Search Results (827)

Boiling is one of the most effective mechanisms for heat transfer enhancement and is therefore widely applied in high-performance cooling systems for electronic devices, power electronics, and compact heat exchangers. A comprehensive understanding of the relationship between surface microstructure geometry and boiling dynamics enables the design of advanced surfaces with improved thermal performance and enhanced operational stability. This study presents an experimental investigation into the effect of inclined microchannel geometry on the pool boiling characteristics of FC-72 and ethanol, two working fluids with significantly different thermophysical properties. The experiments were conducted on copper surfaces with parallel microchannels of various widths, depths, and inclination angles, with the obtained results compared with those for a technically smooth reference surface. The experiments were performed under atmospheric pressure conditions with a gradually increasing heat flux. Boiling curves, heat transfer coefficients (HTCs), and critical heat flux (CHF) values were determined. The results demonstrate that properly designed microchannel geometries can significantly enhance boiling heat transfer by increasing the number of active nucleation sites and modifying the conditions of vapor bubble growth and departure. The most favorable thermal performance was achieved for surfaces with the smallest channel width, confirming the important role of microstructure geometry in governing boiling heat transfer mechanisms. For FC-72, the HTC increased by more than 200% compared with the reference surface, whereas ethanol exhibited higher HTC values and a more stable nucleate boiling regime over the entire investigated heat flux range. The results confirm that optimization of inclined microchannel geometry provides an effective strategy for designing surfaces dedicated to enhanced boiling cooling, while the effectiveness of surface modification depends on both microstructure characteristics and the thermophysical properties of the working fluid. Full article

In this study, a liquid-cooled Battery Thermal Management System (BTMS) incorporating aluminum heat-conducting blocks was numerically investigated to enhance the thermal performance of lithium-ion battery modules used in electric vehicles. The proposed system was designed for a battery module consisting of cylindrical lithium-ion cells, and the effects of different geometric configurations on thermal behavior were analyzed using the Computational Fluid Dynamics (CFD) method. To efficiently evaluate the multi-parameter design space with reduced computational cost, a Taguchi L9 orthogonal experimental design was employed. The cooling channel configuration, aluminum heat-conducting block height, and battery pack geometry were considered as the primary design variables. The performance of each design configuration was assessed based on maximum temperature (T_max) and temperature uniformity (ΔT). Furthermore, an Analysis of Variance (ANOVA) was conducted to quantify the influence of the design parameters on the thermal performance of the system. The results revealed that the configuration comprising eight cooling channels, a 65 mm aluminum block height, and a 1 + 8 cylindrical battery arrangement exhibited the best thermal performance, achieving a maximum temperature of 303.45 K and a temperature difference of 1.25 K. The optimal design configuration provided a more uniform temperature distribution within the battery module, thereby enhancing thermal safety and operational reliability. Overall, the integration of CFD and the Taguchi method offers a systematic and efficient optimization framework for BTMS design, enabling effective evaluation of design alternatives with a reduced number of simulations and shorter computational time. Full article

Thin-walled conformal cooling structures are essential for the thermal management of complex curved electronic and aerospace devices. The traditional topology optimization of conformal cooling structures requires cumbersome post-processing reconstruction and inevitably induces thermal performance deviations of the optimized results. To address this issue, this paper proposes a feature-driven topology-optimization method based on parametric mapping for the design of conformal cooling structures. The parametric mapping is introduced to map 3D complex curved design domains into 2D parametric domain where the B-Spline Offset Feature (BSOF) is defined to model the fluid channels. A generalized extrusion operator is adopted to achieve uniform pseudo-density distribution and consistent physical properties throughout the structural thickness direction. Numerical examples including cylindrical and spherical thin-walled conformal cooling structures are studied to demonstrate the effectiveness of the proposed method. Full article

Abrasive flow machining (AFM) is an effective finishing process for complex internal surfaces, particularly cavities, intersecting holes, and micro-channels that are difficult to access using conventional tools. However, when low-viscosity abrasive media is used (here defined, relative to conventional putty-like viscoelastic AFM carriers (with apparent viscosities of 10³–10⁵ mPa·s), as a water-based slurry with an apparent viscosity below 300 mPa·s over the operating shear-rate range), unfavorable flow conditions during the initial polishing stage can induce local over-polishing, erosion depressions, stepped patterns, and cavitation pits, resulting in non-uniform surface quality. The relationship between these flow behaviors and polishing defects remains insufficiently understood. To address this issue, this study investigates the AFM process applied to turbine blade film cooling holes through combined experimental and numerical approaches. The observed defects include erosion depressions, stepped surface patterns, and cavitation pits. The effects of abrasive injection pressure, flow velocity, hole geometry, abrasive viscosity, and particle size on defect formation are systematically examined. The results show that the initial abrasive filling level strongly affects defect distribution by altering the evolution of shear fields and void regions within the hole. Experimentally, at high Reynolds numbers (Re > 2 × 10⁴), intensified local shear and cavitation promote defect formation, while a moderate inclination angle (45–60°) and a higher aspect ratio (>8) are favorable for polishing uniformity. Complementary numerical simulations further indicate that smaller abrasive particles (<5 μm) and a moderate abrasive viscosity (~60 mPa·s) are predicted to improve polishing uniformity. This study clarifies the fluid-dynamic origin of polishing defects in film cooling holes and provides process guidance for suppressing local over-polishing, cavitation, and uneven material removal. Full article

Injection molding is one of the most widely adopted manufacturing methods in the plastics industry, owing to its high efficiency, design flexibility, and mass production capabilities. Throughout the development and application of Injection molding technology, trade-offs are pervasive, arising from competing requirements such as processability versus material performance, productivity versus quality, and simplicity versus functionality. Injection molding simulation itself embodies such trade-offs, as it is used to design increasingly complex processes and mold systems to achieve improved material properties and part performance, while inevitably balancing physical accuracy against computational efficiency and modeling cost. This review examines typical modeling options in injection-molding simulation from an accuracy–complexity trade-off perspective. The modeling strategies adopted in the primary stages of the molding cycle—namely, the injection, packing, and cooling phases—are systematically reviewed, with emphasis on how simplifying assumptions are introduced to manage numerical complexity. By organizing existing research through the lens of qualitative trade-offs, this review aims to support a more structured understanding of model selection in injection molding simulation for both academic studies and industrial applications. Full article

The rapid expansion of artificial intelligence (AI) is accelerating data center construction and creating downstream implications for households. This study examines how AI-era data center costs (comprising construction, energy, water, grid upgrades, cooling, and lifecycle management) move through service supply chains and affect household prices in healthcare, transportation, education, banking, and commerce. It also considers the productivity and welfare benefits that AI may transmit. This study identifies four pass-through channels: utility-rate socialization of energy costs, cloud-platform pricing, sectoral pass-through from AI-adopting industries, and indirect effects through supply chains and labor markets. It introduces the AI-inflated net good basket, defined as transmitted cost minus transmitted benefit, to show how AI reshapes the overall net cost of household consumption rather than simply inflating individual prices. The study develops the AI Infrastructure Net Cost Pass-Through Model (AI-NCPM), a four-layer conceptual framework tracing net cost flows from data center investment to sectoral allocation and household outcomes. The model’s parameters are analytically specified but not empirically calibrated; numerical examples are illustrative rather than representing estimated effects. Its main contribution is an integrative framework linking cost pass-through, infrastructure cost socialization, two-sided platform allocation, environmental externalities, and household expenditure incidence within a single net-cost account. Because these effects originate in the design, construction, energy and cooling systems, and lifecycle operation of data centers, the analysis connects AI infrastructure economics to the built environment. The framework suggests that low-income, minority, rural, older adult, and disability-affected households may face disproportionate net burdens, as costs fall heavily on essential services while benefits accrue more readily to affluent and digitally connected households. Full article

This paper presents the design and experimental investigation of an indirect regenerative evaporative cooling (IREC) system based on the M-cycle concept for electronic systems operating in high ambient temperature. The proposed heat exchanger consists of dry and wet vertical channels separated by thin copper walls and equipped with an open-water reservoir located at the bottom of the cooler. Airflow is introduced into the dry channels, where it is pre-cooled and directed toward a heat source. Next, it is redirected into the wet channels in a counter-flow arrangement. The heat source consists of power MOSFET transistors operating in current-source mode, with enhanced convective heat transfer achieved through attached heat sinks. Temperature and relative humidity sensors were installed at key measurement points to monitor thermodynamic conditions in the exchanger. The findings demonstrate the potential of the IREC approach as an effective and energy-efficient solution for cooling electronic systems in elevated temperature environments. Full article

The episodic aggregation of shallow-sea organisms near coastal nuclear power plant water intakes can obstruct filtration facilities and threaten cooling-water circulation. Reliable multi-object tracking is therefore required for continuous monitoring and warning-oriented decision support. However, underwater targets commonly show weak texture, similar appearance, partial occlusion, and current-driven nonlinear motion, which cause trajectory fragmentation and identity switches in conventional trackers. This study proposes a feature-enhanced DeepSORT framework for shallow-sea biological target tracking and intake-invasion warning. An improved YOLOv8 detector is used as the detection front end, while the main methodological contribution is an enhanced tracking module. Efficient Channel Attention, RepVGG, and an enhanced Squeeze-and-Excitation block are incorporated into the Re-ID feature extractor to improve appearance discrimination under turbid and low-texture conditions. An extended Kalman filter is further introduced to improve motion prediction for drifting, turning, and short-term occluded targets. Based on the tracked trajectories, equivalent density, and velocity component toward the intake, an invasion-intensity index and graded warning strategy are established. Experiments on shallow-sea biological video data show that the proposed tracker improves IDF1 from 55.7% to 56.3%, MOTA from 43.6% to 44.7%, and MOTP from 74.3% to 75.1% compared with DeepSORT, while reducing identity switches from 779 to 735. These results indicate that the proposed method can provide more stable trajectory information for early warning of biological blockage risks at coastal nuclear power plant intakes. Full article

To satisfy the electricity demands and further improve the cooling performance of scramjets, the supercritical CO₂ Brayton cycle is adopted as a promising cooling and power supplying scheme. However, with the extremely high heat flux level of MW/m², a cooling channel featuring a rectangular cross-section with non-uniform heat flow and different positions of the heated wall relative to the direction of gravity make the flow and heat transfer characteristics of supercritical CO₂ within scramjet cooling channel extremely complex. In this study, the effects of different angles of the heated wall normal direction relative to the direction of gravity (θ) on the flow and heat transfer behavior of supercritical CO₂ within a scramjet cooling channel are comprehensively investigated. The results show that the spanwise heat transfer coefficient on the heated wall decreases while on the opposite wall it increases as θ increases. Moreover, the overall heat transfer performance is insensitive to variations in θ, but the heat transfer characteristics on different walls are sensitive to variations in θ. Moreover, the cases with lower θ provide better heat transfer performance for the heated wall, which is more significant for scramjet cooling due to having the highest heat load. In detail, the averaged HTC on the HW of θ = 180 deg for G = 900 kg/(m²s) is reduced by 11.79% in comparison to that of θ = 0 deg, while it is enhanced by 18.70%, 6.39% and 6.39% for the OW, LW and RW, respectively. Full article

The Yangqu Reservoir is a representative example of a new alpine channel reservoir, making it particularly important for understanding early-stage thermal evolution to ensure regional ecological sustainability. Using high-frequency monitoring data from a water temperature chain within the reservoir area, along with two field measurement datasets, a three-dimensional water temperature model was established using MIKE3 to simulate and predict the water temperature in the reservoir during its initial period of water storage and operation. Prototype observations and simulation results indicate that the vertical distribution of water temperature near the dam is uniform throughout the water storage period. Once storage is completed, the water temperature exhibits seasonal patterns: heating in spring, stratification in summer, a decline in autumn, and stability in winter. During the summer, stratification intensity reaches its peak, with a maximum temperature difference of 13.2 °C between the surface and bottom layers. In winter, the overall water temperature within the reservoir maintains a range of 2.1 to 3.6 °C. Spatially, the water temperature during the warming period is ranked as follows: “the tail of the reservoir < the central part < in front of the dam”. During the cooling period, this order reverses, with the tail of the reservoir being the most affected. A significant lag effect is also observed in front of the dam. These findings demonstrate that the proposed MIKE3 three-dimensional water temperature model is highly applicable and accurate for predictions in this type of reservoir. Ultimately, this model can provide a valuable theoretical foundation and data support for mitigating downstream cold-water pollution, optimizing hydraulic structures (such as ecological retaining walls), and promoting the eco-environmental sustainability of new reservoirs in alpine regions. Full article

This study investigates heat transfer enhancement in the cooling channels of gas turbine blade turbulators using modified transverse baffles with isosceles triangular sawtooth perforations. The proposed baffle design aims to improve convective heat transfer by promoting flow mixing and disrupting the thermal boundary layer. Experiments were conducted in a rectangular channel with an aspect ratio of 3.75 under constant heat flux conditions using air (Pr = 0.7) as the working fluid. The effects of Reynolds number (Re = 6000–24,000), sawtooth width ratio (a/W = 0.0, 0.0625, 0.125, 0.25, and 0.5), and sawtooth height ratio (b/e = 0.0, 0.25, 0.5, 0.75, and 1.0) were systematically investigated. The blockage ratio (e/H) and pitch ratio (P/H) were maintained at 0.3 and 1.5, respectively. Heat transfer characteristics were evaluated using the thermochromic liquid crystal (TLC) technique, while thermal–hydraulic performance was assessed in terms of the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). The results demonstrate that introducing sawtooth perforations significantly enhances heat transfer compared with a smooth channel, yielding Nusselt number ratios (Nu/Nu_s) between 1.6 and 2.6. The highest heat transfer enhancement was achieved at a/W = 0.0625 and b/e = 0.25, where the relatively small sawtooth openings generated stronger jet impingement, enhanced flow mixing, and more effective disruption of the thermal boundary layer. However, these geometric modifications also increased the pressure loss due to intensified flow blockage and recirculation, resulting in friction factor ratios (f/f_s) ranging from 8.9 to 14.9. The maximum pressure-drop penalty occurred at b/e = 0.25 because the smaller openings produced stronger turbulence and increased flow resistance. Despite the increased friction loss, the optimum configuration (a/W = 0.0625 and b/e = 0.25) achieved the highest thermal performance factor of 1.2 at Re = 6000. Full article

Hairpin windings are increasingly adopted in permanent magnet (PM) traction machines owing to their high slot fill factor, compact end-winding structure, and suitability for automated manufacturing. However, limited heat dissipation and high copper losses under peak loading and high-frequency operation result in severe thermal constraints, which restrict the power rating of the machine. This paper presents a multi-physics comparison of different winding cooling topologies for a PM machine with hairpin winding, including hollow conductor cooling, end-winding cooling, and cooling channel insertion at slot-bottom, slot-middle, and slot-opening regions. A coupled electromagnetic–thermal model based on the finite element method (FEM), which accounts the heat transfer between different components, is used to analyze temperature distribution, losses, efficiency, loading capacity, and hydraulic requirements. The results show that the position of the cooling channel has great influence on the thermal behavior and electromagnetic performance of the machine under different working conditions. The study emphasizes the strong coupling between cooling design, conductor geometry, AC loss behavior, and efficiency and provides practical design guidelines for selecting appropriate cooling techniques in high-power-density traction machines. Consequently, an improved cooling system results in a reduced amount of PM for the same output power range. Full article

Single-phase oil immersion is a promising alternative to air cooling for high-power servers, but the high viscosity of dielectric fluids amplifies the bypass flow around the CPU heat sink via the adjacent random-access memory (RAM) channels, degrading thermal performance. A simplified hydraulic-thermal analysis shows that this bypass penalty cannot be eliminated by reducing the fin pitch of a rectangular-fin heat sink alone. A staggered pin-fin heat sink is therefore proposed, with pin diameter D, longitudinal pitch S_d, and transverse pitch S_t optimized by three-dimensional CFD using PAO-6. The optimum geometry is D = 2.8 mm, S_t = 6 mm, S_d = 8.45 mm. The heat sink is fabricated and tested in a commercial server at oil inlet temperatures of 30–45 °C and flow rates of 3–6 LPM. At 3 LPM, the pin-fin immersion server reduces the CPU thermal resistance by 22.29% relative to a rectangular-fin immersion server using the same oil, and by 38.37% relative to an air-cooled server. The partial Power Usage Effectiveness (pPUE) reaches 1.015, an 88.09% improvement over the air-cooled baseline (pPUE = 1.126), confirming that pin-fin geometries effectively mitigate the bypass penalty in single-phase oil immersion cooling. Full article

Efficient heat extraction from fractured geothermal reservoirs is strongly controlled by fracture network heterogeneity, well-layout design, and injection operations. In this study, a two-dimensional discrete fracture network (DFN) model incorporating thermo-hydraulic processes was established to investigate the effects of well layout and injection rate on the long-term heat extraction performance in fractured geothermal reservoirs. Two well-layout orientations, specifically 45°/135° and 0°/90°, were designed according to their geometric relationship with the dominant fracture orientations. For each orientation, four well configurations were considered, including one-injection–one-production, one-injection–two-production, one-injection–three-production, and one-injection–four-production schemes. Three injection rates of 1.0, 1.5, and 2.0 kg/s were then assigned to each well layout, resulting in 24 simulation cases. The spatiotemporal evolution of the temperature field, average outlet temperature, total production mass flow rate, and heat-output power were systematically analyzed. The results show that injected cold water preferentially migrates along connected fractures, and that cooling-front propagation is jointly controlled by fracture connectivity, well spacing, and injection–production alignment. When the well alignment is consistent with the dominant fracture orientation, nearly direct preferential flow channels are more likely to form, leading to a faster outlet-temperature decline and a higher thermal-breakthrough risk. Multi-production-well layouts can activate more fracture pathways and improve the total production mass flow rate, but their enhancement effect is limited by competitive flow diversion and local fracture connectivity. Increasing the injection rate enhances early-stage heat-output power but shortens fluid residence time and accelerates thermal breakthrough, thereby reducing long-term thermal stability. Overall, the 0°/90° multi-production-well layouts exhibit better long-term heat-output performance, while a lower injection rate is more favorable for maintaining a stable outlet temperature and heat-output power. These findings provide useful guidance for well-pattern optimization and injection-scheme selection in fractured geothermal reservoirs. Full article

This study presents a novel one-dimensional solution method to demonstrate the effects of fuel composition and channel roughness on phase-change heat transfer in spiral regenerative cooling systems. The calculated models are grounded in an experimental correlation of liquefied natural gas (LNG) flow boiling, and their accuracy is validated through ignition experiments conducted on a 1 kg/s-class thrust chamber. The experimental data shows that the physical characteristics of LNG contribute to an extended reach within the two-phase region, resulting in a calculated pressure drop that exceeds that of pure liquid methane. Variations in surface roughness influence the pressure drop by altering the frictional coefficient. Specifically, an increase in surface roughness from 2 µm to 8 µm results in a 47.8% rise in pressure drop. The proposed model demonstrates high accuracy, with deviations in the coolant temperature rise and the pressure drop being less than 9.0% and 7.6%, respectively, when compared to experimental data. The findings serve as an engineering guide for designing and optimizing heat transfer in LOX/LNG rocket engine cooling systems. Full article