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Comparison of Lifetime Performance of Pemfc Stacks with Two Cooling Strategies Under Different Humidity

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SSRN 2024年

作者： Yang, Yunjie Bai, Minli Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lv, Jizu Hu, Chengzhi Li, Yang Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

While reducing the size and Pt loading can achieve a lower proton exchange membrane fuel cell (PEMFC) stack cost, it is also very important to focus on the performance changes of the PEMFC stack during the long-term operation. A 3D PtCo catalysts long-term performance model is established in this study, and PEMFC stacks with one cooling unit per cell (1-cell stack) and three cells (3-cell stack) are employed as the computational domains, respectively. The effective area of each cell is 50 cm2, and the changes in current density as well as effective catalytic area of PEMFC stacks with two cooling strategies before and after long-term operation under different humidity conditions are investigated at low Pt loadings. The results show that there are large differences in the output voltage and current density distributions between the three cells due to the poor membrane hydration affected by the non-uniform temperature distribution, although the 3-cell stack can significantly reduce the size. Localized catalyst degradation in both 3-cell and 1-cell stacks is closely related to the geometry of the cathodic flow field, and non-uniform catalyst degradation is found to increase the activation and mass transfer losses and change the distribution of current density within the membrane. In addition, the 3-cell stack is found to perform even better in terms of durability, especially under high humidity conditions, which provides a potential solution to improve the durability of PEMFC stacks operating in harsh conditions. © 2024, The Authors. All rights reserved.

关键词： Durability

Stability and Emission Characteristics of Ammonia/Air Premixed Swirling Flames with Rotating Gliding Arc Discharge Plasma

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SSRN 2022年

作者： Ju, Rongyuan Wang, Jinhua Zhang, Meng Mu, Haibao Zhang, Guanjun Yu, Jinlu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China State Key Laboratory of Electrical Insulation and Power Equipment School of Electrical Engineering Xi’an Jiaotong University Xi’an710049 China School of Aeronautics Engineering Air Force Engineering University Xi’an710038 China

Ammonia received increased attention as a carbon-free fuel and hydrogen carrier. Poor combustion stability and high NOx emission are the main issue for ammonia combustion. Effects of rotating gliding arc (RGA) discharge plasma on the flame stability and NOx emission of NH3/air premixed swirling flames were investigated. The discharge characteristics of the RGA were studied. The flame stabilization mechanisms by plasma were revealed and analyzed according to the flame structure transition and the distribution of key intermediate OH radicals. The NOx emissions were measured by the Gasmet DX4000 Fourier Transform Infrared (FTIR) gas analyzer. Results showed that the RGA discharge plasma can enhance the stability and extend the lean blow-off (LBO) limits from 0.6 to approximately 0.43-0.57. A hysteresis phenomenon about the transition between the lift-off flame and the attached flame was observed without plasma and disappeared with plasma activation. The plasma reduces NO and NO2 emissions mainly due to the kinetic and cracking effects of plasma. Extremely low NO emission below 300 ppm can be observed for very lean ammonia flames with an equivalence ratio (f) lower than 0.6, which are stabilized by plasma, while a large amount of unburned NH3 emission is accompanied. © 2022, The Authors. All rights reserved.

关键词： Ammonia

Research on the Solution of the Thermo-Hydro-Mechanical-Chemical Coupling Model Based on the Unified Finite Volume Method Framework

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SSRN 2024年

作者： Zhang, Weitao Han, Dongxu Wang, Bohong Chen, Yu-Jie Jiao, Kaituo Gong, Liang Yu, Bo Qingdao266580 China School of Mechanical Engineering Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil and Gas Development Beijing Institute of Petrochemical Technology Beijing102617 China National-Local Joint Engineering Laboratory of Harbour Oil and Gas Storage and Transportation Technology Zhejiang Key Laboratory of Petrochemical Environmental Pollution Control Zhejiang Ocean University No.1 Haida South Road Zhoushan316022 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Most existing thermo-hydro-chemical-mechanical (THMC) coupling models for enhanced geothermal systems (EGS) employ a combination of finite volume method (FVM) and extended finite element method (XFEM), facing challenges in framework integration, programming complexity, and solution efficiency. To overcome these limitations, this study develops an innovative FVM-XFVM model based on the embedded discrete fracture model (EDFM) that significantly enhances the THMC coupling modeling process for fractured reservoirs with simplicity and efficiency. Rigorous comparative verification demonstrates the new model maintains accuracy while improving computational performance. For EGS applications, this model effectively captures spatiotemporal dynamics of coupled THMC processes with multi-component water-rock reactions. The approximately 3°C temperature deviation between multi-component and single-component models after long-term operation demonstrates the necessity of incorporating multi-component reactions into THMC models for accurate forecasts. This work substantially improves the predictability and efficiency of long-term heat production forecasts for EGS reservoirs. © 2024, The Authors. All rights reserved.

关键词： Finite volume method

Xct Images-Based Pore-Scale Numerical Investigation for Heat Transfer Using Copper Foam Filled with Paraffin Phase Change Material

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SSRN 2024年

作者： Liu, Xinyu Zhou, Zhifu Wu, Wei-Tao Wei, Lei Hu, Chengzhi Lyu, Jizu Huang, Heng Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'An710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

The principle of phase change heat transfer using copper foam in the paraffin phase change material (PPCM) are not well understood. In this study, based on X-ray computed tomography (XCT), three dimensional (3D) geometric model of copper foam was established, including PPCM domain. We developed a coupled fluid-solid model to explore phase change for heat transfer in the composite phase change material (CPCM) with copper foam and PPCM. The effects of phase change melting behavior, heat transfer characteristics and homogeneity of temperature were considered. Results of numerical simulation demonstrated that the CPCM had completely melted at 669.8 s. Here the melting time decreased by 45%, compared with the pure PPCM at 1218 s. The extensive heat transfer contact area was offered by the copper foam skeleton. Meanwhile, the melting durations of the CPCM ranged from 4368 s, 2236.3 s, 509.4 s, and 284.6 s corresponding to the heat fluxes with 500 W/m2, 1000 W/m2, 5000 W/m2, and 10000 W/m2. The melting process correlated directly with the heat flux, making it adaptable to the operational demands of diverse electronic components. © 2024, The Authors. All rights reserved.

关键词： Heat flux

The Interaction and Activation of Fe2o3/Ceo2 Oxygen Carrier in Chemical Looping Dry Reforming of Methane

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SSRN 2024年

作者： Zhang, Jinrui Liu, Xiaozhi Pan, Yue Wang, Yuhan Yang, Tianlong Li, Peng Shen, Yuanhui Su, Dong Pan, Ying Jin, Hongguang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing100190 China University of Chinese Academy of Sciences Beijing100049 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University 710049 China

Chemical looping dry reforming of methane (CL-DRM) holds great promise for both CO2 utilization and syngas production with high efficiencies. The structure and component of oxygen carriers (OCs) are critical factors that influence the CL-DRM performances, such as reaction activity and production selectivity. Incorporating CeO2 is known to enhance the reactivity and stability of Fe2O3 for chemical looping reforming. However, the underlying mechanism of how CeO2 synergistically interact with Fe2O3 to enhance performances is still not clear. In this work, we comparatively investigate CeO2 supported Fe2O3 OCs in interfacial and physical Fe-Ce contact modes. The OC with sol-gel method achieves 80% CH4 conversion and 96% CO selectivity, significantly improved from OC with the mechanically mixed sample. Additionally, we found a strong interaction between Fe2O3 and CeO2 components, resulting in the formation of CeFeO3 after the first cycle. Our in-situ environmental transmission electron microscopy study shows that the Fe2O3-CeO2 interaction promotes the oxygen release during the reduction. Iron exhibited significant activity with ceria under CO2, dissolving into CeO2 lattice and forming CeFeO3. Density function theory results suggest that the improved reactivity of Fe2O3/CeO2 OC results from the enhanced oxygen ion migration in CeFeO3 © 2024, The Authors. All rights reserved.

关键词： Sol-gels

Degradation of Polystyrene to Aromatic Oils with Nio@C Catalyst in Supercritical Co2

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SSRN 2024年

作者： Liu, Yanbing Mao, Liuhao Kang, Xing Li, Yi Zhao, Qiuyang Jin, Hui Meng, Wei Shi, Jinwen Guo, Liejin International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 28 West Xianning Road Shaanxi Xi’an710049 China Hunan Provincial Key Lab of Dark Tea and Jin-Hua Departmet of Material & Chemical Engineering Hunan City University 518 East Yingbin Road Hunan Yiyang413000 China

One of the most promising ways to dispose of plastic pollution in the future is chemical recycling of plastic, and in particular supercritical fluids with excellent fluidity and transferability have shown great attraction in the disposal of plastic. Herein, catalytic degradation of polystyrene (PS) plastic in supercritical carbon dioxide (Sc-CO2) was realized with high yield of aromatic oils. NiO with simple preparation process, and high catalytic activity and stability in Sc-CO2 was doped with carbon material to prepare NiO@C catalyst with improved catalytic performance. Compared with NiO, NiO@C catalyst had rich porous structure and strong acidic sites, resulting in higher catalytic activity. The NiO@C catalyzed degradation of PS in Sc-CO2 yielded aromatic oils as high as 89.3 ± 0.6 wt% at 300oC with a reaction time of 2 h and a catalyst loading amount of 10 wt%. Moreover, the NiO@C catalyst degraded PS in Sc-CO2 for three cycles without obvious change in the catalytic performance. Sc-CO2 not only played a favorable role in swelling PS, but also inhibited the formation of coke, beneficial for the degradation of PS. Furthermore, CO2 was be consumed as an oxidant to generate new products and reduce greenhouse gas emission. The highly efficient catalytic conversion of PS to aromatic oils in Sc-CO2 via NiO@C catalyst provides a potential route for simultaneously recycling plastic and sequestering carbon. © 2024, The Authors. All rights reserved.

关键词： Carbon dioxide

Simulations on Hybrid Thermal Management of Mini-Channel Cold Plate and Pcm for Lithium-Ion Batteries Under Discharging and Thermal Runaway Conditions

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SSRN 2024年

作者： Liu, Yang Zhou, Zhifu Wu, Wei-Tao Wei, Lei Lyu, Jizu Li, Yang Liu, Xinyu Li, Yubai Song, Yongchen Key Laboratory of Ocean Energy Utilization and Energy Conservation Ministry of Education Dalian University of Technology Dalian116024 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China Department of Mechanical and Energy Engineering Southern University of Science and Technology Shenzhen518055 China School of Mechanical Engineering Guangdong Ocean University Zhanjiang524088 China

In this study, we compared the performance of different structures of mini-channel cold plate (MCP)- phase change material (PCM) hybrid thermal management on discharge and thermal runaway. The heat transfer structures for them can be categorized into three types: (a) uncoupled, (b) semi-coupled, and (c) fully coupled. Among these, the semi-coupled design B exhibits the best performance. Specifically, in the high rate discharge condition, the structure can control the battery temperature at 44.37°C at low coolant mass flow rate, and the temperature at 36.47°C at high mass flow rate, while the temperature difference (TD) of a single cell does not exceed 2.01°C. In a low-multiplier discharge zero-energy system, the pack temperature rise can be limited to no more than 10°C in 35°C environment. Under external short-circuit conditions, a lower coolant mass flow rate is sufficient to keep the pack temperature at 43.22°C. Under internal short-circuit thermal runaway (TR), lower coolant mass flow rate can prolong the TR of the adjacent cell up to 521 s, and higher mass flow rate can completely inhibit the occurrence of TR. The objective of this study is to offer valuable references for the design and implementation of hybrid MCP-PCM cooling systems. © 2024, The Authors. All rights reserved.

关键词： Phase change materials

Investigations on affinity law under gas-liquid conditions in multistage radial and mixed-flow multiphase pumps

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国际流体工程（英文）

国际流体工程（英文） 2024年第1期1卷 52-66页

作者： Liang Chang Chenyu Yang Xiaobin Su Xiaoyu Dai Qiang Xu Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

Affinity laws have been widely used in pump design and simulation under high-temperature and corrosive *** applying such laws,it is possible to shorten development cycles and reduce test ***,current applications of affinity laws are still limited to liquid *** this paper,expressions for affinity laws and their applicability are investigated for multistage radial and mixed-flow multiphase pumps under gas-liquid conditions.A high-pressure(30 MPa)gas-liquid experimental platform is constructed,and three-stage and 25-stage radial pumps and a 15-stage mixed-flow pump are investigated,with specific speeds of 107 and *** gas compressibility taken into account,the gas-liquid two-phase flow rate,head,and power,and the corresponding dimensionless hydraulic coefficients,are defined for multiphase *** deterioration of gas-liquid pressurization performance is found to be divided into three processes with different dynamic mechanisms,corresponding to three flow *** inlet gas volume fraction of pump is used to judge dynamic *** the same inlet gas volume fractions λ1=λ2,when the gas-liquid flows in two pumps have the same flow pattern,dynamic similarity will be *** affinity law that is established shows good applicability to the three-stage radial multiphase pump,with goodness of fit R2 larger than 0.9 for the two-phaseΨm-Φm andΠm-Φm performance ***,experimental results indicate that the affinity law also has good applicability to multiphase pumps with different stage numbers and blade structures under gas-liquid conditions.

关键词： conditions radial affinity gas-liquid investigations mixed-flow multiphase multistage pumps under

Energy Conversion in the Nanochannel Coupled with Surface Charge and Slip Effect

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SSRN 2022年

作者： Liu, Zheng Feng, Yijun Wang, Lin Liu, Qingyuan Liu, Guohua Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing102206 China

Inspired by the universal phenomena in nature and advances in nanotechnology, the ion transport in nanochannel receives increasing attention and shows great promising in energy conversion. The precedent studies generally predicted the ion transport by tuning the single physical parameter, the understanding of ion dynamics in the real multi-physical coupling systems is still scarce. Here, an ion transport model coupled with surface charge and slip effect is proposed to investigate the energy conversion behavior in nanochannel. The results show that the surface charge density increases with the increasing bulk concentration and nanochannel size. The original boundary slip tends to decrease the surface charge density and the surface charge in turn reduces the boundary slip significantly, which manifests the strong coupling effect of diverse factors. The output power and energy conversion efficiency increases first and then decrease with the increasing bulk concentration. The increase of channel size is beneficial for promoting output power, but unfavorable on energy conversion efficiency. More important, the boundary slip greatly enhances the output power and energy conversion efficiency, leading to a maximum output power and energy conversion efficiency is 2.7 pW and 30%, respectively. As a proof of concept, this work shows the distinct deviation in power generation in ion nanochannel with the constant and dependent physical property, providing the useful information to guide the design of real fluidic energy devices © 2022, The Authors. All rights reserved.

关键词： Ions