Search Results (341)

To address the issues of local high temperatures, thermal stress concentration, and the susceptibility to spalling of homogeneous ceramic coatings in disc brakes under high-frequency thermal–mechanical cyclic loading, this paper proposes a surface design scheme incorporating a functionally graded material (FGM) coating along the thickness direction. A three-dimensional thermal frictional contact model of a graded coated brake disc with continuously varying material properties (silicon carbide/gray cast iron) along the thickness direction is established by developing user subroutines on the Abaqus finite element platform. The effects of exponential, power-law, and trigonometric gradient distributions on the transient temperature and stress fields are systematically compared. The results indicate that the high thermal conductivity silicon carbide coating significantly reduces the disc surface temperature; however, a homogeneous coating induces interfacial thermal stress concentration due to a sudden stiffness mismatch. The graded design effectively mitigates the stress concentration through a smooth transition of material properties. Taking the power-law function (n = 1.5) as an example, this design not only significantly reduces the maximum disc surface temperature but also limits the residual equivalent stress at the end of braking to 245 MPa, which is approximately 24.8% lower than that of the homogeneous coating (325.8 MPa). The study demonstrates that the gradient function exerts a stronger regulatory effect on the stress field than on the temperature field, meaning the two cannot be simultaneously optimized. Nevertheless, exponential functions and power-law functions with small exponents can achieve a favorable balance of thermal–mechanical performance. This research reveals the mechanism by which thickness-direction gradient distributions regulate thermal–mechanical coupling behavior, providing a theoretical basis for the gradient design of thermal fatigue-resistant friction components. Full article

Auxiliary bearings in vertical magnetic suspension systems can suffer thermal damage and impact-induced failure during rotor drop events caused by instability. This study aims to clarify the coupled effects of collision, frictional heating, and transient heat transfer on auxiliary bearing response. Dynamic, thermodynamic, and finite element models were established to analyze impact behavior, frictional heating, and temperature-field evolution, and were validated using rotor-drop measurements of impact force, rotor displacement, and outer-ring temperature together with post-test damage observations. The results show that severe impact and friction rapidly convert rotor kinetic energy into thermal energy, producing a non-uniform temperature field in the auxiliary bearings. The highest temperature occurs in the inner ring, followed by the rolling elements and outer ring, with peak temperatures of 169.59 °C, 154.66 °C, and 94.79 °C, respectively. Owing to gravity, gyroscopic motion, and rotor inclination during drop, the upper auxiliary bearing experiences greater impact loads, a faster speed increase, and a higher peak temperature rise than the lower bearing. Experimental evidence, including thermal discoloration, wear positions, and component damage, agrees with the simulated high-temperature regions. These results support thermal-shock-resistant design, structural optimization, and operational safety assessment of auxiliary bearings. Full article

Energy pile groups present a dual-functional solution for structural support and geothermal energy utilization, yet their thermo-mechanical interactions with conventional piles remain insufficiently understood. This study establishes a 3D transient finite element model incorporating thermo-hydro-mechanical coupling to investigate thermal interference and differential settlement in hybrid pile groups under seasonal thermal loading. Systematic parametric analyses of pile length (10–30 m), diameter (1–2 m), and spacing (2D–3D) reveal two key findings: (1) Thermal perturbations in adjacent conventional piles exhibit distance-dependent attenuation characteristics, with measurable temperature variations (1–4 °C) observed within 4D spacing distances; (2) Differential settlement patterns demonstrate significant dependence on thermal operation modes, where heating cycles induce upward thermal stresses while cooling enhances consolidation settlement. The numerical framework is validated against field monitoring data and benchmarked with COMSOL 5.6/ABAQUS 6.14 simulations. Through optimized pile arrangements and spacing configurations, we demonstrate effective mitigation strategies for thermal interference and structural deformation, providing key guidance for the design of geothermal-energy-integrated foundation systems. Full article

Exploitation of deep (>4000 m) tight geothermal reservoirs is constrained by low native permeability and premature thermal breakthrough, limiting sustainable heat recovery. Here, we investigate THM (thermo–hydro–mechanical) controls on fluid flow and heat transport during cold-water reinjection in deep tight sandstone reservoirs through an integrated framework linking two-dimensional mechanistic analysis with three-dimensional field-scale modeling. A two-dimensional thermo-poroelastic model reveals that strong thermal contrasts induced by cold-fluid injection cause contraction of the rock framework and transient pore-space dilation under confinement, producing short-term permeability enhancement. This process alters local flow capacity and redirects early cold-front migration, with persistent impacts on subsequent heat transport. Field-scale simulations further quantify the coupled effects of well spacing and reinjection temperature on thermal breakthrough, defined as a 1 °C decline in production-well temperature. Increased well spacing delays cold-front arrival and significantly retards breakthrough, whereas lower reinjection temperature enhances early heat extraction but accelerates convective transport, leading to earlier breakthrough. The combination of thermally enhanced permeability and intensified convection promotes preferential flow channels, increasing breakthrough risk. Balancing thermal-breakthrough delay against the heat-extraction driving force, the simulations delineate a favorable engineering window for the investigated conditions and clarify how cooling-sensitive permeability evolution affects preferential flow and reservoir-scale thermal response. Full article

In Czochralski (CZ) silicon growth, controlling the ratio of crystal growth velocity to axial temperature gradient ($V/G$) is critical for defect management. However, the $V/G$ value is difficult to measure in real-time. Furthermore, it exhibits strong multivariate coupling and extreme non-stationarity under complex thermal fields. While standard deep learning models like LSTM are used for soft sensing, they often misidentify high-frequency hardware noise as true process dynamics, causing severe error amplification in multi-step predictions. To address this, we propose a Dual Information Filtering LSTM (DIF-LSTM). It utilizes an external context-aware mechanism to screen long-term steady-state redundant information and an internal denoising gate coupled with the LSTM input to explicitly block transient high-frequency noise. Furthermore, a confidence evaluation branch and residual decay fusion ensure stable multi-step forecasting. Experimental results an industrial-scale experimental silicon single crystal furnace show DIF-LSTM achieves superior accuracy, obtaining an $R^2$ of 0.9935 and a Mean Squared Error of $1.60\times {10}^{-6}$ at a 3-step horizon. Even at a 9-step horizon, it maintains an $R^2$ of 0.9422, significantly outperforming the baseline IF-LSTM (0.8498). Full article

Semi-batch nitration processes involve substantial heat release, and local reactant enrichment may induce hot-spot formation and increase the risk of thermal runaway. However, global indicators such as the volume-averaged reactor temperature cannot adequately characterize local thermal hazards or quantitatively describe the redistribution of reaction heat under practical flow conditions. In this study, a three-dimensional transient computational fluid dynamics (CFD) model coupled with reaction kinetics, fluid flow and heat transfer was established for the semi-batch nitration of 4-chlorobenzotrifluoride (4-Cl-BTF). On this basis, a CFD-based quantitative framework was proposed to characterize local heat distribution and hot-spot evolution directly from the predicted temperature field. The roles of feed location, stirring speed, feeding time, and impeller type were then investigated. The results show that hot-spot evolution is dominated by the spatial mismatch between local heat generation and heat transport rather than by the global thermal response alone. Insufficient mixing and excessive instantaneous feed flux intensified local reactant enrichment, thereby promoting early hot spot formation. In contrast, feed location and impeller type mainly affected the migration and connectivity of hot spots by reshaping the internal circulation pathway. The present work provides an initial quantitative description of hot spot propagation under realistic impeller-driven flow conditions, and offers a spatially resolved basis for local thermal risk assessment and operating condition optimization in semi-batch nitration reactors. Full article

To address the time-consuming and labor-intensive procedures associated with traditional approaches for evaluating the integrated burning rate of wire-embedded propellants in solid rocket motors (SRMs), this study proposes an efficient and reliable prediction method. This new method is based on an improved burning-rate–initial-temperature correlation, achieved through Abaqus-Python secondary development that enables fully automated geometric modeling, transient heat-transfer analysis, and temperature-field extraction for wire-embedded propellants. The relative error between the present method and the experimental results is less than 5%. The accuracy and engineering applicability of the present method are verified. The effects of the material parameters and wire diameters on the integrated burning rate is investigated. The results indicate that wires of different materials exhibit substantial variations in burning-rate enhancement efficiency, with smaller diameters and higher thermal diffusivity producing stronger enhancement effects. When the specific heat capacity and density are held constant, the integrated burning rate increases monotonically with the wire’s thermal conductivity, though the growth trend gradually approaches saturation. In contrast, the influences of the wire’s specific heat capacity and density are comparatively weak. The integrated burning rate prediction framework developed in this study demonstrates strong versatility and scalability. It enables rapid performance evaluation of propellants embedded with wires of various sizes and thermophysical properties, providing valuable theoretical guidance and practical tools for the design and optimization of wire-embedded solid rocket motors. Full article

To address heat accumulation, localized hot spots, and non-uniform temperature distribution in large-capacity lithium iron phosphate energy storage battery modules under high ambient temperature and high-rate charge/discharge conditions, this study proposes a fin-enhanced phase change material (PCM)-air hybrid thermal management structure for a 100 Ah prismatic lithium iron phosphate battery and a 2P18S energy storage battery module. First, the battery thermal model is validated using single-cell experimental data reported in the literature. Subsequently, a three-dimensional transient fluid–solid coupled heat transfer model is established by considering transient battery heat generation, PCM solid–liquid phase change, air-side flow and heat transfer, and temperature-dependent thermophysical properties. User-defined functions are employed to implement the transient heat source and temperature-dependent material properties. Under identical boundary conditions, the thermal management performances of three configurations, namely Fin-Air, PCM-Air, and Fin-PCM-Air, are compared. The effects of ambient temperature (20 °C, 25 °C, and 30 °C) and inlet air velocity (1 m/s, 2 m/s, and 3 m/s) on the maximum module temperature, temperature uniformity, PCM liquid fraction evolution, and flow field distribution are quantitatively analyzed. The results show that, compared with the Fin–Air system without PCM and the PCM-Air system without fins, the Fin-PCM-Air configuration reduces the maximum module temperature by 1.57% and 0.25%, respectively, at an ambient temperature of 30 °C and an inlet air velocity of 3 m/s. After four charge–discharge cycles, the peak maximum temperature of the module is approximately 38.56 °C, and the peak maximum temperature difference remains below 3.6 K, indicating good temperature uniformity and latent heat buffering capability. In addition, the air velocity trade-off analysis indicates that increasing the inlet air velocity can improve cooling performance but also increases the air-channel pressure drop and fan power consumption. Therefore, the Fin-PCM-Air structure is more suitable for high-thermal-load conditions, and its practical application should comprehensively consider cooling benefits, additional mass, manufacturing cost, and long-term reliability. This study provides a reference for the design and engineering application of hybrid thermal management structures for large-capacity energy storage battery modules. Full article

During heavy oil development, the gathering and transportation of low-temperature wellhead-produced fluids are often accompanied by high viscosity, pipe-wall deposition, and high flow resistance, threatening the continuous and stable operation of gathering systems. Existing studies on wellhead heating mainly focus on overall steady-state heating performance, while variable-flow heat transfer and start–stop control in local heating systems remain insufficiently explored. This study aims to evaluate the steady-state heating capacity, transient thermal response, and start–stop control performance of a localized electric heating section under variable-flow conditions. A 3D fluid–solid-coupled heat-transfer model of the heating element, pipe wall, and internal fluid was developed using COMSOL Multiphysics. The steady-state temperature field, transient heating and cooling behavior, and start–stop control characteristics were analyzed under different flow rates. The results show that, at a heating power of 15 kW and a flow rate of 20 m³/d, the maximum outer-wall temperature reached 564 K, and the average outlet fluid temperature reached 308.83 K, indicating effective heating performance. As the flow rate increased from 10 m³/d to 30 m³/d, the maximum pipe-wall temperature and fluid temperature rise both decreased, whereas the average fluid-side heat-transfer coefficient increased from approximately 700 W/(m²·K) to 1800 W/(m²·K), demonstrating enhanced convective heat transfer. Under a dual-threshold control strategy of 463.15–483.15 K, the system maintained the target temperature near 473.15 K under all tested conditions, while the load factor increased from 37.83% to 86.15%. These findings provide theoretical references and engineering support for optimizing power configuration and improving temperature control strategies in local heating systems for wellhead-produced fluids. Full article

High rock temperature (HRT) and its associated thermal hazards, alongside secondary mechanical risks such as swelling pressures induced in clay layers, pose severe threats to the construction safety of deep-buried tunnels. This study aims to quantitatively reveal the evolution laws of the surrounding rock temperature field under varying heat source conditions. A combined approach of physical model testing and numerical analysis was adopted. Utilizing an independently developed test system with a 1:13 geometric similarity ratio, the coupled rock-heat-ventilation environment was simulated. A transient conduction-convection 3D numerical model was established in COMSOL and verified against experimental data under benchmark conditions. The research confirms that under the influence of localized block heat sources, the temperature field in the far-field region follows a significant linear attenuation law rather than the traditional exponential distribution, with a prototype-equivalent gradient of approximately 0.69 °C/m. Furthermore, the study quantitatively identifies 8 m³ as the critical volume for heat source geometric saturation, beyond which the incremental temperature rise efficiency decreases by 25%. It is further revealed that the effective cooling depth of conventional ventilation is only approximately 0.35 m, indicating a significant “ventilation shielding effect” within the deep surrounding rock. Full article

In ultra-cold narrow-window drilling, pipe connection causes flow-path switching as the main circulation is interrupted and bypass circulation is established, breaking the initial relative pressure balance of the whole wellbore and inducing asymmetric transient variations in flow distribution, annular friction, and bottomhole pressure response, thereby increasing the risks of wellbore instability, lost circulation, and kicks. To address the poor pressure-control accuracy, long non-productive time, and inadequate low-temperature adaptability of conventional drilling technologies in the Irkutsk block of Russia, this study developed and field-tested an integrated all-electric managed pressure drilling (MPD) and cold-resistant continuous circulation system (CCS). Existing conventional technologies often suffer from high communication latency and hydraulic freezing in extreme cold environments, leading to uncoordinated pressure compensation. To overcome these limitations, the scientific novelty of this work lies in proposing a transient pressure rebalancing mechanism that effectively suppresses the asymmetric pressure disturbances induced by topological flow path switching. Methodologically, the proposed system was validated through a comprehensive industrial field test. An improved Herschel–Bulkley temperature–pressure coupled model was established to dynamically calculate full wellbore annular pressure loss. Furthermore, a dedicated hardware adapter module utilizing multi-protocol conversion was integrated to achieve a communication delay of less than 8 ms, enabling high frequency coordinated pressure regulation. Field results demonstrate that compared to the delayed responses of conventional systems, the proposed integrated approach successfully maintained a dynamic backpressure tracking error within ±0.069 MPa under extreme conditions of −38 °C and a narrow pressure window of 0.08 g/cm³. The rapid suppression of asymmetric transient responses prevented any lost circulation, kicks, or wellbore collapse. These findings highlight the significant advantages of the integrated system in maintaining pressure field stability, thereby providing a robust and innovative engineering solution for complex well interventions. Full article

This study focuses on a 155 mm 32CrNi3MoV steel barrel and presents a thermochemically coupled phase transformation and diffusion dynamics model. The model leverages the significant disparity between radial and axial temperature gradients to simplify the heat conduction problem to a one-dimensional transient formulation. The temperature field distribution during firing sequences is solved analytically, accounting for the dynamic shift in critical phase transformation temperatures under high heating rates. The evolution of the martensitic layer thickness under repeated thermal shock is subsequently calculated. A numerical model for the pulsed diffusion of C and N is established based on Fick’s second law, incorporating the competitive diffusion–phase transformation mechanisms that govern martensite/austenite interface migration. To quantitatively evaluate the synergistic contribution of C and N to austenite stabilization, a carbon equivalent (Ceq) model is introduced, with the weight coefficient of N relative to C determined to be 0.68 and the critical Ceq required to lower the martensite start temperature below 25 °C calculated as 1.15 wt%. Concurrently, the microstructure and elemental distribution within the austenite layer of the retired barrel are systematically characterized using multi-scale techniques. The results indicate that the austenite layer on the inner bore surface arises from the synergistic effects of cyclic thermal-shock-induced phase transformation and elemental diffusion. Based on the Ceq criterion, the austenite layer thickness increases rapidly during the initial ~100 firing cycles, after which the growth rate slows significantly: it reaches approximately 1.27 μm after the first cycle and 2.94 μm after 1000 cycles, with only 0.2 μm of additional thickening between 100 and 1000 cycles—consistent with the experimentally observed range of 1.52–4.16 μm. The martensitic layer formed during the first firing cycle exhibits low thermal conductivity, which impedes subsequent heat transfer and leads to stabilization of its thickness at a characteristic depth. Grain refinement induced by repeated thermal shock provide short-circuit diffusion paths for elemental diffusion, accelerating compositional homogenization within the austenite layer and resulting in a stepped concentration profile at the interface. This study provides a representative example of non-equilibrium coupled phase transformation–diffusion phenomena under extreme transient loading. The established thickness prediction model can provide guidance for service life assessment of large-caliber barrels, offering both theoretical foundations and practical engineering guidance for their material design and performance optimization. Full article

Understanding the variation law and prediction method of thermal conductivity for NaCl-bearing aeolian sand is of great significance for the thermal parameter selection and temperature field analysis of engineering structures including subgrades, foundations and lined water conveyance canals in the saline soil region of southern Xinjiang. The thermal conductivity of NaCl-bearing aeolian sand under different dry densities, moisture contents and salt contents was measured via the transient plane source (TPS) method. The variation law and corresponding influence mechanism were analyzed, and a thermal conductivity prediction model was established. The experimental results indicate that the thermal conductivity of NaCl-bearing aeolian sand increases with increasing dry density and moisture content, showing strong linear correlations with both parameters. At a salt content of 2%, the maximum increase in thermal conductivity induced by increasing moisture content reached 29.3%, which was approximately 1.53 times the increase observed at a salt content of 8% (19.17%). In contrast, the influence of salt content on thermal conductivity exhibited a nonlinear trend. With increasing salt content, the thermal conductivity initially decreased and then increased, and the salt content corresponding to the minimum thermal conductivity shifted toward higher values with increasing moisture content. Specifically, this critical salt content gradually shifted from 2% to 6%. This law reveals that the increase in dry density and moisture content improves the thermal conductivity of the soil mainly by enhancing the solid and liquid heat transfer pathways, whereas the variation of salt content is controlled by the water–salt coupling effect. The model calculation results show that the established prediction model is in good agreement with the measured experimental data (R² = 0.9674), with favorable applicability and high prediction accuracy. It can provide a reliable reference for the thermal calculation of sandy foundations and related engineering materials in saline soil areas. Full article

Polycrystalline diamond has great potential for power-device heat dissipation and precision manufacturing owing to its exceptional hardness, excellent thermal conductivity, and superior wear resistance. However, the challenges of material removal and controlling thermal damage hinder high-quality machining. In this study, a three-dimensional transient temperature field model is developed for multi-pulse nanosecond laser ablation of polycrystalline diamond. The model incorporates the Gaussian spatial distribution of laser energy, Lambert–Beer depth-dependent absorption, multi-pulse energy superposition, and three-dimensional heat conduction. The heat conduction equation is numerically solved using MATLAB, and lateral and longitudinal temperature gradients are introduced to characterize thermal accumulation and material removal behavior. The model is validated by comparing the predicted ablation depths with experimental measurements, which show consistent variation trends. The results indicate that increasing the number of scans, single-pulse energy, and pulse frequency enhances thermal accumulation, expands the microgroove width, and increases the ablation depth, whereas increasing the scanning speed weakens thermal accumulation and reduces the ablation depth. In addition, a shorter pulse width increases the instantaneous power density and strengthens near-surface thermal concentration. This study provides theoretical guidance for controlling the heat-affected region and optimizing process parameters in precision laser machining of diamond. Full article

A multiscale contact model is developed for micro-textured gear interfaces incorporating Micro-Convex-Concave Asperity (MCCA) characteristics to elucidate the synergistic modulation between Interface Enriched Lubrication (IEL) performance and Anti-Scuffing Load-Bearing Capacity (ASLBC) of Micro-Textured Meshing Interfaces (MTMI) under transient Thermal Elastohydrodynamic Lubrication (TEHL) conditions. Homogenization theory is employed to quantify the effects of areal density and depth-to-diameter ratio on IEL characteristics. A time-resolved micro-elastohydrodynamic lubrication model, formulated through dimensionless discretization and adaptive mesh refinement, investigates the influences of autocorrelation length and MCCA amplitude on interfacial behavior. A correlation framework linking Micro-Element Texture (MET) geometric parameters to meshing ASLBC is established to identify optimal textures for simultaneous enhancement of IEL and ASLBC. Experimental observations demonstrate qualitative consistency with numerical predictions regarding the evolutionary trends of temperature fields and dynamic friction coefficients, providing preliminary physical validation for the proposed model. Univariate Sensitivity Analysis (USA) and Multiple Linear Regression (MLR) are further utilized to optimize microtexture parameters by elucidating the influences of MET sizes, area ratio, and configuration on meshing ASLBC and friction coefficients. Full article