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Boosting heat transfer of ultrahigh temperature ceramics (UHTCs) with dimensional‐crossover graphene has become an increasing challenge for improving the thermal protective performance of new‐generation spacecraft. Yet its characteristics of anisotropic and high interfacial thermal resistance inevitably cause heat transfer deterioration at high temperatures. Here we develop a few ZrB2/graphene/ZrB2 interface‐dominated diffuse models that are driven by bonding configurations and thermal converger. It has been found that forming stronger bonding configurations by Zr‐C interfacial bonding and designing a preferred thermal converger by ordered graphene are both unarguable ways of suppressing high‐temperature heat transfer deterioration. Each Zr‐C interfacial bonding serves as an independent sluice gate to accelerate heat flow. More high‐frequency phonons are excited at high temperature, which augments the interfacial thermal conductance from 38.5 to 335.4 MW·m−2·K−1 at 700 K. Impressively, a concept of thermal converger inspires us to adopt ordered graphene for changing the diverging behavior in isotropic ZrB2 composites. Its convergent process combines with anisotropic characteristics to transform the isotropic heat flow into the highly ordered graphene. Their thermal conductance can be regulated from minimum (2.5) to maximum (80.8 W·m−1·K−1) by rotating the ordered graphene from 90° to 7.5°. This work paves an optimal way for manipulating the heat transfer of UHTCs. [ABSTRACT FROM AUTHOR]

ABSTRACT Energy piles are commonly deployed in vertically layered geological conditions due to the geological structure and pile foundation backfill. The imperfect contact between adjacent soil layers results in resistance to heat transfer at the interface, known as the interfacial thermal resistance effect. In this paper, the energy pile was simplified as a finite‐length solid cylindrical heat source, and an analytical model was established for layered heat transfer of energy piles considering the interfacial thermal resistance effect. The Laplace‐domain solutions to the temperatures in the layered ground were derived by using the finite Hankel and Laplace transforms. The Crump method was subsequently employed to numerically invert Laplace‐domain solutions to the time‐domain solutions. The proposed model was validated by comparing with an analytical solution of a homogeneous model and COMSOL numerical solution. These solutions were used to analyze the temperature response around energy piles considering interfacial thermal resistance. Finally, a parametric study was performed to explore the effects of interfacial thermal resistance and other thermal properties of the soil layer on the layered heat transfer of energy piles. [ABSTRACT FROM AUTHOR]

In this work, scanning photothermal radiometry is used for imaging and to characterize a submicron crack. From the thermal images, the evolution of the crack is mapped in the space with micrometer resolution. A vertical contact interface at the steel–steel junction is used to represent a micro-crack with a thickness less than 0.5 μm. The thermal quadrupole approach is used to model the heat transfer within the semi-infinite vertical crack. Then, using the phase mapping and that calculated from the model, the estimation of both the equivalent thermal boundary resistance of the interface and the average interface thickness was done. [ABSTRACT FROM AUTHOR]

Nanofluids have gained considerable attention as potential alternatives to pure fluids in cooling systems, particularly in boiling flow systems operating in two-phase vapor–liquid conditions. While nanofluids enhance heat transfer in cooling systems, a significant challenge associated with their implementation is the issue of nanoparticle deposition and sedimentation. Numerical analyses often neglect the deposition layer formed on the walls of pipes and channels. Disregarding this layer in simulations can lead to significant errors in estimating fluid flow and heat transfer parameters. This study investigates the boiling flow of four different nanofluids (nickel–water, gold–water, aluminum–water, and titanium oxide–water) with a volume fraction of 0.03% and pure water in a vertical tube with a diameter of 1.45 mm using a two-dimensional simulation in MATLAB software. In the simulation, five mass transfer mechanisms including evaporation, condensation, deposition, entrainment, and fluid entry into the sedimentary area are considered. To simulate the sedimentary layer, the rules of the porous media have been used. In addition, Brownian motion of particles and Kapitza resistance are also considered in the calculations. The primary objective is to demonstrate the impact of deposition layer simulation on the heat transfer coefficient (HTC) and critical heat flux (CHF) in various nanofluids. The results indicate that the deposition layer causes an average reduction of 31% in the HTC and 16% in the CHF. The findings emphasize the importance of incorporating deposition layer simulation in analyzing boiling nanofluids. Ignoring sediment phenomenon can result in substantial errors in predicting heat transfer and CHF, with significant implications for the design and optimization of nanofluid-based cooling systems. [ABSTRACT FROM AUTHOR]

The shrinking size of integrated chips poses thermal management challenges. Understanding the size effect of chemical heterogeneity on solid–liquid interfacial thermal transfer is essential for heterogeneous chip design, yet the underlying mechanisms remain lacking. The present work used the liquid n-alkanes as the thermal interface material between solid platinum substrates. To characterize chemical heterogeneity, periodic solid surface patterns composed of patches with alternating solid–liquid affinities were constructed. By using non-equilibrium molecular dynamics simulations, we investigated the size effect of chemically heterogeneous patterns on interfacial thermal resistance (ITR) at the nanoscale. At larger heterogeneity sizes, i.e., larger patch sizes, most alkane molecules directly in contact weak interaction patches cannot interact with strong interaction patches due to long atomic distances. In the case of alkanes in contact a cold substrate, alkanes in contact weak interaction patches transferred thermal energy to the substrate at a lower rate than those in contact strong interaction patches. The different rates resulted in the higher temperature of alkanes in contact weak interaction patches than those in contact strong interaction patches and, therefore, a larger disparity between temperature jump at the strong interaction areas and that at the weak interaction areas. The non-uniformity of temperature jump distribution increased ITR when compared to the heterogeneous surface system characterized by a smaller patch size with a more uniform temperature distribution in the plane perpendicular to the heat flux direction. In addition, the classical parallel thermal resistance model predicted ITR accurately for the heterogeneous surface systems with small size patches but overestimated overall thermal resistance. [ABSTRACT FROM AUTHOR]

Composite materials and structural optimization are important research topics in heat transfer enhancement. The current evaluation parameter for the conductive heat transfer capability of composites is effective thermal conductivity (ETC); however, this parameter has not been studied or analyzed for its applicability to different heat transfer models and composite structures. In addition, the optimized composite structures of a specific object will vary when different optimization methods and criteria are employed. Therefore, it is necessary to investigate a suitable method and parameter for evaluating the heat transfer capability of optimized composites under different heat transfer models. Therefore, this study analyzes and summarizes three typical conductive heat transfer models: surface-to-surface (S-to-S), volume-to-surface (V-to-S), and volume-to-volume (V-to-V) models. The equivalent thermal conductivity ( k eq ) is proposed to evaluate the conductive heat transfer capability of topology-optimized composite structures under the three models. A validated simulation method is used to obtain the key parameters for calculating k eq . The influences of the interfacial thermal resistance and size effect on k eq are considered. The results show that the composite structure optimized for the V-to-S and V-to-V models has a k eq value of only 79.4 W m−1 K−1 under the S-to-S model. However, the k eq values are 233.4 W m−1 K−1 and 240.3 W m−1 K−1 under the V-to-S and V-to-V models, respectively, which are approximately 41% greater than those of the in-parallel structure. It can be demonstrated that k eq is more suitable than the ETC for evaluating the V-to-S and V-to-V heat transfer capabilities of composite structures. The proposed k eq can serve as a characteristic parameter that is beneficial for heat transfer analysis and composite structural optimization. [ABSTRACT FROM AUTHOR]

Surface modification of a crystalline filler is a powerful method for increasing the thermal conductivity (κ) of filler-impregnated composites. Herein, boron nitride (BN) filler was functionalized with cationic molecules of different sizes to directly recognize the effect of an amorphous area on the filler-polymer matrix interface. Measured thermal conductivity and temperature rise for a polymer composite was up to 67.1 % and 15.3 % greater, respectively, in the sample to which the smallest molecule-modified BN was added, compared to the comparable sample with free BN. The smaller the size of the modifier molecule, the better it bonds with the resin and the smaller the non-crystalline area. Such changes improve the heat transfer at the interface by reducing interfacial thermal resistance. These findings can serve as a reference to develop alternative and effective strategies for filler modification, an alternative approach instead of focusing on functional groups and modifiers. [Display omitted] [ABSTRACT FROM AUTHOR]

Heat transfer from the solidified shell to the mold, especially in the meniscus region, significantly affects the surface quality of the strand and the stability of the continuous casting process. The mold slag film serves as the sole heat transfer medium between the shell and the mold, and its performance and structure have a substantial impact on the heat transfer efficiency. Thus, since the 1980s, various testing methods are developed to investigate the heat transfer performance of the slag film, including the pouring method, immersion method, parallel plate method, and mold experiment. In this article, the principles, characteristics, and main study results of these methods are reviewed, and the existing issues are highlighted in these methods. Furthermore, specific requirements that shall be satisfied in future research on the heat transfer of slag film are presented. The new approach for testing heat transfer in slag film necessitates ensuring consistency in the heat flux, surface temperature of the shell, interfacial thermal resistance, and thickness and cooling rate of the slag film, aligning with those observed in a mold. This consistency is crucial to ensure the comparable structure and heat transfer characteristic between the experimental and industrial slag films. [ABSTRACT FROM AUTHOR]

High-temperature driven solid–solid reaction at coke (C)/calcium oxide (CaO) interfaces is attractive for industrial-scale production of calcium carbide (CaC2). However, the reaction rate limited by the low thermal conductivity (k) results from a high Kapitza thermal resistance (Rk) at C/CaO interfaces. Identifying various factors including temperature and absorbed moisture on the k of C/CaO pellets is significant for heat transfer enhancement. Here, we developed a modified effective medium assumption model considering the particle-packed configuration to predict the influence of temperature and moisture on the k of C/CaO pellets, in which the R k is evaluated by the non-equilibrium molecular dynamics. The results show that the k of C/CaO pellets increases from 0.48 to 0.55 W/(m K) when the temperature increases from 300 to 900 K, which is attributed to a 19.7% decrease in the R k of C/CaO interfaces caused by a rising temperature activated inelastic interfacial phonon scattering. Moreover, it is found that the k of C/CaO pellets decreases from 0.48 to 0.44 W/(m K) after inserting absorption water layers with a thickness of 0.5 nm at C/CaO interfaces. A further 38.4% degeneration in k is harvested when increasing the thickness of the absorption water layers from 0.5 to 1.3 nm. This work provides an overall insight into the interfacial effect on the k of C/CaO porous pellets and guides the heat transfer optimization for particle-packed systems. [ABSTRACT FROM AUTHOR]

Iontronic devices, recognized for user-friendly soft electronics, establish an electrical double layer (EDL) at the interface between ion gels and electrodes, significantly influencing device performance. Despite extensive research on ion gels and diverse electrode materials, achieving a stable interfacial formation remains a persistent challenge. In this work, we report a solution to address this challenge by employing CO2 irradiation as a bottom-up methodology to directly fabricate highly conductive, conformable laser-induced graphene (LIG) electrodes on a polyimide (PI)-based ion gel. The PI ion gel exhibits exceptional EDL formation at the electrode interface, primarily attributable to efficient ion migration. Particularly, ionic laser-induced graphene (i-LIG) electrodes, derived from the PI ion gel as a precursor, yield high-quality graphene with enhanced crystallinity and an expanded porous structure in the upward direction. This outcome is achieved through a pronounced thermal transfer effect and intercalation phenomenon between graphene layers, facilitated by the presence of ionic liquids (ILs) within the PI ion gel. Ultimately, in comparison to alternative soft electrode-based vertical capacitors, the utilization of i-LIGs and PI ion gels in the vertical capacitor demonstrates reduced interfacial resistance and increased EDL capacitance, emphasizing the extensive potential of iontronic devices. These results not only highlight these features but also introduce a new perspective for advancing next-generation iontronic devices. [ABSTRACT FROM AUTHOR]

Cooling is important for AlGaN/GaN high-electron mobility transistors (HEMTs) performance. In this paper, the advantages and disadvantages of the cooling performance of three cooling schemes: remote cooling (R-cool), near-chip cooling (NC-cool), and chip-embedded cooling (CE-cool) are compared. The influences of distinct geometric parameters and operating conditions on thermal resistance are investigated. The results show that the thermal resistances of NC-cool and CE-cool are almost the same as each other. Decreasing microchannel base thickness (hb) significantly increases the thermal resistance of CE-cool, and when its thickness is less than a critical value, NC-cool exhibits superior cooling performance than CE-cool. The critical thickness increases when decreasing the heat source pitch (Ph) and the convective heat transfer coefficient (hconv) or increasing the thermal conductivity of the substrate (λsub). Moreover, increasing Ph or λsub significantly improves the thermal resistance of three cooling schemes. Increasing hconv significantly decreases the thermal resistances of NC-cool and CE-cool while hardly affecting the thermal resistance of R-cool. The influence of the boundary thermal resistance (TBR) on the thermal resistance significantly increases at higher λsub and larger hconv. [ABSTRACT FROM AUTHOR]

In this work, breakdown transients of multilayered gate oxide stacks were analyzed to study the impact of the interfaces between oxides on the heat dissipation considering an electromigration-based progressive breakdown model. Using two distinct measurement setups on four different sets of samples, featuring two layers and three layers of Al 2 O 3 and HfO 2 interspersed, the breakdown transients were captured and characterized in terms of the degradation rate. Experimental results show that the number of oxide–oxide interfaces present in the multilayered stack has no visible impact on the breakdown growth rate among our samples. This strongly supports the interpretation of the bulk materials dominating the heat transfer to the surroundings of a fully formed conductive filament that shows no electrical differences between our various multilayered stack configurations. [ABSTRACT FROM AUTHOR]

Heat transfer across fluid–solid interfaces in nanoconfinement has received significant attention due to its relevance in nanoscale systems. In this study, we investigate the Kapitza resistance at the water–graphene interface with the help of classical molecular dynamics simulation techniques in conjunction with our recently proposed equilibrium molecular dynamics (EMD) method [S. Alosious et al., J. Chem. Phys. 151, 194502 (2019)]. The size effect of the Kapitza resistance on different factors such as the number of graphene layers, the cross-sectional area, and the width of the water block was studied. The Kapitza resistance decreases slightly with an increase in the number of layers, while the influence of the cross-sectional area and the width of the water block is negligible. The variation in the Kapitza resistance as a function of the number of graphene layers is attributed to the large phonon mean free path along the graphene cross-plane. An optimum water–graphene system, which is independent of size effects, was selected, and the same was used to determine the Kapitza resistance using the predicted EMD method. The values obtained from both the EMD and the non-equilibrium molecular dynamics (NEMD) methods were compared for different potentials and water models, and the results are shown to be in good agreement. Our method allows us to compute the Kapitza resistance using EMD simulations, which obviates the need to create a large temperature gradient required for the NEMD method. [ABSTRACT FROM AUTHOR]

Interfacial adhesion and interfacial thermal resistance (ITR) are two critical factors in the interfacial force and energy transfer, but it is difficult to simultaneously achieve the desirable interfacial adhesion and ITR. Here, we overcome this challenge by fabricating an elastomer composite consisting of polydimethylsiloxane (PDMS) and micro-scale spherical aluminum (Al) fillers, which offers the high adhesion strength (1.28 MPa), high interfacial adhesion energy (528.4 J/m2), and low ITR (0.028 mm2·K/W) between the PDMS/Al elastomer composite and substrates. We further propose a quantified physical model to establish the relationship between interfacial adhesion and ITR for low phonon mismatch interfaces. This work will contribute to the development of interface science and guide the regulation of force and energy transfer at interface for wide range applications, such as electronic packaging, thermal storage, sensors, and medicine. [ABSTRACT FROM AUTHOR]

In this paper, the one‐dimensional rheological characteristics of multilayered saturated porous rock subjected to a ramp‐type heating is investigated. By introducing the fractional order parameter and material parameters, a viscoelastic constitutive model is proposed to describe the rheological characteristics of multilayered saturated porous rock. The general incomplete thermal contact model is established to predict the interfacial thermal contact resistance of multilayered saturated porous rock. Based on the coupled thermo‐hydro‐mechanical theory, the semi‐analytical solutions of the excess pore water pressure, temperature increment and displacement are obtained by using the Laplace transform method. The accuracy of the present solutions is verified by comparing with the classic elastic and viscoelastic models, and existing solutions. In addition, the influence of fractional order parameter, material parameter ratio, thermal contact transfer coefficient and thermal partition coefficient on the excess pore water pressure, temperature increment and displacement of multilayered saturated porous rock are investigated. [ABSTRACT FROM AUTHOR]

Heat conduction in one-dimensional system is generally found to be anomalous. However, the scaling behavior of thermal conductivity with system length is still up for debate among theoretical, numerical and experimental results. Here with a devised adjustable reflectivity heat reservoir, we re-address the anomalous heat conduction in one-dimensional Fermi–Pasta–Ulam β (FPU- β ) lattices under weak nonlinear conditions. Our results show that, the boundary thermal resistance has an important impact on the divergent thermal conductivity of one-dimensional systems with weak nonlinearity. As an application of this concept, we design a thermal rectification model in one material with asymmetric boundary coupling, which is in sharp contrast to the well-known thermal rectifiers composed of two different materials. Our findings shed light on the intrinsic heat conduction in weak nonlinear lattices, which might be helpful to understand the heat transfer experiments of one-dimensional materials, such as carbon nanotubes, nanowires, and polymer chains. [ABSTRACT FROM AUTHOR]

Understanding the interfacial heat transfer and thermal resistance at an interface between two dissimilar materials is of great importance in the development of nanoscale systems. This paper introduces a new and reliable linear response method for calculating the interfacial thermal resistance or Kapitza resistance in fluid-solid interfaces with the use of equilibrium molecular dynamics (EMD) simulations. The theoretical predictions are validated against classical molecular dynamics (MD) simulations. MD simulations are carried out in a Lennard-Jones (L-J) system with fluid confined between two solid slabs. Different types of interfaces are tested by varying the fluid-solid interactions (wetting coefficient) at the interface. It is observed that the Kapitza length decreases monotonically with an increasing wetting coefficient as expected. The theory is further validated by simulating under different conditions such as channel width, density, and temperature. Our method allows us to directly determine the Kapitza length from EMD simulations by considering the temperature fluctuation and heat flux fluctuations at the interface. The predicted Kapitza length shows an excellent agreement with the results obtained from both EMD and non-equilibrium MD simulations. [ABSTRACT FROM AUTHOR]

Using molecular dynamics simulation, we investigated the mechanism by which the intercalation of a surfactant solution reduces the contact thermal resistance of two solid surfaces. We constructed a model system where two solid surfaces with a gap were immersed in a surfactant solution, and the gap was filled with permeating molecules to form a molecular thin film. By varying the concentration of the surfactant and the distance between the confining surfaces, factors affecting the intersolid heat transfer were explored. It was demonstrated that the overall thermal resistance of the present system was determined by interfacial thermal resistance between the solid and the solution and can be reduced by increasing the surfactant concentration. The surface separation, i.e., the distance between the two solid surfaces, had a significant impact on interfacial thermal resistance, whether or not surfactant molecules were involved. Interfacial thermal resistance was an oscillatory function of the surface separation and displayed minimum values not at the most adsorption amount of liquid molecules but when the density profile of liquid molecules showed a sharp peak, i.e., when the surface separation was commensurable with the size of the solvent molecule. This tendency was most remarkably seen when the liquid film was composed of a single molecular layer. The findings in this study provide helpful insights into the reduction of interfacial thermal resistance utilizing surfactant solutions. [ABSTRACT FROM AUTHOR]

Graphene‐based composites show great potential in the development of lightweight functional devices and systems, and polymers are usually used as binders to enhance the mechanical properties of these composites. Due to the low thermal conductivity of the polymer and the high inherent interfacial thermal resistance between polymer and graphene, however, the developed devices and systems generally possess low thermal conductivity, which seriously limits their further thermal‐related applications. Here, a lightweight two‐phase heat transport device (TPHTD) based on a vapor‐liquid phase transition‐based heat transfer by using a graphene‐based composite material as the casing is generated. The graphene‐based TPHTD has high thermal conductivity of up to 1408 W (mK)−1 and realizes ultra‐high specific thermal conductivity of ≈5600 W (mKg)−1. This graphene‐based device with lightweight and high heat transfer capacity offers new opportunities for efficient thermal management of compact, portable, or wearable electronic and power systems. [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]

Based on the theory of micromechanics, the thermal conductivity of poly(lactic acid) (PLA) composites filled with graphene(GR) sheets was studied by representative volume element method. According to the micrographs, the microstructure characteristics of the composite were analyzed, and a two-dimensional random model was established. The equivalent thermal conductivity of GR composite was calculated by finite element method, and the accuracy of the model was verified by experimental results. The influences of the microstructure parameters to the thermal conductivity of the composite were studied by parametric analysis, and its heat transfer mechanism was analyzed. The results show that the numerical results of the random model are in good agreement with the experimental results. With the increase of graphene mass fraction, the heat transfer performance of the composite is enhanced. The aspect ratio and orientation of graphene in the composites have great influence on the overall thermal conductivity of the GR composite. At the same time, the interfacial contact thermal resistance between graphene and matrix also has great influence on the overall thermal conductivity of the composites. The present model and the parametric analysis results can provide reference for optimal design of the absorbing materials. [ABSTRACT FROM AUTHOR]

This article presents a theoretical analysis of a one-dimensional heat transfer problem in two layers involving diffusion, advection, internal heat generation or loss linearly dependent on temperature in each layer, and heat generation due to external sources. Additionally, the thermal resistance at the interface between the materials is considered. The situation of interest is modeled mathematically, explicit analytical solutions are found using Fourier techniques, and a convergent finite difference scheme is formulated to simulate specific cases. The solution is consistent with previous results. A numerical example is included that shows coherence between the obtained results and the physics of the problem. The conclusions drawn in this work expand the theoretical understanding of two-layer heat transfer and may also contribute to improving the thermal design of multilayer engineering systems. [ABSTRACT FROM AUTHOR]

Thermal rectification effect enables adjustment of the system's thermal transport properties in response to the direction of the temperature bias, thereby assuming a pivotal function in the domain of thermal control technology. Employing molecular dynamics simulations, the solid-liquid thermal rectification is studied by introducing surfactants into the liquid. The thermal rectification ratio of the system can be significantly enhanced by adding surfactants. The underlying mechanism of the thermal rectification is analyzed by calculating the interfacial thermal resistance distribution, temperature profile, and liquid and surfactant density distribution. Such a high thermal rectification factor is primarily due to the different surfactant-adsorption behavior when reversing the temperature bias. Adding surfactants to the liquid enhances forward heat transfer while reverse heat transfer can be suppressed. In addition, the effect of surfactant concentration on the thermal rectification effect is also examined. The results show that the thermal rectification factor can be increased by increasing surfactant concentrations at higher temperature bias. The results of this paper present an innovative approach to improve the efficiency of thermal rectifiers. [ABSTRACT FROM AUTHOR]

• A heat flux-weighted temperature difference-based novel contact resistance model is proposed Considering internal non-uniformities, an analytical expression of thermal resistance is derived. • Parameter sensitivity analysis of the model is conducted and compared to other existing models. • Effective thermal conductivity of pebble bed is obtained and its various effects are analyzed. A novel model for inter-particle contact thermal resistance based on analytical solutions is proposed. By applying the concept of heat flux weighted temperature difference in thermal resistance modeling for the first time, this model offers greater physical significance than traditional thermal resistance models. It effectively describes the dissipation in the heat transfer process and the influence of particle radius on thermal resistance, making it a generalized thermal resistance model suitable for multi-dimensional systems. The impact of applying different levels of uniform heat flux boundary conditions on thermal resistance is analyzed from the perspective of energy dissipation, revealing that a more uniform heat flux input results in lower thermal resistance. The effects of contact radius and particle size on the dimensionless generalized thermal resistance of inter-particle contact were studied, showing that the dimensionless resistance increases with larger particle contact radius and smaller particle size. Using the thermal discrete element method, the thermal resistance model with uniform heat flux density boundary conditions was applied to calculate the effective thermal conductivity of the pebble bed. Considering the distribution of contact radius, differences in effective thermal conductivity at various heights of the pebble bed due to different contact radii were examined and compared with the traditional fixed-coefficient contact resistance model. It was found that the difference between the two models decreases as the contact radius decreases. Finally, multiple sets of fixed contact radii were established under three different particle sizes, revealing that as the contact radius increases, the deviation between the new generalized resistance model and the traditional fixed-coefficient model rises from 8.18 % to 14.64 % for different particle radii. [ABSTRACT FROM AUTHOR]

• A stabilized state-based peridynamic heat conduction model considering the Kapitza thermal resistance is proposed. • The stabilized scheme eliminates numerical oscillations in state-based peridynamic heat conduction. • Embedding discontinuous peridynamics for perfect and imperfect interface problems. As the demand for micro/nano-scale electronic devices and composite materials grows, numerical modeling of interfacial thermal resistance problems has become an integral part of the design for these devices and materials. In this work, a stabilized state-based peridynamic heat conduction model considering the Kapitza thermal resistance is proposed. A stabilized scheme is first developed to eliminate the numerical oscillations in the state-based peridynamics. The main idea is to formulate the temperature gradient for each individual bond by penalty function. The corresponding heat flow state is then constructed based on this newly developed bond-augmented temperature gradient in the framework of the Lagrangian formalism. The stabilization scheme is combined with the embedded discontinuous peridynamic concept to capture the temperature jump conditions of interface thermal resistance. The effectiveness of the proposed model is demonstrated by numerical examples. It paves the way for investigating the interfacial thermal resistance problems of materials with complex heat transfer constitutive relations. [ABSTRACT FROM AUTHOR]

The comparisons of wear resistance and heat transfer behaviours of chromium and brass were conducted. The effects of different values of chromium coating average roughness (1.240, 4.576, 7.388, 9.323 μm) and thickness (15, 35, 55 μm) on the interfacial heat transfer behaviours were investigated with a novel droplet solidification technique. The results revealed that, compared with the brass, the chromium material has a significant improvement in the Vickers hardness and wear performance and a reduction of 25 percent interfacial heat transfer rate. Moreover, with the increase of the coating average roughness from 1.240 to 7.388 μm, the maximum heat flux between molten steel and cooling substrate decreases from 8.27 to 5.56 MW/m2 due to the enlargement of the air gap. As the coating average roughness further increases to 9.323 μm, the maximum heat flux increases to 6.50 MW/m2 because of the increasing contact area between molten steel and the cooling substrate. In addition, the maximum heat flux was reduced from 8.47 to 5.87 MW/m2, considering the enhancement of interfacial thermal resistance when the coating thickness increases from 15 to 55 μm. The results obtained have important implications for heat transfer control of the strip casting process by adjusting the coating average roughness and thickness. [ABSTRACT FROM AUTHOR]

Simulating the heat transfer in a composite material is an important topic in material science. Difficulties arise from the fact that adjacent materials cannot match perfectly, resulting in discontinuity in the temperature variables. Although there have been several numerical methods for solving the heat-transfer problem in imperfect contact conditions, the methods known so far are complicated to implement, and the computational times are non-negligible. In this study, we developed a ResNet-type deep neural network for simulating a heat transfer model in a composite material. To train the neural network, we generated datasets by numerically solving the heat-transfer equations with Kapitza thermal resistance conditions. Because datasets involve various configurations of composite materials, our neural networks are robust to the shapes of material-material interfaces. Our algorithm can predict the thermal behavior in real time once the networks are trained. The performance of the proposed neural networks is documented, where the root mean square error (RMSE) and mean absolute error (MAE) are below 2.47E-6, and 7.00E-4, respectively. [ABSTRACT FROM AUTHOR]

In this work, a thermal energy transfer problem in a one-dimensional multilayer body is theoretically analyzed, considering diffusion, advection, internal heat generation or loss linearly dependent on temperature in each layer, as well as heat generation due to external sources. Additionally, the thermal contact resistance at the interfaces between each pair of materials is taken into account. The problem is mathematically modeled, and explicit analytical solutions are derived using Fourier techniques. A convergent finite difference scheme is also formulated to simulate specific cases. The solution is consistent with previous results. A numerical example is provided, demonstrating the coherence between the obtained results and the physical behavior of the problem. This work was recently published for a two-layer body; the generalization to m -layer bodies allows for conclusions that enhance the theoretical understanding of heat transfer in multilayer materials and may contribute to improving the thermal design of multilayer engineering systems. [ABSTRACT FROM AUTHOR]

Interfacial heat transfer across curved surfaces has not been understood sufficiently well. The present study reports a significant decrease in heat transfer at a convex fluid-solid interface. Effects of curvature on the Kapitza length and the thermal accommodation coefficient are investigated for both gas and liquid phases to understand the occurrence of large temperature jumps. The study also examines the penetration depth of non-equilibrium effects into gas from the convex surface theoretically and reveals the expansion of the Knudsen layer at convex surfaces. [ABSTRACT FROM AUTHOR]

• TBR of vdWs-mediated Si 3 N 4 /SiO 2 point contact is measured by the 3 ω -SThM system. • Quantitative analysis on effect of air tunnel on the heat transfer between surfaces. • Laser heating and spot position on the probe is quantitatively determined. Si 3 N 4 and SiO 2 have been widely used in lithium batteries and optical devices. The high energy density brought by device integration makes the interfacial heat transport at the nano scale a hot spot. To optimize interfacial heat transfer, the roughness of the device surface is continuously reduced down to the nanometer. However, due to the limitation of spatial resolution, it is difficult to realize the measurement of thermal boundary resistance in the case of nanoscale contact by the existing measurement means. There is a great discrepancy between the measurement and simulation results, making the optimization of interfacial heat transfer lack of experimental verification. In this paper, the measurement of thermal boundary resistance of Si 3 N 4 /SiO 2 interface at the nano-scale, was firstly realized by the optimized 3 ω -SThM system. The effect of air tunnel on the heat transfer between real surfaces was also analyzed. The progress made so far provides an effective experimental tool to measure interfacial heat transport at nanoscale point contact. [Display omitted] [ABSTRACT FROM AUTHOR]

• An H-type measurement device was used for the thermophysical characterization of single microparticles. • The interfacial thermal resistance between single microparticles was analyzed by analytical thermal resistance model. • The effects of temperature and size on the heat transfer performance of microparticles were studied. • The uncertainty of the whole experimental system is about 4.4 %. With the incorporation of microparticles in composite materials becoming increasingly widespread, it is important to study the effect of the thermophysical properties and thermal contact between individual microparticles on heat transfer in composite materials. However, studies on the heat transfer performance of single microparticles are scarce, mainly because the micrometre scale size makes the measurement difficult. Furthermore, the area of contact between microparticles is smaller than the micrometre scale, further enhancing the difficulty of heat measurements. In this study, an H-type measurement device was developed for the thermophysical characterization of single microparticles. Through experimental and theoretical analyses, we obtained the thermal conductivity and thermal resistance of single microparticles of silicon dioxide, polyethylene (PE), poly ether ketone (PEEK) and polymethyl methacrylate (PMMA), apart from the interfacial thermal resistance between two PMMA particles. Furthermore, effective experimental methods were also developed for the study of the heat transfer mechanism of composite materials at the microscopic level. [ABSTRACT FROM AUTHOR]

Joule self-heating is the main obstacle limiting the performance of GaN power devices. A nano-diamond (NCD) film for near-junction heat transfer has been approved as an effective approach to overcome this issue. In the present study, we developed a scheme to deposit a smooth NCD film with high thermal conductivity (TC) over the surface of GaN. First, a 10-nm Si 3 N 4 was deposited as the protective layer of GaN, followed by electrostatic seeding to improve nucleation density and particle distribution uniformity. Second, argon and gradient methane gas were introduced to prepare the NCD film based on nucleation and the growth period. The resulting thickness of the NCD film was 150 nm with a roughness of about 20 nm. The thermal boundary resistance (TBR eff) between GaN and NCD film was only 12.8 ± 0.64 m2K/GW, whereas the TC of the NCD film was 200 ± 40 W m−1 K−1, which was similar to the theoretical prediction. Thus, it could be inferred that the high crystallinity of the NCD film contributes to the low TBR eff and high TC through the whole NCD layer. [Display omitted] [ABSTRACT FROM AUTHOR]

Carbon-based nanostructures are extensively employed as solid additives in nanofluids or polymer matrices for applications in light harvesting, energy conversion and storage. To predict heat transfer in carbon-based nanostructures, a quantitative comprehension of thermal energy exchanges at the interface with their external environment is crucial. The Thermal Boundary Resistance (TBR) stands out as a key parameter hindering efficient thermal energy exchanges between nano-objects and their surroundings. In this work we experimentally determine the TBR for the archetypal case of an interface between multi-wall carbon nanotubes (CNTs) and water. Ultrafast energy exchanges are investigated using femtosecond time-resolved optical spectroscopy. Data rationalization via a thermo-optical model allows retrieval of a CNT/water interface TBR of (4.6 ± 2.2) × 10−8 m2K/W. This value constitutes a benchmark for theories aimed at understanding energy transfer between a CNT and water. Notably, the functionalization of the surface of CNTs with covalent groups has been demonstrated to reduce the TBR and facilitate solid–liquid heat exchanges. The measurement and analysis protocol developed in this study is versatile and can be applied to any nanofluid and nanocomposite material. [Display omitted] • Experimental retrieval of the Thermal Boundary Resistance at the Carbon Nanotube/water interface. • Benchmark value for theoretical investigations aimed at rationalizing heat exchange between water and CNT. • Thermal Boundary Resistance retrieval protocol readily transferable to any nanofluid. [ABSTRACT FROM AUTHOR]

The porous medium heat exchanger has been increasingly utilized in cryogenic applications, especially in the milli-Kelvin region. This study focuses on the porous medium heat exchanger with liquid channel commonly used in the dilution refrigerator and proposes a numerical model, which applies the local thermal non-equilibrium (LTNE) model coupled with N–S equations and Brinkman-Forchheimer model. Comparing with literature results validates the numerical model. By analyzing the heat transfer characteristics of the heat exchanger, a thermal resistance network model is developed to capture the heat transfer mechanism. The results show that the total thermal resistance mainly depends on the fluid conductive thermal resistance and Kapitza thermal resistance inside the porous medium. The fluid conductive thermal resistance dominates at higher temperature while the Kapitza thermal resistance dominates at lower temperature. The expression of critical temperature is derived to determine the priority of reducing thermal resistance. At cryogenic temperatures, the porous medium serves to bypass the significant Kapitza thermal resistance by introducing much lower thermal resistances, while at normal temperatures, the porous medium reduces the overall thermal resistance by incorporating a parallel thermal resistance but without magnitude difference. [ABSTRACT FROM AUTHOR]

Excessive carbon emissions are one of the global challenges. Promoting the optimization of high-efficiency heat transfer systems and improving the analysis and evaluation methods of heat exchangers is one of the effective ways to save energy and reduce carbon emissions. The traditional thermal resistance analysis method treats the fluid domain as a uniform whole, which makes it difficult to regulate the heat transfer characteristics in local regions, especially in the near-wall region. To address this problem, this paper obtained the thermal resistance mathematical equation for different regions in the flow field by magnitude analysis. The thermal resistance delamination method for dividing the thermal resistance field is proposed from the channel flow, and the conduction, mixing and advection zones in the flow field are identified. The delamination factor (α) is defined to determine the boundaries of thermal resistance zones. The α values which meet the delamination factor independence under forced convection and natural convection conditions are investigated. By studying the mechanism of the thermal resistance in conduction zone of the enhanced heat transfer structure, the critical value of fin height to achieve maximum enhancement efficiency is determined. The thermal resistance delamination facilitates a comprehensive analysis of heat transfer processes and structure optimization in the near-wall region. • Thermal resistance delamination method based on flow characteristics is proposed. • The expression of each thermal resistance zone was determined by sensitivity analyses and delamination factor. • Analysis of heat transfer in enhanced double-sided channel flow based on thermal resistance delamination method. • Critical fin height for maximum enhancement efficiency determined by local thermal resistance. [ABSTRACT FROM AUTHOR]

The contact area is one of the significant effects on the heat transfer of the material, increasing the heat transfer area between the heating device and the heat sink through topology optimization of the heat sink structure is an efficient and feasible solution. The thermal conductivity of C f /C-Haynes 230 brazed joints is enhanced by forming circular gaps on the surface of the C f /C composite through the pre-oxidation process, which increases the heat transfer area between the braze and the C f /C composite. This study reveals that the thermal conductivity of the joint is as high as 32.2 W·m−1·K−1 after pre-oxidation of C f /C at 650 °C for 5 min, which is an improvement of 34.7% over the initial joint (23.9 W·m−1·K−1). This research provides a way to enhance heat transfer efficiency quickly without changing the materials used. • An oxidizing strategy to increase contact area at C f /C-brazing seam interface. • Ni-Ti compounds hinder the interdiffusion of elements in braze and Haynes 230. • Thermal conductivity of C f /C-Haynes joint increases from 23.9 to 32.2 W·m−1·K1. • Joint exhibits low interfacial thermal resistance of 33 K·mm2·W−1 at 100 °C-30 psi. [ABSTRACT FROM AUTHOR]

The interfacial thermal resistance between adjacent parts is important in the thermal management of micro/nano-scale systems. In this paper, the temperature difference and heat flow methods are adopted to study the interfacial thermal resistance between the smooth surface of metal and the end of carbon nanotube (CNT) by molecular dynamics simulation. The effects of metal type, CNT diameter, and mean interfacial temperature on the interfacial thermal resistance are studied in detail, with the temperature and heat flow conditions applied to the two metal atom groups of a dumbbell-shaped metal–CNT–metal model. For a certain metal type, the diameter and temperature dependences of the interfacial thermal resistance obtained from both the temperature difference and heat flow methods are consistent, the interfacial thermal resistance decreases with increase of CNT diameter exponentially, and the thermal rectification occurs due to different interfacial temperatures. The thermal transfer mechanism at the metal–CNT interface is quantitatively analyzed by calculating the overlap area of the normalized vibrational density of states. The results of this paper will provide in-depth theoretical insights into the heat transfer enhancement at nano-scale interface. [ABSTRACT FROM AUTHOR]

Rapid heat dissipation in dense-power and miniaturised electronic devices is becoming increasingly crucial as electrical technologies improve. Scientists have developed a number of thermal-conductive materials to enhance heat dissipation. Since then, polymer composites have attracted a lot of attention for their lightweight, anti-corrosion, and electrical insulating properties. Interfacial thermal resistance (ITR) is one of the most critical factors to elevate the thermal conductivity of composites. Toward ITR, the molecular dynamic (MD) simulation demonstrates its powerful capabilities for interpreting and predicting macroscopic thermal phenomena based on calculated microscopic structures, thermodynamics, kinetics, and other information. To make full use of MD simulations, one needs to validate the simulation results to ensure that the MD simulation is correctly carried out and the findings are meaningful, reliable and of good repeatability. With these considerations in mind, we highlight the role of MD simulations in heat transfer, the technical issues associated with the nonequilibrium molecular dynamic (NEMD) simulation, the analysis methods for the underlying mechanism, and the strategies to reduce ITR. Furthermore, we also make comments on the perspective of MD simulations in heat transfer. [ABSTRACT FROM AUTHOR]

We introduced an active heat transfer control between graphene and water using interdigitated electrodes (IDEs). Oppositely charged co-planer electrodes embedded on a graphene surface created a non-uniform electric field. Resulted interface localized liquid dielectrophoresis (LDEP) perpendicular to surface enhanced the water/graphene coupling and decreased interfacial thermal resistance (ITR) substantially. We correlated the theoretical calculations of average electric field strength near surface with Kapitza values measured at corresponding electrode configurations. We obtained a unified linear variation of Kapitza as a function of average electric strength independent of electrode size and charge. By increasing the electric field strength, we measured up to 96% decrease of Kapitza near electrodes. Since the IDEs generated electric field was only interface localized, it required lower electrode charges than any parallel-plate capacitor systems. We showed that ITR remains effective in heat transfer behavior for systems as big as 100nm such that interface localized electric field can at least increase the heat removal 50% by eliminating the ITR from both graphene/water interfaces of a channel system. By converting hydrophobic few-layer graphene to super-hydrophilic condition with ultra-low Kapitza, current results are important for graphene-based materials considered for the solution of the thermal management problem of current and next generation micro/nano-electronics. [Display omitted] [ABSTRACT FROM AUTHOR]

This study focuses on the proper characterization of temperature profiles across grain boundaries (GBs) in order to calculate the correct interfacial thermal resistance (ITR) and reveal the influence of GB geometries onto thermal transport. The solid-solid interfaces resulting from the orientation difference between the (001), (011), and (111) copper surfaces were investigated. Temperature discontinuities were observed at the boundary of grains due to the phonon mismatch, phonon backscattering, and atomic forces between dissimilar structures at the GBs. We observed that the temperature decreases gradually in the GB area rather than a sharp drop at the interface. As a result, three distinct temperature gradients developed at the GB which were different than the one observed in the bulk solid. This behavior extends a couple molecular diameters into both sides of the interface where we defined a thickness at GB based on the measured temperature profiles for characterization. Results showed dependence on the selection of the bin size used to average the temperature data from the molecular dynamics system. The bin size on the order of the crystal layer spacing was found to present an accurate temperature profile through the GB. We further calculated the GB thickness of various cases by using potential energy (PE) distributions which showed agreement with direct measurements from the temperature profile and validated the proper binning. The variation of grain crystal orientation developed different molecular densities which were characterized by the average atomic surface density (ASD) definition. Our results revealed that the ASD is the primary factor affecting the structural disorders and heat transfer at the solid-solid interfaces. Using a system in which the planes are highly close-packed can enhance the probability of interactions and the degree of overlap between vibrational density of states (VDOS) of atoms forming at interfaces, leading to a reduced ITR. Thus, an accurate understanding of thermal characteristics at the GB can be formulated by selecting a proper bin size. [ABSTRACT FROM AUTHOR]

When considering the thermal processes of multilayer nanostructures, a significant part of the energy is dissipated at the boundaries of the layers; to take this factor into account, the Kapitza resistance is used in the simulation. In this study, we calculate the thermal resistance at the Si/SiO2 interface (alpha-quartz) structures for the temperature range up to 567 K. The calculations are carried out based on the acoustic and diffuse mismatch models. The results obtained, in particular, can be used in constructing models of heat transfer in microelectronics. [ABSTRACT FROM AUTHOR]

The droplet solidification technique was used to investigate the formation of deposited film and the interfacial heat transfer for the sub-rapid solidification of silicon steels. The composition of deposited films consists of MnO, FeO and SiO2 for both the low and high-silicon steels. The deposited film could improve the wetting condition between the steel droplet and substrate. And the wetting condition between the droplet and substrate improves with the increasing of ejection times from 1 to 9, and thus the final contact angles decrease gradually from 105.1 to 72.8 deg. The peak value of heat flux increases with the number of solidification tests, indicating that the heat transfer condition between the droplet and substrate improves with the deposition of film. The peak value of heat flux increases from 5.64 to 7.42 MW/m2 for low-silicon steel after the 9th ejection, and it is from 6.03 to 9.06 MW/m2 for high-silicon steel. This is because the interfacial thermal resistance between the droplet and substrate reduces gradually with the increasing of test times. A higher Mn content in the high-silicon steel leads to a higher deposited rate of the oxide film than the low-silicon steel. Compared with the low-silicon steel, the increment of MnO content in the film for the high-silicon steel is 6.60 wt pct, and there is no obvious increment of SiO2 in the film, though the increment of Si in high-silicon steel is 6.06 wt pct, and for Mn is only 0.72 wt pct. [ABSTRACT FROM AUTHOR]

Understanding how heat flows across interfaces is vital to energy efficiency and thermal stability of many electrical devices. However, the thermal resistance caused by the interface between two materials, termed Kapitza resistance, remains poorly understood. To that end, several first‐principles molecular dynamic simulations and a detailed analysis of the phonon processes and associated transfer of heat at the interfaces of both c‐Si|a‐SiO2 and c‐Si|c‐Ge are presented. It is found that in both cases the interface properties are very important. In the case of c‐Si|a‐SiO2, it is found that interface modes cause inelastic phonon interactions and play a significant role in the total energy transferred. In the case of c‐Si|a‐SiO2, one is able to quantify this effect and find that there is a small set of interface modes which carry >10% of the heat, and decrease the ultimate thermal boundary resistance by 26.5%. [ABSTRACT FROM AUTHOR]

Nanocomposites based on graphene dispersed in matrices of soft materials are promising thermal management materials. Their effective thermal conductivity depends on both the thermal conductivity of graphene and the conductance of the thermal transport across graphene-matrix interfaces. Here, we report on molecular dynamics simulations of the thermal transport across the interfaces between defected graphene and soft materials in two different modes: in the "across" mode, heat enters graphene from one side of its basal plane and leaves through the other side; in the "non-across" mode, heat enters or leaves graphene simultaneously from both sides of its basal plane. We show that as the density of vacancy defects in graphene increases from 0% to 8%, the conductance of the interfacial thermal transport in the "across" mode increases from 160.4 ± 16 to 207.8 ± 11 MW/m2 K, while that in the "non-across" mode increases from 7.2 ± 0.1 to 17.8 ± 0.6 MW/m2 K. The molecular mechanisms for these variations of thermal conductance are clarified using the phonon density of states and structural characteristics of defected graphene. On the basis of these results and effective medium theory, we show that it is possible to enhance the effective thermal conductivity of thermal nanocomposites by tuning the density of vacancy defects in graphene despite the fact that graphene's thermal conductivity always decreases as vacancy defects are introduced. [ABSTRACT FROM AUTHOR]

With the development of electronic equipment components in the direction of integration, miniaturization, and intelligence, their increasingly high heat dissipation requirements pose a high challenge to the thermal conductivity (TC) of thermal interface materials (TIMs). Polymer‐based composite materials with high TC have gradually been favored because of their good processing performance, low cost, and low density. It is important to summarize the relationship between the problems of low heat conduction and their solutions in relation to polymer‐based composite materials. For this purpose, this review comprehensively discusses the basic mechanisms of heat transfer inside polymer‐based TIMs, the current challenges, and future prospects for improving TC. Strategies involving surface modification and network construction can reduce interfacial thermal resistance and enhance heat conduction. [ABSTRACT FROM AUTHOR]

Construction of particle network is the most effective strategy for polymer composites with high thermal conductivity. However, the disadvantages of this strategy, such as high particle concentration, complex preparation process, weak mechanical properties or thermodynamic instability, still limit the application. The heat transfer mechanism of polymer composites without particle network remains unclear. In this work, for exploring the heat transfer path of polymer composites without particle network, polymer composites are designed with spherical SiO2 particles grafted by 3D crosslinked organosilicone matrix, to minimize influence of interfacial thermal resistance and crystallization. Combining experiment, theoretical models and coarse‐grained molecular dynamics simulations, it is concluded that the heat fluxes concentrate on the matrix among the particles. [ABSTRACT FROM AUTHOR]

Ultrafast chip nanocalorimetry opens up remarkable possibilities in materials science by allowing samples to be cooled and heated at extremely high rates. Due to heat transfer limitations, controlled ultrafast cooling and heating can only be achieved for tiny samples in calorimeters with a micron-thick membrane. Even if ultrafast heating can be controlled under quasi-adiabatic conditions, ultrafast controlled cooling can be performed if the calorimetric cell is located in a heat-conducting gas. It was found that the maximum possible cooling rate increases as 1 / r 0 with decreasing radius r 0 of the hot zone of the membrane. The possibility of increasing the maximum cooling rate with decreasing r 0 was successfully implemented in many experiments. In this regard, it is interesting to answer the question: what is the maximum possible cooling rate in such experiments if r 0 tends to zero? Indeed, on submicron scales, the mean free path of gas molecules l m f p becomes comparable to r 0 , and the temperature jump that exists at the membrane/gas interface becomes significant. Considering the limitation associated with thermal resistance at the membrane/gas interface and considering the transfer of heat through the membrane, we show that the controlled cooling rate can reach billions of K/s, up to 1010 K/s. [ABSTRACT FROM AUTHOR]

In this paper, we present a theoretical study aimed at investigating the rate-limiting factors in thin-film evaporative heat transfer processes, considering the finite-rate evaporation kinetics. The problems of evaporation of a flat thin-film in either pure vapours or vapour-inert-gas mixtures are analysed based on the non-dimensionalised macroscopic transport equations for continuum fluids, coupled with out-of-equilibrium kinetic boundary conditions. Both the full numerical solutions and asymptotic analytical solutions at slow evaporation limit are provided and applied to analyse thin water film evaporation. Existing solutions, assuming negligible heat transfer in the gas domain, or negligible temperature jump across the non-equilibrium kinetic layer, or more boldly a thermodynamically equilibrial interface (i.e. its temperature is at the saturation temperature), can be fully recovered from the more general solutions presented here. Our results show that while these assumptions hold in special cases, they can lead to significant errors in many conditions, especially when the film thickness δ is reduced to a few micrometers or thinner. We show that the conventional views that the rate-limiting factors in thin-film evaporative heat transfer is either the heat diffusion through the liquid film or the mass transfer in the gas domain only apply to thick film (i.e. δ ≫ λ where λ is the mean free path in the vapour phase). As δ decreases to a few micrometer or smaller (more precisely when the Knudsen number Kn increases beyond O (1) in an pure vapour environment or when the kinetic Peclet number Pe is reduced below O (1) in inert gases), the interfacial thermal resistance due to the evaporation kinetics can be on the same orders of magnitude as the thermal resistance in the liquid film. The analysis also allow us to compare the heat transfer processes during the evaporation of a thin-film in pure vapours to those in inert gases, providing deeper insight into the effectiveness of various strategies for exploring the evaporation process in practical thermal management. • Analysis of thin-film evaporation counting for finite-rate evaporation kinetics. • Provision of both dimensionless numerical and analytical asymptotic solutions. • Significant thermal resistance due to kinetics observed in micrometers or thinner films. • Limitations and conditions for existing assumptions to hold are identified. [ABSTRACT FROM AUTHOR]

• An efficient and general salt-resistant strategy is proposed and verified. • Both the evaporation rate and salt-resistant ability of the evaporator with the PVASF strategy are simultaneously enhanced. • Stable evaporation even under 4 suns and in 14 wt% NaCl solution is achieved. During solar-driven interfacial evaporation, non-volatile salts easily precipitate on the evaporator and block the microchannels, thus decreasing the evaporation performance and long-term durability, especially in high-salinity brine and under focused irradiation. Inspired by the peak shaving and valley filling (PSAVF) strategy in electrical systems, a stable and sustainable salt-resistant strategy is proposed in this work. It is achieved by transferring heat from the heat peak to the heat valley to adjust the evaporation distribution and decrease the local salt accumulation rate, thus enhancing the salt-resistant ability. Based on this strategy, a high-efficiency 3D solar evaporator is fabricated by simply assembling a carbonized coconut fiber cloth, a natural coconut fiber cloth, a heat transfer structure, and a thermal insulation material. After optimizing the thermal conductivity and the height of the heat transfer structure, the optimum evaporator can work stably and sustainably with a high evaporation rate of 7.21 kg·m−2·h−1 even under 4 kW·m−2 (four suns) and in 14 wt% brine. Its evaporation rate increases by 20.17 % compared with traditional 2D evaporators, and its salt-resistant ability is significantly enhanced. Moreover, the PSAVF strategy is a universal way to improve the salt-resistant abilities of both symmetric and asymmetric evaporators. With the stable and general salt-resistant performances, the PSAVF strategy provides a new view for stably generating fresh water even under harsh conditions. [ABSTRACT FROM AUTHOR]

Surfactants have been widely used in various industrial fields. Simply adding a small amount of surfactant can greatly enhance the boiling heat transfer of water, which can improve the performance of heat exchanger and has great application prospects in industry, but its mechanism is not fully understood. Many possible factors have been proposed, but their relative importance remains to be examined. In this paper, the possible mechanisms of surfactant effects proposed in the literature are revisited, and their impacts are discussed in depth. Combined with the experimental study, it was found that when the surfactant concentration was low, the change in boiling performance was mainly due to the non-coalescence of growing bubbles on the wall rather than the change of physical properties of the solution. The underlying reason is that surfactants alter the mobility of the vapor-water interface. At high heat flux, the non-coalescence bubbles form wet foam, making it impossible for bulk water to pass through to wet the heating surface, thereby reducing CHF. At the same time, the immobility of the vapor-water interface also increases the interface resistance, making it more difficult for the vapor to escape from the wall. • The change of fluid physical properties is not the main reason for the effect of surfactant on boiling at low concentration. • Surfactant adsorption changes the surface mobility, causing bubbles not to coalesce, which boosts the HTC. • The formation of wet foam and the increase of interfacial drag resistance reduce the CHF. [ABSTRACT FROM AUTHOR]