基于能量流程模拟的过程系统操作调优

以过程系统能量流结构为基础提出了以物料和能量同时优化为目标的、用于整个过程系统操作调优的普遍化目标函数和普遍化的策略方法。运用这个目标函数和策略方法，可以同以物料优化为目标开发成功的各种工艺过程操作调优技术结合起来，实现整个系统物料、能量同时优化。文中举例说明了借助能量流程模拟和经济优化技术的尝试。

基于能量流程图的定位车能量转换建模及节能实现

提出基于能量流程图的节能分析方法,实现定位车能量转换的建模,对能量流向过程进行了细化。针对定位车驱动设计能力远大于实际运行能力的情况,分析了负载与效率曲线图,采用了基于总线控制的定位车减电机运行技术,降低了单耗,增加了单位回馈能量,综合节能效果达到7.47%,具有很高的推广价值。

巧用能量流程图,妙解转化效率问题

“能量流程图”就是在明确研究对象的基础上,画出的输入能量和输出能量之间的关系图。有时为了突出分析重点,输出能量中只画出输出的有用能量。研究对象不同,“能量流程图”也不一样,由于输出的有用能量总小于输入能量,这样就存在“能量转化效率”的问题。

数控机床多源能量流的系统数学模型

机床能量消耗建模研究是机床能量特性及能效优化研究的基础。现有机床能量模型研究主要是从机床总能耗统计分析或主传动系统建模出发的,缺乏机床特别是数控机床全部能量流数学模型的系统研究。针对数控机床多能量源的特性,从能量源构成出发对其能量流的数学模型进行研究。分析数控机床多能量源的系统构成,将数控机床能量源分成加工动力系统、加工关联辅助系统、动力关联辅助系统和其他等4类;基于数控机床各能量流的功率平衡方程分析,建立数控机床多源能量流的能量流程;在数控机床能量流程的基础上,结合4类能量源的运行特点建立数控机床多源能量流的系统数学模型。案例分析结果表明,上述模型可为数控机床运行过程的能量效率分析,能量消耗预测和节能优化等实际问题的解决提供一种基础支持,具有较广阔的应用前景。

IAPⅢ模式中夏季风建立的流场能量强度指数分析

本文采用IAPⅢ模式输出的10模式年资料,计算了夏季风建立期间的流场能量强度指数(即变差度、相似度、场比幅、季风强度指数和突变度),主要结论有:利用相似度可客观确定模式中南海夏季风建立的预兆日期。在南海、南亚夏季风建立及江淮入梅前后,均出现全球变差度明显增大,此时大气环流的剧烈调整具有全球性。IAPⅢ模式中南海夏季风爆发要较实际偏晚10 d,强度也较实际弱。虽在模式中海表面温度取气候值,但南海夏季风建立的预兆日期仍各不相同,且季风强度指数有明显的呈两年周期的变化。模式中南海夏季风爆发在绝大多数年份仍属突变过程,这与实际情况大体相当。

基于线路限速的高速列车运行能耗分析

高速列车在不同线路限速运行时会产生不同的运行时间和能耗。通过分析高速列车能量流程和转化,给出列车运行分项能耗构成和计算方法,对250km/h和350km/h速度等级高速列车在不同线路限速时的运行分项能耗进行计算和分析,结果表明:站间距越长,线路限速越高,速度等级越高的列车节时优势越明显。250km/h线路限速时,高速列车运行阻力能耗占总能耗的60%以上;对限速线路,合理的高速列车速度等级选择可降低列车线路运行能耗。

Volumetric fraction measurement in oil-water-gas multiphase flow with dual energy gamma-ray system

Volumetric fraction distribution measurement is a constituent part of process tomography system in oil-water-gas multiphase flow. With the technological development of nuclear radial inspection, dual-energy γ-ray techniques make it possible to investigate the concentration of the different components on the cross-section of oil-water-gas multiphase pipe-flow. The dual-energy gamma-ray technique is based on materials attenuation coefficients measurement comprised of two radioactive isotopes of 241Am and 241Cs which have emission energies at 59.5 keV and 662 keV in this project. Nuclear instruments and data acquisition system were designed to measure the material’s attenuation dose rate and a number of static tests were conducted at the Multiphase Laboratory, Institute of Mechanics, Chinese Academy of Sciences. Three phases of oil-water-gas media were inves- tigated for their possible use to simulate different media volumetric fraction distributions in experimental vessels. Attenuation intensities were measured, and the arithmetic of linear attenuation coefficients and the equations of volumetric fractions were studied. Investigation of an unexpected measurement error from attenuation equations revealed that a modified arithmetic was involved and finally the system achieved acceptable accuracy in experimental research.

Calculation on inner wall temperature in oil-gas pipe flow

Based on the energy equation of gas-liquid flow in pipeline,the explicit temperature drop formula for gas-liquid steady state calculation was derived.This formula took into consideration the Joule-Thomson effect,impact of terrain undulation and heat transfer with the surroundings along the line.Elimination of temperature iteration loop and integration of the explicit temperature equation,instead of enthalpy energy equation,into the conjugated hydraulic and thermal computation have been found to improve the efficiency of algorithm.Then,the inner wall temperature of gas-liquid flow was calculated by using explicit temperature equation and inner wall convective heat transfer coefficient of mixed flow which can be obtained by liquid convective heat transfer coefficient and gas convective heat transfer coefficient on the basis of liquid holdup.The temperature results of gas-liquid flow and inner wall in the case example presented both agree well with those in professional multiphase computational software OLGA.

Near ground air temperature calculation model based on heat transfer of vertical turbulent and horizontal air flow

In order to calculate the air temperature of the near surface layer in urban environment,the surface layer air was divided into several sections in the vertical direction,and some energy balance equations were developed for each air layer,in which the heat exchange due to vertical turbulence and horizontal air flow was taken into account.Then,the vertical temperature distribution of the surface layer air was obtained through the coupled calculation using the energy balance equations of underlying surfaces and building walls.Moreover,the measured air temperatures in a small area(with a horizontal scale of less than 500 m) and a large area(with a horizontal scale of more than 1 000 m) in Guangzhou in summer were used to validate the proposed model.The calculated results accord well with the measured ones,with a maximum relative error of 4.18%.It is thus concluded that the proposed model is a high-accuracy method to theoretically analyze the urban heat island and the thermal environment.

Study on absorption coefficients of dual-energy γ-rays in determining phase fractions of multiphase flows

This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions.

Temperature-flow regulation rule in indirect connection heating system and its energy-saving contrast analysis

Primary and secondary networks are treated as a whole in indirect heating systems, and an advanced new temperature-flow regulation method is presented whose flow ratio is greater than 60% in a secondary network and 30% in a primary network when under a partial load. Through deducing and optimizing an exponential function flow regulation rule, the formulae of flow regulation and the supply and return water temperatures are obtained, and their relevant curves are plotted. After comparison, it is found that this control method has a huge energy conservation space, and it should therefore be generalized soon.

Dielectric properties and relaxation dynamics in PbF_2-TeO_2-B_2_O3-Eu_2O_3 glasses

Frequency and temperature dependent dielectric dispersion of 20PbF2？20TeO2？（60？x）B2O3？xEu2O3（x=0 to 2.5, mole fraction, %） glasses prepared by the melt？quenching technique were investigated in the frequency range 1 Hz？10 MHz and temperature range 313？773 K. Dielectric relaxation dynamics was analyzed based on the electric modulus behavior. Dielectric losses （tanδ） are found to be negligibly small in the temperature range 313？523 K, proving good thermal stability of the glasses. The present Eu2O3-doped oxyfluroborate glasses showed low dielectric loss at higher frequency and lower temperature, proving their suitability for nonlinear optical materials.

Local Reynolds number and thresholds of transition in shear flows

Recent experimental and numerical investigations reveal that the onset of turbulence in plane-Poiseuille flow and planeCouette flow has some similar stages separated with different threshold Reynolds numbers.Based on these observations and the energy equation of a disturbed fluid element,a local Reynolds number Re L is derived to represent the maximum ratio of the energy supplement to the energy dissipation in a cross section.It is shown that along the sequence of transition stages,which include transient localized turbulence,"equilibrium" localized turbulence,spatially intermittent but temporally persistent turbulence and uniform turbulence,the corresponding thresholds of Re L for plane-Couette flow,Hagen-Poiseuille flow and plane-Poiseuille flow are consistent,indicating that the critical(threshold) states during the laminar-turbulent transition are determined by the local properties of the base flow and are independent of global features,such as flow geometries(pipe or channel) and types of driving forces(shear driving or pressure driving).

Theoretical and Computational Analyses of LNG Evaporator

Theoretical and numerical analysis on the fluid flow and heat transfer inside a LNG evaporator is conducted in this work. Methane is used instead of LNG as the operating fluid. This is because; methane constitutes over 80% of natural gas. The analytical calculations are performed using simple mass and energy balance equations. The analytical calculations are made to assess the pressure and temperature variations in the steam tube. Multiphase numerical simulations are performed by solving the governing equations(basic flow equations of continuity, momentum and energy equations) in a portion of the evaporator domain consisting of a single steam pipe. The flow equations are solved along with equations of species transport. Multiphase modeling is incorporated using VOF method. Liquid methane is the primary phase. It vaporizes into the secondary phase gaseous methane. Steam is another secondary phase which flows through the heating coils. Turbulence is modeled by a two equation turbulence model. Both the theoretical and numerical predictions are seen to match well with each other. Further parametric studies are planned based on the current research.

Phantom energy accretion onto a black hole in Horava-Lifshitz gravity

In this Letter,we examine the phantom energy accretion onto a Kehagias-Sfetsos black hole in Horava-Lifshitz gravity.To discuss the accretion process onto the black hole,the equations of phantom flow near the black hole have been derived.It is found that mass of the black hole decreases because of phantom accretion.We discuss the conditions for critical accretion.Graphically,it has been found that the critical accretion phenomena is possible for different values of parameters.The results for the Schwarzschild black hole can be recovered in the limiting case.

In situ construction of heterostructured bimetallic sulfide/phosphide with rich interfaces for high-performance aqueous Zn-ion batteries

It is still challenging to develop suitable cathode structures for high-rate and stable aqueous Zn-ion batteries.Herein,a phosphating-assisted interfacial engineering strategy is designed for the controllable conversion of NiCo_(2)S_(4) nanosheets into heterostructured NiCoP/NiCo_(2)S_(4) as the cathodes in aqueous Zn-ion batteries.The multicomponent heterostructures with rich interfaces can not only improve the electrical conductivity but also enhance the diffusion pathways for Zn-ion storage.As expected,the NiCoP/NiCo_(2)S_(4) electrode has high performance with a large specific capacity of 251.1 mA h g^(−1) at a high current density of 10 A g^(−1) and excellent rate capability(retaining about 76%even at 50 A g^(−1)).Accordingly,the Zn-ion battery using NiCoP/NiCo_(2)S_(4) as the cathode delivers a high specific capacity(265.1 mA h g^(−1) at 5 A g^(−1)),a long-term cycling stability(96.9%retention after 5000 cycles),and a competitive energy density(444.7W h kg^(−1) at the power density of 8.4 kW kg^(−1)).This work therefore provides a simple phosphating-assisted interfacial engineering strategy to construct heterostructured electrode materials with rich interfaces for the development of high-performance energy storage devices in the future.