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The performance of lithium-ion batteries is closely related to temperature, and much attention has been paid to their thermal safety. With the increasing application of the lithium-ion battery, higher requirements are put forward for battery thermal management systems. Compared with other cooling methods, liquid cooling is an efficient cooling method, which can control the maximum temperature and maximum temperature difference of the battery within an acceptable range. This article reviews the latest research in liquid cooling battery thermal management systems from the perspective of indirect and direct liquid cooling. Firstly, different coolants are compared. The indirect liquid cooling part analyzes the advantages and disadvantages of different liquid channels and system structures. Direct cooling summarizes the different systems’ differences in cooling effectiveness and energy consumption. Then, the combination of liquid cooling, air cooling, phase change materials, and heat pipes is examined. Later, the connection between the cooling and heating functions in the liquid thermal management system is considered. In addition, from a safety perspective, it is found that liquid cooling can effectively manage thermal runaway. Finally, some problems are put forward, and a summary and outlook are given.

As the inlet temperature of the gas turbine exceeds the high temperature limit of the blade materials, efficient leading edge cooling technologies are crucial for the further development of gas turbines. Therefore, this paper reviews the research progress on external cooling technology, internal cooling technology, and composite cooling technology for gas turbine rotating blade leading edge cooling. It focuses on the impact of the geometric shape, arrangement, and flow parameters of film cooling holes on external cooling performance, the influence of jet hole design, configuration, crossflow, ribs on internal cooling efficiency, and the characteristics and influencing factors of composite cooling technologies are also discussed. Among the most promising composite cooling techniques, the impingement jet film composite cooling technology and swirl film composite cooling technology stand out. For impingement jet film composite cooling technology, this paper explores the effects of blowing ratio, nozzle parameters, jet hole characteristics, and flow field parameters on the overall cooling performance of the rotating blade leading edge. Impingement jet film composite cooling technology has been shown to significantly improve the cooling performance of the leading edge compared to traditional single cooling techniques. For applications requiring large area cooling or maintaining film integrity, swirl film composite cooling technology not only enhances heat transfer efficiency but also improves the uniformity of heat transfer. The design of swirl nozzles, coolant flow rate, Reynolds number, and jet temperature all have significant effects on the heat transfer efficiency of swirl film composite cooling. To further advance the development of gas turbine rotating blade leading edge cooling technologies, it is recommended to focus on the study of film composite cooling techniques, particularly investigating the effects of various parameters of impingement, swirl on composite cooling performance.

Amidst the industrial transformation and upgrade, the new energy vehicle industry is at a crucial juncture. Power batteries, a vital component of new energy vehicles, are currently at the forefront of industry competition with a focus on technological innovation and performance enhancement. The operational temperature of a battery significantly impacts its efficiency, making the design of a reliable Thermal Management System (TMS) essential to ensure battery safety and stability. Cylindrical power batteries are widely utilized in the industry. This article outlines the four main structures and their drawbacks of TMS for cylindrical power batteries. Among these structures, air cooling falls short in meeting high heat dissipation requirements. Liquid cooling is expensive, intricate, and adds considerable weight. Phase Change Materials (PCM) are not yet prevalent in practical applications. Similarly, heat pipes are relatively uncommon in large high-power battery packs. To better align with the new energy vehicle industry’s demands for top-notch performance, cost-effectiveness, eco-friendliness, and reliability, this paper strongly recommends delving deeper into composite cooling solutions. The construction of an economically viable and fully optimized composite cooling method is poised to become a significant scientific challenge for future research endeavors.

This study examines the effects of jet Reynolds number (Re) and jet hole diameter (d) on flow and heat transfer in the leading-edge full-impingement cooling channel of a gas turbine nozzle guide vanes (NGV). Experiments via transient liquid crystal and numerical simulations were conducted. Results reveal that the peak Nusselt number (Nu) initially increases and then reaches a fixed value from root to tip in the spanwise direction. The area-averaged Nu presents the descending trend of the shower-head surface, pressure surface, and suction surface. In addition, the bleeding from film holes causes significant local flow acceleration and Turbulence Kinetic Energy (TKE) enhancement of 10.69%, resulting in local heat transfer elevation. The heat transfer enhancement region on both pressure and suction surfaces is inclined towards the shower-head at a 5% span region. Increasing the jet hole diameter (d) results in a decrease in both averaged Nu and TKE on the target surface. Simultaneously, the Nu gradient increases. When d = 1.6 mm, there is a recirculation zone near the hub on the suction surface and a strong crossflow near the hub on the pressure surface. The jet flow on the target surface is bending towards the shower-head. When d = 0.8 mm, the overall heat transfer is highest. However, considering heat transfer uniformity, a jet hole diameter of d = 1.2 mm offers better application.

Axial flux motors, characterized by compact axial dimensions and high torque density, are well-suited for space-constrained applications such as in-wheel drives and flying vehicles. However, conventional axial flux permanent magnet synchronous motors (AFPMSMs) face challenges such as high-temperature demagnetization, reduced efficiency at high speeds, and elevated manufacturing costs. Electrically excited synchronous motors (EESMs) offer a promising alternative, providing high-temperature reliability and superior high-speed capability while maintaining high torque density. In this paper, a novel composite-cooled axial flux electrically excited synchronous motor (AFEESM) is proposed. From an electromagnetic design perspective, the effects of key parameters such as shaft-to-outer-diameter ratio, inner-to-outer-diameter ratio, slot depth, and yoke thickness on output performance are systematically investigated, and a dedicated design procedure is established. Through multi-objective optimization, the motor’s torque output is increased by 19.6%. Comparative simulations are conducted to evaluate differences in torque density, efficiency, and cost between the proposed AFEESM, a conventional radial flux EESM, and an AFPMSM. To address the cooling requirements of double-sided windings on both the stator and rotor, a dual-channel composite cooling structure is developed, integrating internal–external double-loop water cooling for the stator and axial through-hole air cooling for the rotor, reducing the peak temperature by over 36%. Finally, a prototype is manufactured, and no-load characteristics and load efficiency validate the effectiveness of the electromagnetic design and the structural reliability of the motor.

In order to deeply explore the influence and mechanism of the impingement chamber structure and the number of cooling units on the film cooling performance. Based on the Realizable k-ε turbulence model with finite volume composite cooling structure as the research object, the cold flow in the cooling structure with different volumes and shapes of impingement chambers and different numbers of cooling units is investigated in this paper. The numerical method is verified by the existing experimental results, and the grid independence analysis is carried out. The changes of flow field structure and cooling effectiveness under different working conditions are comprehensively analyzed. The results indicate that the volume and shape of the impingement chamber influence the flow structure of the cold flow in the chamber, thereby affecting the flow state of the cold flow in the film hole, ultimately resulting in different momentum distributions of the cold flow at the outlet of the film hole. The strength of the kidney-shaped vortex pair on both sides of the film is directly affected by the momentum distribution of the cold flow at this location, leading to the difference in the film cooling flow on the wall. It is found that the composite cooling structure with a volume of 0.8Vr and a circle impingement chamber has better cooling flow ductility and wall adhesion. The momentum distribution of the film hole outlet section of the increased cooling unit is affected by the film flow with regarding the impingement hole, impingement chamber and film hole as a single cooling unit, and the surface-averaged film cooling effectiveness at Nu=4 is improved by approximately 78.47% compared to Nu=1.

The cooling performance of combined cooling depends on the cooling performance of individual structures, such as film cooling and impingement cooling, and the interaction between the two structures. This paper uses a numerical simulation method to thoroughly study a flat plate model with a combined cooling structure of impingement/film cooling, employing the Shear Stress Transport (SST) turbulence model. The aim is to reveal the impact of different impingement and film structures on the overall cooling effectiveness, providing theoretical guidance for engineering applications. At a typical blowing ratio of 1.5, various impingement cooling structures with different hole diameters, impingement distances, and hole shapes are considered, combined with two types of outer film cooling holes (simple cylindrical and cratered holes). The results indicate that the three variations in the internal cooling structure positively impact the internal heat transfer coefficient and the overall cooling effectiveness on the outer wall. Among them, the influence of the hole diameter factor is the most significant, while the impact of the impingement distance is less pronounced. Benefiting from the anti-kidney vortex pairs of the cratered film cooling holes, the cratered 2 improves the area-averaged overall cooling effectiveness by 38.69% compared with the simple cylindrical reference film cooling hole. Within the blowing ratio range of 0.5–2.5, using cratered 2 and the optimal impingement cooling structure, the overall cooling effectiveness is improved by 20.39–39.14% compared with the standard impingement structure and cylindrical film cooling hole combined structure.

The internal heat transfer performance and flow structures of a sweeping jet and film composite cooling on a flat plate were numerically studied. Sweeping jet and film composite cooling consists of a fluidic oscillator and 20 cylindrical film holes; the direct jet is formed by removing the feedback from the fluidic oscillator, which is different from the traditional cylindrical nozzle. Four different mass flow rates of coolant were considered, and the inclination angle of the film hole was 30°. The Conjugate Heat Transfer method (CHT) and Unsteady Reynolds Averaged Navier Stokes equation (URANS) were employed. The results indicated that the flow resistance coefficients of the sweeping jet were larger than those of the direct jet, and the Nusselt number monotonously increased with the increase in the mass flow rate. Compared to the direct jet, the sweeping jet had a more spatially uniform heat removal rate, and the area-averaged Nusselt number was slightly lower. Therefore, the sweeping jet and film composite cooling caused the distribution of the flat plate heat transfer to be more uniform. It is worth noting that the novel direct jet nozzle in the present work had considerable area-averaged impingement cooling effectiveness.

Against the background of increasing gas turbine inlet temperature and decreasing amount of cooling air, laminated cooling structure (LCS) is a highly efficient composite cooling structure with the advantages of lower cooling air consumption and higher cooling efficiency, which is a promising development direction for future wall cooling technology. In this review, we provide an overview of LCS's structural optimization research. The experimental and simulation studies therein were reviewed, and the major influencing parameters in the structure were analyzed in detail. The characteristics of various optimization methods were investigated, and the research methodology and optimization process of multi-objective optimization of laminated cooling structure were summarized. The review shows that laminated cooling structure, as a kind of composite cooling structure, has numerous geometrical and flow factors affecting its cooling efficiency. Multi-objective optimization techniques have effective application prospects in this field. In the future, researchers should focus on enhancing the efficiency and accuracy of multi-objective optimization algorithms. They should also explore the application of machine learning and artificial intelligence in LCS optimization, thereby promoting the intelligence and automation of design optimization.

Based on the actual operation parameters and temperature-dependent material properties of a gas turbine unit, composite cooling blade model and corresponding reliable boundary conditions were established. Transient thermal-fluid-solid coupling simulations were then comprehensively conducted to analyze the transient flow and the temperature field of the blade under startup, shutdown, and variable loads condition. Combined with the obtained transient temperature data, the non-linear finite element method was exploited to examine the effect of these transient operations on the turbine blade thermal stress characteristics. Results show that the temperature and pressure on the blade surface increase with the load level and vice versa. As the startup process progresses, the film cooling effectiveness and the heat convection of airflows inside the blade continuously grow; high-temperature areas on the pressure surface and along the trailing edge of the blade tip gradually disappear. Locally high-temperature zones with the maximum of 1280 K are generated at the air inlet and outlet of the blade platform and the leading edge of the blade tip. The high thermal stresses detected on the higher temperature side of the temperature gradient are commonly generated in places with large temperature gradients and significant geometry variations. For the startup/shutdown process, the rate of increase/decrease of the thermal stress is positively correlated with the load variation rate. A slight variation rate of the load (1.52%/min) can lead to an apparent alteration (41%) to the thermal stress. In operations under action of the variable load, although thermal stress is less sensitive to the load variation, the rising or falling rate of the exerted load still needs to be carefully controlled due to the highly leveled thermal stresses.