Search Results (2,225)

This study systematically investigates the influence of laser pulse duration on cutting efficiency, heat-affected-zone (HAZ) formation, and mechanical integrity during carbon fiber-reinforced polymer (CFRP) laser cutting. Three distinct pulse-width lasers—picosecond, nanosecond, and quasi-continuous-wave (QCW)—are compared. Results show that pulse duration governs material removal mechanisms and HAZ extent: the nanosecond laser achieves the smallest HAZ and minimal porosity; the picosecond laser exhibits limited thermal accumulation due to low average power; and the QCW laser induces the largest HAZ (11.6 times that of the nanosecond laser) and significant porosity. Cutting efficiency scales inversely with pulse width, with single-hole processing times of 480.4 s for picosecond-laser cutting, 76.8 s for nanosecond-laser cutting, and 4.028 s for QCW-laser cutting, reflecting a transition from thermal ablation to mechanical spallation. Mechanical testing reveals that while tensile and flexural strengths vary by less than 5% across laser types, damage morphology and failure modes differ significantly. In situ digital image correlation (DIC) and 3D CT imaging show that longitudinal plies fail via fiber pull-out, whereas transverse plies fail via interfacial debonding. QCW-laser-cut specimens exhibit more uniform strain distribution and higher damage tolerance. An optimized process parameter is proposed: nanosecond-laser cutting at 200 W and 20 kHz achieves a HAZ of less than 50 µm and a cutting time of less than 80 s, offering the best balance between efficiency and quality. Full article

Helical coiled tube (HCT) heat exchangers (HXs) are used in the nuclear industry, particularly in the residual heat removal systems of nuclear power plants (NPPs) and steam generators for small modular reactors. In this study, a single-phase CFD model was developed to investigate non-uniform circumferential distributions in the local wall heat transfer characteristics of a vertical HCT to obtain localized information critical for the safety of NPPs. In a comparison, the predicted circumferential heat transfer characteristics agreed well with the measured data. Governed by centrifugal/gravitational forces, these non-uniform distributions are clearly visible in the results, explaining the test data. We performed additional simulations of the conjugated heat transfer from the hot fluid of the shell side to the cold fluid of the tube side, confirming that the inhomogeneity of circumferential distributions in HCTs is due to the assumption of a constant heat flux boundary condition. Full article

This study focuses on the high-precision microhole machining of 304 stainless steel and explores a backwater-assisted picosecond laser trepanning technique. The laser used is a 30 W green picosecond laser with a wavelength of 532 nm, a repetition rate of 1000 kHz, and a pulse width of less than 15 ps. Experiments were conducted under both water-based and non-water-based laser processing environments to systematically investigate the effects of laser power and scanning cycles on hole roundness, taper, and overall hole quality. The experimental results further confirm the advantages of the backwater-assisted technique in reducing slag accumulation, minimizing roundness variation, and improving hole uniformity. In addition, thermal effects during the machining process were analyzed, showing that the water-based environment effectively suppresses the expansion of the heat-affected zone and mitigates recast layer formation, thereby enhancing hole wall quality. Compared with conventional non-water-based methods, the backwater-assisted approach demonstrates superior processing stability, better hole morphology, and more efficient thermal management. This work provides a reliable technical route and theoretical foundation for precision microhole machining of stainless steel and exhibits strong potential for engineering applications. Full article

In slab continuous casting, achieving uniform cooling in the secondary cooling zone is essential for ensuring both surface integrity and internal quality. To optimize the process for ship plate steel, a solidification heat transfer model was developed, incorporating radiation, water film evaporation, spray impingement, and roll contact. The influence of secondary cooling water flow on slab temperature distribution was systematically investigated from multiple perspectives. The results show that a weak cooling strategy is crucial for maintaining higher surface temperatures and aligning the solidification endpoint with the soft reduction zone. Along the casting direction, a “strong-to-weak” cooling pattern effectively prevents abrupt temperature fluctuations, while reducing the inner-to-outer arc water ratio from 1.0 to 0.74 mitigates transverse thermal gradients. In addition, shutting off selected nozzles in the later stage of secondary cooling at medium and low casting speeds increases the slab corner temperature in the straightening zone by approximately 50 °C, thereby avoiding brittle temperature ranges. Overall, the proposed multi-dimensional uniform cooling strategy reduces temperature fluctuations and significantly improves slab quality, demonstrating strong potential for industrial application. Full article

This study investigates the asymmetric effects applying heat transfer as a diagnostic tool in dendritic networks with symmetrical branching, characterized by the geometric property of self-similarity. Using a Computational Fluid Dynamics (CFD) model, we analyze five structural isomers of a three-level dichotomous branching network to evaluate the relationship between fluid dynamics, heat transfer, and geometric configuration. The main constraints are geometrical; that is, the volume at each branching level remains constant, and homothetic relationships respect the Hess–Murray law both for diameters and angles between sister tubes. The model considers an incompressible and stationary Newtonian fluid flow with Reynolds numbers ranging from 10 to 2000 and heat transfer in the range 1 to 1000 W/m². Our results show that significant asymmetries in flow distribution and temperature profiles emerge in these symmetric structures, primarily due to the successive alignment of tubes between different branching levels. We found that the isomer with the lowest pressure drop is not the same as the one providing the most uniform flow distribution. Crucially, thermal analysis proves to be more sensitive than fluid dynamic analysis for detecting flow asymmetries, particularly at low Reynolds numbers less than 50 and q″ = 1000 W/m². While heat transfer does not significantly alter the fluid dynamic asymmetry, its application as a diagnostic tool for identifying flow asymmetries is effective and crucial for such purposes. Full article

This study reviews and experimentally investigates critical logistics and transport models in stainless-steel (SS) fluid storage tanks, focusing on stainless steel grades 316 and 304L. Conceptual vessel schematics emphasize hygienic drainability, refill uniformity, and thermal control, supported by representative 316L properties for heat-transfer, stress, and fluid–structure analyses. At the logistics scale, modelling integrates component-level simulations, computational fluid dynamics (CFD), and Finite Element Method (FEM) with network-level approaches, such as Continuous Approximation, to address facility location, refilling schedules, and demand variability. Experimental characterization using EDS and XRF confirmed the expected Cr/Ni backbone and grade-consistent Mo in 316, while unexpected C, Mn, and Cu readings were attributed to instrumental limits or statistical variance. Unexpected detection of Europium in 304L highlights the need for further mechanical testing. Overall, combining simulation, logistics modelling, and compositional verification offers a coherent framework for safe, efficient, and thermally reliable stainless-steel tank design. Full article

Pipeline anticorrosion patch spray coating is a critical process in pipeline construction and maintenance. It directly affects the adhesion between the pipe exterior and the heat-shrink sleeve and indirectly determines the quality of the coating bond. This study employs ANSYS FLUENT numerical simulations, complemented by on-site automated spray-gun experiments, to systematically investigate the influence of two key parameters—spray distance and gun traverse speed—on coating thickness distribution and uniformity. For both flat and cylindrical specimens, response surface methodology (RSM) applies to construct mathematical deposition models and to optimize process parameters. Simulation results indicate that increasing spray distance leads to edge thinning, while excessive traverse speed causes non-uniform thickness. Optimization improves coating uniformity by 18% on flat specimens and up to 15% on cylindrical specimens. Field validation demonstrates that the optimized process reduces process deviation from the target thickness to within ±10%. At the same time, the maximum relative error between simulation and experiment remains within 13.5%, and the deviation from the standard thickness is 12.25%. These findings provide solid theoretical foundations and practical guidance for automated spray-coating optimization, thereby enhancing the anticorrosion performance of pipeline joints. Full article

Power modules in silicon carbide (SiC)-based modular multilevel converters (MMCs) suffer from notably severe thermal imbalance and localized overheating. This paper puts forward an asymmetric SiC power module with direct integration of a vapor chamber (VC), designed to balance the thermal distribution inside MMC SMs. Specifically, the chips on the lower side of the HBSM are soldered onto a VC, which is additionally mounted on the direct bonding copper (DBC). Endowed with merits such as favorable temperature uniformity, exceptional thermal conductivity, compact size, flexible design, high integration level, and reasonable cost, the VC serves as an outstanding heat diffuser significantly expanding the effective thermal conduction area and reducing thermal resistance. Moreover, in this structure, the VC also functions as a conductor for device current. Finite element method (FEM) simulation results reveal that the proposed structure can notably reduce the hotspot temperature (from 109 $°\mathrm{C}$ to 71.8 $°\mathrm{C}$), the maximum temperature difference among chips (from 45 $°\mathrm{C}$ to 13.89 $°\mathrm{C}$), and the low-frequency temperature swing (TSL) (from 68 $°\mathrm{C}$ to 38 $°\mathrm{C}$). Consequently, the issues of localized overheating and thermal imbalance in SiC-MMC SMs are effectively addressed. Lifetime analysis further indicates that the proposed structure can reduce the annual damage rate of the chip solder layer by 92.6%. Full article

TiAl alloys are ideal candidates to replace nickel-based superalloys in aero-engines due to their low density and high specific strength, yet their industrial application is hindered by narrow heat treatment windows and unbalanced mechanical performance. To address this, this study investigates the microstructure and mechanical properties of Ti-44.9Al-4.1Nb-1.0Mo-0.1B-0.05Y-0.05Si (TNM-derived) alloys hot-rolled in the (α₂ + γ) two-phase region. The research employs varying heat treatment temperatures (1150–1280 °C) and cooling rates (0.1–2.5 °C/s), combined with XRD, SEM, EBSD characterization, and 800 °C high-temperature tensile tests. Key findings: Discontinuous dynamic recrystallization (DDRX) of γ grains is the primary mechanism refining lamellar colonies during deformation. Higher heat treatment temperatures reduce γ/β phases (which constrain colony growth), increasing the volume fraction of lamellar colonies but exerting minimal impact on interlamellar spacing. Faster cooling shifts γ lamella nucleation from confined to grain boundaries to multi-sites (grain boundaries, γ lamella peripheries, α grains) and changes grain boundaries from jagged and interlocking to smooth and straight, which boosts nucleation sites and refines interlamellar spacing. Fine lamellar colonies and narrow interlamellar spacing enhance tensile strength, while eliminating brittle βo phases and promoting interlocking boundaries with uniform equiaxed γ grains improve plasticity. Full article

This article presents a novel approach to looking at steady-state thermoelastic boundary value problems in isotropic elastic plates with curvilinear holes using a complex variable approach and rational conformal mappings. The physical domain with a non-circular opening is mapped conformally to the unit disk. A thermoelastic potential combines the temperature distribution, which is determined by the Laplace equation with Neumann boundary conditions. Gaursat functions, which are shown as truncated power series, show the complicated stress and displacement fields. They are found by putting boundary constraints at certain collocation points. This procedure presents us with a linear system that can be solved using the least squares method. The method is applied in an annular shape that is exposed to a radial temperature gradient. This experiment shows how changes at the boundary affect the distribution of stress. According to numerical simulations, stress distributions are more uniform when boundaries are smoother, but stress concentrations increase with the size of geometric disturbances. The suggested approach remarkably captures the way geometry and thermal effects interact in two-dimensional thermoelasticity. It is a reliable tool for researching intricate, heated elastic domains. Full article

Coke is an essential raw material in the blast furnace (BF) ironmaking process. Its moisture content significantly impacts BF ironmaking production. This study employs a coupled Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) approach to simulate the drying process of wet coke within a coke silo (CS) dryer. Initially, the model was validated by comparing numerical results with experimental data from the literature. Subsequently, it investigated the gas flow dynamics, heat and mass transfer characteristics, and differences in drying behaviour across distinct dryer zones. Finally, the effects of inlet gas velocity and inlet gas temperature on the drying process were systematically quantified. Simulation results reveal that the bottom of the CS dryer exhibits a low-velocity laminar state, while the middle and upper regions display intense gas flow motion. Consequently, the bottom region exhibits insufficient particle drying in comparison to other zones, with the average particle moisture content decreasing by less than 20%. Under the continuous heat exchange between the hot gas and the particles, the moisture content of the particles decreases rapidly. Based on the drying rate behaviour, the drying process exhibits the following three different stages: the pre-heating period, the constant-rate period, and the falling-rate period. Compared to zones 1 and 3, zone 2 exhibits higher temperatures due to its high heat transfer efficiency, which significantly promotes a reduction in particle moisture content. An increase in inlet gas velocity enhances the particle drying rate and heat flux, accelerates moisture reduction, and raises the temperature. The impact of inlet gas velocity is most pronounced after the constant-rate period, with particle drying uniformity decreasing as the inlet gas velocity increases, consequently leading to a decline in drying quality. Increasing inlet gas temperature significantly increases particle temperature and heat flux throughout the drying period and accelerates the high-rate drying stage. These findings provide fundamental insights for further understanding and studying the coke drying process. Full article

Ensuring thermal stability is a major concern in lithium-ion battery systems. Although phase change materials (PCMs) provide a passive approach for temperature regulation, they are limited by poor heat conduction and potential leakage during phase transitions. This study develops a novel composite PCM (CPCM) using paraffin (PA) as the matrix, copper foam (CF) as a conductive skeleton (10–30 pores per inch, PPI), and a low-melting-point alloy (LMA) as an encapsulant to prevent leakage. The effects of CF pore size on thermal conductivity, impregnation ratio, and leakage resistance were systematically investigated. Results show that CPCM with 10 PPI CF achieved the highest thermal conductivity (4.42 W·m⁻¹·K⁻¹), while LMA encapsulation effectively eliminated leakage. The thermal management performance was evaluated on both a single 18,650 LIB cell and a 2S2P module during rate discharging at 1C, 2C, and 3C. For the module at 3C, the 10 PPI CPCM significantly lowered the maximum temperature from 75.9 °C to 44.6 °C and critically reduced the maximum temperature difference between cells from 10.2 °C to a safe level of 1.2 °C, significantly improving temperature uniformity. This work provides a high-conductivity and leakage-proof CPCM solution based on LMA-encapsulated CF/PA for enhanced thermal safety and uniformity in LIB modules. Full article

This paper presents an analytical investigation of the free vibration behavior of fiber metal laminate (FML) beams with three types of boundary conditions, considering the temperature-dependent properties and the interfacial slip. In the proposed model, the non-uniform temperature field is derived based on one-dimensional heat conduction theory using a transfer formulation. Subsequently, based on the two-dimensional elasticity theory, the governing equations are established. Compared with shear deformation theories, the present solution does not rely on a shear deformation assumption, enabling more accurate capture of interlaminar shear effects and higher-order vibration modes. The relationship of stresses and displacements is determined by the differential quadrature method, the state-space method and the transfer matrix method. Since the corresponding matrix is singular due to the absence of external loads, the natural frequencies are determined using the bisection method. The comparison study indicates that the present solutions are consistent with experimental results, and the errors of finite element simulation and the solution based on the first-order shear deformation theory reach 3.81% and 3.96%, respectively. At last, the effects of temperature, the effects of temperature degree, interface bonding and boundary conditions on the vibration performance of the FML beams are investigated in detail. The research results provide support for the design and analysis of FML beams under high-temperature and vibration environments in practical engineering. Full article

Electromagnetic Railguns Face Severe Ablation and Melting Risks Due to Extremely High Transient Thermal Loads During High-Speed Launching, Directly Impacting Launch Reliability and Service Life. To address this thermal management challenge, this study proposes and validates the effectiveness of spray cooling technology. Leveraging its high heat transfer coefficient, exceptional critical heat flux (CHF) carrying capacity, and strong transient cooling characteristics, it is particularly suitable for the unsteady thermal control during the initial launch phase. An experimental platform was established, and a three-dimensional numerical model was developed to systematically analyze the dynamic influence mechanisms of nozzle inlet pressure, flow rate, spray angle, and spray distance on cooling performance. Experimental results indicate that the system achieves maximum critical heat flux (CHF) and rail temperature drop at an inlet pressure of 0.5 MPa and a spray angle of 0°. Numerical simulations further reveal that a 45° spray cone angle simultaneously achieves the maximum temperature drop and optimal wall temperature uniformity. Key parameter sensitivity analysis demonstrates that while increasing spray distance leads to larger droplet diameters, the minimal droplet velocity decay combined with a significant increase in overall momentum markedly enhances convective heat transfer efficiency. Concurrently, increasing spray distance effectively improves rail surface temperature uniformity by optimizing the spatial distribution of droplet size and velocity. Full article

As an effective engineering countermeasure against frost heave damage in seasonally frozen regions, thermal insulation boards (TIBs) were employed in embankments. This study established a test section featuring a thermal insulation–waterproof geotextile embankment in Dingxi, Gansu Province. Temperature and water content at various positions and depths within both the thermal insulation embankment (TIE) and an ordinary embankment (OE) were monitored and compared to analyze the effectiveness of the TIB. Following the installation of the insulation layer, the temperature distribution within the embankment became more uniform. The TIB effectively impeded downward heat transfer (cold energy influx) during the winter and upward heat transfer (heat energy flux) during the warm season. However, the water content within the TIE was observed to be higher than that in the OE, with water accumulation notably occurring at the embankment toe. While the TIB successfully mitigated slope damage and superficial soil frost heave, the waterproof geotextile concurrently induced moisture accumulation at the embankment toe. Consequently, implementing complementary drainage measures is essential. In seasonally frozen areas characterized by dry weather and relatively high winter temperatures, the potential damage caused by concentrated rainfall events to embankments requires particular attention. Full article