% at Ra = 104 and to a highest value of 56.5% at Ra = 106. Notably, this work presents a sensitivity analysis based on response surface methodology, demonstrating subtle connections between magnetohydrodynamics, Rayleigh number, and porous material effects. These findings provide important perspectives for improving thermal control and energy efficiency in advanced magnetohydrodynamic systems. [ABSTRACT FROM AUTHOR]

The fundamental problem in electronic cooling systems is the implementation of a cavity such that it can be used to provide localized cooling to specific components, such as CPUs or GPUs, enhancing their performance and longevity. It can also be used in microfluidic devices for controlled drug delivery, where precise control of fluid flow is crucial. The present article numerically explores the free convection non-Newtonian Casson hybrid nanofluid phenomena that occur within an H-shaped cavity while heated from the middle. The heating efficiency and heat flow in a cavity are influenced by perpendicular hot walls that connect two vertical closed channels. A numerical solution is obtained by implementing the Galerkin finite element method to solve the partial differential equation. The numerical outcomes are depicted on the contour of streamlines and isotherms for different parameters in the following ranges: 0.1 ≤ η ≤ 0.4, 0.005 ≤ ϕ h p ≤ 0.020 , 0.1 ≤ γ ≤ 2, and 103 ≤ Ra ≤ 106 at fixed Pr = 6.2. In addition, line graphs show rate of heat transfer within the enclosure using the average Nusselt number for these parameters. Increased aspect ratios (η = 0.4) result in a minimal rate of heat transfer enhancement, whereas decreasing η leads to a significantly higher average Nusselt number and maximum heat transfer within the cavity. The convective rate of heat transfer increases with the presence of hybrid nanoparticles inside an H-shaped cavity for all Rayleigh numbers. The rotation of the Casson hybrid nanofluid also rises as the volume ratio of nanoparticles increases. For a fixed aspect ratio (A.R) of 0.1, the heat dissipation is 6.91% at a lower ϕhp value of 0.005 at a fixed Ra value of 105. However, it increases to 7.072% for a higher ϕhp value of 0.02 at Ra = 105. With increasing Ra number, ϕhp, and γ, the number NuAve increases. [ABSTRACT FROM AUTHOR]