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Background: The current transformation of the entire energy system leads to a large‐scale expansion of extra‐high‐voltage underground transmission lines (UTL). Knowledge of the impact on soil temperature and soil moisture dynamics is fundamental for environmental evaluation. Aims: We investigated the impact of an existing 320 kV underground cable in continuous operation on soil temperature and moisture dynamics. Methods: A soil‐monitoring programme was established at four study sites in Western Germany. Data were continuously recorded in soil up to 120 cm depth using soil sensors over a period of 1 year. Results: Soil warming was in a range of 0.6 K in the topsoil, approx. 1–1.3 K in the rooting zone and 1.7 K in the subsoil at 120 cm depth and was restricted mainly to the immediate vicinity of the cable route. Likewise, the impact on soil moisture dynamics was on average in a range of −1.00 wt.‐% in 0–60 cm depth and −2.45 wt. 2‐% in the subsoil relative to control. Although at a calculated maximum load capacity of 100% in regular operation, soil warming might remain moderate, with 1.5 K in the topsoil, 2.3–3.1 K in the rooting zone and 4.1 K in the subsoil. Conclusions: It is assumed that the reasons for the low‐to‐moderate influence of the UTL are to be found in the operational cable load (on average 65%), heat loss of cables (approx. 12 W m−1 per cable) and the quality of the imbedding material for the cables. [ABSTRACT FROM AUTHOR]

In this study, we comprehensively investigate thermal lens (TL) spectroscopy, known for its ultra-sensitivity in probing molecular properties through nonlinear heating responses to femtosecond lasers. Using time-resolved TL spectroscopy and numerical simulations, we focus on the influence of convection on heat generation and the resulting phase shift in the probe beam. We examined single-beam, dual-beam same wavelength, and dual-beam different wavelength scenarios, systematically investigating power dependence, pump beam spot size, and sample length limitations. Our findings reveal a direct relationship between the TL effect and pump power, resulting in decreased probe beam transmittance with increasing convection. Additionally, the TL strength grows within the Rayleigh regime as the sample length increases. Utilizing the same wavelength for the probe beam enhances the TL effect in dual-beam setups. Notably, tight focusing of the pump beam substantially reduces the lag between convection and conduction. Our empirical results closely match the experimental data, providing a thorough explanation of the TL process and its underlying principles. These insights can be applied to design and optimize TL-based optical devices and systems for higher sensitivity, highlighting the potential of TL spectroscopy in advanced molecular property probing. [ABSTRACT FROM AUTHOR]

Deriving from the motion of a three-dimensional compressible viscous heat-conducting fluid in an infinite layer bounded above by a free surface, the paper is concerned with the asymptotic behavior of solutions to the linearized compressible Navier-Stokes equations in a strip domain. With the help of the explicit solution formula for the corresponding resolvent problem we have achieved, the time-decay estimates of solutions to this problem in $ L^p $ spaces, $ 2\le p<\infty $, are well established. Moreover, since we are interested in the linearized dynamic boundary condition of the surface wave problem, some exponential decay properties of the solutions are revealed. Our result is crucial and indispensable for developing the $ L^p $ theory for the free boundary problem of the full compressible Navier-Stokes equations. [ABSTRACT FROM AUTHOR]

Growing technical demand for thermal management stems from the pursuit of high–efficient energy utilization and the reuse of wasted thermal energy, which necessitates the manipulation of heat flow with electronic analogs to improve device performance. Here, recent experimental progress is reviewed for thermal switching materials, aiming to achieve all–solid–state thermal switches, which are an enabling technology for solid–state thermal circuits. Moreover, the current understanding for discovering thermal switching materials is reshaped from the aspect of heat conduction mechanisms under external controls. Furthermore, current challenges and future perspectives are provided to highlight new and emerging directions for materials discovery in this continuously evolving field. [ABSTRACT FROM AUTHOR]

We present a first-principles-based electron-temperature model that can be used in atomistic calculations. The electron–phonon coupling coefficient in the model is derived from the density of states as a function of electron temperature, and the thermal conductivity of tungsten from our model shows significant improvement over the baseline atomistic calculations in which only ion-thermal contribution to the thermal conductivity is available. The correction to the thermal conductivity also changes damage cascades as cascades cool down more rapidly within our model. The mobility of defects is consequently reduced, leaving more residual damage than the predictions without an electron-temperature model. [ABSTRACT FROM AUTHOR]

With the continuous advancements in electronics towards downsizing and integration, efficient thermal dissipation from chips has emerged as a critical factor affecting their lifespan and operational efficiency. The fan-less chip cooling system has two critical interfaces for thermal transport, which are the contact interface between the base and the chip dominated by thermal conduction, and the surface of the fins dominated by thermal radiation. The different thermal transfer modes of these two critical interfaces pose different requirements for thermal management materials. In the study, a novel approach was proposed by developing graphene thermal transport functional material whose morphology could be intentionally designed via reformed plasma-enhanced chemical vapor deposition (PECVD) methods to meet the diverse requirements of heat transfer properties. Specifically, graphene with multilevel branching structure of vertical graphene (BVG) was fabricated through the hydrogen-assisted PECVD (H2-PECVD) strategy, which contributed a high emissivity of ∼ 0.98. BVG was deposited on the fins' surface and functioned as the radiation enhanced layer to facilitate the rapid radiation of heat from the heat sinks into the surrounding air. Meanwhile, the well-oriented vertical graphene (OVG) was successfully prepared through the vertical electric field-assisted PECVD process (EF-PECVD), which showed a high directional thermal conductivity of ∼ 53.5 W·m−1·K−1. OVG was deposited on the contact interface and functioned as the thermal conduction enhanced layer, allowing for the quick transmission of heat from the chip to the heat sink. Utilizing this design concept, the two critical interfaces in the chip cooling system can be jointly enhanced, resulting in a remarkable cooling efficiency enhancement of ∼ 30.7%, demonstrating that this novel material possessed enormous potential for enhancing the performance of cooling systems. Therefore, this research not only provided new design concepts for the cooling system of electronic devices but also opened up new avenues for the application of graphene materials in thermal management. [ABSTRACT FROM AUTHOR]

Friction spot joining (FSpJ) has been proven to be a highly competitive process for fabricating hybrid joints composed of metal and carbon fibre-reinforced thermoplastic. However, previous research has rarely focused on optimizing joint performance by controlling thermal conduction through modifying tool structures. This study systematically explores the effect of the recessed tool shoulder geometry on mechanical strength of 6061-T6 Al alloy and carbon fibre-reinforced polyamide-6 (CF/PA6) pinless-FSpJ joint. An experimentally validated three-dimensional (3D) finite element model was built to investigate the heat generation and thermal conduction. Results show that the recessed tools with different external diameters achieve higher average interface strength in lap joints compared to flat shoulder tools. Under fixed plunge depth conditions, increasing the depth of the recessed area results in a lower rate of temperature rise and a more uniform temperature distribution during heating stage. As a result, the duration of resin decomposition in the molten state is further reduced, but the time in a single molten state is extended. This benefits the wetting process of molten resin on the silanized Al surface and subsequent chemical reaction with the silane film, while alleviating decomposition defects to a certain extent. The reduction in residual tension stress at the center of Al upper surface indirectly indicates the improving effect of increased recessed tool depth on the stress state of the joint.

Advancements in phonon engineering have propelled the study of heat conduction within nanostructures, focusing on the wave nature of phonons for thermal conductivity manipulation. This work investigates the annealing‐induced structural transformation of titanium–chromium oxide crystals, highlighting a role in modulating thermal conductivity through the regularization of crystallographic shear (CS) plane spacing. Utilizing high‐angle annular dark‐field scanning transmission electron microscopy and selected‐area electron diffraction, a transformation from disordered to ordered arrangements of CS planes was observed through annealing at high temperatures. The thermal conductivity increased following annealing. The variability observed in the spacing of CS planes before annealing implies that phonon Anderson localization might play a role in the changes in thermal conductivity. [ABSTRACT FROM AUTHOR]

The 2D materials exhibit numerous technological applications, but their scalable production is a core challenge. Herein, ball milling exfoliation in supercritical carbon dioxide (scCO2) and polystyrene (PS) is demonstrated to completely exfoliate hexagonal boron nitride nanosheets (BNNSs), graphene, molybdenum disulfide (MoS2), and tungsten disulfide (WS2). The exfoliation yield of 91%, 93%, 92%, and 92% and average aspect ratios of 743, 565, 564, and 502 for BNNSs, graphene, MoS2, and WS2, respectively, are achieved. Integrating exfoliated BNNSS in the polystyrene matrix, 3768 % thermal conductivity in the axial direction and 316% in the cross‐plane direction at 12 wt.% loading is increased. Also, the in‐plane and cross‐plane electrical conductivity of 6.3 × 10−4 S m−1 and 6.6 × 10−3 S m−1, respectively, and the electromagnetic interference (EMI) of 63.3 dB is achieved by exfoliated graphene nanosheets based composite. High thermal and electrical conductivities and EMI shielding are attributed to the high aspect ratio and ultrathin morphology of the exfoliated nanosheets, which exert high charge mobility and form better the percolation network in the composite films due to their high surface area. The process demonstrate herein can produce substantial quantities of diverse 2D nanosheets for widespread commercial utilization. [ABSTRACT FROM AUTHOR]

A liquid helium-free cryostat for radio frequency (RF) test of the superconducting cavity is designed and constructed. Gifford-Mcmahon (G-M) cryocoolers are used to provide cooling capacity, and the heat leakage at 4 K is less than 0.02 W. Vertical and horizontal tests of two Nb3Sn cavities are carried out in the cryostat with different surface treatments outside the cavities. Both of the cavities achieve stable continuous wave (CW) operation. A novel treatment, which cold-sprayed a 3.5 mm thick Cu layer onto the outside of the cavity, enables the maintenance of an average temperature of 5.5 K in the cavity at a RF loss of 10 W, implying that the thermal stability and uniformity of the cavity has been significantly improved. Through the synergistic control of four metal film resistors, a cooling rate of 0.06 K/min near 18 K is realized, and the cavity temperature gradient is reduced to 0.17 K/m, which effectively improves the RF performance of the cavity. The maximum E a c c of the cavity reaches 3.42 MV/m, and the Q 0 is 1.1 × 109. An electromagnetic–thermal coupling simulation model for the superconducting cavity is established and is in good agreement with the experimental results. The simulation results show that the cavity with a Cu-spraying treatment and the thermal links of 5N Al can satisfy the E a c c of 10 MV/m under conduction cooling. [ABSTRACT FROM AUTHOR]

Two-dimensional SiC has been successfully prepared in an experiment (Phys. Rev. Lett2023,130, 076203), which provides new material candidates for power devices. In this work, molecular dynamics simulations are employed to investigate the tunable thermal transport properties of the SiC monolayer by grain boundaries (GBs). The thermal conductivity of SiC shows a pronounced dependence on the number and angle of the GBs interfaces. The inherent pentagon-heptagon structure at GBs induces atomic forces between atoms at the GBs, leading to a certain out-of-plane displacement of these atoms at the interface. Appropriate external strain can flatten the GB interface, thereby enhancing the thermal conductivity. However, further increasing the strain will decrease the thermal conductivity due to enhanced phonon anharmonicity. Moreover, the interface thermal conductance at the GBs also exhibits obvious dependence on the angle of GBs and temperature, which is explained by the atomic stress at the GBs interface. Furthermore, using phonon packet analysis, we found that the phonon interface scattering at GBs differs from that in the two-dimensional heterostructure. This finding reveals the intrinsic thermo-mechanical coupling mechanism governing thermal conduction in two-dimensional SiC, also suggesting its application in thermal management in the thermo-mechanical sensor. [ABSTRACT FROM AUTHOR]

As buildings evolve to meet the challenges of energy efficiency and indoor comfort, phase change materials (PCM) emerge as a promising solution due to their ability to store and release latent heat. This paper explores the transformative impact of incorporating PCM on the hygrothermal dynamics of multi-zone constructions. The study focuses on analyzing heat transfer, particularly through thermal conduction, in a wall containing PCM. A novel approach was proposed, wherein the studied system (sensitive balance) interacts directly with a latent balance to realistically define the behavior of specific humidity and mass flow rates. In addition, a numerical model implemented in MATLAB software has been developed to investigate the effect of integrating PCM on the hygrothermal balances inside the building. The obtained results indicate a consistent response in internal temperatures, specific humidity, and mass flow rates, with temperature differences ranging from 5°C to 13°C and a maximum phase shift of 13 h. In addition, the findings provided valuable insights into optimizing the design and performance of multi-zone constructions, offering a sustainable pathway for enhancing building resilience and occupant well-being. [ABSTRACT FROM AUTHOR]

Increasing stockpile of scrap rubber tires imposes a serious threat to the safety of surrounding ecological environment. Rubber particle of excellent thermal insulating properties with comparison of granular soils makes it an ideal candidate for developing sustainable construction materials. While thermal conduction behaviors of rubber-sand mixtures have not been clearly revealed. Several series of thermal probe tests were conducted on scrap rubber tire-sand mixtures with varied rubber contents, moisture contents, and dry densities. A predictive model was proposed by resorting to the artificial neural network technology to capture the thermal conductivity data. The results showed that an obvious decrease in thermal conductivity is taken after the addition of rubber, and the decreasing rate is related to moisture content of mixtures. The presence of pore water is beneficial to the improvement of thermal conductivity. The critical moisture content of investigated rubber-sand mixtures is approximately 8 %, further increase in moisture content leads to a faint increment of thermal conductivity. Rubber-sand mixtures of high dry density have good particle contact behaviors, exhibiting a high thermal conductivity value. The influences of rubber content, moisture content, and dry density on thermal conductivity are intertwined together that should be comprehensively analyzed. The developed model exhibits satisfactory accuracy for thermal conductivity prediction, as reflected by correlation coefficient higher than 85 % and relative error being controlled under 10 %. Additional study is recommended to evaluate the thermo-mechanical behaviors and durability of rubber-soil mixtures. The outcomes of this study provide one of available answers for reusing scrap rubber tire in engineering fields.

MoAlB, known for its exceptional oxidation resistance and anti-ablation properties, holds significant promise as a protective thin film for high-temperature components in military equipment. However, the high thermal conductivity of MoAlB poses a challenge to its compatibility with infrared stealth performance. In this study, structural defects were intentionally implanted into the MoAlB thin film by leveraging the amplified Kirkendall effect to hinder heat propagation. The results revealed that the MoAlB MAB phase thin film with a notable amount of edge dislocations was achieved by subjecting the post-annealed (Mo–B)/Al nanostructured multilayers (NMs) to an elevated temperature of 700 °C. The room-temperature resistivity of the thin film was 1.43 μΩ m. Furthermore, the infrared emissivity of the thin film was assessed within the mid-infrared wavelength range, ranging from 0.11 to 0.25. Simultaneously, the resulting thin film was found to possess a low thermal conductivity of 11.44 W m−1 K−1, consequently achieving excellent infrared stealth capability. [ABSTRACT FROM AUTHOR]

Herein, we report a cooling fabric with thermal conduction and radiative cooling capabilities through grafting hydroxylated boron nitride (BN-OH) nanosheets onto the surface of cotton fibers. The thermal conduction layer formed by BN-OH nanosheets enables the modified fabric with excellent thermal conductivity, which is 42% higher than that of the original cotton fabric. Resulting in the modified fabric exhibits great cooling power and increases the cooling setpoint temperature by 1 °C, which corresponds to reduced 11.2% indoor cooling energy consumption. Additionally, the Mid-infrared emissivity and solar reflectivity are increased to 90% and 70.4%, respectively, suggesting that wearing modified fabric under direct sunlight can enable the artificial skin to avoid overheating by 7.8 °C compared to bare skin. Moreover, the modified fabric also presents a considerable contact cool feeling, impressive wearability, and durability. We expect this work to present new insights for the design of personal thermal management textiles. [ABSTRACT FROM AUTHOR]

The stability of earth-rock dams is a critical factor in hydraulic engineering, directly impacting the safety of reservoirs and downstream regions. Seepage and thermal conduction, key physical processes influencing dam stability, are typically studied independently. However, as environmental changes become increasingly significant, the interaction between these processes--the coupling effect--cannot be overlooked. This paper delves into the coupled effects of seepage and thermal conduction in earth-rock dams, initially establishing a coupled control equation for the seepage and temperature fields. Subsequently, a numerical model for the seepage process under thermal conduction coupling effects is developed. Through precise simulation, this study aims to enhance the predictive capability of dam behavior under various environmental conditions, thereby providing a scientific basis for dam design and maintenance. The research identifies that existing models often neglect the impact of temperature on seepage characteristics and exhibit biases in parameter selection and boundary condition settings, leading to inaccurate simulations of dam behavior in complex environments. Therefore, the numerical model in this study, considering key parameters such as convective heat transfer coefficients, offers a more comprehensive assessment of the stability and functionality of earth-rock dams in real-world conditions. [ABSTRACT FROM AUTHOR]

The proliferation of high-power, highly informationized, and highly integrated electronic devices and weapons equipment has given rise to increasingly conspicuous issues about electromagnetic (EM) pollution and thermal accumulation. These issues, in turn, impose constraints on the performance of such equipment and jeopardize personnel safety. Carbon materials, owing to their diverse and modifiable structures, offer adjustable thermal and electric conductivity, rendering them highly promising for applications in fields such as thermal management and EM protection which have garnered extensive research and review. The pursuit of integrated device and equipment development has elevated the demand for multifunctional materials, prompting significant research into carbon-based composite materials that include both thermal management and EM protection functionalities. Notably, there are no relevant reviews on this topic at present. Consequently, this work consolidates research findings from recent years on carbon matrix composites exhibiting dual attributes of thermal management and EM protection. These attributes include thermally conductive electromagnetic interference (EMI) shielding materials, thermally insulating EMI shielding materials, thermally conductive EM wave (EMW) absorbing materials, and thermally insulating EMW absorbing materials. The paper elucidates the fundamental principles underpinning thermal conduction, thermal insulation, EMW absorbing, and EMI shielding. Additionally, it engages in discussions surrounding areas of contention, design strategies, and the functional properties of various material designs. Ultimately, the paper concludes by presenting the challenges encountered and potential research strategies about composites endowed with both thermal management and EM protection functionalities, while also envisaging the development of novel multifunctional EM protection materials. [ABSTRACT FROM AUTHOR]

The sluggish ion transport kinetics and poor interface compatibility are the major challenges for developing high‐performance solid‐state zinc metal batteries. Here, using the densified polyacrylonitrile/silicon dioxide (PAN‐SiO2) nanofiber membrane as a unique multifunctional mediator, a novel mediator‐bridged type of ultrathin (28.6 µm) polymer electrolyte that is rationally designed. The PAN/SiO2 /polyethylene oxide/Zn(OTf)2(PSPZ) polymer electrolyte is demonstrated to significantly enhance multiple kinetics. In addition to superior mechanical properties, the efficient thermal conductive effect endows it with good high‐temperature structural stability. Interestingly, a unique PAN skeleton‐locking‐anion‐enabled fast ion transport mechanism is uncovered to achieve a high Zn2+ migration number (0.71). Moreover, an efficient dendrite‐free Zn deposition guided by a flat dense SEI is demonstrated. In this case, highly reversible Zn metal anodes can be realized in the temperature range extending to −25–80 °C, as well as an impressive 4800 h‐cycle lifespan at the condition of 0.1 mA cm−2. Beyond that, wide‐temperature, high‐rate, durable PSPZ‐based solid‐state Zn/VO2 batteries are also successfully verified. This brand‐new concept of multiple‐kinetics‐enhanced polymer electrolyte design can provide a new perspective for developing all‐climate fast‐charging solid‐state batteries, including but not limited to zinc metal batteries. [ABSTRACT FROM AUTHOR]

In this work, steel fibers were used to strengthen the shells for investment casting while improving the shell's thermal conduction. The fibers were dispersed by ultrasound, and the influence of ultrasonic time on the dispersion of fibers in silica sol and effect of fibers dispersion in shell on the resulting green strength, fired strength, high-temperature self-load deformation and thermal conductivity of matrix were investigated. The results suggest that increasing the ultrasonic agitation time can effectively improve the dispersion of fibers in silica sol. When the ultrasonic power was 1000 W and the ultrasonic agitation time was 3 min, the fibers had been dispersed. When power became 1200 W, the fibers can be dispersed in only 2 min. And the green bending strength reached 3.26 MPa. The fired bending strength was 6.39 MPa. The high-temperature self-load deformation of the shell was 0.49%. The dispersion of fibers in the shell is an important factor affecting the performance of the shell. When the fibers are in the state of agglomeration, it cannot bond well with the shell and not play the role of bracing the shell. Meanwhile, when heat passes through the agglomerative fibers, it cannot be transferred out quickly, and even accumulate heat in the shell. When the fibers are in monofilaments state, the fibers in the shell can effectively resist the fracture load of the shell and enhance the bending strength of the shell through its debonding and pulling out with the matrix, as well as its own deformation and fracture. And, the mesh structure formed between the monofilaments can brace the shell and resist the deformation of the shell. Moreover, when the direction of heat transfer is parallel to the axial direction of the monofilaments, the heat can be quickly transferred to the outer wall of the shell through the monofilaments. [ABSTRACT FROM AUTHOR]

A reliable early detection of dew condensation can efficiently protect target solid surfaces from numerous negative effects such as surface fogging and corrosion. Achieving this goal beneficially requires a specially designed moisture sensor whose surface needs to be thermally identical with the target surface via a thermal conductor. However, the effect of the geometrical shape of the thermal conductor on the thermal conduction process is yet to be experimentally emphasized. In this study, we examined the potential detection of dew condensation events at our recently developed moisture sensor chip (MSC) under an effective control of its surface temperature via an attachment with Al-based thermal conductors. Precise and practical dew condensation detections were carried out in a multi-step and a one-step temperature-controlling modes, respectively. The experimental results revealed that the MSC response current (as a measure of dew condensation detection) increased when its surface temperature was dropped below the dew point. Moreover, the geometrical shape of thermal conductor attached to the backside of MSC can affect its thermal resistivity leading to a remarkable improvement in dew condensation detection. Therefore, it can be concluded that the geometrically designed thermal conductor can work effectively to minimize the temperature difference between MSC and target surface. This finding is believed to enable MSC to detect the target surface condition precisely in real time. [ABSTRACT FROM AUTHOR]

This research analyzes the influence of temperature changes on the vibration of single-walled carbon nanotubes (SW-CNTs) composite joined conical-cylindrical shells. The governing dynamic equations of temperature-dependent CNTs with initial thermomechanical stresses are established using the Love shell assumptions and classical shell theory. The initial thermomechanical stresses are derived from the linear membrane approach method. Two possibilities are assumed for the calculation of temperature change: a uniform temperature distribution and steady-state heat transfer by conduction through the thickness of the shell. The initial thermomechanical stresses are determined using the linear membrane approach. The generalized differential quadrature (GDQ) method is used to solve the equations after combining it with continuity conditions between the conical part and the cylindrical part and various boundary conditions. After validating the natural frequency and the different types of temperature distribution with the studies of other researchers, the effects of semi vortex of the cone, the volume fraction, and the type of distribution on the temperature rise are given as the results. The type of temperature distribution has the greatest influence among the parameters. [ABSTRACT FROM AUTHOR]

Temperature changes affect the nonlinear consolidation process in soils, and there is limited associated theoretical research. In this study, the governing equations for nonlinear consolidation and thermal conduction are developed, and a mathematical model for one-dimensional nonlinear thermal consolidation in saturated clay under the impeded drainage boundary is established, where the temperature-dependent compressibility and permeability are considered. Meanwhile, the finite-difference solutions for nonlinear consolidation and the analytical solutions for thermal conduction are obtained, respectively. Furthermore, the proposed model's reasonableness is verified by comparison with other theoretical models. Based on this, the impact of several factors on nonlinear thermal consolidation behaviors is investigated. With a rise in temperature increment (ΔT), the dissipation rate of excess pore water pressure (EPWP) accelerates in the later consolidation stage, and the final settlement becomes larger. In addition, the EPWP dissipation rate grows remarkably with an increasing impeded drainage boundary parameter (μ). In particular, the impeded drainage boundary can be degraded into a drainage boundary when the value of μ becomes large (e.g., μ = 100 m−1). Increasing preconsolidation pressure (pcR) results in a reduction in settlement, and the maximum values of EPWP decline with a rising linear loading time (tc). Overall, this study contributes to the accurate prediction of the nonlinear consolidation process taking the thermal effect into account. This study might provide a basis for the analysis of soil consolidation features in geotechnical projects that involve thermal effects, which have been growing in number in recent decades. For instance, an approach that combines thermal treatment with surcharge preloading has started to be employed for soft soil reinforcement. When this method is used in practical engineering projects, the changes in EPWP and settlement can be predicted based on the model developed in this study. In addition, this study reveals that increasing the temperature by 60°C can lead to an increase in the final settlement of saturated clay by approximately 25%, compared with ambient temperature treatment. Besides, compacted clay, which typically serves as a bottom engineering barrier, might be subject to consolidation deformation due to varied temperatures and external loading. The model presented could contribute to properly predicting the porosity change in compacted clay under this scenario. [ABSTRACT FROM AUTHOR]

In physical engineering, a rock surface, whether naturally or artificially formed, is rough. When irradiating rocks, microwaves produce reflections and diffractions on the surface of rough rocks, which significantly affect the absorption of microwave energy by rocks, thus influencing the result of microwave irradiation. In order to explore the influence of rough rock surfaces on the effect of microwave-assisted rock breaking, microwave irradiation tests were carried out on basalt samples with different values of roughness to test the temperature and P-wave velocity of the samples before and after microwave irradiation. Numerical test methods were used to systematically study the influence of rough rock surfaces on microwave irradiation. The results show that, under the same microwave irradiation conditions, the effect of microwave irradiation on rough surface basalt is more significant than that of flat surface basalt. The surface temperature distribution range of flat surface specimens is narrow, the surface temperature range of rough surface specimens is wider and more inhomogeneous, and the maximum surface temperatures of rough surface specimens are much higher than those of flat surface specimens. After irradiation, new macroscopic cracks were generated on the surface of the samples, and the crack propagation of the rough surface samples was more obvious. The decrease in P-wave velocity before and after the irradiation of flat surface samples is small, and that of rough surface samples is larger. The main factors affecting the effect of microwave irradiation on the rough surface are the refraction and reflection of electromagnetic waves, heat conduction, and stress concentration on the surface. [ABSTRACT FROM AUTHOR]

1-3 piezoelectric composites have been widely used in transmitting transducers, medical devices, navigation, aerospace, etc. However, due to poor thermal conduction of inside piezoelectric composites, performance degradation and service life shortening of transmitting transducers are easily caused while working under high-power or continuously operated states. In this paper, a solution is provided by designing and creating highly efficient thermally conductive paths in 1-1-3 piezoelectric composite. This novel design resulted in two-fold increase in heat dissipation rate compared with traditional 1–3 piezoelectric composites, while maintaining high piezoelectric properties. Furthermore, we designed and fabricated an efficient heat dissipation transducer (EHDT) with the novel 1-1-3 piezoelectric composite as the core material, which can relief heat accumulation effectively compared with conventional transducers (CT). The EHDT can achieve three times more power output than the CT at the same temperature threshold of 90 °C.

A liquid helium-free cryostat for radio frequency (RF) test of the superconducting cavity is designed and constructed. Gifford-Mcmahon (G-M) cryocoolers are used to provide cooling capacity, and the heat leakage at 4 K is less than 0.02 W. Vertical and horizontal tests of two Nb3Sn cavities are carried out in the cryostat with different surface treatments outside the cavities. Both of the cavities achieve stable continuous wave (CW) operation. A novel treatment, which cold-sprayed a 3.5 mm thick Cu layer onto the outside of the cavity, enables the maintenance of an average temperature of 5.5 K in the cavity at a RF loss of 10 W, implying that the thermal stability and uniformity of the cavity has been significantly improved. Through the synergistic control of four metal film resistors, a cooling rate of 0.06 K/min near 18 K is realized, and the cavity temperature gradient is reduced to 0.17 K/m, which effectively improves the RF performance of the cavity. The maximum Eacc of the cavity reaches 3.42 MV/m, and the Q0 is 1.1 × 109. An electromagnetic–thermal coupling simulation model for the superconducting cavity is established and is in good agreement with the experimental results. The simulation results show that the cavity with a Cu-spraying treatment and the thermal links of 5N Al can satisfy the Eacc of 10 MV/m under conduction cooling.

Heat recovery from an enhanced geothermal system (EGS) is a complex process involving heat transport in both fracture networks and rock formations. A comprehensive understanding of and the ability to model the underlying heat transport mechanisms is important for the success of EGS commercialization but remains challenging in practice due to the generally insufficient characterization of EGS reservoirs. In the present study, we analyze an extensively monitored intermediate-scale EGS field experiment performed in a well-characterized testbed. The high-resolution, high-quality measurements from the field experiment enable the development of a high-fidelity model incorporating a well-constrained fracture network. Based on the field experiment, we investigate the complex heat transport processes in an EGS-relevant environment and validate the capability of a numerical approach in simulating these inherently coupled heat transport processes. A series of numerical simulations were performed to study the effects of different heat transport mechanisms, including thermal convection with fracture flow, thermal conduction in rock formations, and the Joule-Thomson effect. The agreement of thermal responses between field measurements and simulation results indicates that our numerical approach can appropriately model the heat transport processes pertaining to heat recovery from EGS reservoirs.

Heat recovery from an enhanced geothermal system (EGS) is a complex process involving heat transport in both fracture networks and rock formations. A comprehensive understanding of and the ability to model the underlying heat transport mechanisms is important for the success of EGS commercialization but remains challenging in practice due to the generally insufficient characterization of EGS reservoirs. In the present study, we analyze an extensively monitored intermediate-scale EGS field experiment performed in a well-characterized testbed. The high-resolution, high-quality measurements from the field experiment enable the development of a high-fidelity model incorporating a well-constrained fracture network. Based on the field experiment, we investigate the complex heat transport processes in an EGS-relevant environment and validate the capability of a numerical approach in simulating these inherently coupled heat transport processes. A series of numerical simulations were performed to study the effects of different heat transport mechanisms, including thermal convection with fracture flow, thermal conduction in rock formations, and the Joule-Thomson effect. The agreement of thermal responses between field measurements and simulation results indicates that our numerical approach can appropriately model the heat transport processes pertaining to heat recovery from EGS reservoirs.

A multifunctional microwave absorber with high thermal conductivity for 5G base station packaging comprising silylated GO/FeSiAl epoxy composites were fabricated by a simple solvent-handling method, and its microwave absorption properties and thermal conductivity were presented. It could act as an applicable microwave absorber for highly integrated 5G base station packaging with 5G antennas within a range of operating frequency of 2.575–2.645 GHz at a small thickness (2 mm), as evident from reflection loss with a maximum of −48.28 dB and an effective range of 3.6 GHz. Such a prominent microwave absorbing performance results from interfacial polarization resonance attributed to a nicely formed GO/FeSiAl interface through silylation. It also exhibits a significant enhanced thermal conductivity of 1.6 W/(mK) by constructing successive thermal channels. [ABSTRACT FROM AUTHOR]

On maritime vessels, external factors such as explosions, collisions, and grounding can cause the emulsification of lubricating oil by seawater pollution, which can affect the lubrication of a ship's thrust bearing. To explore the influence of the mixed emulsification of lubricating oil and seawater on the lubrication performance of thrust bearings, this study conducted an emulsification experiment, from which the viscosity equation of the oil–water mixture was obtained. A thermal hydrodynamic model (THD) of bearings considering oil–water mixed emulsification was established, and the Finite Difference Method (FDM) was used for analysis. The results show that according to the characteristics of the manifold, the mixture is divided into water-in-oil (W/O) and oil-in-water (O/W). In the W/O flow with higher viscosity, the film thickness becomes higher, but the power loss increases. In the O/W manifold with low viscosity, the thin film easily causes mixed friction. In the demulsification stage of the mixed liquid, the thickness loss of the film is huge, and the collision between the thrust-bearing pad and the inference plate may cause the pad to be ablated. The influence of specific heat capacity on temperature is greater than the temperature rise caused by viscosity. [ABSTRACT FROM AUTHOR]

Maximizing thermoelectric efficiency is typically addressed as identical to minimizing parasitic thermal conduction. Such an approach relies on the assumption that the adopted strategy mainly affects phonons, leaving electrons intact, and is not justified in many cases of non-uniform nanostructures such as width-modulated nanowaveguides, where both electrons and phonons are significantly affected by width modulation. Here, we address the question of maximizing the thermoelectric efficiency of this class of metamaterials by exploring the effect of the modulation extent on both electron and phonon transport. We investigated the effect of increasing modulation degree on the thermoelectric efficiency, considering the cases of (a) a two-QD modulation and (b) multiple-QD modulations in periodic and aperiodic sequences. We show that the thermoelectric efficiency depends on the coupling between the modulation units and the interplay between periodicity and aperiodicity in the modulation profile. We reveal that the maximization of the thermoelectric power factor is for periodic width-modulation, whereas the maximization of the thermoelectric efficiency is for aperiodic width-modulation profiles that form quasi-localized states for electrons. Our work provides new insight that can be used to optimize width modulation for maximum thermoelectric efficiency. [ABSTRACT FROM AUTHOR]

The exergy concept originates from the field of static thermodynamics and expresses the maximum theoretically recoverable mechanical work from a system while it evolves toward its dead thermodynamic state. It accounts for both mechanical and thermal mechanisms, and it allows to separate reversible and irreversible losses in the system's transformations. The physical insight provided by this concept motivated the development of an exergy-based performance evaluation method in the field of aerodynamics. The resulting formulation has the advantage of being independent of the feasibility of a drag/thrust breakdown (ambiguous for highly integrated engine concepts) and includes thermal effects in the performance metrics. It, however, relies on an adapted definition of exergy, in particular involving a dead state in motion. This adapted definition is not trivial and raises theoretical concerns due to fundamental thermodynamic properties of exergy not being always satisfied. This paper aims at proposing a corrected version of this definition that ensures that the fundamental properties of exergy are respected. First, the exergy concept is presented alongside the concerns raised by its original adaptation, which, to the best of the authors' knowledge, has been used in all exergy-based flowfield analyses in the field of applied aerodynamics. Then, an unsteady exergy balance is derived in the geocentric reference frame (in which there are no ambiguities in the definition of exergy) and then transformed to a reference frame in translation. The corrected adaptation of the exergy definition for aerodynamics applications is extracted from this transformation and the impact on the exergy balance is analyzed. [ABSTRACT FROM AUTHOR]

Double-sided packages for heat dissipation are an efficient thermal management mechanism for power semiconductor devices. A fan-out panel-level packaging (FOPLP), as one of the double-sided forms, exhibits excellent electro–thermal characteristics and provides low stray inductance and thermal resistance. Besides, the temperature at each point within the structure is closely related to its thermo–mechanical properties and device reliability. However, thermal resistance is limited in describing the temperature distribution. Finite element analysis (FEA) requires time-consuming construction of 3D models. Therefore, to depict the temperature distribution of FOPLP rapidly and accurately, a numerical heat transfer model was proposed for the double-sided package structure. The solution was obtained from the steady-state thermal balance Laplace equation using the separation of variables method. Several boundaries were analyzed to determine the specific parameters in the model. Finally, the temperature field predicted by the derived numerical model was compared with finite element simulation results. The proposed model was consistent with both Silicon (Si) and Silicon Carbide (SiC) FOPLP structures within the error of 15 % at the center of the device, which verified the validity and accuracy of the numerical model for double-sided heat dissipation. The proposed models and results could contribute to the development of effective thermal design tools for double-sided thermal power modules.

The degradation of Nafion membrane easily occurs after a long run of proton exchange membrane fuel cell. Graphene-oxide (GO) is regarded as an ideal material to form composite membrane. In this work, a multistate empirical valence bond (MS-EVB) method and molecular dynamics method are employed to investigate the effect of GO on transport and solvation characteristics of protons in the degraded hydration membrane. The hydrophilic cluster and its connectivity are analyzed. The interaction between GO, Nafion membrane and water molecules is discussed. The influence of GO on the thermal conduction of Nafion membrane is also evaluated. The results demonstrate that with the addition of GO, the water cluster connectivity of Nafion membrane becomes better. The distribution of hydronium ions and membranes in the water is more uniform, which increases the proton conductivity. The larger GO may not interact well with water molecules, but promotes the thermal conductivity of degraded Nafion membrane more obviously. • MD simulation is conducted for degraded membrane with graphene oxide. • Impact of graphene oxide size on degraded membrane is analyzed. • Influence of graphene oxide on thermal conduction of membrane is evaluated. [ABSTRACT FROM AUTHOR]

The arrangement of a water thermal accumulator (WTA) containing phase change materials (PCM) is presented and analyzed. The hot or cool water is used as a working body. The accumulator contains two concentric cylindrical tubes. The inner tube is used for hot or cool water flowing, while the volume between the inner and outer tubes is filled with PCM. The thermal energy in the accumulator is stored as a result of flowing the hot water through the inner tube due to the phase transition in PCM. This accumulated energy can be extracted from PCM as a result of flowing the cool water through the inner tube. For the enhancement of the thermal conduction coefficient, the PCM is doped with the nanocarbon particles having a thermal conductivity coefficient exceeding that of PCM by 4–5 orders of magnitude. The thermal balance of the accumulator is calculated on the basis of the solution of the time-dependent heat conduction equation by taking into account the heat absorbed and released as a result of the phase transition as well as the convection thermal exchange in the melted PCM. The calculation results determine the interconnection between the thermal conductivity of PCM and the characteristic time of thermal exchange between PCM and the working body. The calculations indicate that the characteristic thermal exchange time decreases as the thermal conduction coefficient enhances, so that the dependence becomes close to saturation at the thermal conductivity coefficient of about 5 W/m K. Such a coefficient can be reached by doping the paraffin-based PCM with a reduced graphene oxide at a content of about 2% (weight). [ABSTRACT FROM AUTHOR]

Aligning the European Union goals for climate neutrality by 2050 and the ambition for carbon equivalent emissions reduction to almost half by 2030 demands the exploration of alternative decarbonisation pathways. Energy consumption across all sectors is identified as a crucial contributor to this challenge, with a number of legislative and regulatory frameworks and commitments to be introduced every year. In response to these trends, the concept of exploiting a building's thermal mass through the integration of phase change materials (PCMs) enhances the ability of building elements to reserve and deliver large amounts of energy during phase transitions. However, the incorporation of PCMs into building elements requires the thorough understanding of their thermal behaviour. This study evaluates and predicts the thermophysical properties of mineral particles carrying PCMs and coated with a cementitious layer able to be utilised as fillers in construction applications. By employing deep learning and predictive modelling techniques, the numerical data-driven model developed in this paper enhances accuracy and efficiency in property estimation and prediction, facilitating material selection, system design, and optimisation. A model in a MATLAB simulation environment is presented, evaluating and predicting the thermophysical properties of semi-organic particles able to enhance building envelope thermal mass as a hybrid energy storage solution. These findings show the time needed for a building block to undergo cooling, demonstrating a clear upgrade in the thermal discharge of the walls. Substituting traditional EP with PCM-enhanced EP leads to a minimum reduction of 1 °C per hour in the discharge rate, thereby extending the comfort duration of indoor spaces without necessitating additional space heating. These models offer the potential for assessing diverse material compositions and usage scenarios, offering valuable insights to aid decisions in optimizing building energy efficiency. [ABSTRACT FROM AUTHOR]

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The purpose of this study is to determine the thermal conductance of concrete hollow bricks, which is necessary for the evaluation of the energy efficiency of a building. The three varieties of hollow concrete bricks that are often used to build walls in Morocco are the subject of this study. A computational model created using the finite volume method is used to evaluate the conjugate heat transfer through concrete hollow bricks. According to the results, the use of hollow brick type Ah3 reduces the heat flux by approximately 86% compared with type Ah1. It is undeniable that hollow bricks type Ah3 with a thermal conductivity of 1 W/m K can improve the thermal characteristics of building walls. [ABSTRACT FROM AUTHOR]

The oil film separates the shaft-bearing system to reduce the frictional force of contact surfaces with large temperature variations owing to thermal conduction. Multiple impact factors seriously affected the lubrication behavior of the bearing during actual working process. An applicable model regarding the lubrication analysis of a hydrodynamic-static hybrid bearing with deep-shallow chambers is proposed and validated with published literature. The lubrication behavior includes film pressure, load capacity, bearing stiffness and flow rate is numerically calculated with centered finite difference method by solving the Reynolds equation. The influence of film thickness and working temperature are considered, over a range of eccentricity ratio. Moreover, the temperature variation caused by thermal conduction is analyzed in details. To investigate the influence of thermal conduction on the lubrication behavior, the results show that the load capacity, bearing stiffness, friction power, and flow power significantly decline with the consideration of thermal conduction. This study proposes an accurate model that is helpful for the design of hydrodynamicstatic hybrid bearings with deep-shallow chambers under low rotational speed, heavy load, and high temperature conditions. [ABSTRACT FROM AUTHOR]

Typical application forms of thermal conduction and EMW absorption integrated polymer composites. [Display omitted] Polymer composites have essential applications in electronics due to their versatility, stable performance, and processability. However, with the increasing miniaturization and high power of electronics in the 5G era, there are significant challenges related to heat accumulation and electromagnetic wave (EMW) radiation in narrow spaces. Traditional solutions involve using either thermally conductive or EMW absorbing polymer composites, but these fail to meet the demand for multi-functional integrated materials in electronics. Therefore, designing thermal conduction and EMW absorption integrated polymer composites has become essential to solve the problems of heat accumulation and electromagnetic pollution in electronics and adapt to its development trend. Researchers have developed different approaches to fabricate thermal conduction and EMW absorption integrated polymer composites, including integrating functional fillers with both thermal conduction and EMW absorption functions and innovating processing methods. This review summarizes the latest research progress, factors that affect performance, and the mechanisms of thermal conduction and EMW absorption integrated polymer composites. The review also discusses problems that limit the development of these composites and potential solutions and development directions. The aim of this review is to provide references for the development of thermal conduction and EMW absorption integrated polymer composites. [ABSTRACT FROM AUTHOR]

Over the past years, multiple fire accidents have been witnessed in ancient wooden buildings around the world, thereby causing major losses of cultural relics and social impact. Because of the damage of the ancient wood structure caused by the problem of aging, this enables its thermal conduction properties to change. For this reason, the way how the fire spread also changes. This study was based on the concept that the environmental characteristics of ancient building wood subjected to long-term natural aging, and so the artificially accelerated and alternate process of dry and wet aging method used for wood materials was determined. To that end, the common wood types of ancient buildings were selected as the research objects, so as to obtain the varying degrees of dry and wet aging wood materials. Furthermore, the characteristics of pores on the outer surface of aging wood materials were analyzed through the experiments conducted with a scanning electron microscope. Through the thermophysical property test, the variation law of thermophysical property parameters of aging wood materials with temperature was appraised, and the influence mechanism of the alternate process of dry–wet aging on the thermal conductivity of wood was revealed. The results demonstrated that the cell wall of wood underwent plastic deformation during the alternate process of dry and wet aging. Also, the local wood structure collapsed to different degrees, and so the surface tear degree increased. Because of the joint influence of the elastic stress and the mechanical adsorbed creep stress generated in the alternate process of dry and wet aging, the surface pore deformation of wood was periodic and dampened with the aging degree, so that the heat conduction properties of wood all manifested the change law of sinusoidal damping with the deepening of the aging degree. It is hoped that the research results could provide a theoretical basis for both the early prediction about and the accurate warning of fire spread in ancient wooden structures. [ABSTRACT FROM AUTHOR]

Radio jets and the lobes they inflate are common in cool-core clusters and are known to play a critical role in regulating the heating and cooling of the intracluster medium (ICM). This is an inherently multi-scale problem, and much effort has been made to understand the processes governing the inflation of lobes and their impact on the cluster, as well as the impact of the environment on the jet–ICM interaction, on both macro- and microphysical scales. The developments of new numerical techniques and improving computational resources have seen simulations of jet feedback in galaxy clusters become ever more sophisticated. This ranges from modeling ICM plasma physics processes such as the effects of magnetic fields, cosmic rays, and viscosity to including jet feedback in cosmologically evolved cluster environments in which the ICM thermal and dynamic properties are shaped by large-scale structure formation. In this review, we discuss the progress made over the last ∼decade in capturing both the macro- and microphysical processes in numerical simulations, highlighting both the current state of the field, as well as the open questions and potential ways in which these questions can be addressed in the future. [ABSTRACT FROM AUTHOR]

Though thermoresponsive lower critical solution temperature (LCST) hydrogels have attracted intense attention to be applied in smart windows, less efforts are paid on the LCST effect on the heat transfer process. Herein, the research mainly focuses on heat transfer process of thermoresponsive PNIPAm hydrogels. It is the first time reported that LCST behaviors can decrease thermal conductivity upon heating process. To be utilized as a smart window, thermal conduction flux is investigated yet the thermal conduction energy occupies little to manage the thermal transfer process in a model house. It is found that radiation thermal transfer predominates the heat transfer process for PNIPAm‐based smart windows. These results are meaningful to provide basic data for energy transfer in using thermoresponsive hydrogels. [ABSTRACT FROM AUTHOR]

Wide‐bandgap, layered hexagonal boron nitride (h‐BN) possesses excellent electrical insulation and ultrahigh thermal conductivity simultaneously, offering a perfect candidate for the growing demands of heating dissipations in modern chip industries and power electronics. Hybrids of h‐BN with polymers fulfill the thermal management materials (TMMs) requirement of flexibility, while the composite poses severe challenges in the interfacial bonding and excess thermal resistance. To date, the practical bonding between h‐BN intrinsic surfaces and polymer matrices remains elusive. This work reports on the effective alignment of h‐BN micro‐lamellae by introducing nitrogen‐atoms‐containing polymers as inter‐lamellae bridging mediums. Based on theoretical calculations the hydrogen bonding between polymer chains and the BN surface is revealed by differential charge densities mapping. It is shown experimentally that the neuron‐like polymer bundles strongly bonding surfaces of two neighboring h‐BN platelets as direct, microscopic evidence of the structure models. An extra alignment of h‐BN induced by this strong interfacial interaction leads to a higher degree of h‐BN stacking order, boosting the thermal conduction by eight times. These results reveal one unprecedented method to non‐covalently functionalize the h‐BN surface and expand the TMMs family in the dimension of the filler size, paving the way for exploring the larger‐sized ceramic TMMs. [ABSTRACT FROM AUTHOR]

A new type of interface using a conduction hot spot reflecting the user's intention is presented. Conventional methods using fingertips to generate conduction hot points cannot be applied to those who have difficulty using their hands or cold hands. In order to overcome this problem, an exhaling interaction using a hollow rod is proposed and extensively analyzed in this paper. A preliminary study on exhaling interaction demonstrated the possibility of the method. This paper is an attempt to develop and extend the concept and provide the necessary information for properly implementing the interaction method. We have repeatedly performed conduction hot-point-generation experiments on various materials that can replace walls or screens to make wide use of the proposed interfaces. Furthermore, a lot of experiments have been conducted in different seasons, considering that the surface temperature of objects also changes depending on the season. Based on the results of an extensive amount of experiments, we provide key observations on important factors such as material, season, and user condition, which should be considered for realizing contactless exhaling interfaces. [ABSTRACT FROM AUTHOR]

A rotary-concentrating device for thermal conduction is constructed to control and guide thermal energy transmitting in elastic plates. The designed device has the ability of concentrating for thermal conduction and controlling the processes of thermal diffusion in a plate. The multilayered isotropic material properties of the rotary-concentrating device are derived based on the transformation and rotary medium method and a rotation parameter to control the thermal diffusion process is introduced. The efficiency of the rotary-concentrating device for thermal conduction is verified. Stability of temperature fields in a plate with the rotary-concentrating device is analyzed to study the performance of rotary-concentrating. Numerical examples show that the constructed rotary-concentrating device for thermal conduction can effectively rotate and focus on the thermal energy into the device for a wide range of diffusion temperatures, which can enhance the thermal conduction. Therefore, this study can provide a theoretical support for potential applications in fields of energy harvesting and thermal conduction control. [ABSTRACT FROM AUTHOR]

We present a first-principles-based electron-temperature model that can be used in atomistic calculations. The electron–phonon coupling coefficient in the model is derived from the density of states as a function of electron temperature, and the thermal conductivity of tungsten from our model shows significant improvement over the baseline atomistic calculations in which only ion-thermal contribution to the thermal conductivity is available. The correction to the thermal conductivity also changes damage cascades as cascades cool down more rapidly within our model. The mobility of defects is consequently reduced, leaving more residual damage than the predictions without an electron-temperature model.