An automotive thermoelectric generator (ATEG) integrated with phase change material (PCM) is developed for exhaust waste heat recovery in vehicles. A CFD and thermal-electrical numerical model including the PCM phase transition is established to evaluate system performance. To overcome the heat transfer bottleneck caused by the low thermal conductivity of PCM, the Taguchi method is applied to analyze the influence of five key parameters-expanded graphite mass fraction (MEG) (0-25%), fin relative height (10-100%), fin spacing (3.25-5.25 mm), and the thickness (3.8-5.8 mm) and side length (40.8-56.8 mm) of the PCM unit-on the thermal-electrical behavior of the PCM-ATEG. The analysis shows that fin relative height and MEG exert the most significant effects on total power generation (Eout) and effective conversion efficiency (eta eff). Two optimized structures identified through the Taguchi method achieve the highest Eout and eta eff, respectively. Compared with the initial PCM-ATEG (Eout = 4.715 kJ, eta eff = 1.92%), the power-optimized configuration increases total power generation to 5.526 kJ and eta eff to 2.10% (enhancements of 17.20% and 9.38%), while the efficiency-optimized configuration attains eta eff = 2.12% and Eout = 5.515 kJ (improvements of 10.42% and 16.97%). This study demonstrates that properly designed PCM storage can enhance exhaust heat-to-power conversion in automotive thermoelectric systems.
To elucidate the mechanism by which aggregate surface roughness influences salt corrosion damage at the asphalt-aggregate interface, this study employed molecular dynamics simulations to construct interface models with varying surface roughness. By analyzing parameters such as adhesion energy, radial relative concentration, and diffusion coefficient, the migration patterns of salt solutions and the evolution mechanism of damage were revealed. Results indicate that under dry conditions, increased roughness causes localized asphalt adsorption deficiencies. However, the overall interfacial adhesion strength is enhanced due to expanded contact area. During salt solution erosion, the rough surface configuration of aggregates effectively delays salt migration at the interface, reducing the associated risk of asphalt hardening. However, the rough aggregate surface also increases adsorbed water content at the interface, posing a latent risk of long-term performance degradation. H2O migrated the fastest, followed by the NaCl solution, while the Na2SO4 solution showed the slowest rate. Among these, H2O and NaCl solutions ultimately cause complete asphalt delamination. Impermeable hydrated clusters formed by Na2SO4 create a diffusion barrier, which directs the water molecules toward the asphalt interface with a more vertical trajectory. This transforms the primary attack mechanism into a concentrated prying force, causing partial rather than complete delamination.
Significant girder-end cumulative displacements (GECDs) of suspension bridges can occur under operational loads, leading to premature wear of restraint devices in bridges such as bearings, expansion joints, and dampers, which are mainly caused by vehicle loads. Therefore, analyzing the mechanisms and response characteristics of vehicle-induced girder-end longitudinal displacement (GELD), as well as the variability of GELD under vehicle loads, is crucial for effective bridge monitoring and maintenance. First, the relationship between vehicle load distribution and GELD under the coupled deformation of the main cable, hangers, and stiffening girder of the suspension bridge was theoretically derived. The generation mechanism of the antisymmetric characteristics and approximate rigid-body motion behavior of the GELD under vehicle loads was revealed. Second, long-term monitoring data over 13 years from an in-service long-span suspension bridge were applied to reveal the time-frequency domain response characteristics of GELD. Additionally, the antisymmetric characteristics and rigid-body motion behavior of vehicle-induced GELD were first verified based on a spatial-temporal correlation analysis of monitoring data, further supporting the theoretical analyses. Finally, the variability in GELD and GECD under vehicle loads was investigated using weigh-in-motion data. This analysis elucidates the dominant role of the proportion of heavy vehicles and their gross vehicle weight on GECD and clarifies the underlying mechanisms of this influence. The conclusions offer valuable insights for the monitoring and maintenance of restraint devices in suspension bridges, helping to prevent premature damage.
To address the issue of non-uniform temperature distribution in thermoelectric generators (TEGs), this study proposes and designs a novel divergent splitter column structure, integrated into a hexagonal thermoelectric generator (HTEG) system. The cross-sectional area of the splitter column gradually increases along the exhaust flow direction, enhancing downstream heat transfer and improving temperature uniformity. A coupled fluid-thermal-electrical multiphysics model is employed to systematically analyze the effects of the splitter column's front-end area and divergence angle under varying exhaust mass flow rates and inlet temperatures. Results indicate that, compared with the traditional splitter column, the proposed divergent splitter column can improve the temperature uniformity at the heat exchanger surface within the present numerical framework, reducing the maximum hot-side temperature difference of the thermoelectric modules by 40.01%, while increasing the output power and conversion efficiency by 9.38% and 5.81%, respectively. This study demonstrates the effectiveness of the divergent splitter column in enhancing overall HTEG performance and provides theoretical guidance and structural design references for optimizing TEG systems.
A key challenge in traditional biological nutrient removal is the competition for limited organic carbon, which compromises the efficiency of both denitrification and phosphorus removal when carbon is scarce. To overcome this limitation, this study focused on low C/N ratio wastewater, and sequencing batch biofilm phosphorus recovery reactors (SBBPRs) were developed and constructed. This approach integrates simultaneous nitrification, denitrification and phosphorus removal (SNDPR) with phosphorus recovery (PR), reducing carbon source competition while achieving phosphorus resource recycling. Compared with the control groups (without PR), the nitrogen and phosphorus removal efficiencies of SBBPRs were remarkably enhanced. At C/N ratios of 5.0 and 3.0, the nitrogen removal efficiencies reached 87.7 % and 69.7 %, respectively, and the phosphorus recovery efficiencies were 53.7 % and 57.0 %, respectively. Based on the analysis of carbon source distribution within the SBBPRs, it can be observed that the phosphorus recovery process enhanced the storage of carbon sources in glycogen accumulating organisms (GAOs), thereby strengthening the endogenous denitrification process and ensuring the denitrification efficiency of the system. Electron transfer capacity and enzyme activity were also enhanced. The analysis of microbial community structure revealed that Candidatus_Competibacter, a denitrifying glycogen-accumulating organism (DGAO) was enriched in 31.0 % and 21.5 % at C/N ratios of 5.0 and 3.0, respectively, which provided a guarantee for endogenous denitrification. Meanwhile, the prediction of microbial Bugbase function reflected the system's excellent metabolic ability. This study provided new insights into lowcarbon, high-efficiency nitrogen and phosphorus removal from wastewater.
