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91.
轴流管壳式换热器壳侧流体优化分布数值研究 总被引：1，自引：0，他引：1
针对大型、超大型轴流管壳式换热器壳侧流体的流动分布不均的问题,提出在进出口处增加流体分布挡板用以改进流体分布不均的现象.并且在此之前的理论研究基础上,采用多孔介质--分布阻力模型,对不同结构参教的流体分布挡板进行教值模拟研究,研完结果表明,在壳侧进出口安装流体分布挡板能够有效促进流体的均匀分布,理论分析的教学模型与数值研完结果表现为一致,通过几种不同的结构参数分布挡板的数值结果对比,表明采用第三种结构形式的挡板不但流体分布均匀,而且由于挡板存在所造成的压力损失最小. 相似文献
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以纳米级45S5生物玻璃粉体为原料,采用冷冻干燥法,以丙三醇(甘油)、聚乙二醇为分散剂,制备多孔生物陶瓷材料。实验结果表明:通过冷冻铸造法制备的复合陶瓷呈薄层状结构,在950℃下烧结的材料能保持多孔形貌,但是孔隙分布不均匀,大多为2-10μm的微孔,由阿基米德排水法测得的孔隙率知道孔隙在60%以上,孔径内部连通性良好;1 050℃下生物玻璃粉体出现玻璃软化,冻干胚体经烧结出现塌陷,微孔消失,孔径的连通性较差,大多数孔隙为不连通的半开孔。高温烧结定向多孔结构陶瓷胚体,温度高于1 000℃生物玻璃发生软化难以保持材料的定向多孔结构。生物玻璃粉体烧结多孔陶瓷的温度为950℃。 相似文献
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研究了一种新型的基于硅基半导体技术的酒精传感器,该传感器具有低功耗、高精度,可用于交通警察的安全检查设备.针对该传感器设计出了相应的检测系统. 相似文献
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Wen-Bei Yu Zhi-Yi Hu Jun Jin Min Yi Min Yan Yu Li Hong-En Wang Huan-Xin Gao Li-Qiang Mai Tawfique Hasan Bai-Xiang Xu Dong-Liang Peng Gustaaf Van Tendeloo Bao-Lian Su 《国家科学评论(英文版)》2020,7(6):1046
Active crystal facets can generate special properties for various applications. Herein, we report a (001) faceted nanosheet-constructed hierarchically porous TiO2/rGO hybrid architecture with unprecedented and highly stable lithium storage performance. Density functional theory calculations show that the (001) faceted TiO2 nanosheets enable enhanced reaction kinetics by reinforcing their contact with the electrolyte and shortening the path length of Li+ diffusion and insertion-extraction. The reduced graphene oxide (rGO) nanosheets in this TiO2/rGO hybrid largely improve charge transport, while the porous hierarchy at different length scales favors continuous electrolyte permeation and accommodates volume change. This hierarchically porous TiO2/rGO hybrid anode material demonstrates an excellent reversible capacity of 250 mAh g–1 at 1 C (1 C = 335 mA g–1) at a voltage window of 1.0–3.0 V. Even after 1000 cycles at 5 C and 500 cycles at 10 C, the anode retains exceptional and stable capacities of 176 and 160 mAh g–1, respectively. Moreover, the formed Li2Ti2O4 nanodots facilitate reversed Li+ insertion-extraction during the cycling process. The above results indicate the best performance of TiO2-based materials as anodes for lithium-ion batteries reported in the literature. 相似文献
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Frank F Yun Zhenwei Yu Yahua He Lei Jiang Zhao Wang Haoshuang Gu Xiaolin Wang 《国家科学评论(英文版)》2020,7(2):366-372
Room-temperature liquid metal is discovered to be capable of penetrating through macro- and microporous materials by applying a voltage. The liquid metal penetration effects are demonstrated in various porous materials such as tissue paper, thick and fine sponges, fabrics, and meshes. The underlying mechanism is that the high surface tension of liquid metal can be significantly reduced to near-zero due to the voltage-induced oxidation of the liquid metal surface in a solution. It is the extremely low surface tension and gravity that cause the liquid metal to superwet the solid surface, leading to the penetration phenomena. These findings offer new opportunities for novel microfluidic applications and could promote further discovery of more exotic fluid states of liquid metals. 相似文献
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Mechanical properties of micro-structured porous silicon film (PS) were studied combining X-ray diffraction with micro-Raman spectroscopy. The micro-structured porous silicon samples with different porosities ranging from 30.77% to 96.25% were obtained by chemical etching. Lattice parameters of the samples were measured using X-ray diffraction and its maximal change is up to 1.0%. This lattice mismatch with the bulk silicon substrate may introduce residual stress to the porous film. The residual stress measurement by micro-Raman spectroscopy reveals that the maximum of tensile residual stress has reached GPa level in the porous film. Moreover, the lattice mismatch and its corresponding residual stress are increasing with the porosity of PS, but average elastic modulus is about 14.5 GPa, one order of magnitude lower than that of substrate Si. The mechanical properties of PS have aclose relation with its micro-pore structure. 相似文献
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利用模板浸渍法制备了准一维聚苯胺纳米管阵列．通过扫描电子显微镜观察可知：纳米管是中空的管状结构,纳米管的外径约230nm,与所用模板孔径基本相当．纳米管阵列排列整齐,长度均一,彼此相互平行,管径均匀．紫外-可见光谱证明：聚苯胺纳米管阵列中高分子链部分保留了在溶液中的伸展链构型． 相似文献
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谭启建 《四川教育学院学报》2013,29(5):105-108
利用Darcy定律和质量守恒定律,得到了含多种多孔介质区域中可压缩流体流动的数学模型;在适当的假设条件下,利用上下解方法,得到了模型解的存在唯一性。 相似文献