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排序方式: 共有7551条查询结果,搜索用时 209 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(20):11007-11027
Cathode channel of a PEM fuel cell is the critical domain for the transport of water and heat. In this study, a mathematical model of water and heat transport in the cathode channel is established by considering two-phase flow of water and air as well as the phase change between water and vapor. The transport process of the species of air is governed by the convection-diffusion equation. The VOSET (coupled volume-of-fluid and level set method) method is used to track the interface between air and water, and the phase equilibrium method of water and vapor is employed to calculate the mass transfer rate on the two-phase interface. The present model is validated against the results in the literature, then applied to investigate the characteristics of two-phase flow and heat transfer in the cathode channel. The results indicate that in the inlet section, water droplets experience three evolution stages: the growing stage, the coalescence stage and the generation stage of dispersed water drops. However, in the middle and outlet sections of the channel, there are only two stages: the growth of water droplets, and the formation of a water film. The mass transfer rate of phase change in the inlet section of the channel varies over time, exhibiting an initial increase, a decrease followed, and a stabilization finally, with the maximum and stable values of 1.78 × 10?4 kg/s and 1.52 × 10?4 kg/s for Part 1, respectively. In the middle and outlet sections, the mass transfer rate increase firstly and then keeps stable gradually. Furthermore, regarding the distribution of the temperature and vapor mass fraction in the channel, near the upper surface of the channel, the temperature and vapor mass fraction first change slightly (x < 0.03 m) and then rapidly decrease with fluctuations (x > 0.03 m). In the middle of the channel, the temperature and vapor mass fraction slowly decrease with fluctuation. 相似文献
2.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
3.
《International Journal of Hydrogen Energy》2021,46(62):31778-31787
NdSrCo2O5+δ (NSCO) is a perovskite with an electrical conductivity of 1551.3 S cm−1 at 500 °C and 921.7 S cm−1 at 800 °C and has a metal-like temperature dependence. This perovskite is used as the cathode material for Ce0.8Gd0.2O2-δ (GDC)-supported microtubular solid oxide fuel cells (MT-SOFCs). The MT-SOFCs fabricated in this study consist of a bilayer anode, comprising a NiO–GDC composite layer and a NiO layer, and a NSCO–GDC composite cathode. Three cell designs with different outer tube diameters, GDC thicknesses, and NSCO/GDC ratios are designed. The MT-SOFC with an outer tube diameter of 1.86 mm, an electrolyte thickness of 180 μm, and a 5NSCO–5GDC composite cathode presents the best performance. The flexural strength of the aforementioned cell is 177 MPa, which is sufficient to confer mechanical integrity to the cell. Moreover, the ohmic and polarization resistance values of the cell are 0.22 and 0.09 Ω cm2 at 700 °C, respectively, and 0.15 and 0.03 Ω cm2 at 800 °C, respectively. These results indicate that the NSCO-GDC composite exhibits high electrochemical activity. The maximum power densities of the cell at 700 and 800 °C are 0.46 and 0.67 W cm−2, respectively, exceeding those of existing electrolyte-supported MT-SOFCs with similar electrolyte thicknesses. 相似文献
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分析了乐滩灌区工程北干渠溯河隧洞段长约1.06 km穿合山煤矿采空区的地质情况.借鉴高速公路煤矿采空区的成功处理经验,通过科学分析,对采空区变形和区域内覆岩的稳定性做了评价,论述了输水线路穿采空区段采取全充填压力注浆法的工程处理方法. 相似文献
8.
腐蚀阴极尖端的新方法 总被引:1,自引:0,他引:1
给出一种腐蚀阴极尖端的新方法,使得对阴极常用金属材料(W,Mo,Ir,Ta等)制作的阴极尖端的腐蚀效果明显,针尖对称性和重复性都很好,成品率和质量都有所提高. 相似文献
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The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献