Heat Transfer Conditions Research Articles

Investigation of the drafting-kissing-tumbling movement of two particles with conjugate heat transfer

The conjugate heat transfer at the particle-fluid interface and the collision between particles play a crucial role in the sedimentation process of particles. In this work, the recent volumetric lattice Boltzmann method for thermal particulate flows with conjugate heat transfer is adopted to investigate the drafting-kissing-tumbling movement in the sedimentation process of two particles in a closed channel. This volumetric lattice Boltzmann method is based on double distribution functions, with the density distribution function for the velocity field and the internal energy distribution function for the temperature field. It is a single-domain approach, and the nonslip velocity condition within the solid domain can be strictly ensured. The difference in thermophysical properties between the solid and fluid can be correctly handled, and the conjugate heat transfer condition can be automatically achieved without any additional treatments. Based on this particle-resolved simulation, the influences of the solid-to-fluid specific heat ratio, the Grashof number, and the particle’s initial temperature on the drafting-kissing-tumbling movement are discussed in detail. It is found that the fluid cooled by the particle and thus subjected to the downward buoyancy force can promote particle sedimentation. As the specific heat ratio increases, the particle’s temperature rises relatively slowly. In the sedimentation of two cold particles, the drafting and tumbling durations of the drafting-kissing-tumbling movement decrease when the heat capacity ratio increases. In contrast, the kissing duration increases as the heat capacity ratio increases. When the Grashof number increases, the heat transfer between the particle and fluid is enhanced, and the drafting duration significantly decreases while the kissing and tumbling durations remain almost unchanged in the sedimentation of two cold particles. The particle’s initial temperature significantly influences the occurrence moment of the drafting-kissing-tumbling movement. To be specific, the drafting-kissing-tumbling movement occurs at the earliest moment for the sedimentation of two cold particles, followed by the sedimentation of one cold and one hot particle, and the latest for the sedimentation of two hot particles. The promoting effect of the low particle’s initial temperature on the drafting-kissing-tumbling movement mainly takes place in the dragging and kissing stages. The particle’s initial temperature has almost no influence on the tumbling duration.

Numerical Analysis of Magnetohydrodynamic Convection in an Inclined Cavity with Three Fins and a Ternary Composition of Nanoparticles

The natural convection heat transfer of a trihybrid nanofluid comprising Fe2O3, MoS2, and CuO nanoparticles dispersed in water (Fe2O3 + MoS2 + CuO/H2O) has been investigated within a cavity exposed to a uniform magnetic field. Three cold fins were strategically positioned on the top, right, and left walls of the enclosure. The study employs numerical simulations conducted using a custom-developed FORTRAN code. The computational approach integrates the finite volume method and full multigrid acceleration to solve the coupled governing equations for continuity, momentum, energy, and entropy generation, along with the associated boundary conditions. Prior to obtaining the results, a meticulous parameterization process was undertaken to accurately capture the fluid dynamics and thermal behavior characteristic of this geometric configuration. The findings underscored the key parameters’ significant impact on the flow structure and thermal performance. The results revealed that natural convection is more dominant at high Rayleigh and low Hartmann numbers, leading to higher Nusselt numbers and stronger dependence on the tilt angle α. Moreover, the optimal heat transfer conditions were obtained for the following parameters: Ha = 25, α = 45°, ϕ = 6%, and Ra = 106 with a rate of 4.985. This study offers valuable insights into achieving a balance between these competing factors by determining the optimal conditions for maximizing heat transfer while minimizing entropy generation. The findings contribute to enhancing the design of thermal systems that utilize magnetic nanofluids for efficient heat dissipation, making the research particularly relevant to advanced cooling technologies and compact thermal management solutions.

Heat and mass transfer process simulation and structure design of a water-cooled fin solid metal hydride storage system

The heat transfer efficiency of a metal hydride reactor significantly affects its hydrogen absorption and desorption performance. Incorporating additional heat transfer structures can effectively enhance the heat transfer efficiency of hydrogen storage tank. To explore the impact of internal heat transfer structure on the hydrogen absorption capability of the reactor, a novel designed hydrogen storage tank with multi-ring hollow heat transfer fins was proposed. Firstly, a mathematical model is developed to describe the heat and mass transfer process during the hydrogen absorption, and the model is verified by hydrogen absorption experiments. Secondly, the heat transfer structure of multi-ring hollow fin reactor with three-fin structure is determined by comparing the effects of the structure of heat exchanger pipe and the number of heat exchanger fins on the heat transfer efficiency and hydrogen absorption rate of the system. Finally, the effects of flow velocity, temperature of heat transfer fluid and hydrogen absorption pressure on the hydrogen absorption efficiency of the system were compared. The numerical results show that the proposed reactor has shown an improvement in average heat exchange efficiency and average hydrogen absorption rate by 75.49% and 55%, respectively, compared to the initial reactor. The flow velocity and temperature of the heat transfer fluid have an influence on the heat exchange performance of the system, with an impact ranging from 7.69% to 62%, but little effect on the average hydrogen absorption rate of the system, and the hydrogen absorption pressure significantly affects the hydrogen absorption rate. The higher hydrogen absorption pressure can effectively extract the hydrogen absorption rate of the system, but the higher hydrogen absorption pressure imposes greater requirements for the heat transfer conditions of the system.

Particle-resolved simulation of the pyrolysis process of a single plastic particle

Particle-resolved simulations have been performed to study the pyrolysis process of a high-density polyethylene (HDPE) particle in an inert hot nitrogen flow. The simulations resolve the velocity and temperature boundary layers around the particle, as well as the gradients of temperature and concentration within the particle. The objective of this work is to gain an in-depth understanding of the effect of particle morphology-specifically, the particle size and shape-on the interplay between heat transfer and pyrolysis progress, as well as to assess the applicable particle size when using the Lagrangian concept for simulating plastic pyrolysis. In all simulation cases, the pyrolysis reaction is initiated at the external surface of the particle, where the particle is heated the fastest. The reaction front propagates inward toward the core of the particle until it is fully pyrolyzed. For particle diameters larger than 4 mm, distinct temperature gradients within the particle can be detected, leading to a temperature difference of more than 10 K between the core and the external surface of the plastic particle. In this case, the Lagrangian simulations yield a considerably slower conversion compared with the particle-resolved simulations. Moreover, the cylindrical particle in longitudinal flow has been found to be pyrolyzed more slowly compared with the spherical and shell-shaped particles, which is attributed to the enhanced heat transfer conditions for the cylindrical particle. The results reveal the importance of considering particle morphology when modeling plastic pyrolysis. In addition, the Lagrangian approach, which assumes particle homogeneity, is only applicable for particle diameters smaller than 2 mm when modeling plastic pyrolysis.

Corrigendum to “Experimental study on flow boiling and circumferential non-uniform heat transfer characteristics in helically-coiled tube under coupled heat transfer conditions” [Appl. Therm. Eng. 258(Part C) (2025) 124844

Corrigendum to “Experimental study on flow boiling and circumferential non-uniform heat transfer characteristics in helically-coiled tube under coupled heat transfer conditions” [Appl. Therm. Eng. 258(Part C) (2025) 124844

ANALYSIS OF THE EFFECT OF SWIRL FLAME SHAPING ON EMISSIONS FROM THE CO-FIRING OF AMMONIA AND METHANE

This paper presents experimental and numerical insights into the behaviour of lean swirl flames with co-combustion of ammonia and methane. In order to evaluate the accuracy of the emissions modelling for CH4/NH3/air preheated (473K) mixtures with an increasing share of ammonia, experimental investigations were performed, varying the share of ammonia up to 25% in the fuel and the equivalence ratio of air to fuel of 0.71. A burner featuring swirl outflow blades with a 30-degree angle of outflow and a convergent-divergent nozzle was employed in the experimental setup. In order to determine the size of the reaction zone, the concentrations of NO and CO along the probing radius inside the combustion chamber were measured. A complete geometry of the combustion chamber and burner was modelled with RSM and EDC models. The outcomes of the Okafor, Xiao, and San Diego mechanisms were compared to the test data. A further DES simulation was conducted to assess the potential applicability of the models. For the flames tested with 3D RSM, a good agreement was achieved for NO emissions. In the case of a fuel containing between 10% and 25% ammonia, the Okafor mechanism demonstrated the most favourable qualitative and quantitative agreement. The reactor volume, residence time and heat transfer conditions for the CRN reactor network were calculated using numerical CFD methods. A satisfactory correlation was observed between the calculated and experimental NO emissions, with a discrepancy of only 10%. In view of the considerable computational expense associated with the models employed and the high degree of accuracy demonstrated in the emission predictions, the 3D RSM simulation was deemed to be an appropriate means of modelling small-scale applications.

Multiscale concurrent topology optimization of transient thermoelastic structures

Previous multiscale concurrent topology optimization methods for thermoelastic structures were primarily based on static loading and steady-state heat transfer conditions, which do not account for transient effects associated with time-dependent loads. To address this limitation, this paper establishes a novel generic multiscale concurrent topology optimization method that incorporates transient thermoelastic coupling based on transient heat conduction and structural dynamics. In this study, first, a transient multiscale thermoelastic sensitivity equation is innovatively derived through adjoint sensitivity analysis. The effectiveness of this equation is then demonstrated through comparative cases involving transient heat conduction, structural dynamics, and transient thermoelastic (including multimaterial and 3D problems) optimization. Furthermore, the research finds that the topology optimization of transient thermoelastic structures also presents transient effects at microscale. This method demonstrates good versatility and applicability across various optimization cases. The method has great potential in the integrated design of materials and structures involving coupling between time-dependent thermal loads and time-dependent mechanical loads.

Performance analysis of heat pipe micro-reactor with Stirling engine based on full-scope multi-physics coupled simulation

Heat pipe micro-reactors (HPMRs) with Stirling engines for power conversion are emerging as a promising surface power technology. We developed a comprehensive multi-physics solver using the open-source finite-volume code OpenFOAM to perform high-fidelity analysis of HPMR systems’ steady-state and dynamic performance. The solver couples a 3D coarse-mesh multi-group neutron diffusion model with a 3D fine-mesh thermal conduction model using a mapping approach to accurately simulate multi-physics phenomena in the reactor core. Additionally, it integrates a 2D high-temperature heat pipe model as boundary conditions for heat transfer in the core, a 1D Stirling engine model for energy conversion, and a lumped parameter radiator model for heat dissipation. Applied to the HOMER-15 reactor system, the solver aided to identify the optimal working point of the system, achieving 3 kW of electric power with a conversion efficiency of 25.2 % under 20-Hz Stirling engine frequency and 3.34-MPa pressure. The transient full-scope simulation with the solver shows that the load-follow strategy based on gas charging and venting in Stirling engines is capable to accommodate 35 % step increase of external load. When the unexpected reactivity insertion is within 0.1$, the peak temperature in the reactor core is below the allowable limit temperature. Analysis of single failure of Stirling engines indicates that the system safety and reliability can be enhanced by either incorporating an appropriate number of engines or enhancing heat transfer between Stirling engine channels.

Decomposition thermokinetics and heat balance analysis of depressurized methane hydrate deposits under poor heat transfer conditions

Methane hydrate is an important form of natural gas resource found in submarine deposits, with exploitation efficiency mainly determined by in-situ hydrate decomposition. During the depressurization exploitation process of large-scale hydrate deposits, the heat transfer situation of far-wellbore deposits is highly likely to be worse than that of near-wellbore deposits; However, the thermodynamic and kinetic characteristics of hydrate decomposition under poor heat transfer conditions are still unclear, particularly lacking heat balance analysis theory. This study adopted an external temperature control technique in experiments to worsen the heat transfer situation and investigate its effects on the decomposition thermokinetics of depressurized methane hydrate deposits to 2.9 MPa. The stable decomposition rates of methane hydrates under different heat transfer situations were found to be linear with temperature difference, and decomposition stagnation was observed as heat transfer worsened. Based on these results, a novel heat balance model of depressurized deposits with hydrate decomposition was developed, which can accurately predict the dynamic temperature response of hydrate decomposition deposits with a deviation of no >8.9 %. In addition, the low hydrate decomposition rate under a worse heat transfer condition induced synergistic fluctuations in pressure and temperature, which can be improved with progressive warming. This study reveals the thermodynamic and kinetic behaviors of methane hydrate decomposition under poor heat transfer conditions for the first time and can help predict the spot exploitation characteristics of far-wellbore hydrate deposits.

Effect of Thermal Runaway Trigger Methods for Battery Safety Characterization

Lithium-ion batteries are prone to risks with fire hazard due to the possibility of thermal runaway propagation. During battery product development and subsequent safety tests for design validation and safety certification, the thermal runaway onset is triggered by various test methods such as nail penetration, thermal ramp, or external short circuit. This failure initiation method affects the amount of heat contributions and the composition of gas generations. This study1 compares two such trigger methods, by external heating and by using a thermally activated internal short circuit device (ISCD). The effects of the trigger method on total heat generation are experimentally investigated within 18650 cylindrical cells at single cell level as well as at multiple cell configuration level.During thermal abuse conditions, it is known that internal short circuits occur before thermal runaway, but this joule heating does not contribute much to heat generation2. But during internal short circuits initiating at lower temperatures, joule heating plays a major role in thermal runaway process. Previous modeling studies have enhanced our understanding of the role of multiple physical processes during thermal runaway3-4. In this study we use a combination of models and experiments to characterize battery safety in terms of abuse tolerance, severity of thermal runaway and propagation. The severity of failure was observed to be worse for cells with ISC devices at single cell level whereas quite opposite results were observed at multiple cell configuration level. A preliminary numerical analysis was performed to better understand the battery safety performance with respect to thermal runaway trigger methods and heat transfer conditions. Mallarapu, A., Sunderlin, N., Boovaragavan, V., Tamashiro, M., Peabody, C., Pelloux-gervais, T., Li, X., Sizikov, 2024, Effects of Trigger Method on Fire Propagation during the Thermal Runaway Process in Li-ion Batteries, Journal of The Electrochemical Society, 171 040514Ren, D., Feng, X., Liu, L., Hsu, H., Lu, L., Wang, L., He, X., Ouyang, M., 2021, Investigating the relationship between internal short circuit and thermal runaway of lithium-ion batteries under thermal abuse condition, Energy Storage Materials 34, 563–573Feng, X., He, X., Ouyang, M., Wang, L., Lu, L., Ren, D., Santhanagopalan, S., 2018, An electrochemical-thermal coupled overcharge-to-thermal-runaway model for lithium ion battery, Journal of The Electrochemical Society, 165 A3748Coman, P. T., Darcy, E. C., Veje, C. T., White, R. E., 2017. “Modelling Li-Ion cell thermal runaway triggered by an internal short circuit device using an efficiency factor and arrhenius formulations.” Journal of The Electrochemical Society, 164 A587

Energy consumption analysis of building air-conditioning systems using centrifugal compressor with gas bearing under annual operating conditions

The water chiller using centrifugal compressor with gas bearing is an important development direction for building energy saving, but the additional refrigerant cycle for bearing and motor colling leads to more complex performance especially under the various operating condition. Based on the heating and cooling loads of a building in Nanjing and the local climate conditions, this paper innovatively establishes an air conditioning system model using centrifugal compressor with gas bearings (CCGB), and analyzes the performance of air-cooling and water-cooling methods. Considering the heating and cooling loads, the annual energy consumption of two systems was compared consider the climate condition. The results show that the COP of water-cooling system is larger than that of air-cooling system due to the better heat transfer condition. The larger power consumption of compressor for air-cooling system leads to the larger motor cooling load. The cooling methods have obvious influence on the vapor-injected mass flow rate, but have small impact on the mass flow rate of motor cooling and bearing gas supply. The energy efficiency of air-cooling and water-cooling system in summer are 3.77 and 5.12 respectively, and the total energy consumption in the whole year are 32.4 tons and 33.5 tons of standard coal.

Heat Transfer Efficiency While Cooling with a Water Spray, Air-Assisted Water Spray and Water Jet Under Boiling and Single-Phase Forced Convection Conditions

The main purpose of this paper was to determine and compare the boundary conditions of heat transfer on the cooled surface of a cylindrical sensor made of Inconel 600 alloy while cooling with a water jet, water spray and air-assisted water spray under high-temperature conditions. The inverse method for the heat conduction equation was used to determine the boundary conditions. Experimental tests were carried out, including temperature measurements at several points inside the cylinder while cooling with all the tested systems from a temperature of 900 °C for three values of water pressure: 0.05 MPa, 0.1 MPa and 0.2 MPa. Temperature measurements were used as the input data to identify the heat transfer boundary conditions. The temperature field of the axially symmetric sensor was determined using the finite element method. The boundary conditions were determined as average values of the heat transfer coefficient and heat flux and local values of the heat transfer coefficient. A comparison of the amount of thermal energy dissipating from the sensor surface as a result of boiling and a forced single-phase convection is also presented in the paper. The highest uniformity of cooling was obtained during air-assisted water spray-cooling.

Experimental study on flow boiling and circumferential non-uniform heat transfer characteristics in helically-coiled tube under coupled heat transfer conditions

Helically-coiled tube steam generator has been widely used in nuclear reactor, energy power, petrochemical and other systems. In the liquid metal reactor, the liquid metal on the primary side of the helically-coiled tube steam generator exchanges heat with the water on the secondary side. Due to the coupled heat transfer between liquid metal and water, the distribution of the wall temperature or heat transfer coefficient of helically-coiled tube are significant different in the circumferential direction of the tube cross-section. An experimental system of helically-coiled tube steam generator was set up in this paper. The non-uniform heat transfer characteristics of secondary side fluid of helically-coiled tube steam generator were studied under the coupled heat transfer conditions between the heat transfer of primary side and secondary sides fluid. It was found that the wall temperature or heat transfer coefficient in the circumferential direction of tube cross-section were significantly different, the maximum and minimum wall temperature appeared on the inside and bottom of the tube cross-section, respectively, the maximum and minimum heat transfer coefficient appeared on the outside and top of the tube cross-section, respectively. The effect of secondary side refrigerant pressure, secondary side refrigerant supercooling degree, mass flux of secondary side refrigerant, primary side heating water temperature and mass flux of primary side heating water on the maximum wall temperature, minimum wall temperature, maximum heat transfer coefficient, minimum heat transfer coefficient were obtained. Beside, The local and overall non-uniformity of the wall temperature and heat transfer coefficient in the circumferential direction of tube cross-section were obtained and the influence of each parameter on the local and overall non-uniformity were revealed, respectively. Finally, it was concluded that the non-uniformity of heat transfer coefficient in the circumferential direction of tube cross-section under coupled heat transfer conditions was more obvious than that under constant heat flux conditions. And the the overall non-uniformity of heat transfer coefficient (δh) obtained in our experimental were larger than the δh of Chang et al. [33], Zheng et al. [38], Kong et al. [34], Yao et al. [36] and Niu et al. [37] by 130.67%, 48.10%, 289.48%, 151.28% and 271.67%, respectively.

A study of pump-driven heat pipe loop and heat pump loop under the same heat transfer environment based on entransy theory

Both pump-driven heat pipe loops and heat pump loops can operate in heat transfer environments where the temperature of the heat source is higher than that of the heat sink. To investigate the fundamental utilization of input work during heat transfer processes in two distinct loops, this study employed the theory of entransy to conduct an in-depth analysis of the heat transfer processes in pump-driven heat pipe loops and heat pump loops. The research initially explored these loops’ limiting conditions for cyclic heat transfer. Subsequently, the concept of antransy was introduced to elucidate the substantial role of input work in the heat transfer processes. By the antransy, this paper further analyzed the practical utilization degree of input work, providing theoretical insights for optimizing heat transfer systems. The results indicate that the form of loops and the heat transfer conditions influence the magnitude of input work. Precisely, the input work in the loops compensates for the entransy loss that occurs when the working fluid exchanges heat with the environment. More input work does not necessarily translate into more substantial heat transfer. Furthermore, the utilization degree of input work in different loops depends on factors such as the heat transfer environment, the amount of heat transferred, and the heat capacity of the working fluid. The concept of antransy effectively assesses the efficient utilization of input work in these loops. By analyzing the antransy generated in the system, we can better understand how efficiently the input work is utilized in the heat transfer process. The research findings have enriched the field of entransy theory, providing new insights and perspectives into this area of study. Moreover, the results can promote and offer fresh ideas for optimizing cyclic heat transfer systems.

Effect of Source-Sink Misalignment and Sink Cavity Aspect Ratio on the Thermal Performance of Gallium Heat Sinks

Herein, we numerically investigated methods to improve heat dissipation from the base of a phase-change material (PCM) heat sink exposed to high heat flux (15 W/cm2). The sink cavity exhibited a rectangular cross-section with two opposite vertical walls of high thermal conductivity. These walls serve as heat-dissipating fins. We used gallium, a metallic PCM with high thermal conductivity and a low melting point to improve heat dissipation by leveraging buoyancy-driven circulations within the molten gallium. We adopted a method to position the sink base on top of the heat source surface in such a way to augment temperature gradients within the liquid to induce imbalances in gallium density and consequent internal circulations. In this technique, one vertical wall is subjected to forced-convective heat exchange with the surroundings, while the other remains adiabatic. Subsequently, for the case which showed optimum performance, we relaxed the adiabatic thermal boundary condition applied at one of the vertical walls and replaced it with convective heat transfer condition, and assessed the sink performance based on that. Further, we analyzed the impact of various aspect ratios of the sink cavity on the induced internal circulations and base cooling. Sink cavities with aspect ratios of 1.33, 0.96, and 0.64 corresponding to sink heights of 20, 17, and 14 mm, respectively, were examined under a consistent heat flux applied across a 15-mm base length. We also investigated the precise positioning of the sink base relative to the heat source surface and explored its influence on temperature gradients and gallium density imbalances crucial for induced internal circulations. Results indicate that a sink cavity aspect ratio of 0.96 yields the optimal heat dissipation from the base. Further, aligning the left bottom edge of the sink base with the left edge of the heat source surface maximizes heat dissipation to the ambient surroundings, thereby prolonging latent-heat dumping into the sink before the gallium completely melts. Any misalignment between the sink base and the surface of the heat source may have a profound impact on the temporal evolution of induced internal circulations within the molten gallium, essentially affecting heat dissipation from the sink base.

Thermodynamic Langevin equations.

The physical significance of the stochastic processes associated to the generalized Gibbs ensembles is scrutinized here with special attention to the thermodynamic fluctuations of small systems. Differently from the so-called stochastic thermodynamics, which starts from stochastic versions of the first and second law of thermodynamics and associates thermodynamic quantities to microscopic variables, here we consider stochastic variability directly in the macroscopic variables. By recognizing the potential structure of the Gibbs ensembles, when expressed as a function of the potential entropy generation, we obtain exact nonlinear thermodynamic Langevin equations(TLEs) for macroscopic variables, with drift expressed in terms of entropic forces. The analysis of the canonical ensemble for an ideal monoatomic gas and the related TLEs show that introducing currents leads to nonequilibrium heat transfer conditions with interesting bounds on entropy production but with no obvious thermodynamic limit. For a colloidal particle under constant force, the TLEs for macroscopic variables are different from those for the microscopic position, typically used in stochastic thermodynamics; while TLEs are consistent with the fundamental equationobtained from the Hamiltonian, stochastic thermodynamics requires isothermal conditions and entropy proportional to position.

INVESTIGATION OF FLOW AND HEAT TRANSFER PERFORMANCE OF GYROID STRUCTURE AS POROUS MEDIA

There are active and passive methods used to improve heat transfer. One of the passive methods is utilising porous media with high heat transfer surface area. Porous media are divided into two groups: regular and irregular structures. One of the regular structures is triply periodic minimal surfaces (TPMS), which have been studied quite frequently recently. In this study, heat transfer and flow analysis of a Gyroid geometry, one of the most used TPMS in the literature, is investigated numerically considering the conjugate heat transfer conditions. A single porosity is considered (ε = 0.6), and aluminium, ceramic and PLA are selected for the heat exchanger material to examine the temperature change in the heat exchanger. To understand the different flow characteristics, Reynolds numbers (Reh) are assumed to be 19.12, 95.61 and 172.09. The fluid inlet temperature is assumed to be constant at 298.15 K, and the initial temperature of the heat exchanger is assumed to be constant at 278.15 K to be consistent with the regenerative heat recovery temperature difference in ventilation standards. Nu numbers under different operating conditions are compared, and it is the ceramic material with low thermal diffusivity is at the highest level despite its low thermal conductivity. At the highest Re number, it provided approximately 6% better heat transfer than the aluminium heat exchanger.

Advanced numerical simulation of hybrid nanofluid radiative flow with Cattaneo-Christov heat flux model over a rotating disk: Innovative iterative techniques

This paper investigates the effect of nonlinear thermal radiation on SWCNT-TiO2 and MWCNT-CoFe2O4 nanoparticles suspended in a water-based hybrid nanofluid, flowing past rotating disks. The study employs the Cattaneo-Christov heat flux model to capture the influence of non-Fourier heat conduction. The rotational motion of the disks generates the fluid flow, and the governing partial differential equations are transformed into dimensionless forms using similarity variables. These equations are then solved using a New Iterative Technique (NIT) in Mathematica, which is known for its rapid convergence and accuracy. The analysis focuses on the behavior of various parameters, including velocity components (û, vˆ, ŵ), temperature (Tˆ), and thermal conductivity (kˆ), under different heat transfer conditions. Graphical representations illustrate the effects of these parameters, providing insights into the thermal and fluid dynamic performance of the hybrid nanofluid. The study demonstrates that the NIT is highly effective for solving complex fluid dynamics problems, offering precise and swift solutions. NIM provide an efficient and accurate solution for complex nonlinear problems, overcoming the limitations of traditional methods. This approach enhances computational efficiency and solution accuracy in modeling hybrid nanofluid behavior. This research contributes to the understanding of hybrid nanofluids in engineering applications, particularly in optimizing heat transfer in systems involving rotating machinery.

Numerical Modeling and Experimental Validation of Icing Phenomena on the External Surface of a U-Bend Tube

The regasification of liquefied natural gas (LNG) is a crucial process that involves certain challenges created by the low temperature of LNG and the risk of ice formation on the external surfaces of the tubes of heat exchangers, which can hinder heat transfer and increase flow resistance. This study presents a numerical model for ice formation on the external surface of the U-bend tube of shell-and-tube heat exchangers. The numerical model has been further enhanced by applying a custom user-defined function. The numerical results were validated using experimental data and demonstrated excellent predictive capability, particularly for the surface temperature of the tubes and the thickness of the ice layer. Hence, this model can reliably capture the overall behavior of the ice formation on the external surfaces of the tubes of shell-and-tube heat exchangers. By highlighting the importance of maintaining stable heat transfer conditions to prevent freezing, this study offers valuable insights that can guide the optimization of heat exchanger designs for LNG regasification.

Bioconvective magnetohydrodynamic flow of tangent hyperbolic nanofluid across a stretched surface, with Arrhenius activation and convective heat and slip conditions

The current study investigates mixed convective flow of an unsteady MHD tangent hyperbolic nanofluid due to a stretching surface with motile microorganisms via convective heat transfer and slip conditions. The flow analysis's governing equations were converted into a nondimensional relation by using the proper alteration. The pertinent similarity transformations are utilized in the main equations, and the solutions are obtained using the integrated bvp4c software. A good agreement with previously published data indicates the efficacy of the numerical technique. The following are the main findings: increasing the magnitude of the radiation and mixed convection parameters improves the velocity profile, whereas the Weissenberg number and magnetic field demonstrate the opposite influence; improvements in heat transfer occur due to the thermal radiation parameter, Brownian movement, and thermophoretic effects; activation energy improves concentration profile, whereas Lewis number shows opposite effect; bioconvection Lewis number and Peclet number declines the Motile microorganism density. Additionally, a tabular analysis of the skin friction, motile microorganism density, Nusselt number, and Sherwood number is also provided.