Search Results (63)

The High Temperature Gas-cooled Reactor (HTGR) is a Generation IV advanced nuclear reactor, which can realize inherent safety and prevent core melt. The Institute of Nuclear and New Energy Technology (INET) of Tsinghua University developed a commercial-scale 200 MWe High Temperature gas-cooled Reactor Pebble bed Module project (HTR-PM), which entered commercial operation on 6 December 2023. A passive Reactor Cavity Cooling System (RCCS) was designed for HTR-PM to export heat from the reactor cavity during normal operation and also in accident conditions, keeping the safety of the reactor pressure vessel (RPV) and reactor cavity. The RCCS of HTR-PM has been designed as three independent sets; the normal operation of two sets of RCCS can guarantee the safety of the PRV and reactor activity. The heat can be transferred from the RPV to the final heat sink atmosphere through thermal radiation and natural convection in the reactor cavity, and the natural circulation of water and air in the RCCS. The CAVCO code was developed by the INET to simulate the behavior of an RCCS. In this paper, assuming different RPV temperatures and different ambient temperatures, as well as assuming all or parts of the RCCS sets work, the performances of RCCS are studied by CAVCO to evaluate its operational reliability, so as to provide a reference for further optimization. The analysis results indicate that even under hypothetically extremely RPV temperatures, two sets of RCCS could effectively remove heat without causing water boiling or system failure. However, during the winter when ambient temperatures are low, particularly when the reactor operates at a lower RPV temperature, additional attention must be given to the operational safety of the system. It is crucial to prevent system failure caused by the freezing of circulating water and the potential cracking of water-cooling pipes due to freezing. Depending on the reactor status and ambient conditions, one or all three sets of RCCS may need to be taken offline. In addition, the maximum heat removal capacity of the RCCS with only two sets operational exceeds the design requirement of 1.2 MW. When the ambient temperature fluctuates significantly, it may be advisable to increase the number of available RCCS sets to mitigate the effect of abrupt changes in cooling water temperature on pipeline thermal stress. Full article

This paper proposes an enhanced cooling method for multi-chip power modules (e.g., in MMC inverters) with uneven power loss in all-electric propulsion ships based on sintered heat pipe parameter optimization and special-shaped design. First, five key parameters of straight sintered heat pipes were optimized: placement directly under hotspot chips, 10 mm in diameter, quantity matching the number of hotspot chips, length equal to the heatsink side length, and direction perpendicular to heatsink fins. Then, a C-shaped heat pipe was designed using the parallel thermal resistance principle, which forms two parallel low-thermal-resistance paths and outperforms conventional U-shaped ones. Finite element simulations showed that the hotspot temperature of the conventional heatsink was 91.26 °C, while it dropped to 87.35 °C with optimized straight heat pipes and further to 80.85 °C with C-shaped ones. Experiments verified an 11.65% temperature reduction (from 86.7 °C of conventional heatsinks to 76.6 °C of C-shaped heat pipe heatsinks). This method effectively lowers hotspot temperatures, reduces device failure rates, improves the thermal reliability of power modules, and provides a generalized design methodology for heatsinks of various power electronic converters. Full article

This study generated an AI (Artificial Intelligence)-based prediction model for identifying high-risk groups of failures in urban district heating pipelines using pipeline attribute information and historical failure records. A total of 324,495 records from normally operating pipelines and 2293 failure cases were collected. Because the dataset exhibited severe imbalance, a KNN (K Nearest Neighbors)-based similarity selection was applied to reclassify the top 10% of normal data most similar to failure cases as high-risk. Input variables for model development included pipe diameter, purpose, insulation level, year of burial, and burial environment, supplemented with derived variables to enhance predictive capacity. The dataset was trained using XGBoost (eXtreme Gradient Boosting) v3.0.2, LightGBM (Light Gradient-Boosting Machine) v4.5.0, and an ensemble model (XGBoost + LightGBM), and the performance metrics were compared. The XGBoost model (K = 2) achieved the best results, with an F2-score of 0.921 and an AUC of 0.993. Variable importance analysis indicated that year of burial, insulation level, and purpose were the most influential features, highlighting pipeline aging and insulation condition as key determinants of high-risk classification. The proposed approach enables prioritization of failure risk management and identification of vulnerable sections using only attribute data, even in situations where sensor installation and infrared thermography are limited. Future research should consider distance functions suitable for mixed variables, sensitivity to unit length, and SHAP (Shapley Additive exPlanations)-based interpretability analysis to further generalize the model and enhance its field applicability. Full article

Buried pipelines in permafrost areas are affected by harsh environments, especially those with defects and damages, which are prone to failure or even leakage accidents. However, current research is limited to single-factor analysis and fails to comprehensively consider the interaction relationships among temperature fields, moisture fields, and stress fields. Therefore, based on the thermodynamic equilibrium equation and the ice–water phase transition theory, this paper constructs the temperature field equation including the latent heat of phase transition, the water field equation considering the migration of unfrozen water, and the elastoplastic stress field equation. A numerical model of the heat–water–force three-field coupling is established to systematically study the influence laws of key parameters such as burial depth, water content, pipe diameter, and wall thickness on the strain distribution of pipelines with defects. The numerical simulation results show that the moisture content has the most significant influence on the stress of pipelines. Pipelines with defects are more prone to damage under the action of freeze–thaw cycles. Based on data analysis, the safety criteria for pipelines were designed, the strain response surface function of pipelines was constructed, and the simulation was verified through experiments. It was concluded that the response surface function has good predictability, with a prediction accuracy of over 90%. Full article

The article presents a method for selecting spray coating systems for furnace walls and heat exchangers, aimed at protecting them and intensifying heat exchange processes. Calculations were made of the effect of the mutual emissivity coefficient between the heating medium (exhaust gases) and the surface of the exchanger—both uncoated and coated—on the heat flux value. Selected coating systems were applied in laboratory conditions by spraying them onto the boiler surfaces and then measuring their heat exchange efficiency with the cooling medium (water) flowing through the piping system. The results of the laboratory tests were verified under industrial conditions in metallurgical installations, confirming the accuracy of the calculations and the validity of using spray coatings to increase thermal efficiency. The use of appropriately selected coating systems increases heat absorption, extends the service life of exchangers, reduces the risk of cooling system failure, and lowers the cost of heating equipment repairs. Full article

The increasing complexity of Water Distribution Systems (WDSs), driven by urbanization, climate change, and aging infrastructure, necessitates robust methods for risk assessment and visualization. This study presents a practical methodology for mapping the risk of water supply disruption or reduction using five parameters: Probability (P), Consequences (C), Water Pipe category (WP), Inhabitants exposed (I), and response Efficiency (E). The approach enables comprehensive analysis of the risk associated with specific pipeline segments within an Analyzed Supply Area (ASA). The method integrates statistical and operational data, allowing utilities to evaluate vulnerability, identify Critical Infrastructure (CI), and prioritize maintenance. The investigation conducted during the study revealed that cast iron and steel pipes with large diameters (e.g., 400 mm) show the highest failure probability and impact. Despite a calculated risk value (r_LW = 80), effective response measures—including specialized repair teams and equipment—kept the risk acceptable. The results demonstrate that historical failure and response data enhance risk identification and management. The generated risk maps facilitate spatial visualization of high-risk areas, supporting decision-making processes, renovation planning, and emergency preparedness. Integration with GIS tools, including GeoMedia and Google Earth programmes, enables dynamic map creation and simulation of response scenarios. The methodology is scalable and adaptable to any WDS, and potentially to other municipal systems such as wastewater and heating networks. By accounting for both technical and social dimensions of risk, the method supports improved water safety planning and infrastructure resilience. Future development should include real-time data integration and climate-related risk scenarios to increase predictive accuracy and system adaptability. Full article

This study experimentally analyzes the performance of a passive thermal management system using a three-dimensional (3D) pulsating heat pipe (PHP) designed for pouch cell batteries in electric vehicles. The term “3D” refers to the complex spatial arrangement of the PHP, which features multiple interconnected loops arranged in three dimensions to maximize heat dissipation efficiency and improve temperature uniformity around the battery pack. Lithium-ion pouch cells are increasingly favored for compact and lightweight battery packs but managing their heat generation is crucial to maintaining efficiency and preventing failure. This research investigates the operational parameters of a 3D PHP by testing two working fluids (R134a and Opteon-SF33), three filling ratios (30%, 50%, and 80%), and various condenser conditions (natural and forced convection at 5 °C, 20 °C, and 35 °C). The effectiveness of the PHP was tested using simulated battery discharge cycles, with power inputs ranging from 5 to 200 W. The results show that the 3D PHP significantly improves battery thermal management. Additionally, Opteon-SF33, an environmentally friendly refrigerant, offers excellent heat transfer properties, making 3D PHP with this fluid a promising passive cooling solution for electric vehicle batteries. Full article

Aimed at solving the problem of insulation failure caused by the local overheating of the oil-immersed converter transformer, this paper investigates the heat transfer characteristics of the 500 kV converter transformer based on the electromagnetic-flow-heat coupling model. Firstly, this paper used the finite element method to calculate the core and winding loss. Then, a two-dimensional fluid-heat coupling model was used to investigate the effects of the inlet flow rate and the radius of the oil pipe on the heat transfer characteristics. The results show that the larger the inlet flow rate, the smaller the specific gravity of high-temperature transformer oil at the upper end of the tank. Increasing the pipe radius can reduce the temperature of the heat dissipation of the transformer in relative equilibrium. Still, the pipe radius is too large to lead to the reflux of the transformer oil in the oil outlet. Increasing the central and sub-winding turn distance, the oil flow diffusion area and flow velocity increase. Thus, the temperature near the winding is reduced by about 9%, and the upper and lower wall temperature is also reduced by about 4%. Based on the analysis of the sensitivity weight indicators of the above indicators, it is found that the oil flow rate has the largest share of influence on the hot spot temperature of the transformer. Finally, the surface temperature of the oil tank when the converter transformer is at full load is measured. In the paper, the heat transfer characteristics of the converter transformer are investigated through simulation and measurement, which can provide a certain reference value for the study of the insulation performance of the converter transformer. Full article

The extensive use of lithium-ion batteries and other energy storage systems (ESS) in recent years has resulted in a critical need for effective thermal management solutions that ensure safe and reliable operations. Carbon-based materials (C-bMs) are a promising candidate for addressing the thermal challenges in ESS due to their unique thermal, electrical, and structural properties. This article provides a concise overview of C-bM thermal management solutions for improved battery safety. The key thermal management requirements and failure modes associated with battery systems are highlighted, underscoring the importance of effective battery thermal management (BTM). Various forms of C-bMs, including graphite, graphene, carbon nanotubes, carbon foams, nanodiamonds, and graphdiyne, are examined for their potential applications in battery thermal management systems. The recent innovations and advancements in C-bM thermal management solutions, such as phase change composites, heat pipes, and thermal interface materials, are highlighted. Furthermore, the latest research trends focus mainly on the development of hybrid battery thermal management solutions, carbon-based aerogels, and complex C-bM structures with tailored thermal pathways for optimized thermal management. Most of the current innovations are still at the laboratory scale; hence, future research efforts will be focused on developing integrated multi-functional C-bMs, sustainable and scalable manufacturing techniques, self-healing C-bMs composites, intelligent C-bMs, and further explorations of uncommon C-bMs. These advancements are bound to enhance performance, sustainability, and application-specific adaptations for BTM. This article provides valuable insights for researchers, and stakeholders interested in leveraging C-bMs for BTM. Full article

Aiming at the requirement of high stress ratio reinforcement in space steel structures, a novel method for enshancing the load-bearing capacity of casings through indirect welding to produce a reinforced steel pipe is introduced. To investigate how the mechanical properties of steel pipe members change when reinforced using this method, a series of welding reinforcement axial compression tests were designed, incorporating local reinforcements at various positions and with different initial stress ratios. By comparing the reinforced specimens with those left unreinforced, we obtained insights into the failure modes, ultimate bearing capacities, and strain data of the steel pipes. To further validate the findings, 236 finite element models were developed. These models allowed for a comprehensive analysis of the numerical results alongside the experimental data, taking into account the thermal effects of welding. Quantitative analyses were performed to assess the impact of the initial stress ratio, initial defects, welding heat effects, slenderness ratio, the area ratio between the reinforcement and the pipe, and the length of the reinforcement on the ultimate bearing capacity of the reinforced members. The findings indicate that residual stresses resulting from the welding process have a minimal influence on the ultimate bearing capacity. The method maintains over 75% of its efficiency even at initial stress ratios up to 0.8. Additionally, the study elucidates the rules governing the impact of localized reinforcement on the mechanical properties of loaded steel pipe members. Combining the theoretical calculations with numerical simulations, an empirical formula for estimating the ultimate bearing capacity of the reinforced pipe specimens was derived. The relative error of the formula is less than 10% with the experimental outcomes and the finite element analysis results thereby offering a reliable tool for engineering applications. Full article

Due to its advantages of simple structure and high inherent safety, the heat pipe cooled reactor (HPR) could be widely applied in deep-sea navigation, deep-space exploration and land-based power supply as a promising advanced special nuclear power equipment option. In HPRs, the space between the components (fuel rods and heat pipes) is filled with solid matrix material, forming a continuous solid reactor core. Thermo-mechanical response of the solid core is a special issue for HPRs and has great impacts on reactor safety. Considering the irradiation and burnup effects, the thermal and mechanical modeling of an HPR was conducted with ABAQUS-2021 in this study. The thermo-mechanical response under long-term normal operation, accident transients and single heat pipe failed conditions was simulated and analyzed. The whole core presents relatively good isothermality due to the high thermal conductivity of the solid matrix. As for the mechanical performance, the maximum stress was about 300 MPa, and the maximum displacement of the matrix could be as high as 3.7 mm. It could lead to significant variation of the reactor physical parameters, which warrants further attention in reactor design and safety analysis. Reactivity insertion accidents or single heat pipe failure has obvious influence on the thermo-mechanical performance of the local matrix, but they did not cause any failure risks, because the HPR design eliminates the dramatic power flash-up and the solid-state core avoids the heat transfer crisis caused by the coolant phase transition. A quantitative evaluation of thermo-mechanical performance was completed by this research, which is of great value for reactor design and safety evaluation of HPRs. Full article

Due to the severe corrosion environment, corrosion problems caused by sulfur deposition are one important reason for the failure of composite pipes in the long-term service process when Incoloy825/X65 bimetallic composite pipes are used in high-sulfur oil and gas transportation. In this paper, an Incoloy825/X65 bimetallic composite pipe was subjected to an immersion corrosion test in suspended sulfur solution to observe the corrosion morphology and characterize the corrosion products using a SEM, EDS, and XRD. The adsorption behavior of the Incoloy825 alloy in terms of sulfur elements was investigated. The results show that the heat-affected zone (HAZ) of the welding joint is the preferred region for pitting corrosion. The film of corrosion product on the Incoloy825 was mainly composed of NiS, FeS, and Cr₂S₃, and its thickness was 7–13 μm. With prolongation of the immersion time, the pitting resistance of the surface product film of nickel-based alloys is weakened and then enhanced, and the corrosion product film can act as a barrier to anion transfer and inhibit the occurrence of pitting. Full article

Overheating failure is one of the common causes of motor converter failure, so it is very important to improve the heat dissipation of the converter. In response to the inefficiency of traditional converter heat dissipation devices, we propose a novel heat dissipation device. The device combines micro-heat pipe arrays (MHPAs) and interleaved fins, and the MHPAs were initially applied in the converter. The device leverages the exceptional thermal conductivity of the MHPA to rapidly transfer heat from the heat source to various parts of the fins, ultimately achieving efficient heat dissipation and lowering the temperature. This study investigates the thermal resistance, heat dissipation performance, and overall temperature distribution of both the new and traditional heat dissipation devices using theoretical modeling, multi-condition experimental comparisons, and numerical simulation analysis. The experimental results demonstrate that the new heat dissipation device exhibits lower thermal resistance, higher heat dissipation, and greater convective heat transfer intensity compared to the conventional device. In a scenario with 6.3 kW power and 4.3 m/s wind speed, the new heat dissipation device decreases thermal resistance by 15 times, boosts heat dissipation by 30%, enhances convective heat transfer by 12.5%, and lowers the heatsink object temperature by 30%. As power and wind speed increase, the heat dissipation performance of the new heat dissipation device can be further improved. Additionally, the new heat dissipation device exhibits a characteristic where the temperature of the fins is higher on the outside and lower on the inside. Increasing the length of the fins helps improve the device’s heat dissipation performance. The feasibility of the MHPA being applied in converter heat dissipation systems is validated in this study. This device significantly enhances converter heat dissipation efficiency and is crucial for advancing the high-power capabilities of motors. Full article

The migration of acid gases through the pressure sheath of flexible pipes may induce a corrosive environment that can lead to steel armors’ failure by SCC (stress corrosion cracking). This permeation process depends on temperature, partial pressures, materials, and the pipe’s geometry. However, there are few works related to permeation modeling in flexible pipes, and these works usually contain significant simplification in pipes’ geometry. Hence, this work proposes two finite element (FE) permeation models and discusses the effects of the pipe’s characteristics. The models were developed in Ansys^®, considering two- (2DFE) and three-dimensional (3DFE) approaches, and rely on gas fugacities instead of concentrations to describe the mass transport phenomenon. A radial temperature gradient is also considered, and the heat transfer is uncoupled from the mass transfer. Dry and flooded annulus analyses were conducted with the proposed models. In dry conditions, the results obtained with the 2DFE and the 3DFE approaches showed no significant differences, demonstrating that 3D effects are irrelevant. Hence, the permeation phenomenon is ruled by the permeation properties of the polymeric layers (pressure and outer sheaths) and possible shield effects promoted by the metallic armors. In contrast, the flooded annulus analyses resulted in a non-uniform fugacity distribution in the annulus with significant differences between the 2DFE and the 3DFE approaches, showing the importance of modeling the helical geometries of the metallic armors in this condition. Finally, a conservative 2DFE approach, which neglects the contribution of the pressure sheath, is proposed to analyze the flooded annulus condition, aiming to overcome the high computational cost demanded by the 3DFE approach. Full article

This study applied a risk assessment technique to the steam reforming process in hydrogen production facilities to generate baseline data for preparing safety protocols in related workplaces. To this end, consequence analysis (CA) was conducted using DNV-PHAST v.8.9., focusing on the reforming process, which operates at the highest temperature and pressure among related processes. This study predicted jet fire damage resulting from the total failure of a 65 mm syngas pipe at the rear end of the reformer, with a projected flame length of up to 23.6 m based on a radiant heat of 5 kW/m². As per the assessment, a vapor cloud explosion (VCE) caused damage of up to 42.6 m at an overpressure of 0.07 bar (1 psi), while a flash fire had an impact range of approximately 12.7 m based on hydrogen’s LFL (lower flammable limit). This quantitative risk assessment of the general steam reforming process provides valuable basic data for the design and operation of related facilities. Full article