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排序方式: 共有113条查询结果,搜索用时 46 毫秒
41.
A. C. Eapen S. M. Rao S. M. Agashe R. L. Ajmera V. N. Yelgaonkar 《Isotopes in environmental and health studies》2013,49(9):424-429
A variety of applications of radiotracers are in vogue in industries with significant economic advantage. Some of the applications in steel, petroleum and maritime industries provide interesting case studies. Different approaches are possible for arriving at the cost to benefit ratio. These include: (1) direct cost comparison with alternative technique, (2) savings due to increased production and reduction in interruption of process, (3) savings due to avoidance of infructuous expenditure. The case studies quoted based on experience in India include: (1) the monitoring of wear condition of refractory lining in blast furnaces. (2) location of leakages in a 140 km long underground crude petroleum pipeline, (3) study of sediment movement in sea bed for selecting the dumping ground for dredged spoils, in connection with harbour maintenance and expansion operations. Cost to benefit ratio is worked out in each case. The ratios range from 1:10 to 1:4500 depending on application and method of calculation of cost benefit ratio. 相似文献
42.
针对高超声速飞行器工作时前缘恶劣的气动加热环境, 为了保证飞行器前缘的尖锐外形, 提出内嵌高温热管前缘结构. 针对热管内部复杂流动与换热情况, 对内嵌高温热管前缘结构进行一体化建模, 将模型的核心部件液态金属热管工作状况的计算与实验进行对比以验证模型的可靠性. 本文还分析了给定工况下内嵌高温热管前缘结构的热防护效果, 其中壁面最高温度下降了11.6%, 最低温度上升了8%, 高温区和低温区均被封闭在前缘外层区域, 内层温度更加均匀, 实现了热流由高温区向低温区的转移, 削弱了高温区的热负荷. 本文还分析了接触热阻对热管冷却前缘结构效果的影响.
关键词:
热管
前缘
疏导式热防护
气动热 相似文献
43.
The aim of this paper is to present a kinetic numerical scheme for the computations of transient pressurised flows in closed water pipes. Firstly, we detail the mathematical model written as a conservative hyperbolic partial differentiel system of equations, and then we recall how to obtain the corresponding kinetic formulation. Then we build the kinetic scheme ensuring an upwinding of the source term due to the topography performed in a close manner described by Perthame and Simeoni (2001) [1] and Botchorishvili et al. (2003) [2] using an energetic balance at microscopic level. The validation is lastly performed in the case of a water hammer in an uniform pipe: we compare the numerical results provided by an industrial code used at EDF-CIH (France), which solves the Allievi equation (the commonly used equation for pressurised flows in pipes) by the method of characteristics, with those of the kinetic scheme. It appears that they are in a very good agreement. 相似文献
44.
Pietro Campaner Daniele D'Amico Pierluigi Ferri Luigia Longo Alfonso Maffezzoli Cristina Stifani Antonella Tarzia 《Macromolecular Symposia》2010,296(1):526-530
The aim of this work is the development of composite pipes using renewable resources. The pipes, manufactured by filament winding technology, were obtained using an epoxy resin crosslinked with a cardanol based novolac as matrix and jute fibres as reinforcement. Cardanol is a natural oil extracted from the shell of the cashew (Anacardium occidentale L.) nut. An amount of natural materials higher than 50% by weight was achieved in the final composites. Tensile and parallel plate compression tests were carried out on the composite pipes. 相似文献
45.
Articulated Pipes Conveying Fluid Pulsating with High Frequency 总被引:1,自引:0,他引:1
Stability and nonlinear dynamics of two articulated pipes conveying fluid with a high-frequency pulsating component is investigated. The non-autonomous model equations are converted into autonomous equations by approximating the fast excitation terms with slowly varying terms. The downward hanging pipe position will lose stability if the mean flow speed exceeds a certain critical value. Adding a pulsating component to the fluid flow is shown to stabilize the hanging position for high values of the ratio between fluid and pipe-mass, and to marginally destabilize this position for low ratios. An approximate nonlinear solution for small-amplitude flutter oscillations is obtained using a fifth-order multiple scales perturbation method, and large-amplitude oscillations are examined by numerical integration of the autonomous model equations, using a path-following algorithm. The pulsating fluid component is shown to affect the nonlinear behavior of the system, e.g. bifurcation types can change from supercritical to subcritical, creating several coexisting stable solutions and also anti-symmetrical flutter may appear. 相似文献
46.
工质热物性显著影响脉动热管的流动与传热特性。本文通过理论计算及实验研究,定性分析了工质热物性对临界直径、毛细滞后阻力、启动运行及传热极限等方面的影响。研究表明,为保证脉动热管的运行性能,在设计阶段应综合考虑工质、管材及管径大小等因素。首先,根据使用场合的热流密度及运行温度高低合理选取工质种类;然后,选用合适的管壁材料,尽可能减少液塞与管壁之间前、后接触角不同引起的毛细滞后阻力;最后,确定管内直径范围。本文工作旨在为脉动热管的设计和选用提供一些依据和参考。 相似文献
47.
The flow characteristics of aqueous foams were studied in a thin flow channel and a round pipe instrumented for pressure gradient and flow rate measurements. The quality of the foam was varied by controlling the volumetric flow rate of liquid and gas, and different flow types were identified and charted. Uniform foams move as a rigid body lubricated by water generated by breaking foam at the wall. A lubrication model leading to a formula for the thickness of the lubricating layer is presented. The formula predicts a layer thickness of 6–8 μm in the channel and 10–12 μm in the pipe. The thickness depends weakly on foam quality. An overall correlation for the friction factor as a function of Reynolds number which applies to both channel and pipe is derived. This correlation is consistent with a model in which a rigid core of foam is lubricated by laminar flow of a water layer in the range of measured thickness. 相似文献
48.
G. L. Komissarova 《International Applied Mechanics》2007,43(9):988-999
The properties of harmonic surface waves in an elastic cylinder made of a rigid material and filled with a fluid are studied.
The problem is solved using the dynamic equations of elasticity and the equations of motion of a perfect compressible fluid.
It is shown that two surface (Stoneley and Rayleigh) waves exist in this waveguide system. The first normal wave generates
a Stoneley wave on the inner surface of the cylinder. If the material is rigid, no normal wave exists to transform into a
Rayleigh wave. The Rayleigh wave on the outer surface forms on certain sections of different dispersion curves. The kinematic
and energy characteristics of surface waves are analyzed. As the wave number increases, the phase velocities of all normal
waves, except the first one, tend to the sonic velocity in the fluid from above
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 48–62, September 2007. 相似文献
49.
50.
A theoretical analysis for the free vibration of simply supported buried pipes has been investigated using the wave propagation approach. The pipe modeled as a thin cylindrical shell of linear homogeneous isotropic elastic material buried in a linear isotropic homogeneous elastic medium of infinite extent. The vibrations of the pipe are examined by using Flüggle shell equation. The natural frequencies are obtained for the pipes surrounded by vacuo or elastic medium. The results are compared with those available in the literature and agreement is found with them. It is found that the free vibration frequency of the pipe does not appear for some of the axial or circular vibration modes and the real natural frequencies of the pipe are significantly dependent on the rigidity of the surrounding medium. 相似文献