Parametric and internal study of the vortex tube using a CFD model

A computational fluid dynamics (CFD) model is used to investigate the energy separation mechanism and flow phenomena within a counter-flow vortex tube. A two-dimensional axi-symmetric CFD model has been developed that exhibits the general behavior expected from a vortex tube. The model results are compared to experimental data obtained from a laboratory vortex tube operated with room temperature compressed air. The CFD model is subsequently used to investigate the internal thermal-fluid processes that are responsible for the vortex tube's temperature separation behavior. The model shows that the vortex tube flow field can be divided into three regions that correspond to: flow that will eventually leave through the hot exit (hot flow region), flow that will eventually leave through the cold exit (cold flow region), and flow that is entrained within the device (re-circulating region). The underlying physical processes are studied by calculating the heat and work transfers through control surfaces defined by the streamlines that separate these regions. It was found that the energy separation exhibited by the vortex tube can be primarily explained by a work transfer caused by a torque produced by viscous shear acting on a rotating control surface that separates the cold flow region and the hot flow region. This work transfer is from the cold region to the hot region whereas the net heat transfer flows in the opposite direction and therefore tends to reduce the temperature separation effect. A parametric study of the effect of varying the diameter and length of the vortex tube is also presented.     

铜冶炼行业空分设备选型浅析

随着铜冶炼工业的迅速发展,为之提供气体的空分设备向着新型化、大型化发展。结合铜冶炼工艺,详细分析了铜冶炼行业在空分设备选型时需考虑流程、产品压力、流量和能耗等因素,同时指出选型时要考虑空分设备的变负荷能力,并要综合长、短期效益,使投资具有最高的性价比。     

Stacked Attention Networks for Referring Expressions Comprehension

Referring expressions comprehension is the task of locating the image region described by a natural language expression, which refer to the properties of the region or the relationships with other regions. Most previous work handles this problem by selecting the most relevant regions from a set of candidate regions, when there are many candidate regions in the set these methods are inefficient. Inspired by recent success of image captioning by using deep learning methods, in this paper we proposed a framework to understand the referring expressions by multiple steps of reasoning. We present a model for referring expressions comprehension by selecting the most relevant region directly from the image. The core of our model is a recurrent attention network which can be seen as an extension of Memory Network. The proposed model capable of improving the results by multiple computational hops. We evaluate the proposed model on two referring expression datasets: Visual Genome and Flickr30k Entities. The experimental results demonstrate that the proposed model outperform previous state-of-the-art methods both in accuracy and efficiency. We also conduct an ablation experiment to show that the performance of the model is not getting better with the increase of the attention layers.     

Optimization of the Power Consumption of Light-Diode Scale Indicator Devices

The technique used in the investigation of the energy characteristics of scale representations of information in measurement science is analyzed. Analytic expressions are obtained for a two-cycle information model. Using these expressions, the energy consumption of indicator devices with scale based on an array of light diodes may be estimated. Methods for improving the economical performance of these devices are illustrated and practical recommendations for achieving greater efficiency are given.__________Translated from Izmeritel’naya Tekhnika, No. 6, pp. 42–46, June, 2005.     

进气温度与压力对锥形涡流管性能的影响

以氮气为工质,对锥形涡流管能量分离特性进行了实验研究,结果表明入口气流温度对锥形涡流管的工作性能影响较小.进气压力越高,能量分离性能越强,不同压力下都在冷气流率约0.2时,可得到最大制冷效应和制冷效率,冷气流率约为0.5时,可获得最大制热效应.升高压力可提高锥形涡流管的能量分离性能,但提高幅度逐渐减小,当压力升高到一定...     

邯钢20000m~3/h空分设备技术特点及运行性能

介绍邯钢新建20000m3/h空分设备的主要性能指标和工艺流程,分析了主要配套设备的特点,从能耗指标、操作维护、运行安全性和设备投资等方面对空分设备的技术性能和经济效益进行了评价。     

Saturation in the Classical Theory of the Free-electron Laser

The emitted energy and gain in the region of strong field asymptotics are derived for the free-electron laser from the classical equations of motion. The resulting expressions are shown to be identical to those derived using a quantum-mechanical formulation.     

Aerodynamic design and analysis of a 10 kW horizontal-axis wind turbine for Tainan,Taiwan

The purpose of the present study is to develop a small-scale horizontal-axis wind turbine (HAWT) suitable for the local wind conditions of Tainan, Taiwan. The wind energy potential was first determined through the Weibull wind speed distribution and then was adapted to the design of the turbine blade. Two numerical approaches were adopted in the design and analysis of the HAWT turbine blades. The blade element momentum theory (BEMT) was used to lay out the shape of the turbine blades (S822 and S823 airfoils). The geometry of the root region of the turbine blade was then modified to facilitate integration with a pitch control system. A mathematical model for the prediction of aerodynamic performance of the S822 and S823 airfoils, in which the lift and drag coefficients are calculated using BEMT equations, was then developed. Finally, computational fluid dynamics (CFD) was used to examine the aerodynamic characteristics of the resulting turbine blades. The resulting aerodynamic performance curves obtained from CFD simulation are in agreement with those obtained using BEMT. It is also observed that separation flow occurred at the turbine blade root at the tip speed ratios of 5 and 7.     

衡阳盈德21000m^3／h填料下塔空分设备设计和运行总结

由杭氧设计、制造的衡阳盈德21000m^3／h空分设备,由于采用规整填料下塔、增设氩回收装置、优化阀门和管道配置,使冷箱体积明显缩小,运行能耗降低,变负荷范围增大,达到了节能降耗的效果。文章简介21000m^3／h空分设备的主要性能指标、流程组织方案,详细叙述了主要配套部机及成套空分设备的技术特点和运行情况。     

Modeling and analysis of laminated rubber bearings under axial tensile loading

To analyze the tension performance of laminated rubber bearings under tensile loading, a tension model for analyzing the rubber layers is proposed based on the theory of elasticity. Applying the boundary restraint condition and the assumption of incompressibility of the rubber layers, stress and deformation expressions for the tensile rubber layers are derived. Based on the derived expressions, the stress distribution and deformed pattern specifically for deformed shape of the free edges of rubber layers are analyzed, and the theory of cracking energy is applied to analyze the distributions of predicted cracking energy density and gradient direction. Prediction of crack initiation and crack propagation direction of the rubber layers is investigated. The analytical results show that the stress and deformation expressions can be used to simulate the stress distribution and deformed pattern of the rubber layer for laminated rubber bearings in the elastic range, and the crack energy method for predicting the failure mechanism is feasible according to the experimental phenomenon.     

煤化工配套空分设备安装与安全运行分析

以久泰能源KDON-40000/12000型内压缩流程空分设备为例,简介煤化工配套空分设备的性能参数和流程组织,阐述空压机组和空分主体设备的安装经验,总结国内西北地区煤化工配套空分设备的防冻措施和安全、经济长周期运行经验。     

新型多孔材料在惰性气体Xe/Kr分离中的应用

惰性气体氙与氪的分离在大气放射性核素监测、惰性气体工业制备和乏燃料处理等领域中均有重要应用。常规的方法是利用低温精馏将氙与氪从大气中分离,需要耗费大量能源,成本高。因此,作为替代方法在常温下通过多孔材料高效吸附分离氙与氪具有重要意义。近年来发展的以金属有机框架材料、多孔有机分子笼材料等为代表的新型多孔材料在惰性气体氙与氪的分离中展现出了优异的性能与良好的应用前景。系统地综述了新型多孔材料在Xe/Kr分离中的研究进展,从计算模拟在Xe/Kr分离研究中的应用、高浓度氙/氪分离研究与极低浓度Xe/Kr分离研究3个方面进行论述与总结,最后对未来研究趋势进行了总结与展望。     

河南杭氧20000m~3/h空分设备的优化设计和技术特点

河南杭氧20000 m3/h空分设备采用立式径向流分子筛吸附器、规整填料下塔和双层主冷等先进技术,达到了节能降耗的目的。介绍20000 m3/h空分设备的主要性能指标、流程组织、主要配套部机及成套空分设备的技术特点。     

Numerical investigation of gas species and energy separation in the Ranque-Hilsch vortex tube using real gas model

A three dimensional Computational Fluid Dynamics (CFD) model is used to investigate the phenomena of energy and species separation in a vortex tube (VT) with compressed air at normal atmospheric temperature and cryogenic temperature as the working fluid. In this work the NIST real gas model is used for the first time to accurately compute the thermodynamic and transport properties of air inside the VT. CFD simulations are carried out using the perfect gas law as well. The computed performance curves (hot and cold outlet temperatures versus hot outlet mass fraction) at normal atmospheric temperature obtained with both the real gas model and the perfect gas law are compared with the experimental results. The separation of air into its main components, i.e. oxygen and nitrogen is observed, although the separation effect is very small. The magnitudes of both the energy separation and the species separation at cryogenic temperature were found to be smaller than those at normal atmospheric temperature.     

Hollow Nanostructures for Photocatalysis: Advantages and Challenges

Photocatalysis for solar‐driven reactions promises a bright future in addressing energy and environmental challenges. The performance of photocatalysis is highly dependent on the design of photocatalysts, which can be rationally tailored to achieve efficient light harvesting, promoted charge separation and transport, and accelerated surface reactions. Due to its unique feature, semiconductors with hollow structure offer many advantages in photocatalyst design including improved light scattering and harvesting, reduced distance for charge migration and directed charge separation, and abundant surface reactive sites of the shells. Herein, the relationship between hollow nanostructures and their photocatalytic performance are discussed. The advantages of hollow nanostructures are summarized as: 1) enhancement in the light harvesting through light scattering and slow photon effects; 2) suppression of charge recombination by reducing charge transfer distance and directing separation of charge carriers; and 3) acceleration of the surface reactions by increasing accessible surface areas for separating the redox reactions spatially. Toward the end of the review, some insights into the key challenges and perspectives of hollow structured photocatalysts are also discussed, with a good hope to shed light on further promoting the rapid progress of this dynamic research field.     

Optical Performance of Large Ground-based Telescopes

Abstract

Images taken with ground-based telescopes are dominated by atmospheric seeing. Analytical expressions of long-exposure optical functions, namely the modulation transfer function, point spread function and encircled energy are established, under the assumption that dome and telescope seeing are brought to negligible values, and that the diameter of the telescope is larger than the atmospheric coherence length. The influence of guiding errors and axisymmetrical telescope aberrations is also assessed, and a definition of optical quality is proposed. The results are generalized and the optical performance of a ground-based telescope is expressed in terms of effective diameter and signal-to-noise ratio.     

Grazing-incidence Monk-Gillieson monochromator based on surface normal rotation of a varied-line-spacing grating

A geometric theory of a grazing-incidence varied-line-spacing plane-grating monochromator system whose scanning is made by a simple grating rotation about the grating normal has been developed for designing Monk-Gillieson monochromators capable of covering an energy range of 0.6-2.5 keV. Analytic expressions are given for the grating equations, focal conditions, dispersion, spectral image shape, and optimization of groove parameters. On the basis of the theory, two monochromator systems have been designed: system I for moderate resolution and system II for relatively high resolution. The validity of the analytic formulas and the expected performance of the designed systems have been evaluated by means of ray tracing. The results show that the analytic formulas are sufficiently accurate for practical applications and that systems I and II would provide resolving power of approximately 1450-600 and 7500-2000, respectively, in the wavelength region of 0.5-2.0 nm.     

Cross-tie domain wall ground state in thin films

Cross-tie domain wall is a complex two dimensional magnetic domain wall structure, often found experimentally in this soft ferromagnetic films with thicknesses of about several exchange lengths. The structure of such a wall can roughly be imagined as a sequence of magnetic vortices and anti-vortices, arranged along a straight line. In this work, equilibrium energies of different one-dimensional magnetic domain wall configurations, existing in this soft ferromagnetic films, are calculated (fully taking into account the exchange and long range dipolar interaction), based on the various classical Ritz models. They are compared to the energy of two-dimensional cross-tie domain wall, thus, estimating the region of the film thicknesses, where the cross-tie structure is the lowest energy domain wall configuration. The upper boundary of this region is estimated here for the first time. Convenient approximate analytical energy expressions in terms of elementary functions are given here both for classical and for cross-tie domain walls.     

The applications of zeolitic imidazolate framework-8 in electrical energy storage devices: a review

In order to meet the requirement of electric vehicles (EVs), hybrid electric vehicles (HEVs) and smart grids, effective energy storage devices will become imperative in the future energy technologies. However, it is necessary to further improve the energy density, rate performance and cycle performance of the energy storage devices. Zeolitic imidazolate framework-8 (ZIF-8) is a kind of porous materials that has attracted enormous attention due to its high surface areas, controllable structures and tunable pore sizes. Besides the applications in gas storage and separation, catalysis, sensor, and drug delivery, ZIF-8 is receiving increasing research interest in the field of electrochemical energy storage due to the advantage of synthetic method, such as simplicity and safety. By focusing on recent advances, we summarize the applications of ZIF-8 in electrical energy storage devices, such as rechargeable batteries and supercapacitors. We also list the current problems in applications and give the future study direction.