Search Results (169)

With the continuous development and innovation of thermal management technology for lithium-ion batteries, the advantages of direct immersion liquid cooling technology have become increasingly prominent. However, at present, there is relatively little research on immersion liquid cooling systems, and current research is still mainly focused on small-capacity battery systems. Therefore, taking a large-capacity battery pack as the research object, a new type of single-phase immersion liquid cooling system was designed. The battery pack has a charge and discharge rate of 1C, consists of 52 cells, and has a total capacity of 52.249 kWh. It was compared with traditional liquid cooling and static immersion liquid cooling. Then, the effects of the aperture of the flow distributor, the inlet flow rate of the cooling liquid, and the type of cooling liquid on the cooling performance of the dynamic immersion battery pack were discussed. The holes on the flow distribution plate are primarily designed to facilitate a relatively uniform distribution of incoming liquid flow. Our research found that compared with traditional liquid cooling and static immersion liquid cooling, the overall cooling performance of the dynamic immersion cooling system was significantly improved, with the maximum temperature T_max decreasing by 7.8 °C and 6.6 °C, the maximum temperature difference ΔT_max of the entire pack decreasing by 5.5 °C and 5.8 °C, and the maximum temperature difference U-DΔT_max between the top and bottom surfaces of the battery pack decreasing by 10.1 °C and 8.96 °C. An appropriate aperture had a positive impact on the cooling effect of the battery pack, with the best effect at a aperture of 4 mm. T_max and ΔT_max gradually decreased with an increase in the flow rate of the cooling liquid, with T_max decreasing from 42.3 °C to 31 °C and ΔT_max decreasing from 14.8 °C to 7.9 °C, but the rate of the temperature decrease gradually decreased. Deionized water in the cooling liquid had the best cooling effect, while ethyl silicone oil had the worst cooling effect. The novel single-phase immersion cooling system developed in this study serves as a valuable reference for the design of immersion liquid cooling systems in large-capacity battery packs, contributing to enhanced temperature uniformity and improved system safety. Full article

To investigate the residual load-bearing capacity of composite steel truss bridge girders after vehicle fire, a 100 m simple supported composite steel truss bridge girder was selected as the research object, and a typical oil tanker fire was taken as the fire scenario. This study identifies the most critical conditions associated with an oil tanker fire and outlines the degradation pattern of the residual load-bearing capacity of composite steel truss bridge girders after a vehicle fire. It also proposes a damage classification standard and an evaluation method for the load-bearing capacity based on the structural failure path and load-displacement curve. The results indicate that the most critical scenario during a vehicle fire occurs when the fire is located on the bridge deck, particularly in the middle section of the longitudinal bridge and the outermost lane of the transverse bridge. During a vehicle fire, the top chord is the component most affected by the thermal history. Under immersion cooling conditions, the remaining load-bearing capacity of the girder decreases more significantly compared with natural cooling. After the fire, the upper chord first reaches the yield strength, causing load transfer to adjacent horizontal inclined members. The stress of the horizontal inclined rod will develop rapidly, leading to structural instability and eventual failure. Four grades of load-bearing capacity damage for composite steel truss bridge girders after vehicle fire are defined to serve as references for practical engineering applications. Full article

As the popularity of electric vehicles (EVs) continues to increase, the need for effective and efficient driveline lubricants and dielectric coolants has become crucial. Commercially used mineral oils or synthetic ester-based coolants, despite performing satisfactorily, are not environmentally friendly. The fatty esters of vegetable oils, after overcoming their shortcomings (like poor oxidative stability, higher viscosity, and pour point) through chemical modification, have recently been used as potential dielectric coolants in transformers. The benefits of natural esters, including a higher flash point, breakdown voltage, dielectric character, thermal conductivity, and most importantly, readily biodegradable nature, have made them a suitable and sustainable substitute for traditional coolants in electric transformers. Based on their excellent performance in transformers, research on their application as dielectric immersion coolants in modern EVs has been emerging in recent years. This review primarily highlights the beneficial aspects of natural esters performing dual functions—cooling as well as lubricating, which is necessary for “wet” e-motors in EVs—through a comparative study with the commercially used mineral and synthetic coolants. The adoption of natural fatty esters of vegetable oils as an immersion cooling fluid is a significant sustainable step for the battery thermal management system (BTMS) of modern EVs considering environmental safety protocols. Continued research and development are necessary to overcome the ongoing challenges and optimize esters for widespread use in the rapidly expanding electric vehicle market. Full article

The study investigated the sperm motility and morphometry of pre-freeze and post-thaw boar epididymal semen cooled at increasing holding times at 18 °C. A total of 50 testes of heterogeneous boars were collected (5 testes/day) from the local abattoir and transported to the laboratory at 5 °C within 30 min after slaughter. Semen was retrieved from the caudal part of the epididymis using the slicing float-up method, diluted with Beltsville Thawing Solution extender, pooled in a 50 mL centrifuge tube/5 testes/day, and cooled at 18 °C. Following each holding time (0, 3, 6, 9, 12, 24, and 48 h), the cooled semen sample was re-suspended with Fraction A extender and stored at 5 °C for an additional 45 min. A cooled resuspended semen sample was then diluted with Fraction B extender, loaded into 0.25 mL straws, and frozen using liquid nitrogen vapour. Thawing was accomplished by immersing the semen straws in warm (37 °C) water for 1 min and the samples were evaluated for sperm motility and morphometry traits using the computer-assisted sperm analyzer system. The data were analyzed using variance analysis. Descriptive statistics were used to assess sperm morphometry, establishing the minimum and maximum values. Boar epididymal sperm survived for up to 48 h when held at 18 °C. Furthermore, the highest post-thawed sperm motility rates were observed in semen frozen after 3 h of holding time, with a sperm total motility of 85.9%, a progressive motility of 60.3%, and a rapid motility of 33.2%, as compared to other holding times (p < 0.05). The acceptable ranges for pre-freeze and post-thawed sperm morphology were head length (8.4–9.1 µm), width (4.4–4.8 µm), area (29.9–38.2 µm²), perimeter (20.1–23.7 µm), midpiece width (1.1–2.8 µm), and sperm shape, were consistent regardless of the holding time. A holding time of 3 h enhances the cryoresistance of sperm cooled at 18 °C. Therefore, these findings suggest that boar epididymal sperm can be effectively conserved and can maintain fertilization capability when cooled for 3 h at 18 °C before freezing. Full article

In response to the global imperative to reduce greenhouse gas emissions and fossil fuel dependency, electric vehicles (EVs) have emerged as a sustainable transportation alternative, primarily utilizing lithium-ion batteries (LIBs) due to their high energy density and efficiency. However, LIBs are highly sensitive to temperature fluctuations, significantly affecting their performance, lifespan, and safety. One of the most critical threats to the safe operation of LIBs is thermal runaway (TR), an uncontrollable exothermic process that can lead to catastrophic failure under abusive conditions. Moreover, thermal runaway propagation (TRP) can rapidly spread failures across battery cells, intensifying safety threats. To address these challenges, developing advanced battery thermal management systems (BTMS) is essential to ensure optimal temperature control and suppress TR and TRP within LIB modules. This review systematically evaluates advanced cooling strategies, including indirect liquid cooling, water mist cooling, immersion cooling, phase change material (PCM) cooling, and hybrid cooling based on the latest studies published between 2020 and 2025. The review highlights their mechanisms, effectiveness, and practical considerations for preventing TR initiation and suppressing TRP in battery modules. Finally, key findings and future directions for designing next-generation BTMS are proposed, contributing valuable insights for enhancing the safety and reliability of LIB applications. Full article

We demonstrate the use of Laser Power Converters (LPCs) driven by fiber laser light while immersed in transformer oil for heat management purposes. Reliability tests performed via extended continuous operation using 6–7 W of input power from 808 nm and 976 nm light propagating through oil show no degradation of components nor transmission losses from the oil for up to 1000 h. The operation of a bare die designed for use with 1040–1080 nm light and in direct contact with oil is also shown to be feasible. We discuss how the use of transformer oil can be beneficial to transfer excess heat away from LPCs in special applications. Full article

As the climate continues to warm, and municipal leaders look for cost-effective and timely approaches to urban sustainability, one increasingly sought-out approach is the use of tree canopy to cool neighborhoods. Despite widespread efforts to expand tree canopy in cities, an overwhelming body of evidence suggests that urban green space is declining across the U.S., yet little is known about the factors that propel these changes. Understanding the institutional and governance systems can help identify the opportunities for slow consistent declines. Using social network analysis (SNA) metrics, we examined stakeholder roles in power structures and decision-making processes within Portland, Oregon’s urban forest management. Our results reveal a highly decentralized urban forestry network (density = 0.0079), with weak cohesion (5.4%) among 162 stakeholders. Moving forward, while network governance may face obstacles from conflicting interests among community and interagency groups, transforming governance models at all levels will require developing periodic, collaborative urban forestry management plans to address nature-based planning challenges. These planning documents should strongly emphasize not only the prioritization of tree equity-related ordinances but also the optimization of eco-literacy and awareness through virtual reality (VR) technology. As a novel approach, immersive simulations demonstrate practical potential for showcasing urban forestry benefits in network governance outreach and consensus-building. Full article

As data centers expand, immersion cooling systems are gaining attention for thermal management of memory devices. To enable widespread adoption, it is essential to evaluate the impact of coolants on the reliability of memory packages. In this study, high-voltage direct current (DC) stress tests were conducted on commercial dynamic random access memory (DRAM) packages in both single-phase coolant and air environments to analyze heat generation and electrical characteristics. A DC voltage ranging from 2.5 to 3.1 V, which is higher than the regular operating voltage of 1.2 V, was applied. Temperature changes were measured using an infrared camera in the air, and a contact-based thermometer in the coolant. The leakage current was also evaluated through I-V curve analysis. Heat generation and changes in leakage currents were not significant in either environment until the applied voltage stress exceeded approximately twice the standard voltage (2.5–2.8 V). However, the package’s degradation accelerated when the applied voltages exceeded 3.0 V, demonstrating a nonlinear increase in temperature and leakage current. Full article

In this study, straight and looped heat pipes were designed and manufactured, and their performance in cooling cylindrical lithium-ion batteries known as standard 18,650 batteries on the market was investigated. Pure water, methanol, and thermasolv IM2 liquid were used as working fluids in heat pipes. Nanofluid solutions were measured and prepared on a precision balance as 2% by weight according to the working fluid. These nanosolutions were injected into the heat pipes at a ratio of one-third by volume of the working fluids. In the designed experimental setup, the coils were placed 1 cm above the evaporator part of the heat pipes. Thanks to the designed electrical circuits, the amount of load given to and withdrawn from the batteries is controlled. The heated batteries evaporate the liquid in the heat pipe, the vapor rises and reaches the condenser. As a result of the evaporation, efficient heat transfer from the evaporator to the condenser takes place by transporting nanoparticles. At a certain flow rate, the refrigerant is transferred to the refrigerant as a result of the withdrawal of the refrigerant from the heat pipe. In this study, it is seen that the immersion method of the evaporator part in the pool full of IM2 liquid is repeated and the results are examined. Full article

The increasing demand for ultra-fast charging in electric vehicles (EVs) necessitates advancements in thermal management strategies to mitigate Joule heating, which arises due to electrical resistance in charging connectors and cable cores. This study presents a numerical analysis of immersion cooling performance for ultra-fast chargers under realistic charging conditions. The simulated results are validated by experiments with a maximum deviation of 5.5% at 600 A and 700 A currents. The novelty of this work lies in the consideration of a realistic charging cable length of 5 m, the evaluation of temperature characteristics in the charger connector, and the analysis of geometric symmetry in the charging cable and coolant configuration to ensure uniform heat distribution. Key operating conditions were systematically analyzed, including applied currents, ambient temperatures, coolant flow rates, cable core cross-sectional areas, and different types of coolants. Results indicate that increasing the applied current from 400 A to 800 A raised the connector temperature from 60.73 °C to 97.33 °C. As the ambient temperature increased from 20 °C to 50 °C, the connector temperature rose significantly from 42.71 °C to 74.99 °C, while the maximum cable core temperature increased from 65.26 °C to 100.61 °C. Increasing the cable core cross-sectional area from 20 mm² to 30 mm² reduced the connector temperature from 77.20 °C to 74.99 °C. Meanwhile, increasing the coolant flow rate from 2 LPM to 5 LPM had a negligible effect on the connector temperature. Among the three tested coolants, Novec 7500 exhibited the highest cooling efficiency, achieving the lowest contact temperature (74.76 °C) and the highest performance evaluation criteria (PEC) value of 3.8. This study provides valuable guidelines for enhancing symmetry-driven thermal management systems and demonstrates the potential of immersion cooling to improve efficiency, safety, and operational reliability in next-generation high-power EV chargers. Full article

The purpose of this study is to examine the performance of a new cooling system whose mechanism is integrated with an immersion cooling system and a heat pipe mechanism. The study comprises an experimental test and a numerical analysis using the 1-D model. In the experiment, a metal heating block that simulated the pouch-type cell was used. It was composed of multiple heaters and thermal sensors, working as a heating model of the battery while observing the thermal behavior of the cell at the same time. The temperature of the heating block was influenced by the types of working fluid and wick structure, which are the key points of this system. Their role is to promote the heat exchange process by facilitating the evaporation and condensation processes. Their performance was evaluated based on different types of shapes and materials of wicks. The simulation model was designed and its feasibility verified with the experiment results. Furthermore, different types of dielectric working fluids and variations in porosities were examined through the simulation model, which are crucial to determining the characteristics of the wick structure. Full article

This study elucidates the underlying formation mechanisms and mitigation strategies for the W-shaped solidification profile in slab continuous casting. Through the development of a multiphysics coupling numerical model, integrated with measured nozzle cooling characteristics in the secondary cooling zone, the effect of steel flow patterns in mold and non-uniform cooling conditions in the secondary cooling zone on solidifying shell evolution is systematically studied. A principal finding is that wide-face shell erosion, induced by both the radial expansion jet and the lower recirculation, constitutes the primary determinant of uneven shell thickness. An increase in the immersion depth and inclination angle of the nozzle side-hole exacerbates the non-uniformity of the solidified shell. Non-uniform cooling in the secondary cooling zone further amplifies the shell thickness differences, culminating in characteristic dumbbell-shaped solidified shell geometry. Strategic implementation of localized enhanced cooling on the wide face in the secondary cooling zone demonstrates significant improvement in shell uniformity, with implementation efficacy contingent upon a critical process window (Segments 1–6). These findings establish mechanistic foundations and deliver practical guidance for minimizing centerline segregation through optimized continuous casting parameter configuration. Full article

The accelerated growth of electric vehicle (EV) powertrains has prompted the development of specialized fluids that meet stringent thermal and electrical requirements for immersion cooling systems, including interactions with non-metallic components like fluoroelastomer (FKM). This research investigates the interactions between fluoroelastomer (FKM) and two potential base fluids—polyalphaolefin (PAO4) and a polyol ester (POE)—to assess their suitability for immersion cooling applications. Immersion tests, following an adapted ASTM D7216 standard, evidenced changes in FKM’s mass, Shore A hardness, and tensile strength. Furthermore, the physical, electrical, and thermal properties of the tested fluids were analyzed before and after immersion to determine whether contact with the FKM elastomer compromised their performance. The findings of this study reveal that the fluid exerts a greater influence on the elastomer than vice versa. This study bridges a knowledge gap in regards to EV fluid development and material science, contributing to the development of durable and efficient thermal management solutions. Full article

Thermal technologies that effectively deliver thermal stimulation through skin-integrated systems and enable temperature perception via the activation of cutaneous thermoreceptors are key to enhancing immersive experiences in virtual and augmented reality (VR/AR) through multisensory engagement. However, recent advancements and commercial adoption have predominantly focused on haptic rather than thermal technology. This review provides an overview of recent advancements in wearable thermal devices (WTDs) designed to reconstruct artificial thermal sensations for VR/AR applications. It examines key thermal stimulation parameters, including stimulation area, magnitude, and duration, with a focus on thermal perception mechanisms and thermoreceptor distribution in the skin. Input power requirements for surpassing thermal perception thresholds are discussed based on analytical modeling. Material choices for WTDs, including metal nanowires, carbon nanotubes, liquid metals, thermoelectric devices, and passive cooling elements, are introduced. The functionalities, device designs, operation modes, fabrication processes, and electrical and mechanical properties of various WTDs are analyzed. Representative applications illustrate how flexible, thin WTDs enable immersive VR/AR experiences through spatiotemporal, programmable stimulation. A concluding section summarizes key challenges and future opportunities in advancing skin–integrated VR/AR systems. Full article

When the inlet flow velocity in the disc-type winding region of an oil-immersed transformer operates within a high Reynolds number range, it leads to an uneven distribution of oil flow. This phenomenon results in the abnormal occurrence of reverse oil flow in the bottom oil ducts, causing the hotspot temperature to rise instead of decrease. To address this issue, a three-node flow resistance module was introduced at the intersection of T-shaped oil ducts based on the flow paths of oil in the main and branch ducts within the disc-type winding region. A flow network model for the transformer winding region was subsequently constructed. The accuracy of the model was validated through CFD simulations and experiments conducted on a transformer winding region test platform, with a maximum relative error of 4.02%. The model successfully predicted the flow distribution of the cooling oil within the winding region. Furthermore, by considering the structural characteristics of the winding region and the principles of heat transfer, particular attention was given to variations in local Nusselt number correlations. This led to the development of a thermal network model tailored to the winding region experiencing reverse oil flow. Comparative analysis of the model’s calculation results yielded a maximum relative error of only 1.12%, demonstrating its ability to rapidly and accurately elucidate the reverse oil flow effect. This study provides a theoretical foundation for the identification and mitigation of reverse oil flow in future applications. Full article