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排序方式: 共有971条查询结果,搜索用时 296 毫秒
31.
Hrvoje Mikulčić Eberhard von Berg Milan Vujanović Peter Priesching Luka Perković Reinhard Tatschl Neven Duić 《Chemical engineering science》2012,69(1):607-615
Calcination is a thermo-chemical process, widely used in the cement industry, where limestone is converted by thermal decomposition into lime CaO and carbon dioxide CO2. The focus of this paper is on the implementation and validation of the endothermic calcination reaction mechanism of limestone in a commercial finite volume based CFD code. This code is used to simulate the turbulent flow field, the temperature field, concentrations of the reactants and products, as well as the interaction of particles with the gas phase, by solving the mathematical equations, which govern these processes. For calcination, the effects of temperature, decomposition pressure, diffusion and pore efficiency were taken into account. A simple three-dimensional geometry of a pipe reactor was used for numerical simulations. To verify the accuracy of the modelling approach, the numerical predictions were compared with experimental data, yielding satisfying results and proper trends of physical parameters influencing the process. 相似文献
32.
Parallel Operation of Centrifugal Pumps: Effects of Rotational Speed Differences due to Motor Slip 下载免费PDF全文
In industrial plants, centrifugal pumps are frequently operated in parallel configuration, not least for redundancy and operational reliability reasons. However, regarding the resulting pressure pulsations and energy consumption, this operation mode has so far not been in the focus of scientific studies. The object of the present article is to clarify the effect of parallel operation with respect to the observable pressure pulsations. Measurements were carried out with two identical centrifugal pumps operating in parallel mode in an industrial‐scale closed‐loop piping system. The results suggest that, regarding both the resulting pressure pulsations and the operating point of each pump, this operation mode is quite sensitive to smallest rotational speed deviations as they may occur due to different motor slip. The results indicate furthermore that, for minimum pressure pulsations, equal power consumptions of the two pumps are crucial, but not necessarily equal rotational speeds. 相似文献
33.
Fraktionsfreisetzungsgrad – Ein neuer Ansatz zur Quantifizierung der Staubungsneigung von Pulvern 下载免费PDF全文
Eberhard Schmidt 《化学,工程师,技术》2015,87(5):638-643
The handling of dispersed solids may lead to undesirable release of particles. Size and quantity of the particles transferred into the gas depend on the holding and separating forces in the powder. These in turn are determined by characteristic parameters of the powder and of the process. Analogous to the fractional collection efficiency describing the dust separation, a fractional release rate to quantify the release of dust is introduced. The application is demonstrated by an example and the way to further development of this new approach is demonstrated. 相似文献
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36.
David Wenger Wolfgang Polifke Eberhard Schmidt-Ihn Tarek Abdel-Baset Steffen Maus 《International Journal of Hydrogen Energy》2009
In recent years, significant research and development efforts were spent on hydrogen storage technologies with the goal of realizing a breakthrough for fuel cell vehicle applications. This article scrutinizes design targets and material screening criteria for solid state hydrogen storage. Adopting an automotive engineering point of view, four important, but often neglected, issues are discussed: 1) volumetric storage capacity, 2) heat transfer for desorption, 3) recharging at low temperatures and 4) cold start of the vehicle. The article shall help to understand the requirements and support the research community when screening new materials. 相似文献
37.
Jason B. K. Pang Marc O. Eberhard John F. Stanton 《Canadian Metallurgical Quarterly》2010,15(3):231-239
A new beam-to-column connection has been developed for assembling precast concrete bridge bents in regions of high seismicity. The connection is made with a small number of large column bars, which are grouted into large corrugated-metal ducts embedded in the cap beam. Bents built with these connections can be erected quickly and permit generous construction tolerances. To evaluate the seismic performance of the proposed connection, lateral-load tests were performed on three manifestations of the connection, as well as on a comparable cast-in-place connection. The tests demonstrated that the force-displacement response and damage progression in the precast connection are similar to those of typical cast-in-place concrete connections. Deliberate partial debonding of the longitudinal reinforcement only slightly affected the force-displacement response and observed damage. 相似文献
38.
Investigations on metal-cutting machining processes that were conducted since the second half of the twentieth century have
considerably contributed to disclosing the principles underlying the cutting process. Although numerous studies have been
carried out on this subject, a generally valid model of the cutting process and the interactions in the separating processes
does not exist yet. Such a model could guarantee the disclosure of the principles of thermodynamic interactions between the
cutting process and the involved machine structure. This contribution is twofold and presents an experimental setup used to
determine cutting forces and temperatures in orthogonal cutting processes. The results are then used as a reference for simulations
made with the Discrete Element Method (DEM). The DEM is due to its meshless nature well suited to capture large deformations
and rupture of material which is included very naturally. It is examined to which extent the measured results can be captured
with the DEM model. 相似文献
39.
Ni‐Mn‐based Heusler alloys exhibit a variety of features related to martensitic transformations and are materials that are sought to be employed in actuation applications. To be able to exploit their properties, it is necessary to understand the rich variety and subtle magnetic coupling mechanisms occurring in these alloys. We review complementary neutron polarization analysis and ferromagnetic resonance experiments and give an account on the complex magnetism of these alloys in the austenite and martensite states. 相似文献
40.
Montcalm C Grabner RF Hudyma RM Schmidt MA Spiller E Walton CC Wedowski M Folta JA 《Applied optics》2002,41(16):3262-3269
We present our results of coating a first set of optical elements for an extreme-ultraviolet (EUV) lithography system. The optics were coated with Mo-Si multilayer mirrors by dc magnetron sputtering and characterized by synchrotron radiation. Near-normal incidence reflectances above 65% were achieved at 13.35 nm. The run-to-run reproducibility of the reflectance peak wavelength was maintained to within 0.4%, and the thickness uniformity (or gradient) was controlled to within +/-0.05% peak to valley, exceeding the prescribed specification. The deposition technique used for this study is an enabling technology for EUV lithography, making it possible to fabricate multilayer-coated optics to accuracies commensurate with atomic dimensions. 相似文献