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The fabrication of most current thermal insulation materials from polymeric foams has created an unfavorable impact on the environment. With the aim of reducing the use of foam plastic, this paper focuses on honeycomb paperboard, an alternative thermal insulation material which is recyclable and cost-effective, and evaluates its heat transfer performance under different conditions. The experimental results show the effective thermal conductivity of honeycomb paperboard increases as the honeycomb height or the side length increases. This paper also establishes a novel theoretical model based on a newly developed convective heat transfer correlation to predict the effective thermal conductivity under different conditions. The model's results conform well to the experimental results, and the effect of convective heat transfer is investigated quantitatively using this model. As the vertical adiabatic boundary surfaces are replaced by honeycomb walls, the convection heat transfer strictly depends on the thermal boundary condition of the honeycomb walls and highly depends on honeycomb height and side length. • The novel theoretical models involving convective heat transfer are established under different conditions. • The different heat transfer paths are quantitatively investigated based on the proposed models. • Under the condition of hot-above and cold-below, convective heat transfer in honeycomb paperboard increases as the honeycomb height increases, but decreases as the side lengths increases. • Under the condition of cold-above and hot-below, convection heat transfer in honeycomb paperboard increases as the honeycomb height or the side length increases. [ABSTRACT FROM AUTHOR]

In the integrated circuit industry, heat is transferred through the contact between wafers and the chemical vapor deposited (CVD) 3C–SiC wafer susceptor. Understanding the out-plane thermal conductivity of CVD 3C–SiC is crucial in this context. The influence of grain size and grain boundary characteristics on out-plane thermal conductivity for <111>-oriented CVD 3C–SiC was discussed in this study. The out-plane thermal conductivity sharply decreases from 146.4 W/m⸱K to 122.3 W/m⸱K when the grain size approaches 11.04 μm. This paper suggests that the significant accumulation of dislocations at high-angle grain boundaries is the primary cause of this phenomenon. The substantial lattice strain impedes phonon transfer between grain boundaries, reducing overall phonon mobility. These findings suggest that manipulating the grain boundary angle is an effective means to fine-tune heat transfer in <111>-oriented CVD 3C–SiC. [ABSTRACT FROM AUTHOR]

In this paper, we propose a second-order adaptive DLN algorithm with different subdomain variable time steps for the 3D closed-loop geothermal system. Theoretically, the stability and convergence of the algorithm in the case of variable time steps are analyzed. In numerical experiments, the DLN algorithm is combined with an adaptive algorithm to verify not only its effectiveness and second-order convergence under any arbitrary sequence of time steps but also to improve computational efficiency. We overcome the difficulty of 3D programming, and verify the applicability and accuracy of the proposed algorithm by simulating the flow characteristics and heat transfer of the closed-loop geothermal system with 3D convection. [ABSTRACT FROM AUTHOR]

The Institute for Microelectronics and Microsystems of the Italian National Research Council (Italy) has designed and fabricated a water-fed MEMS vaporizing liquid microthruster (VLM) in collaboration with the University of Salento (Italy) and KU Leuven (Belgium). Previous studies have demonstrated the device's functioning and highlighted the presence of a strong thermoelectric-hydraulic coupling that severely affects the heating and propulsive efficiencies and reliability of the device. In this regard, the current work provides a preliminary experimental investigation of a pulsed heating system actively controlled by temperature using PI-D logic (proportional and integrative actions applied to the error; derivative action applied to the output). The overall performance assessment focuses on evaluating power consumption during steady-state operation and analyzing the dynamic response of the VLM undergoing such an actively controlled pulsed heating, which has been built using both manual and data-driven offline adaptive tuning of the PID parameters. Concerning the steady-state operation, results highlight a promising enhancement of the heating efficiency to values above 0.9. The dynamic response analysis shows that operating with a single set of fixed PID parameters is not feasible and that the manual tuning is a trial-and-error approach highly dependent on the operator's experience, operating conditions, and reference temperature profile. Furthermore, shorter rise and response times require a higher proportional gain, and the overshoot experienced when crossing the saturation temperature cannot be avoided. In this paper, we show that the response of the data-driven adaptive controller solves these issues, exhibiting a reduced maximum settling time from around 59 s to less than 10 s, while the overshoot is avoided thanks to the temporal adjustment of the PID parameters. • Thermoelectric-hydraulic coupling impacts VLM heating and propulsion efficiency. • PI-D controlled pulsed heating investigated for VLM propulsion. • Steady-state efficiency boosted beyond 0.9. • Adaptive controller reduces settling time. • Data-driven approach minimizes overshoot. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose an efficient numerical scheme to deal with heat transfer problems in pipe flow with a large length/diameter ratio. The generalized finite difference method (GFDM) is combined with a space stepping algorithm (SSA) for the solution. The SSA divides the solution domain into a number of overlapping sections in the length direction of the pipe. Due to the large Peclet number, the heat transport process is dominated by advection, which allows an approximate boundary condition to be applied at the downstream cross section. The problem is then solved section by section. Using the uniform distributed points, the solution matrix for each section does not change, and only the right hand side needs to be refreshed for the changing boundary conditions. This leads to a highly efficient scheme for problems with a large pipe length. To show the accuracy of the numerical scheme, a problem with available analytical solution is studied. Then the method is applied to problems of single pipe with different pipe wall temperature and flow Reynolds number, and concentric annular pipe. Numerical results confirm the stability and efficiency of the GFDM-SSA. The method can be applied to many real world transient heat transfer problems in which the pipe is heated or cooled along its length with arbitrary wall temperature for heat exchange and other purposes. [ABSTRACT FROM AUTHOR]

• A fully coupled three-dimensional THMC model (DEHydrate) is developed for simulating hydrate dissociation. • The numerical results obtained from the proposed model are in good agreement with those from other simulations. • Only a small fraction of gas produced from radial hydrate dissociation is collected from the wellbore. • The model provides an effective tool to predict the mechanical behavior during hydrate dissociation. Due to high energy density and huge reserves, many trial projects worldwide have been conducted to exploit natural gas hydrates (NGH). However, most of them did not meet the commercialization requirements because of submarine hazards, low gas production and sand production. Therefore, it is important to investigate the NGH dissociation process. In this paper, a fully coupled multiphase, strongly nonlinear three-dimensional (3D) thermal–hydro–mechanical–chemical model (DEHydrate) is developed to consider the multiphysics behaviours including solid-liquid-gas multiphase flow, heat transfer, NGH phase transition and solid deformation during hydrate dissociation. The model is solved using a fully implicit finite element method. The gas-liquid flow and heat transfer are simulated by low-order elements while the solid deformation is calculated by high- or low-order elements. The behaviours of the multiphase seepage and geomechanics are fully coupled and the physical properties of the reservoir are updated iteratively based on changes in pressure, temperature and displacement. The DEHydrate simulator provides an effective tool to predict the evolution of reservoir mechanical behavior during hydrate dissociation, including transient pressure, temperature, displacement and stress in the reservoir, as well as multiphase saturation, hydrate dissociation rate/mass and gas production rate/mass. During the NGH dissociation, the initial stage exhibits a rapid dissociation rate of up to 206.23 kg/(d·m) for NGH layer with a length of 600 m and a thickness of 22 m, which subsequently decreases to 11.64 kg/(d·m). Only a small portion of the gas generated during NGH dissociation is collected at the wellbore (approximately 35.6 % after 100 days), while the majority remains trapped in the reservoir. In addition, throughout NGH dissociation, the reservoir matrix continues to move toward the wellbore in the horizontal direction. While in the vertical direction, the reservoir matrix below the wellbore moves upwards, with decreasing displacement due to low-pressure diffusion, while the reservoir matrix above the wellbore moves downwards, with increasing displacement. The largest displacements occur near the wellbore during the early stage of NGH dissociation, while in the late stage, the largest displacements occur above the reservoir. [ABSTRACT FROM AUTHOR]

In our previous work, the coaxial electrostatic spinning method was applied to construct nanofiber/SiBCN ceramic aerogel with an elytra-mimetic structure. The material presented excellent mechanical, insulation, oxidation resistance, and other properties. Based on preliminary experiments and literature reports, the integrated heat transfer behavior of nanofiber/SiBCN composite ceramic aerogels in high-temperature environments was affected by several factors, such as coaxial fiber size properties, fiber particle content, interactions, and spatial distribution. Moreover, the above factors overlapped and interacted with each other, and it was hard to generalize a clear law of action through traditional experiments and characterization. Therefore, the paper constructed a representative volume unit (RVE) model based on the complex spatial distribution characteristics of composite aerogels, using fractal theory, Rosseland equation theory, and multiphase model theory. This paper investigated the fiber and particle content, the size characteristics of the coaxial fibers, and the overall heat transfer process in high-temperature environments using the finite element method. The finite element simulated the effective thermal conductivity of multiphase aerogel composites under multiple parameters, such as fiber occupancy, fiber core-shell diameter ratio, temperature, and heat transfer mode. We obtained the property parameters of the complex composition of the material through fractal theory. The model was combined with finite elements to study the fiber particle content, the size characteristics of coaxial fibers, and the integrated heat transfer process in high-temperature environments. The fibers improved the absorption and reflection of thermal radiation with increasing fiber mass fraction, leading to improved ability of ceramic fiber aerogel to extinguish light. The fibers had a larger area to absorb and reflect thermal radiation. Based on the excellent extinction ability of SiC fibers, the composite ceramic aerogel had improved thermal performance at a specifically fiber-to-shell diameter ratio through a comprehensive multifactor simulation analysis. [ABSTRACT FROM AUTHOR]

The non-Fourier heat transfer model has gained significant attention in practical engineering applications, particularly under extreme conditions. However, solving the three-dimensional non-Fourier hyperbolic heat conduction equation remains a challenge. A method for solving the three-dimensional Maxwell-Cattaneo-Vernotte hyperbolic heat conduction equation on unstructured grids is proposed, where the total diffusion term is divided into normal diffusion term and cross diffusion term, and the temperature gradient is solved by reconstruction gradient. The convergence and accuracy of this method are verified by calculating the heat transfer process of a three-dimensional hollow cylinder, and the numerical solutions are found to be consistent with existing analytical solutions. Furthermore, the effects of relaxation time on the non-Fourier heat transfer process in three-dimensional hollow cylinder and complex ceramic part are discussed. Importantly, the method presented in this paper is not influenced by the coordinate system or the shape of the calculated region, providing a theoretical reference for solving complex three-dimensional non-Fourier heat transfer problems. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a novel collocation method to solve nonlinear transient heat transfer problems in typical intelligent materials. The new method is derived from the weighted residual method in which the weight of Jacobian is proven to be the best choice. In the paper, the physical variables and their fluxes are respectively approximated by two series of Lagrange interpolation polynomials at Chebyshev-Gauss-Lobatto nodes. In the proposed method, the mass matrices of the final linear system of equations are diagonal and the explicit time discretization method can be employed. Using the proposed method, we solved the heat transfer in intelligent materials and it is proven to be quite efficient and accurate, which benefits from that no large sparse matrix is generated and solved. By the proposed method, one can easily solve the problems with complex geometries. [ABSTRACT FROM AUTHOR]

• The nonlinear dynamics and thermal bidirectional coupling model of a rotor-ball bearing system is constructed. • The coupling characteristics of the interaction between vibration response and temperature variation are obtained. • The complicated jump phenomena and motion patterns in vibration response and temperature variation are demonstrated. • The characteristics affected by initial radial clearance, rotor eccentricity and lubricant viscosity are discussed. This paper focuses on the nonlinear dynamics and thermal bidirectional coupling characteristics of a rotor-ball bearing system. The motion equations of the rotor system are formulated by the Lagrange method, where the radial clearance of the ball bearing affected by thermal characteristics is considered. The heat transfer model of the ball bearing is established by combining the lumped parameter with the full thermal network, in which the frictional heat generation induced by the dynamic load of the ball bearing is considered. The heat transfer model is coupled with the motion equations of the rotor system via the mechanical model of the ball bearing. The dynamics and thermal bidirectional coupling model is solved by the step-by-step iterative solving procedure to detect the interaction between the vibration response of the rotor and the temperature variation of the ball bearing. The results show that the thermal expansion of the ball bearing results in the dynamical variation of the effective radial clearance, which makes a significant influence on nonlinear dynamics and thermal characteristics of the rotor-ball bearing system. On the other hand, the nonlinear dynamic response of the rotor leads to the nonlinear thermal characteristics of the ball bearing through the influence of the dynamic load. It is observed that there are more complicated jump phenomena and motion patterns in the vibration response and temperature variation compared to the case without thermal effects. Moreover, the jump phenomena affected by the initial radial clearance, rotor eccentricity, and lubricant viscosity are analyzed in detail. The results obtained in this paper can provide more insight into the bidirectional coupling mechanism of the nonlinear dynamics and thermal characteristics. [ABSTRACT FROM AUTHOR]

The current technologies to treat hypersaline produced water (PW), such as thermal evaporation, are usually energy-intensive and cost-prohibitive. This study developed a low-cost, robust, solar-driven carbon black and airlaid paper-based evaporator (CAPER) for desalination of PW in the Permian Basin, United States. The study aims to better understand the removal of aromatic organic compounds and heavy metals during solar distillation, water output, and heat transfer. Outdoor experiments using CAPER assisted with polystyrene foam in a single slope, single basin solar still achieved an enhanced average evaporation rate of 2.23 L per m2 per day, 165% higher than that of a conventional solar still. Analysis of heat transfer models demonstrated that CAPER solar evaporation achieved an evaporative heat transfer coefficient of ∼28.9 W m−2·K−1, 27.9% higher than without CAPER. The maximum fractional energy of evaporation and convection heat transfer inside the solar still with and without CAPER was ∼81.4% and ∼78.2%, respectively. For the PW with a total dissolved solids concentration of 134 g L−1, solar distillation removed 99.97% salts and over 98% heavy metals. The high removal efficiency of 99.99% was achieved for Ca, Na, Mg, Mn, Ni, Se, Sr, and V. Organic characterization revealed that solar distillation removed over 83% aromatic compounds. Solar desalination using CAPER provides a low-cost and high-performance process to treat PW with high salinity and complex water chemistry for potential fit-for-purpose beneficial uses. Image 1 • A carbon black and airlaid paper-based solar evaporator (CAPER) was developed. • Outdoor distillation of produced water (PW) achieved evaporation of 2.23 L m−2·d−1. • The evaporation rate of PW with CAPER is 165% higher than without CAPER. • Heat transfer coefficient with CAPER is 27.9% higher than without CAPER. • 99.97% salts, 98% metals, >83% aromatic compounds removed from 134 g L−1 TDS PW. [ABSTRACT FROM AUTHOR]

In this paper, we study the magnetohydrodynamic (MHD) flow and heat transfer of the fractional Jeffrey fluid in a straight channel, of which the cross section is a two-dimensional irregular convex domain. We consider a spatial fractional operator to modify the classical Fourier's law of thermal conduction, and obtain the time-space fractional coupled model. The fractional coupled model is solved numerically by the L 2 − 1 σ method in the temporal direction and the unstructured mesh finite element method in the spatial direction. Besides, we prove the stability and convergence of the numerical scheme. In order to reduce the computational time, a fast method is proposed. Finally, a numerical example is given to verify the theoretical analysis and the efficiency of the fast method. Furthermore, an example is considered to discuss the effects of the fractional parameters on the MHD flow and heat transfer of the fractional Jeffrey fluid. [ABSTRACT FROM AUTHOR]

• Time-varying buckling and post-buckling of tapered columns in fire. • Temperature-dependent material properties. • The convective–radiative condition. • Geometric nonlinearity and yield strength. • Effects of transient localised fire on the tapered column. This paper presents time-varying flexural buckling and post-buckling responses of tapered columns under a transient fire of which the temperature is non-uniform along the length. First, the transient temperature field within the column is determined by solving a dimensionally reduced transient heat transfer problem considering the convection-radiation boundary conditions and temperature-dependent (TD) material properties. Subsequently, the von Kármán geometric nonlinear theory is applied to obtain the nonlinear equilibrium equation. The nonlinear heat transfer and equilibrium equations are solved by the differential quadrature (DQ) method. According to a yield criterion, the ultimate load at which the material failure occurs is predicted. The influences of a transient localised fire on the temperatures, buckling and post-buckling responses of tapered steel tubular columns are discussed. [ABSTRACT FROM AUTHOR]

This comment concerns a rightful doubt involved in the above paper. In the reviewed article, a novel model without empirical constants was proposed to evaluate the effective thermal conductivity of three-phase soils, and such a model was claimed to be workable for soils with porosity ranging from 0.0349 to 0.4764 at all saturation degrees. However, sufficient reasons and pictorial explanations were given in this comment to prove its inapplicability for high degrees of saturation. Besides, the inapplicable range is constantly changing, depending on the porosity, i.e. the larger the porosity, the smaller the inapplicable saturation region. Similar issues were further discussed due to its great influence on the follow-up research in this field, i.e. whether can achieve a full coverage of the applicable saturation range [0,1] for a given porosity. [ABSTRACT FROM AUTHOR]

Abstract The present comment concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

The diffusion characteristics of liquid kerosene in a supersonic combustor equipped with a thin strut under the effect of evaporation and combustion heat-release were discussed in this paper. A series of experiments and numerical simulations were carried out both in cold inflow (T t = 300 K) and high enthalpy inflow (T t = 1680 K). The experimental data of kerosene diffusion and combustion were captured by high-speed camera and schlieren equipment. Based on the Euler-Lagrangian method, the evaporation and diffusion process of liquid kerosene under different inflow and heat-release conditions were studied. Through the analysis of the basic data of the ground test and numerical simulation, the kerosene diffusion and penetration depth were obtained and analyzed. The results showed that the diffusion of kerosene vapor is affected by both the injection momentum and the evaporation momentum. The evaporation of liquid kerosene could effectively improve the penetration depth of kerosene vapor, and the maximum proportion could reach 60%. The combustion heat-release greatly enhanced the diffusion ability of kerosene vapor by increasing evaporation strength of liquid kerosene and pressure in the heat-release zone, and the diffusion and combustion of kerosene were positively coupled with each other. With the investigation in this paper, a mechanism on kerosene diffusion in the supersonic combustor was explained. • Kerosene diffusion characteristics were analyzed with evaporation characteristics. • Evaporation momentum was defined and effect on kerosene diffusion was discussed. • The enhancement of kerosene diffusion with combustion heat-release was discussed. [ABSTRACT FROM AUTHOR]

Abstract The search for lightweight, flexible, thermally stable and thermally conductive materials with good electromagnetic interference (EMI) shielding ability remains the most serious prospect in recent years. Herein, a polyacrylonitrile (PAN) based multi-phase system is fabricated using hollow cenospheres (CS), mesocarbon microbeads (MCMB) and multiwall carbon nanotubes (MWCNTs) with or without iron oxide via homogenization and vacuum assisted filtration technique. Resulting composite paper is stabilized to provide enough strength to the composite paper with thickness 0.18 mm and density 0.31–0.33 g/cm3 which can vary in accordance with cenospheres loading. Composite paper exhibits very high EMI SE value of −75.6 dB on 20 wt% cenospheres loading while a synergistic effect of dual dielectric (CS) and magnetic (iron oxide) materials in the composite paper, results in excellent EMI shielding value of −80.5 dB at a frequency of 10.3 GHz. Furthermore, the composite paper shows good thermal stability and enough thermal conductivity required for proper heat transfer management. Therefore, the development of multi-functional composite paper in one entity may get benefits of excellent EMI performance, good thermal stability and significant heat dissipation capability with the advantage of lightness and flexibility. Graphical abstract Free standing, flexible and light weight hybrid composite paper was developed by simple strategy using cenospheres and iron oxide nanoparticles as filler in a mesocarbon microbeads and multiwall carbon-nanotubes based matrix which exhibits exceptional EMI SE of −80 dB in X-band with efficient heat dissipation ability. Image 1 [ABSTRACT FROM AUTHOR]

• The comment concerns a paper published in Chemical Engineering Science Journal. • The problem is non-similar. However the authors treated the problem as similar. • In non-similar problems one x-dependent parameter is used. The authors used three. [ABSTRACT FROM AUTHOR]

This paper mainly analyzes the heat transfer of Carreau fluid over an infinite rotating disk, and two models with variable thermal conductivity are considered. Firstly, the governing partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs) by similarity transformation. Then, the boundary value problem is solved by improved bvp4c method, which reduced sensitivity to the initial values. For shear-thinning and shear-thickening fluids, the effects of Carreau fluid index n and Prandtl number Pr on velocity and temperature fields are shown and analyzed when 0.5 ≤ n ≤ 1.5 , 1 ≤ P r ≤ 10. Furthermore, the thermal conductivity is computed under two cases. [ABSTRACT FROM AUTHOR]

On-orbit Servicing in the form of space-manufacturing, refuelling, assembly and robotic manipulation are deemed to become a fundamental part of the space market in the short-to-middle term. One of the key aspects to reach extensive use of OOS operations is having a standardized, reliable, and cost-effective interface that embeds as much functionality as possible to simplify operations. In this context, SENER Aeroespacial has developed SIROM (Standard Interface for Robotic Manipulation), which provides mechanical coupling, electric interface, thermal and data transfer in a single compact solution. In this paper, the current design for SIROM is presented, with a focus on the electronics subsystem and the integration of the electromechanical design. A functional breakdown of the electronic boards is presented after a review of the current state of the art. For the validation, a TRL6 Test Campaign that was successfully passed in early 2021, including vibration, temperature, vacuum and life tests. Its results are presented here, along with the details of the functional validation on the context of the EROSS project in May/June 2021. To conclude the paper, on-going projects involving the SIROM interface are reviewed, finishing with future lines of development on the SIROM roadmap. • On Orbit Servicing is becoming a fundamental part of the space market. • SENER designed the SIROM interface for this purpose, developing a fully integrated model in 2021. • SIROM has passed a qualification campaign for Technology Readiness Level 6. • SIROM has been validated in the H2020 project EROSS in an On Orbit Servicing scenario. • SIROM is developing to reach TRL 8 as part of European projects (MIRROR, PERIOD). [ABSTRACT FROM AUTHOR]

Two mistakes exist in [1]. [ABSTRACT FROM AUTHOR]

This paper describes an accurate model of the Electrical Power Subsystem (EPS) of the Thermal Analysis Support and Environment Characterization Laboratory (TASEC-Lab), a university experiment developed for using in high-altitude balloon missions to measure and analyze the convection heat transfer. A Li-ion battery and two high efficient DC–DC converters have been characterized through laboratory tests and fitting to the experimental results. The developed mathematical models described in this paper are used to carry out accurate EPS simulations and are validated by comparison with the experimental data. • Design and modeling of the electrical power subsystem of a stratospheric balloon experiment. • New Li-lion battery discharging model that describes the three main parts: initial decay, linear, and exponential decay. • Formulation of a new DC/DC converter efficiency model. • Simulation and model validation of the electrical power subsystem. [ABSTRACT FROM AUTHOR]

• The present paper explores the fluid dynamics, heat and mass transmission characteristics within hexagonal enclosure with square object. • The phenomenon encompasses the interplay of various physical mechanism, including micro-rotation of fluid particles, Joule heating, thermal radiation, porous materials, and magnetic field. • The governing nonlinear partial differential equations are transformed into non-dimensional form and then investigated numerically using continuous Galerkin finite element method. The pressure component of the momentum equation is removed by employing the Penalty parameter. • The validation of findings is ensured by establishing a consensus with previous studies. Flow, heat and mass distributions are depicted using streamlines, isotherms and isoconcnetrations. • Graphical representation of average Nusslet number and Sherwood number are also provided. It is anticipated to offer novel concept for enhancing the performance of cooling systems and optimizing the energy efficiency in diverse engineering applications. The present paper explores the fluid dynamics, heat and mass transmission characteristics within hexagonal enclosure with square object. The phenomenon encompasses the interplay of various physical mechanism, including micro-rotation of fluid particles, Joule heating, thermal radiation, porous materials, and magnetic field. The governing nonlinear partial differential equations are transformed into non-dimensional form and then investigated numerically using continuous Galerkin finite element method. The pressure component of the momentum equation is removed by employing the Penalty parameter. In order to achieve the consistent solution the value of Penalty parameter is set to 10 7. The analysis includes several physical parameters, such as Buoyancy ratio (−1–1), micropolar parameter (2–6), Joule heating parameter (0–5), Richardson number (0.5–5), thermal radiation parameter (0.1 – 0.5), Lewis number (0.1–5), Darcy number (0.001–0.1) and Hartmann number (0–50). Results reveal notable trends regarding the impact of key parameters on flow behavior and thermal-solutal transfer within cavity. Increasing Darcy numbers intensify fluid motion and subsequently augments thermal and solutal transfer. The flow regime shifts from shear fricition-dominated at low Richardson number to buoyancy-induced at high Richardson numbers. For concentration-dominant counter flow, a uniform distribution pattern emerges, while aiding flow leads to increased fluid velocity, temperature, and concentration. Additionally, the micropolar parameter influences flow velocity, with varying effects on heat and mass transfer rates depending on the Hartmann number. Mass distribution expands with increasing Lewis number, while temperature rises significantly due to variations in radiation and Joule heating parameters. These findings contribute to a deeper understanding of enclosed flow dynamics and have implications for the optimization of diverse engineering systems. [ABSTRACT FROM AUTHOR]

The investigation of jump cooling performance on turbine endwall independently causes its actual cooling effectiveness to deviate from the design values. In this paper, the endwall jump cooling structure with combustor-turbine interface cavity and combustor liners is modeled. Taking the realistic combustor-turbine interface features into account, the effect of jump coolant on turbine endwall film cooling and heat transfer characteristics is numerically studied. Under different endwall misalignment modes, the aerodynamic interaction mechanisms of realistic combustor outflow profile, jump coolant jet and cascade secondary flows at turbine endwall region are revealed. The modification effects of combustor-turbine interface features on jump cooling of the endwall are investigated. The results show that the combustor outflow severely ingests into the combustor-turbine interface cavity after flowing across several steps. Two branches of cavity vortex are subsequently generated in the middle-pitch region of cascade to affect the jump coolant jet. At low coolant blowing ratio, the attachment and separation sides of cavity vortex individually result in high and low cooling regions, while the horseshoe vortex leads to a large wedge-shaped cooling region. At z / C ax < 0, the backward step leads to a higher cooling effectiveness than forward step by 0.2. The jump coolant only leads to phantom cooling effect on downstream part of the vane suction side surface. The net heat flux reduction (NHFR) between two cavity vortexes and at pressure side junction are individually 0< NHFR <0.2 and −0.2< NHFR < −0.1. At high blowing ratio, the jump coolant can cover the pressure side junction with the highest cooling effectiveness of 0.5. The jump coolant can flow across the horseshoe vortex and directly upwash the vane surface. The weak protection regions between two cavity vortexes and near the attachment line of the pressure side horseshoe vortex enlarges. Compared with the forward step, the backward step achieves a lower NHFR by up to 0.1 and a higher Nusselt number. This paper provides an in-depth analysis of the aero-thermal physics of endwall jump cooling concerning realistic combustor-turbine interface conditions. [ABSTRACT FROM AUTHOR]

• A comprehensive review on numerical simulations of boiling heat transfer from atomistic to mesoscopic and macroscopic scales is presented. • Critical issues related to nanoscale bubble nucleation mechanisms, pool boiling, and flow boiling are highlighted. • Potential solutions and future research in the field of boiling heat transfer using the MDS, LB and CFD methods are proposed. Boiling is an efficient heat transfer mode with significant potential for thermal management in high-power electronic equipment. However, a comprehensive understanding of the boiling process, which encompasses bubble nucleation, growth, coalescence, slipping, and detachment across various scales, remains challenging. Molecular dynamics simulation, lattice Boltzmann, and computational fluid dynamics methods are popular and powerful tools for investigating boiling heat transfer phenomena at microscopic, mesoscopic, and macroscopic scales. These methods enable researchers to uncover the underlying boiling mechanisms and propose heat transfer enhancement techniques. Therefore, this paper provides a comprehensive review of boiling heat transfer, spanning from atomistic to mesoscopic and macroscopic scales, utilizing these three numerical methods. It addresses critical issues related to nanoscale bubble nucleation mechanisms, pool boiling, and flow boiling, and proposes potential solutions and future researches, supplementing our previous review [Some advances in numerical simulations of multiscale heat transfer problems and particularly for boiling heat transfer, Annu. Rev. Heat Transf., 6 (2022) 217–269]. Besides, by shedding light on the characteristics of these numerical methods in studying boiling heat transfer, this paper aims to foster their development and advance enhanced heat transfer technologies. [ABSTRACT FROM AUTHOR]

With the highly integrated development of electronic components, higher requirements are put forward for heat transfer components, there is an urgent need for high-performance heat transfer components. Oscillating heat pipe (OHP) is novel types of heat pipe with excellent heat transfer capability. However, the heat transfer limit hinders their operation and application. This paper proposes an OHP under trans-critical conditions with the working fluid of R218 and explores its operating characteristics and heat transfer capability. Visualization experiments and pressure monitoring were conducted to analyze the state changes within the OHP under trans-critical conditions. After evaporation section temperature surpassing the critical temperature of R218, the pressure increases with the temperature, once the pressure reached near the critical pressure, OHP can transcend the limitation of the critical temperature and realize efficient oscillating operation under trans-critical conditions. With stable operation, the working fluid velocity can reach up to 1.49 m/s, and the OHP under trans-critical conditions presented excellent heat transfer performance with the thermal resistance of 0.22 °C/W. This paper proves the feasibility of the OHP under trans-critical conditions and provides a basis for further research. [ABSTRACT FROM AUTHOR]

Surfactant aids boiling enhancement, but the related mechanism is not yet comprehensively understood. For mechanism investigation on surfactant molecule, most of existing studies focused on its hydrophobic part, while research on hydrophilic part is scarce. In this paper, a group of non-ionic Triton surfactants with same functional group but different hydrophilic chain lengths were experimentally tested for pool boiling on flat copper. At critical micelle concentration (CMC), long-chain Tx-405 exhibited higher heat transfer coefficient (97.4 kW/(m2·K)) than Tx-100 (77.1 kW/(m2·K)) and Tx-114 (77.4 kW/(m2·K)). Long-term test indicated a gradually deteriorating trend of heat transfer performance from days on. Solution properties and bubble dynamics were measured. At low concentration, surfactant with shorter hydrophilic chain has better heat transfer performance due to greater surface tension reduction. The increase of hydrophilic chain length improves water affinity of surfactant and thus leads to higher CMC. If there is no restriction for surfactant concentration, a longer hydrophilic chain is favorable for higher heat transfer coefficient at CMC. The results in this paper provide insights for mechanism investigation on surfactant, promote further design of new surfactant, and contribute to the prediction of heat transfer enhancement effect. • Nucleate pool boiling of Triton surfactant solutions on flat copper was experimented. • Bubble behaviors during boiling and related solution properties were measured. • At CMC, Tx-405 with longer hydrophilic chain showed higher HTC of 97.37 kW/(m2·K). • At low concentration, Tx-114 with shorter hydrophilic chain was favorable. • Heat transfer enhancement mechanism regarding hydrophilic chain length was discussed. [ABSTRACT FROM AUTHOR]

The distributed energy supply system provides a good scheme for energy supply. The micro gas turbine with a recuperator is a common power device in distributed energy supply systems. In recent years, several achievements have been made in the development of micro gas turbine recuperators. Plate-fin and primary surface recuperators have been used in mature applications. Moreover, the thermodynamic properties of the heat transfer channel have been studied in detail. Among them, the cross wavy primary surface recuperator developed by Capston Company is one of the important achievements. This paper reviews the technical development of thermodynamic performance of micro gas turbine recuperator in recent years. The micro gas turbine recuperators are divided into plate-fin and primary surface recuperators commonly. In this paper, the correlation formula, heat exchange enhancement, optimum design and the influence of recuperator on the overall machine performance are reviewed. It has been found that the plate-fin recuperators have been sufficiently studied by scholars, and the results are more comprehensive. As for the primary surface recuperators, which have just become popular in recent years, the research results are less comprehensive due to their unique structure. In the future development of micro gas turbine recuperators, this will be the future research and development trend due to the high heat exchange efficiency and the lack of comprehensive research on primary surface recuperators. [ABSTRACT FROM AUTHOR]

Micro fins on the internal surface of the tube improves its heat transfer ability. This paper investigates the thermal performance of tube flow numerically by adding axial straight micro fins (ASMF) on internal tube surfaces. The numerical method is experimentally validated using a tube featuring ASMF. The effects of fin height e , fin number N f , and fin shape of the tube with ASMF on the thermal performance are numerically studied within the range of Reynolds number (Re) from 1280 to 7687. Compared to a smooth tube, the Nusselt number (Nu) for tube with ASMF is reduced over the entire range of Re. In order to assess the performance of heat transfer, the ratio of the heat transfer coefficient (h) multiplying the heat transfer area (F) of ASMF tube (hF) to that of the smooth tube (h s F s) is utilized. Parametric studies were performed. The optimal fin height, fin number are found to be 0.0429 and 32. The optimal fin profile is found to be quadratic function profile. By combining the optimal fin height, fin number and fin profile, the maximum value of hF /(h s F s) can reach 1.32. Besides, the heat transfer enhancement mechanism induced by ASMF is also disclosed in this paper. [ABSTRACT FROM AUTHOR]

This communication concerns some doubtful results included in the above paper. [ABSTRACT FROM AUTHOR]

Despite extensive investigations on the mechanism of laser-irradiated solid propellants, formulating an accurate model that characterizes more details of laser-target interactions remains a challenging task. In this paper, a thermal model for nanosecond pulsed laser ablation of aluminum was developed using the finite volume method which considers the instant recession on the propellant surface and the non-Fourier effect during heat conduction. The robust coupling iteration scheme adopted in the model tracks the dynamic boundary condition due to instant propellant removal. In particular, the pre-qualified threshold is used as discriminator for phase explosion and the thermal relaxation time is introduced to quantify the non-Fourier effect on heat conduction. In addition, the temperature-dependent physical and optical parameters of the propellant were also regarded in the proposed model. The numerical implementations for Gaussian laser ablation of aluminum were performed at different laser fluences and thermal relaxation times. The theoretical computation of the ablation depth coincides well with the experimental results to validate the feasibility of the model. • The thermal interaction of an ultra-short pulsed laser with metal was investigated. • The material moving front during heat transfer was modeled using finite volume method. • A modified critical threshold was used as a discriminator for metal phase explosion. • The thermal relaxation time was introduced to quantify the non-Fourier effect. [ABSTRACT FROM AUTHOR]

In this paper, we propose a hot-spot aware Thermoelectric Cooler (TEC)-based active cooling technique, called TEC-Array , which can perform targeted cooling of the spatially and temporally changing on-chip hot spots in any multi-core processor. It is in contrast to many existing works, where TECs were used for spatially homogeneous cooling, which leads to high energy costs. The proposed cooling system involves a 2D array of TEC modules where each TEC module is individually controllable. This enables the ability to spatially vary the cooling for hot spots across the chip's surface while the processor is under load. This way, the areas of the chip consuming more power, and consequently generating more heat, can be cooled more intensely than the areas that are consuming very little power. To dynamically control the TEC-Array, the proposed approach applies machine learning predicted full-chip power-density maps to generate discrete voltage maps which are in turn used to dynamically configure the voltage settings of the TEC-Array. In addition, we also propose a numerical simulation framework, which employs an accurate 3D coupled multi-physics model for TEC devices to consider Peltier, heat transfer, Joule heating and complex electro-thermal coupling effects by solving the coupled heat conduction and current continuity equations. The numerical results on an Intel quad-core chip shows that the proposed TEC-Array cooling can substantially reduce the peak temperatures compared to the traditional passive heat sink cooling method. Furthermore, compared to the existing single TEC module based cooling method, the proposed method can reduce both TEC power and temperature gradients across chips under the same maximum temperature constraints, which can further reduce spatial temperature induced stress such as thermal cycling, thermo-migration and unbalanced aging etc. As a result, the new TEC-Array cooling can enable more aggressive chip performance with increased thermal design power (TDP) while maintaining the chip design lifetime. • Optimize active cooling on spatially and temporally changing on-chip hot-spots. • Individually controllable 2D array of TECs that can spatially vary the cooling. • TEC is controlled by chip's spatial power information with machine learning. • An accurate 3D coupled multiphysics-based numerical simulation framework. • Reduce both TEC power and temperature gradients across the processor. [ABSTRACT FROM AUTHOR]

• A non-Fourier heat transfer analysis method of orthotropic plate with uninsulated cracks is established. • A peridynamic model considering the non-Fourier effect, orthotropy of medium and crack thermal resistance is developed. • Multi-cracks in brittle metal bismuth are analyzed by the non-Fourier theory. • The crack thermal resistance is positively related to the maximum temperature difference at the crack. • The thermal relaxation has the greatest influence on the cracks parallel to the heating boundary. In this paper, the transient temperature response of a cracked plate under thermal shock is investigated. To eliminate the problems caused by the assumption of infinite heat propagation speed, the non-Fourier heat transfer theory is adopted. A peridynamic model is developed to consider the non-Fourier effect, the orthotropy of thermal conductivity, and the crack thermal resistance. This model avoids the spatial derivative and is efficient to analyze the problems with discontinuities. Based on the Kapitza thermal resistance model, a thermal resistance bond is proposed to deal with the uninsulated crack. The explicit and implicit discrete schemes of peridynamic formulation are presented to solve the temperature field. The model is verified by the analytical solution and excellent agreements are obtained. For the non-Fourier phenomenon observed in bismuth, numerical examples are presented for analyzing the effects of crack thermal resistance, crack orientation angle, and multi-crack distribution on non-Fourier heat transfer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electro permanent magnet is proposed for magnetocaloric refrigeration. • Electro permanent magnet is numerically and experimentally evaluated. • Its energy efficiency above 80% is reached with magnetic energy recovery. • Magnetic field can be switched between min and max up to 50 times per second. • Fast switching of magnetic field can be used with thermal switches. Magnetocaloric energy conversion represents an alternative to existing refrigeration, heat pump and energy harvesting technologies. A crucial part of a magnetocaloric device concerns the magnetic field source. It uses mainly rare-earth materials and consists of moving parts and a drive system while displaying a limited energy efficiency and unavailability of fast and variable control of the magnetic field. Recent advances in efficient heat transfer for high-frequency magnetic cooling call for new developments of magnetic field sources that can operate with high efficiency at high frequencies. We report the concept of an electro-permanent magnetic (EPM) field source that efficiently recovers magnetic energy. In contrast to existing magnets, it allows very well-controlled operation without any moving parts. The main objective of this paper is to present a numerical and experimental study in which such an EPM was designed, built and tested. An extensive numerical investigation of the proposed design was carried out in terms of various geometrical and operating parameters. One of the design variations was built and experimentally evaluated for its energy efficiency and temperature increase at various operating frequencies. We demonstrate an energy efficiency of these magnets of over 80% and operation with frequencies up to 50 Hz, which is crucial for future high-power-density and high-frequency magnetocaloric devices. Considering high energy efficiency at high operating frequencies, such EPMs would allow for miniaturization, making them a viable option for future compact magnetocaloric devices. [ABSTRACT FROM AUTHOR]

This paper is the second of a two-part series that presents experimental data and analysis on the liquid nitrogen quenching heat transfer process of a stainless-steel tube with an inner surface low-thermal conductivity thin-film coating. This paper focuses on the effects of different flow directions and two tube wall thicknesses. Additionally, this paper also provides an analysis on the chilldown thermal efficiency of the quenching process. Three flow directions with four different inner surface coating modifications, and three tube wall thicknesses were examined. The experimental data covers the Reynolds numbers ranging from 3500 to 140,000. The chilldown efficiency, along with chilldown time and LN 2 (liquid nitrogen) mass consumption were analyzed to assess the overall performance of the LN 2 line chilldown process. For thin tube wall cases, the chilldown efficiencies cover a range between 3% and 41%, and the maximum chilldown efficiency value is found for the tube with 3 L coating at Re = 5278 in the vertical up flow direction. For thick wall tube cases, the efficiencies cover a range between 4% and 52%, and the maximum chilldown efficiency value was found for the tube with 4 L coating at Re = 5308 in the vertical up flow direction. [ABSTRACT FROM AUTHOR]

This paper formulates quadrilateral elements for the NURBS-enhanced finite element method (NEFEM). The objective is to extend the application of NEFEM to problems where the use of quadrilateral elements is preferred. By leveraging a mapping, between reference and physical spaces, that encapsulates the exact boundary representation of the domain, a tight integration with computer aided design (CAD) systems is achieved. The contribution of this work is an enhanced quadrilateral finite element that incorporates the exact CAD geometry purely from the boundary representation (B-rep) from CAD and without the need for a whole volume representation (V-rep) as a NURBS entity. Numerical examples involving heat transfer and linear elastic problems are used to numerically demonstrate the optimal convergence properties of the method under mesh refinement. [Display omitted] • This paper aims to reduce the gap between CAD and analysis. • A new NEFEM bilinear superparametric element is presented. • The shape functions are redesigned and solely reside in the parametric space. • Heat transfer and elasticity problems show that NEFEM achieves higher accuracy. [ABSTRACT FROM AUTHOR]

Strip-casting is a key step among processes for manufacturing the Nd-Fe-B permanent magnets. Current research on the process parameters of the strip casting process mostly relies on the trial-and-error method. In this paper, the influence of the cooling roller speed on the strip-cast Nd-Fe-B flakes is investigated by a combination of simulation and experiment. The microstructures of the strip-cast flakes prepared at different roller speeds are observed and analyzed. The simulation is further performed by using the thermal-fluid coupling method. The temperature field and cooling water flow field of the cooling rollers at different roller speeds are obtained to explain the principle of the microstructural evolution. The temperature field distribution affects the uniformity of the columnar grains on both sides of the strip-cast flake. Higher or lower temperature can also lead to the formation of α-Fe, cluster rare earth (RE) rich phases, or ultra-fine equiaxed grains. An increase in cooling water flow rate is helpful to obtain the columnar grain with even thickness. The simulation results are consistent with the microstructural results. Furthermore, the simulated results and microstructural analyses are combined to indirectly evaluate the trend of magnetic properties of final sintered magnets from the tested strip-cast flakes. By verifying the performance of magnets prepared under the condition of only changing the roller speed during the entire process flow, the measurement results are consistent with the evaluation results, proving that the combined analysis proposed in this paper can reasonably predict the trend of magnetic properties of sintered Nd-Fe-B permanent magnet materials from the strip-cast flakes prepared at different roller speeds. This paper can provide a transferable idea and method for using numerical simulation to assist in the design and production of Nd-Fe-B flakes and sintered magnets. • Formation of the microstructure of Nd-Fe-B strip-cast magnetic flakes was explained. • Effect of roller speed on the microstructure of magnetic flakes was discussed. • Thermal-fluid coupling during strip-casting was adopted to understand heat transfer. • Simulation and microstructure were combined to predict the trend of properties. • A method based on test and simulation was proposed to help the development of magnet. [ABSTRACT FROM AUTHOR]

The selection of optimal design and the most efficient operational parameters for energy devices constitute a priority task for sustainable development and increasing energy efficiency within the net-zero emissions strategy. This is particularly important in adsorption cooling and desalination systems with poor performance due to unfavourable heat transfer conditions in conventional packed beds of adsorption chillers (ACs). Therefore, looking for additional ways of performance improvement is still challenging, especially covering different design variants and operational strategies. The existing complex, time-consuming and costly analytical, numerical and experimental methods, usually focused on a specific design and operating parameters of conventional packed adsorption beds, cannot tackle these comprehensive problems. Since artificial intelligence (AI) based models are considered tools that sometimes may overcome the shortcomings of the programmed computing approach and the experimental procedures, the paper introduces automated machine learning (AutoML) as a general approach for the design and optimization study of adsorption cooling and desalination systems. The double-effect, i.e. specific cooling capacity (SCP) and specific daily water production (SDWP) of various adsorption chillers (ACs) operating in large-, pilot- and small-scale adsorption cooling and desalination systems, is considered in the study. The paper also presents a novel big data optimization procedure for selecting the best operating and design strategy in adsorption cooling and desalination technology. Finally, a new concept of fluidized bed-type application in adsorption chillers is proposed, which allows for enhancing the performance of ACs. The presented approach can be referred to as a complementary design technique in adsorption cooling and desalination systems, besides the existing complex analytical and time-consuming numerical methods and expensive experiments. • Double-effect desalination and cooling production in adsorption chillers (AC) are evaluated • The new approach allows considering various cooling and desalination adsorption systems. • The novel concept of fluidized bed application in adsorption systems is proposed. • The developed models constitute powerful tools for optimizing ACs systems' performance. [ABSTRACT FROM AUTHOR]

• Local condensation heat transfer in smooth channels and pin fin array is presented. • The effect of operating parameters on the heat transfer characteristics was analyzed. • Sensitivity analysis is performed of heat transfer to identify the critical parameters. • Condensation heat transfer increases with heat flux in the range of vapor quality above 0.4. In this paper, an experimental study of flow condensation was carried out of R134a in a multiport mini channel and a mini channel with pin fin array. The former comprised 20 parallel rectangular channels with an equivalent diameter of 0.64 mm. The latter is a narrow rectangular mini channel containing 10 rows of diamond pin fins with a staggered configuration, and height and longitudinal/transverse pitch of 0.5 mm and 2 mm respectively. To acquire the local value of heat flux and heat transfer coefficient, air jet impingement cooling devices were adopted to condense the vapor of refrigerants. The effects of vapor quality, mass flux, heat flux, and saturation pressure on flow condensation heat transfer coefficient were investigated with the operating conditions: vapor quality from 1 to 0, mass flux from 160 to 450 kg/(m2s), heat flux from 10.0 to 39.8 kW/m2, and saturation pressure from 600 to 1500 kPa. The experimental results indicated that the pin fin array significantly improves the condensation heat transfer coefficient up to nearly 186 % compared to the multiport mini channel in the high vapor quality region. For both channels, the local heat transfer coefficient increases with an increase in vapor quality, mass flux, and heat flux whereas decreases with increase in saturation pressure. The influence of heat flux and mass flux on heat transfer coefficient was more pronounced in the high vapor quality region than in the low vapor quality region. A sensitivity analysis was performed at different vapor quality levels. The most influential parameters in the smooth channel and the pin fin array are saturation pressure and mass flux, respectively. The relative contribution of heat flux is more obvious in the high vapor quality region. Some of the existing correlations have good prediction performance for the smooth channel experimental data in this paper, and the corresponding MAD is within 20 %. However, their deviations are much greater for the applications of pin fin array. [ABSTRACT FROM AUTHOR]

The current work aims to understand and model thermal runaway (TR) events in lithium-ion (LIB) 18650 cells within the context of aircraft battery applications. The primary goal is to comprehend the phenomenon and discuss strategies for mitigating its consequences during aircraft operation. TR is modeled using Arrhenius kinetic equations and is implemented in both lumped parameters (Matlab SimulinkTM), and 3D CFD simulations (Ansys FluentTM) using User Defined Functions. To validate the thermochemical model, cells are initially simulated in an oven test, where a cell is exposed to a temperature-controlled atmosphere, triggering exothermic reactions. With a strong correlation between lumped parameters and 3D models, the latter is simulated under battery module installation conditions. An internal short-circuit is then implemented within the cell to observe how thermal runaway is triggered by an internal heat source. The trigger cell is subsequently placed in a battery module assembly to assess the dominant heat transfer modes and the likelihood of TR induction from one cell to its neighbors. This work's main objective and innovation are to compare different materials in which cells are immersed while observing the main heat transfer parameters for each material. Three conditions are tested: ceramic paper fiber and G7 as solid separators, and no separator material, where air fills the gaps between cells. The analysis of heat transfer modes reveals radiation's dominance in the case of air interstice, suggesting the possibility of using a special coating to reduce the cell surface emissivity as an alternative to decrease the likelihood of TR propagation. Thus, two values of surface emissivity were tested in the case of air. Considering a cell triggered by an internal short-circuit, a thermal runaway temperature spike is not observed in any of the four cases. However, the air interstice case with regular emissivity is the most critical one, with the closest cell reaching peak temperatures as high as 136 °C in 490 s. The ceramic paper fiber is considered the best separator material, as it postpones the temperature increase in the closest cell while also being lighter than G7. The results and discussions concerning heat propagation presented herein can serve as guidelines for developing strategies to mitigate thermal runaway in battery modules. [ABSTRACT FROM AUTHOR]

Nanochannels consisting of hot and cold walls with periodic rectangular and triangular nanostructures were simulated by molecular dynamics in this paper, the periodic size dimensionless parameters φ was defined to describe the dimension of nanostructures on the wall. The results show that the addition of nanostructures leads to the variation of mass density distribution of fluid near the wall. A hot wall with nanostructures can promote the appearance of a fluid high-potential area near it. The discrepant attraction for fluid from the wall caused by the different wall conditions leads to different flow characteristics in nanochannels. Fluid velocity growth rate near the hot wall is 10.5% higher than that near the cold wall. Average velocity of the fluid near the hot wall is 5.1% higher than that of fluid near the cold wall. A wall with rectangular nanostructures at φ = 0.28 shows minimum flow resistance among rough hot walls, while a wall with triangular nanostructures at φ = 0.14 has minimum flow resistance among rough cold walls. Heat is transferred from the hot wall to the cold wall through fluid flow. Wall conditions impact the heat transfer situation of fluid in flow boundary by changing the fluid mass density contribution. The addition of nanostructures and decrease of nanostructures size is beneficial for heat transfer while unfavorable for fluid flow, convective heat transfer was influenced by their combination. For a wall with 300 K, the addition of rectangular nanostructures at φ = 0.07 has the best convective heat transfer performance. For a wall with 200 K temperature, increasing triangular nanostructures at φ = 0.14 on the wall can reach the best convective heat transfer capacity. This paper can provide a theoretical foundation for the optimization of nanochannels to achieve best convective heat transfer ability. [ABSTRACT FROM AUTHOR]

The presence of magnetic field results in a reduction in natural convective heat transfer and entropy generation in cavities. The use of nanofluids improves the performance of thermal systems. The present paper discusses the impact of uniform and non-uniform magnetic fields on the second-law performance of nanofluid-filled and porous cavities, introduces artificial intelligence (AI) approaches, and examines the applications of AI in optimizing heat transfer and entropy generated in these systems. The mathematical formulation is presented in terms of the entropy generation for natural convection in cavities. This paper demonstrates the influences of various important non-dimensional parameters on entropy generation in cavities. Besides, advances in the second-law performance of cavities and the role of AI techniques in the field are discussed and future directions are provided. [ABSTRACT FROM AUTHOR]

• The liquid metal cross flow tube bundle under pulsation condition is simulated. • The effect of different pulsation frequency and amplitude are analyzed. • Circumferential flow field and temperature field of the single tube are analyzed. • The vortex characteristics and turbulent structure are analyzed with PSD and CWT. Liquid metal has a broad application prospect in tube bundle heat exchangers because of its excellent thermal conductivity. However, conventional in-line tube bundle arrangements often exhibit limited secondary flow, so new methods are urgently needed to improve heat transfer. The topic of this paper is to combine two methods, liquid metal cross flow tube bundle and pulsating flow, to improve the heat transfer performance in-line tube bundles. Firstly, the applicability of the model was validated through experimental data from existing literature, encompassing overall flow dynamics, heat transfer performance, and circumferential pressure distribution around the tubes. Subsequently, numerical simulations are conducted involving liquid metal cross flow in-line tube bundles at varying pulsating frequencies, amplitudes, and Reynolds numbers. Circumferential pressure distributions and temperature profiles for individual tubes were analyzed and compared. The amplitude of reduction in thermal resistance compared to the no-oscillation condition increases gradually from a minimum of 8 % in the first row to a maximum of 40 % in the third row, while the reduction in the rear row of tubes is similar to that of the third row. Remarkably, a reversal in the trend of thermal resistance for the first three rows of tubes under pulsating flow were observed, contrasting conventional flow except for the case with an amplitude of 0.1. By analyzing the local transient flow field distribution near single tube and the corresponding circumferential heat transfer performance, the influence of the vortex evolution characteristics on the heat transfer performance at different phases of the pulsating velocity is revealed, which transient Nu is up to three times that of flow with no pulsating. Finally, a series of coherence analyses reveal that as frequency rises, turbulence exhibits a richer spectrum of small-scale vortex structures, intricately linked to enhanced energy cascade efficiency. Amplitude augmentation intensifies velocity fluctuations, particularly at high amplitudes, resulting in substantial energy peak amplification. The integrated heat transfer performance PEC factor varies in the range of 1.25 to 1.51 for all the conditions simulated in this paper, which indicates that the liquid metal coupled pulsating flow approach can significantly increase the comprehensive performance of the tube bundle heat exchangers. These findings hold significant promise for advancing heat exchanger design and enhancing thermal efficiency, with implications for various engineering applications. [ABSTRACT FROM AUTHOR]

In this paper, the barrel of small-caliber automatic rifle is taken as the research object. An experiment was taken on the gun barrel and an infrared thermal imager was used to measure the change of barrel temperature field during the continuous shooting, and the finite difference model of barrel heat transfer was established. The formula of the correction coefficient of heat transfer of gunpowder gas on the inner surface of the body tube was obtained by fitting with the experimental results. The barrel transient heat transfer analysis calculation software with independent intellectual property rights was developed by C++, and the characteristics of temperature field were analyzed. The experimental results show that the temperature of the outer surface of the barrel rises and then falls along the axial direction from the bottom of the barrel to the muzzle, and the rising slope will decrease in the next 30 rounds of continuous firing. The calculation results of the small-caliber barrel with chromium layer show that the temperature of the outer surface of the chromium layer of each shot rises instantaneously and then drops rapidly, in the form of pulse, and the temperature of the steel matrix rises continuously, but it is significantly lower than the peak temperature of the chromium layer, and the presence of the chromium layer provides buffer protection for the barrel matrix material. There is still an influence region in the matrix behind the interface between the chromium layer and the barrel matrix, and the temperature of the steel matrix in this region fluctuates. The thickness of the influence region is determined by analysis. The temperature of the inner surface of the barrel reaches a maximum at the tail of the barrel along the axial axis and then slowly decreases in the direction of the muzzle, the radial temperature distribution of the barrel is steeper at the tail end and the muzzle area is relatively flat. The calculation results of the model in this paper are basically consistent with the experimental results, which provides a rapid calculation model and tool for the thermal design and analysis of the gun barrel. [ABSTRACT FROM AUTHOR]

Laser-induced fluorescence (LIF) is a robust and vigorous method for non-intrusive measurement of temperature, pressure, concentration, and pH in fluids. The application of LIF for measurement is also extendable to solid and gaseous environments. In this method, the fluorescent molecules are transferred to a higher energy state by absorbing the energy of a laser beam and subsequently undergo spontaneous emission of light in the form of fluorescence during the transition to the ground. The emitted fluorescence is commonly captured using a setup consisting of a solvent, fluorescent material, detecting cameras, lenses, and filters, which enables the determination of the thermophysical parameters of the measuring environment using pertinent mathematical formulae. This method can be used for precise measurements in a wide range of engineering and medical applications. Despite the numerous studies on the utilization of LIF for measurement, there is not a comprehensive review paper with a focus on various types of LIF techniques and their applications in temperature measurement. This paper seeks to address this gap by fully discussing these approaches, demonstrating temperature measurements in different environments and circumstances, and outlining their benefits and drawbacks. Accordingly, one-dye one-color, two-dye two-color, one-dye two-color, one-dye three-color, two-dye three-color, volumetric LIF, and encapsulation techniques are fully discussed as the main LIF approaches and their applications for the temperature measurement in fluid flows, droplets, microfluidics, and gas environments. [Display omitted] • Classification of different laser induced fluorescence technique for temperature measurement. • Classification of dyes and their corresponding properties used in LIF technique. • Detailed description of LIF techniques and their application in temperature measurement. • Full description of the advantageous and disadvantageous of LIF for temperature measurement. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lewis number deviates from one in the entrance length. • The catalyst activity do not modify the initial Nu and Sh inside of the channels. • Re modifies the thermal entrance length because of the reduction of the flow area. This paper is devoted to the multi-scale model of the heat and mass transfer inside of a honeycomb monolith substrate. Due to computational limitations, monoliths are modelled as a continuum in full-scale catalytic reactors models. That makes it necessary to use correlations or sub-models derived from channel scale results to account for a physically consistent heat and mass transfer inside of the substrate. In this paper detailed computational models at a channel and reactor scales are analyzed. Catalytic oxidation of CO is used as a reaction and the fluid properties are considered to be temperature-dependent. First, a channel scale model is used to analyze Nusselt, Sherwood, Lewis, and Damköhler numbers inside of the monolith channels. Secondly, sub-models obtained at a channel level are implemented in a full-scale reactor model using the continuum approach, to evaluate the impact of using detailed vs. highly simplified correlations for heat and mass transfer. The reactor scale model accounts for the transitions of the flow regime, entrance length effects, an-isotropic substrate thermal conductivity and temperature-dependent fluid properties. According to the results, the Lewis number can deviate significantly from one in the entrance length, however, it approaches asymptotically to unity as the flow develops. Regarding Nusselt and Sherwood, current interpolating methodologies are not able to predict the correct value in the entrance region when Damköhler is low, nonetheless, are reasonably accurate for the asymptotic one. [ABSTRACT FROM AUTHOR]