Lithium-ion batteries (LIBs) are increasingly being adopted for applications requiring high energy density, such as energy storage power stations and electric vehicles. However, their thermal safety remains a significant concern, particularly due to the risks of thermal runaway (TR) and battery fires. Efficient battery thermal management systems (BTMS), particularly those based on phase change materials (PCMs), have emerged as a promising solution to address these issues. PCM-based BTMS offer advantages such as effective heat dissipation, temperature uniformity, and low energy consumption. However, the inherent flammability of PCMs poses additional risks, highlighting the need for advancements in their flame-retardant properties and overall thermal stability. Research into PCM-based BTMS has focused on enhancing the thermophysical properties of modified PCMs, including their thermal response rate, latent heat, and flame retardancy. The use of carbon-based, metallic-based, nanomaterial-based and polymer-based additives has been shown to improve the thermal response rate property of PCMs, making them more suitable for demanding applications. Additionally, the development of structure-enhanced PCM-based BTMS, which incorporates design elements aimed at mitigating thermal hazards, has been explored to further improve safety and performance. Despite these advancements, challenges remain in optimizing heat dissipation and improving TR propagation suppression in PCM-based BTMS. Future research directions should prioritize the development of flame-retardant PCMs that can effectively manage both regular operation and extreme conditions, such as TR events. This comprehensive approach is essential for building resilient, self-safety BTMS that ensure the reliability and longevity of LIBs in high-energy applications. By addressing these challenges, future designs can better safeguard against thermal hazards, contributing to the broader adoption of LIBs in various industries.

The pouch cells are typically assembled into modules with mechanical preload to meet voltage/capacity requirements, and the stress state is a critical factor influencing the failure behavior of lithium-ion batteries during external short circuits. This study comparatively analyzes performance differences between mechanically preloaded and unconstrained batteries during external short circuits, quantitatively investigating dynamic trends and safety boundaries of electro-thermo-mechanical signals during short circuits in fully charged (100% SOC) batteries across preloads of 500~3500 N. Key findings indicate that under the 50C external short-circuit (ESC) condition, mechanical constraint significantly reduces the central peak temperature of the 100% SOC battery, with a measured reduction of 31.6 °C. Moreover, constrained cells exhibit well-defined lamellar graphite structures, unlike the surface cracking observed in unconstrained anodes, confirming enhanced safety. Rupture temperatures consistently ranged between 112.00 and 124.00 °C across all conditions, with stable temperature rise rates (~0.5 °C·s−1) during short circuits indicating minimal preload impact on heat generation, though excessively high or low preloads accelerated physical damage. Further SOC investigations (10%~100%) demonstrate that lower SOC increases temperature rise rates due to polarization-induced resistance rise, resulting in shorter discharge durations with lower peak temperatures/swelling forces without leakage, while high-SOC cells exhibit prolonged discharge, yielding higher peak temperatures/swelling forces at rupture. This study provides critical insights for enhancing process safety in lithium battery energy storage systems. These findings collectively guide safer battery pack design, module constraint strategies and emergency response protocols to reduce cascading failure risks in stationary energy storage applications.

External short circuits (ESCs) in lithium-ion batteries are often abrupt and difficult to predict in advance; therefore, rapid suppression at the early stage of ESC abuse is essential for preventing its escalation into thermal runaway and mitigate the resulting hazards. Low-pressure water mist provides a promising approach for cooling and heat-removal capability; however, its early-stage suppression behavior and parameter-dependent mechanisms under ESC conditions remain insufficiently understood. In this study, the effects of water mist flow rate, spray application surface, and intervention timing on the early-stage suppression of external-short-circuit-induced thermal runaway were experimentally investigated. The suppression behavior was further analyzed by considering the coupling between water mist deposition, evaporative cooling, and battery heat-accumulation regions. The results show that the suppression performance of water mist strongly depends on the matching between atomization conditions and the targeted battery surface. Under appropriate flow-rate and spray-surface configurations, water mist effectively prevented open flame and severe casing damage, and remained effective during the high-temperature pre-runaway stage. Propagation tests further demonstrated that water mist can delay or inhibit cell-to-cell thermal runaway propagation. These findings provide a practical basis for rapid early-stage mitigation of ESC-induced thermal runaway in lithium-ion batteries.

The supercritical carbon dioxide (SCO2) Brayton cycle is a promising technology for renewable thermal power generation, recognized for its compact layout and high thermodynamic efficiency. Achieving higher cycle efficiency requires cooling the working fluid near its critical point, where the thermophysical properties of SCO2 undergo drastic changes near the pseudo-critical temperature, leading to abnormal heat transfer. It poses a critical challenge for cooler design in SCO2 systems. The present study investigates the heat transfer characteristics of SCO2 during cooling in a horizontal double pipe through numerical simulation. The effects of key boundary conditions (mass flux, heat flux, and operating pressure) are examined, and the mechanisms underlying abnormal heat transfer phenomenon, including heat transfer enhancement (HTE) and deterioration (HTD), are analysed. Results reveal that these phenomena are primarily induced by the flow deceleration effect. A new heat transfer correlation considering the effect is developed, which predicts 87.23 % of the numerical data within a +/- 20 % error band, outperforming existing models. The findings provide a theoretical basis for the optimized design of cooler in SCO2 Brayton cycle.

Atmospheric water harvesting is a promising solution to freshwater shortage because it is not limited by location. Metal-organic frameworks (MOFs) have attracted much attention for low-humidity applications due to their large surface areas and strong water adsorption capacities. In this study, the desorption efficiency of MOF-based adsorbents under solar heating was improved by adding efficient photothermal materials. MOF-303 was combined with Fe3O4, MWCNTs, and Ti3C2 by ball milling. Characterization analysis of the composite materials' morphology, elemental distribution, crystal structure, and functional group changes demonstrated that the composite formation was successful. The results showed that compared to the original MOF-303, adding 10 wt % photothermal material greatly improved light absorption, leading to faster solar heating and quicker water desorption. However, the introduction of photothermal materials leads to a reduction in the effective adsorption sites within the composite materials, resulting in lower saturated water absorption capacities for all three composites compared to the original MOF-303. Among the three composite materials, Ti3C2/MOF-303 shows the best overall performance. Under 40% RH conditions, the material increased water vapor adsorption from 0 g/g to 0.382 g/g within 30 min. After 20 min of irradiation at 1 sun, the surface temperature of the material rapidly rose to 87.4 °C, reducing the remaining water content to 11.3%. Under the same conditions, the original MOF-303 had a water vapor adsorption of 0.42 g/g, a surface temperature of 59.8 °C after irradiation, and a remaining water content of about 31.7%. Taking 30% RH as an example, the Ti3C2/MOF-303 water vapor adsorption capacity is about 8.1% lower than that of the original MOF-303. During desorption at 85 °C, it takes approximately 20 min to achieve complete desorption, which is 20% shorter than that of the original MOF-303.

The integration of phase change materials (PCMs) represents a promising approach for mitigating thermal runaway (TR) propagation in electrochemical energy storage systems, as their phase transition enables significant heat absorption. However, composite PCMs exhibit a wide range of thermophysical properties, and the mechanisms through which they suppress TR under different critical conditions remain insufficiently clarified. In this study, the inhibition behavior of composite PCMs is systematically examined under critical property distributions, both as standalone materials and in combination with insulator strategies. Various factors are examined to assess the effectiveness of the proposed strategies, including the variation effect of state of charge (SOC) and cell spacing. The results indicate that increasing SOC from 30% to 70% markedly alters thermal stability and propagation behavior, while enlarging cell spacing from 1 mm to 2 mm delays peak temperature occurrence, reduces the temperature rise rate, and slightly lowers peak temperatures, thereby slowing the overall thermal response, although propagation still occurs. When composite PCMs are coupled with insulating layers, the integrated system demonstrates substantial suppression performance. Compared with CPCM-only configurations, the CPCM/insulator designs reduce the temperature rise rate by approximately 75-85%, depending on the specific CPCM/insulation pairing. These findings provide valuable theoretical insights and recommendations for the safety design and risk assessment of battery packs.

Fouling accumulation in plate heat exchangers (PHE) significantly deteriorates thermal performance and increases operational costs. Accurate early prediction of fouling is essential for optimizing cleaning schedules and maintaining energy efficiency. This study proposes a fouling prediction framework integrating accelerated fouling experiments and time-series models to achieve effective health monitoring of heat exchangers. An experimental platform was established to simulate composite fouling involving both crystallization and particulate deposition. Throughout the experiment, temperatures, flow rates, and pressures on both the hot and cold sides were systematically monitored. The predictive performance of multilayer perceptron (MLP) model, Long Short-Term Memory (LSTM) model and CNN-BiLSTM-Attention hybrid model was comparatively evaluated. Results demonstrated that the CNN-BiLSTM-Attention hybrid model demonstrates excellent performance in predicting the cold-side outlet temperature (R2 = 0.9975). This represents a significant improvement over MLP models (R2 = 0.8697) and LSTM models (R2 = 0.9815). Furthermore, a health condition value (HCV) based on fouling thermal resistance was introduced for dynamic assessment and early warning of performance deterioration. The findings reveal that the proposed HCV index effectively captures the temporal evolution of fouling accumulation. Alerts are triggered when the HCV reaches the predefined threshold, thereby improving operational reliability and reducing risks of unplanned downtime or safety incidents.

Based on a bidirectionally strongly coupled multiphysics transient model, this study investigated the dynamic characteristics and influencing factors of solid oxide fuel cells (SOFCs) during start-up stage. The effects and mechanisms of operating temperature, flow channel structure, and operational parameters on start-up duration, temperature distribution, current density, and fuel utilization were explored. Additionally, the dynamic impacts of fluctuations in voltage, temperature, and inlet flow velocity on operational stability were analyzed. Results showed that increasing the switching temperature (ST) from 473 K to 973 K reduced the SOFC start-up duration by 38.6%. Maximum temperature gradients were observed at the initial and final stages of start-up. Compared with straight channels, wavy channels prolonged the start-up duration by 23% but enhanced the steady-state current density by 17.5%, with only a 1.3% increase in average temperature. Fluctuations in operating temperature dominated the effects on current density, fuel utilization, and average temperature, while the impact of inlet flow velocity was negligible. Current density responded most rapidly to parameter fluctuations (600-1400 s), and average temperature responded the slowest (2300-2400 s). A 40% reduction in operating temperature led to a 98.4% plummet in current density and a 40.7% decrease in average temperature. This study provided theoretical and practical support for the development of rapid start-up strategies and optimized flow channel designs for SOFCs.

Supercritical CO2 (scCO2) rock breaking devices have seen preliminary engineering applications, yet existing studies focus mainly on post-breaking outcomes, overlooking pre-breaking flow field evolution - critical for fracturing performance. This study conducts transient simulations of pressurization and jetting in scCO2 phase change fracturing, employing a user-defined real gas model (UDRGM) and user-defined functions (UDFs) to characterize CO2 thermophysical properties. The multi-stage flow evolution within the expansion tube and supersonic jet dynamics are systematically analyzed. Results show that during the phase change pressure boosting stage, buoyancy forces drive a triangular axial distribution of scCO2 volume fraction along the tube axis, increasing with axial distance. Within 30 ms, intense phase change and natural convection occur, with axial velocity peaking at 19 m/s. After 80 ms, most of the fluid converts into scCO2 with a sharp pressure surge. During the jet induced fracturing stage, the initial jet velocity exhibits an inverted "N" -shaped variation. The non-uniform exit back-pressure distribution induced by asymmetric filling in the jet region, combined with asymmetric shock wave-boundary layer interactions and internal non-uniformities of the expansion tube, causes the Mach disk to tilt. Injection pressure exerts a stronger influence on jet characteristics than temperature, with the maximum volume-averaged velocity increasing by approximately 11.31% as the initial injection condition rises. After 1.90 ms, impact energy gradually dissipates and internal flow resistance increases, causing the volume-averaged velocity to decline. This study elucidates flow field evolution during scCO2 pressurization and jetting, offering theoretical support for optimizing phase-change fracturing processes and selecting engineering parameters.

Interactions at liquid-solid interfaces hold significant relevance in both natural phenomena and industrial applications, with droplet impact behavior on superhydrophobic surfaces being particularly illustrative. The dynamic behavior of droplets impacting dusty superhydrophobic surfaces of photovoltaic modules was investigated in this paper, with a focus on dust entrainment mechanisms and droplet motion characteristics. Through experimentally validated high-speed imaging and parameterized analysis, the effect of factors such as dust accumulation density on droplet spreading, rebound, bouncing, and sliding behaviors were examined. Results indicate that dust deposition significantly alters surface wettability and energy dissipation pathways, leading to reduced rebound efficiency and enhanced droplet-dust interactions. At a low dust density of 10.4 g/m2, spreading and rebound were predominantly governed by droplet kinetic energy. However, with growing droplet volume and drop height, both spreading and rebound were increasingly suppressed. Specifically, for 50 mu L droplets, as the dust density increases from 0 to 31.2 g/m2, the maximum spreading factor drops from 2.0 to 1.4, while the minimum rebound factor decreases from 1.0 to 0.3. The maximum slip coefficient reaches 3.0 under clean conditions but increases to 4.0 when the drop height is raised to 3 cm, indicating that greater initial kinetic energy directly strengthens droplet mobility, reflecting a partial compensation for energy dissipation due to particulate resistance under higher kinetic energy. The findings provide insights into the self-cleaning mechanisms of superhydrophobic surfaces and offer guidance for optimizing photovoltaic module maintenance strategies.

This study systematically investigates the internal short circuit (ISC) characteristics of lithium-ion batteries (LIBs) for electric vehicles under nail penetration abuse coupled with charge/discharge operations. By establishing a nail penetration coupled with dynamic charge/discharge experimental platform and using commercial NCM pouch cells as test subjects, it comprehensively analyzes the effects of different charge/discharge operations (charging, discharging, resting) and C-rates (0.2 C-3 C) on battery surface temperature, voltage, current, mass loss, and thermal runaway behavior. The research finds that a mutual inhibitory effect exists between discharge operation and ISC, manifested as reduced discharge current along with decreased surge current, temperature rise rate, and voltage drop, significantly lowering the battery's thermal runaway risk. In contrast, charging operation exacerbates ISC severity, causing increases in surge current, temperature rise rate, maximum temperature, and mass loss with higher C-rates, substantially enhancing thermal hazards. The study further reveals the underlying mechanisms: during discharge, a "Li+ competition" effect suppresses the short-circuit current, whereas during charging, the external power source and the battery jointly form the short-circuit current, intensifying heat generation. This research provides important experimental evidence and theoretical support for the thermal safety design and risk assessment of LIBs under operating conditions.

The application of supercritical CO2 (S-CO2) for coal and rock fragmentation has emerged as an important research direction in the field of carbon capture, utilization, and storage (CCUS). This study employs computational fluid dynamics to numerically simulate the jet structure and flow characteristics during S-CO2 release from the expansion tube of a fracturing device. User-defined real gas models (UDRGM) and user-defined functions (UDFs) are used together with a table-lookup method and pressure-temperature bilinear interpolation. The mixture multiphase model, Lee phase-change model, and SST k–ω turbulence model are coupled to capture transient variations in flow and thermodynamic properties during jetting. The effects of nozzle diameter and nozzle location on the flow field, pressure characteristics, and velocity distribution of confined S-CO2 jets are systematically investigated. Results indicate that increasing nozzle diameter significantly improves the impact loading characteristics associated with fracturing effectiveness. The average maximum wall pressure increases from 6.01 MPa to 9.84 MPa (63.73%), while the pressure-duration product increases from 39.18 MPa·ms to 71.50 MPa·ms (82.49%). Moving the nozzle closer to the high-pressure source prolongs the high-pressure loading duration on the rock wall and increases the average maximum wall pressure from 7.67 MPa to 9.80 MPa (27.77%). Comparative analysis indicates that nozzle diameter is the dominant parameter governing fracturing effectiveness, while nozzle position plays a secondary role. These findings provide theoretical support for nozzle optimization and the design of S-CO₂ jet fracturing devices.

Conventional compressed carbon dioxide energy storage systems face performance limitations due to low expander inlet temperatures. Adding thermal energy through conventional fossil fuel combustion raises operational complexity and economic costs, with limited environmental advantages. This study introduces a trans-critical compressed carbon dioxide energy storage system that integrates solar energy, offering significant potential for development. Thermodynamic models of trans-critical compressed carbon dioxide energy storage system, incorporating distinct heat recovery sources (compression heat recovery and exhaust waste heat recovery), have been developed. Thermodynamic analyses were conducted using temperature-entropy diagrams. Under identical power consumption, the solar energy conversion efficiencies of systems are 21.22 % and 27.29 %. The round-trip efficiencies, at 81.86 % and 81.92 %, represent increases of 9.70 % and 9.76 % over conventional compressed carbon dioxide energy storage systems. Additionally, the electricity generation per unit volume of storage improved from 0.22 kWh/m3 to 0.38 kWh/m3. From a thermodynamic perspective, the trans-critical compressed carbon dioxide energy storage system utilizing exhaust waste heat recovery outperformed the system with compression heat recovery. Exergy analysis indicates that the established systems exhibit exergy efficiencies of 45.12 % and 51.75 %, respectively. The systems were further analyzed for exergy flow and exergy destruction, revealing that the trough solar collector is the primary source of exergy destruction in the solar thermal storage-equipped trans-critical compressed carbon dioxide energy storage system, accounting for 65.43 % and 59.03 %, respectively. In summary, the proposed system mitigates the limitations of renewable energy generation while enhancing operating parameters and efficiencies of the trans-critical compressed carbon dioxide energy storage system. This work provides a reference for selecting coupled solar energy schemes in next-generation long-duration energy storage systems.

Compared with air, carbon dioxide exhibits superior physical properties. These superior properties render carbon dioxide a highly promising medium for large-scale Compressed Carbon Dioxide Energy Storage (CCES) applications. However, conventional CCES systems are limited by low power output and cycle efficiency, primarily due to the low temperature at the expander inlet. Although conventional fossil fuel combustion can be used to raise the inlet temperature, this approach increases system complexity, economic costs, and environmental impact. To address these limitations, this study proposes a transcritical compressed CO2 energy storage (TC-CCES) system integrated with renewable energy and augmented by solar heating. Two configurations based on distinct heat recovery methods were designed and analyzed: a solar-augmented TC-CCES system with compression heat recovery (System 2) and a solar-augmented TC-CCES system with exhaust waste heat recovery (System 3). An economic analysis was established for the systems. Based on the thermodynamic model of a baseline TC-CCES system (System 1), Systems 2 and 3 were developed. Although the energy storage density remained largely unchanged, the round-trip efficiency (RTE) values for System 2 and System 3 increased by 9.70% and 9.76%, respectively, compared to System 1 (72.16%). System 3 achieved an annual total revenue of 3.53 million CNY, resulting in an annual net profit of 1.70 million CNY, which is approximately 3.7% higher than that of System 2 (1.64 million CNY).

To address the issue of reduced heat transfer efficiency in plate heat exchangers caused by fouling, this study proposes a fouling thermal resistance prediction method based on a Long Short-Term Memory-Kalman Filter fusion model. An experimental platform was constructed using the equivalent scaling method, where inlet/outlet temperature, pressure, and flow rate data from the cold/hot sides were collected, and fouling thermal resistance was calculated via heat transfer principles. In experiments, calcium carbonate fouling was generated through a chemical reaction between NaHCO3 and CaCl2, and aluminum oxide (Al2O3) powder was added to simulate particulate fouling. To distinguish fouling characteristics, a multi-feature Long Short-Term Memory (LSTM) model (with cold-side pressure drop and flow rate as inputs) was developed and compared with a single-feature LSTM model; the Kalman Filter (KF)was then introduced to optimize prediction accuracy. Results demonstrate that the multi-feature LSTM model significantly outperforms the single-feature model (reducing MAE by 7.5% and MSE by 20.8%). After fusing with the KF, the model further enhances stability via noise suppression and trend correction (achieving MAE = 4.84 & times; 10-6 and MSE = 4.03 & times; 10-11). This study uncovers the system-level impact mechanism of heat exchanger fouling, providing a theoretical foundation for the dynamic monitoring of industrial equipment.

Nanofluids obtained by the incorporation of nanoparticles into ternary carbonates be capable of enhancing the low heat transfer and the capacity for thermal storage as well as the poor fluidity of carbonate. In this study, 31.5 mass

To further improve the efficiency of the next-generation solar thermal power generation systems, higher temperature requirements were imposed on heat transfer materials. Ternary carbonates had a wider operating temperature range, meeting the requirements of the next generation of solar thermal power generation systems. Meanwhile, adding SiO2 to the ternary carbonates can improve their heat transfer and storage performance. This study explored the mechanism of nanoparticle enhanced thermal and physical properties of the ternary carbonates, and provided a more comprehensive analysis of the mechanism by which nanoparticles improve the thermal conductivity (TC) and specific heat capacity (SHC) of the carbonates. including Brownian motion, microconvection, solid-liquid interfacial layers, and particle agglomeration, the key factors for enhancing the SHC and TC of the ternary carbonates with nanoparticles were revealed. The result demonstrated that the microconvection effect previously proposed in literature as a mechanism for enhancing heat transfer efficiency be unable to elucidate the observed TC improvement in nanofluids. The enhancement in TC can be ascribed to the Brownian motion occurring between particles, the presence of 0.3 nm solid-liquid interfacial layers around nanoparticles, and nanoparticles agglomeration. Investigations into heat storage mechanism revealed that semisolid layers, the high SHC of nanoparticles, and the good dispersibility contribute to increase SHC of the carbonates. While validating existing theories, this study identified Brownian motion as an additional factor enhanced TC, systematically validating the mechanism behind thermophysical property reinforcement in the ternary carbonates. These findings serve as reference framework for informing the selection and design processes of nanocomposite materials in subsequent investigations.