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排序方式: 共有245条查询结果,搜索用时 15 毫秒
1.
Fabio Fantozzi Sauro Filippeschi Enrico Maria Latrofa 《Superlattices and Microstructures》2004,35(3-6):339
Upward and downward two-phase heat and mass transfer has been considered in the present paper. The heat and mass transfer with the condenser located below the evaporator has been obtained by inserting an accumulator tank in the liquid line of a loop thermosyphon and enforcing a pressure pulsation. In previous papers these heat transfer devices have been called pulsated two phase thermosyphons (PTPT). A mini PTPT has been experimentally investigated. It has shown a stable periodic heat transfer regime weakly influenced by the position of the condenser with respect to the evaporator. In contrast a classical loop mini thermosyphon (diameter of connecting pipes 4 mm) did not achieve a stable functioning for the investigated level differences between evaporator and condenser lower than 0.37 m. The present study shows that the functioning of a PTPT device does not directly depend on the level difference or the presence of noncondensable gas. In order to obtain a natural circulation in mini or micro loops, a periodically operating heat transfer regime should therefore be considered. 相似文献
2.
A linear three‐dimensional hydrodynamical numerical model, with the application of the Galerkin Method for the vertical dependence, is here presented. The spherical coordinate system is used, in order to allow large‐scale simulations. The equations and mathematical development of the model are shown in detail, together with the boundary and initial conditions, and the sequence of equations' solution. The model is applied to the South Atlantic Ocean, for estimating typical seasonal circulations, and the results are summarized in maps of currents at surface and 1000 m depth, and in transport values of the Brazil Current between 30°S and 40°S. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
3.
The effect of the biomass presence on the overall circulation velocity, the linear velocities both in the riser and the downcomer
and the overall gas hold-up was studied in a three-phase internal loop airlift reactor (ILALR). The measured data were compared
with those obtained using a two-phase system (air—water). All experiments were carried out in a 40 dm3 ILALR at six different biomass concentrations (ranging from 0 g dm−3 to 7.5 g dm−3), at a temperature of 30°C, under atmospheric pressure. Air and water were used as the gas and liquid model media, respectively.
Pellets of Aspergillus niger produced during the fermentation of glucose to gluconic acid in the ILALR were considered solid phase. In addition, liquid
velocities were measured during the fermentation of glucose to gluconic acid using Aspergillus niger. All measurements were performed in a bubble circulation regime. At given experimental conditions the effect of the biomass
on the circulation velocities in the ILALR was negligible. However, increasing of the biomass concentration led to lower values
of the total gas hold-up.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献
4.
Two important considerations in the design of an aerobic particulate immobilized cell bioreactor are the provision of sufficient
oxygen to maintain the desired metabolism of the immobilized organism, and the biomass holdup (which is proportional to the
number of immobilized cell particles in the reactor).
The Circulating Bed Reactor, a reactor developed for use with those forms of immobilization that result in particles of essentially
neutral buoyancy, operates with an expanded bed of circulating particles. The particle number density attainable in such a
reactor has been found to be dependent upon the circulation cell aspect ratio, the individual particle properties, the static
bed voidage of the particles, and the superficial gas velocity. The oxygen mass transfer characteristics have been found to
be dependent upon the circulatory nature of the system, the particle (solids) holdup, the particle porosity, and the superficial
gas velocity. 相似文献
5.
Chiaki Yamanaka Kazuhiko Hashimoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(23):4158-4166
New polyurethanes with lactone groups in the pendants and main chains were synthesized by the polyaddition of two kinds of L ‐gulonolactone‐derived diols (2,3‐O‐isopropylidene‐L ‐gulono‐1,4‐lactone and 5,6‐O‐isopropylidene‐L ‐gulono‐1,4‐lactone) with hexamethylene diisocyanate and methyl (S)‐2,6‐diisocyanatohexanoate and by the subsequent deprotection of isopropylidene groups. They were hydrolyzed more quickly than the polyurethane derived from methyl β‐D ‐glucofuranosidurono‐6,3‐lactone in a phosphate buffer solution, the pH value of which was 8.0, at 27 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4158–4166, 2002 相似文献
6.
Auf der Grundlage des Zirkulations-Diffusions-Prinzips wurden zwei Trennrohre für die Hochanreicherung von Gasen enytwickelt. Als Modellgasmischungen dienten H2-N2 Kr-CH4 und Luft. Neben Wasserdampf wurden Methanol- und Äthaanoldämpfe als Treibmittel benutzt. Gute Trennungen wurden in einem nur 20 cm langen Rohr erzielt, dessen Trennspalt horizontal durch Lamellen in kleine Sektionen und durch ein Drahtdiaphragma vertikal in zwei Ringkammern geteilt wird. Drei Rohre dieses Typs wurden in einer rechteckigen Kaskadenanordnung getestet. Die Theorie des Transportes im Trennrohr sowie die Behandlung des hydrodynamischen Problems werden angegeben. Eine Anwendung des beschriebenen Trennrohres zur Isotopentrennung und zur Gashochanreicherung erscheint aussichtsreich. 相似文献
7.
优质农产品溯源系统的引入,既能提升有效供给、缩短流通时间,又能降低流通中的数量损耗和价值损失,由此带来了双渠道供应链系统在投资、销售、定价等方面的系列决策问题。考虑制造商开辟电子渠道、从溯源系统降低流通损耗和提高质量出发,分别构建制造商主导型的双渠道供应链决策模型。通过对比分析应用前后各成员在投资、定价及销售方面的最优策略,得到相关的核心边界值。数值仿真结果表明:核心边界值主要与双重损耗的改善程度及其他参数相关,各成员及系统接受溯源系统的应用成本不同,应用成本对各渠道销量的影响程度亦不相同,但各成员调整定价的应用成本边界值是一致的。 相似文献
8.
9.
自然循环过冷沸腾流动不稳定性的实验研究 总被引:2,自引:0,他引:2
本文以氟里昂作工质,对自然循环过冷沸腾流动不稳定性进行了实验研究.实验过程中发现自然循环系统内可能发生高频脉动和低频脉动二种类型的过冷沸腾流动不稳定性.通过实验研究揭示了这二种类型流动不稳定性的发生机理,证实高频脉动属于声波型脉动,低频脉动属于密度波型脉动.通过实验得出了判断系统稳定性的界限,并使用积分方程无因次分析方法得出了预测密度波型流动不稳定性的经验公式. 相似文献
10.
海气相互作用的若干时频特征 总被引:2,自引:0,他引:2
章新平 《新疆大学学报(理工版)》1990,7(2):93-99
本文利用交叉谱分析方法分析了北大西洋、北太平洋以及印度洋六个海区与500百帕四个大气活动区之间的关系,揭示了它们之间的时空特点.进而分析了中低纬度海气相互作用的时频特点,并对三大洋副热带高压之间的相互关系进行了讨论,得到了一些有意叉的结果.这给利用海气关系进行长期天气过程分析提供了可靠依据。 相似文献