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291.
Flow pattern and flow characteristics for counter-current two-phase flow in a vertical round tube with wire-coil inserts 总被引:1,自引:0,他引:1
Flow pattern, void fraction and slug rise velocity on counter-current two-phase flow in a vertical round tube with wire-coil inserts are experimentally studied. Flow pattern and slug rise velocity are measured visually with a video camera. The void fraction is measured by the quick-closing valve method. Four kinds of coils with different coil pitches and coil diameters are used as inserts. The presence of wire-coil inserts induces disturbance into gas and liquid flows so that the shape and motion of gas slug or bubbles in a wire-coil inserted tube are quite different from those observed in a smooth tube without insert. The bubbly flow occurs in the low gas superficial velocity region in the wire-coil inserted tube, while the slug or churn/annular flow only appears in the smooth tube without insert over the all test range. The measured slug rise velocity in the wire-coil inserted tube is higher than that in the smooth tube. With modified mean flow velocity calculated with core area, the slug rise velocity in wire-coil tube inserted is in good agreement with Nicklin's correlation. The void fraction in a wire-coil inserted tube is lower than that in a smooth tube in the range of high gas superficial velocities. By introducing a simple assumption on considering the effective flowing area, the measured void fractions in a wire-coil inserted tube are in relatively good agreement with the predicted result based on the drift flux model proposed by others with the correlation for slug rise velocity given by others when the coil pitch is dense. 相似文献
292.
Jianning Lv Wenrui Li Jiani Li Zhejiaji Zhu Anwang Dong Huixia Lv Prof. Dr. Pengfei Li Prof. Dr. Bo Wang 《Angewandte Chemie (International ed. in English)》2023,62(11):e202217958
Two-dimensional conductive metal-organic frameworks (2D-c-MOFs) have attracted extensive attention owing to their unique structures and physical-chemical properties. However, the planarly extended structure of 2D-c-MOFs usually limited the accessibility of the active sites. Herein, we designed a triptycene-based 2D vertically conductive MOF (2D-vc-MOF) by coordinating 2,3,6,7,14,15-hexahydroxyltriptycene (HHTC) with Cu2+. The vertically extended 2D-vc-MOF(Cu) possesses a weak interlayer interaction, which leads to a facile exfoliation to the nanosheet. Compared with the classical 2D-c-MOFs with planarly extended 2D structures, 2D-vc-MOF(Cu) exhibits a 100 % increased catalytic activity in terms of turnover number and a two-fold increased selectivity. Density functional theory (DFT) calculations further revealed that higher activity originated from the lower energy barriers of the vertically extended 2D structures during the CO2 reduction reaction process. 相似文献
293.