中压循环液化装置论述

文章介绍空分设备所配中压循环液化装置的两种流程———带冷冻机的中压循环液化流程与带高温膨胀机的中压循环液化流程及其特点 ,最后阐述了配置部机的要求与选择。图 2     

液化流程中氧液化器的流程组织和相关参数确定

简介了中压循环液化和低压循环液化两种主要的液化流程,对两种流程进行了比较;分析了在中压循环液化流程中单独设置氧液化器的必要性;探讨了在低压氧液化和中压氧液化时不同的氧液化器流程组织形式;提出了低压氧液化时合理的流程组织方案和相关参数。     

大型氦液化装置的优化设计

一、液化循环的程序日本神户制钢所研制的氦液化装置的工艺流程有两种,如图1所示。现有文献所发表的几种流程基本上属于克劳德循环。1.液化量液化循环的熵—温度曲线如图2所示。液化气体所需的热力学的最小功为:     

煤层气液化装置流程及经济性分析

介绍了三种典型的煤层气液化装置流程,即级联式液化流程、混合制冷剂液化流程和带膨胀机的液化流程,针对我国分散小煤矿煤层气,提出采用混合制冷剂液化流程为宜,并对1000m^3／h煤层气液化装置进行了详细的经济性分析,得出小型煤层气液化装置的投资回收期约为4～5年的结论。     

基于氮制冷循环预冷的氢液化流程研究北大核心CSCD

为寻求简单可靠的预冷方法作为氢液化高能耗替代,提出一种基于氮气逆布雷顿循环预冷的氢液化流程,相比于混合工质预冷循环,该流程结构简单,成本较低,适用于中小型氢液化系统。利用MATLAB软件建立了该流程的热力学模型,并利用Globalsearch求解器进行了优化分析;经对各种预冷方式的计算比较,氮气循环的能耗(2.68 kWh/kg)介于混合工质及液氮预冷之间,但其总热流比混合工质预冷更少。通过进行优化计算,该流程在传统液化系统的基础上能耗显著降低,能够达到8.33 kWh/kg。     

小型混合工质循环气体液化系统实验及优化

小型混合工质循环(MRC)气体液化流程以其机组设备简单、流程清晰、液化效率高等特点,备受国内外工程设计和研究的关注.SYSU-BP中心设计建立了一个常规压缩机驱动混合工质循环的小型气体液化装置,成功进行了多次低温实验,最低制冷温度在稳定工况下达到-182℃以下,并制得液化空气.依据实验数据,对系统的降温特性进行了分析,并在已有实验参数基础上,以实际运行条件为约束,系统最大COP为目标函数,利用模拟程序计算,对混合工质组分的配比进行了优化分析,并最终获得了混合工质的主要组分变化范围及优化组分.     

双膨胀中压循环液化工艺研究及其透平膨胀机设计要点

本文简要介绍了最新液化工艺—双膨胀中压液化循环工艺流程及特点,着重介绍双膨胀中压循环液化工艺及透平膨胀机的设计关键和运行控制,为推广和使用这类流程提供了设计参考依据。     

膨胀机对修正克劳特氦液化循环的影响及其热力学分析

以膨胀机为研究对象,分析了膨胀机对基于两级膨胀机串联的修正克劳特氦液化循环的影响.通过对系统中的部件进行逐个分析,用编程的方式实现了对氦液化循环的模拟,得到了不同膨胀机分流量、一级膨胀机出口压力、膨胀机效率下循环的液化率,并从热力学角度进行分析.研究结果表明膨胀机的分流量为80％时循环液化率最大,该值会随一级膨胀机出口...     

低温液化气船的制冷装置—再液化装置

本文介绍了低温液化气船上的特殊的制冷装置——再液化装置，分析了再液化装置的功能、基本类型以及基本要求；介绍一个典型的再液化装置流程及设备组成     

现代大型氮液化流程

提出了建立在透平压缩机和透平膨胀机及中压板式换热器基础上的、并带有冷冻机预冷系统的大型氮液化流程。并针对这种流程,较全面地分析了循环压力、预冷温度及膨胀机参数对流程经济性的影响,提出了这种流程优化设计思想和方法。图6参3。     

Discussion on refrigeration cycle for regenerative cryocoolers

Based on review and analysis of thermodynamic efficiency ε of the Carnot cycle and the cycle with two isothermal and two polytropic processes, another thermodynamic cycle with two isentropic and two polytropic processes, which can achieve the Carnot value of thermodynamic efficiency, is testified theoretically. Thermodynamic efficiency expressions of a number of ideal regenerative refrigeration cycles are derived, including the ideal pulse tube refrigeration cycle. A classified branch chart and a plot of ideal thermodynamic efficiency of regenerative refrigeration cycles are given for the purpose of comparison.     

High temperature low cycle fatigue

Fatigue at high temperature is a complex phenomenon as it is influenced by a number of time-dependent processes which become important at elevated temperatures. These processes include creep, oxidation, phase instabilities and dynamic strain ageing (DSA), acting either independently or synergistically influence fatigue behaviour, often lowering the fatigue life. Current design approaches employ linear summation of fatigue and creep damage with suitable factors on permissible damage to take care of uncertainties in interaction between cyclic and time-dependent processes. It is, therefore, important to develop a deeper understanding of the processes that occur during high temperature fatigue so that realistic life predictions could be made. Results on the high temperature fatigue behaviour of austenitic stainless steels, ferritic steels and nickel base alloys are presented here. The important mechanisms of interaction of high temperature time-dependent processes with fatigue under various conditions are discussed in detail. Emphasis is placed on cyclic stress response, fatigue life, deformation substructure and fracture behaviour. This is followed by a review of important life prediction techniques under combined creep-fatigue loading conditions. Life prediction techniques considered here include linear damage summation, strain range partitioning, ductility exhaustion approach, frequency modified and frequency separation methods, techniques based on hysteresis energy and damage rate models, and methods based on crack-cavitation interation models.     

Drive cycle development for tricycles

The absence of protocols through which an alternative technology for two stroke tricycles could be evaluated makes it difficult to compare these technologies and determine the best alternative. This study demonstrates the process of the development of a dynamometer test cycle that would be reflective of the actual driving conditions in Metro Manila. The development of such test cycle would be vital to the development of emission factors. The study covers the gathering of actual speed-time data, development of the instrumentation device for the said activity, analysis of the data gathered and extraction of a test cycle. Results were compared to the Indian drive cycle to demonstrate the inappropriateness of adapting drive cycles derived from other areas.     

Evaluating Six Sigma failure rate for inverse Gaussian cycle times

Six Sigma is a quality philosophy and methodology that aims to achieve operational excellence and delighted customers. The cost of poor quality depends on the sigma quality level and its corresponding failure rate. Six Sigma provides a well-defined target of 3.4 defects per million. This failure rate is commonly evaluated under the assumption that the process is normally distributed and its specifications are two-sided. However, these assumptions may lead to implementation of quality-improvement strategies that are based on inaccurate evaluations of quality costs and profits. This paper defines the relationship between failure rate and sigma quality level for inverse Gaussian processes. The inverse Gaussian distribution has considerable applications in describing cycle times, product life, employee service times, and so on. We show that for these processes attaining Six Sigma target failure rate requires higher quality efforts than for normal processes. A generic model is presented to characterise cycle times in manufacturing systems. In this model, the asymptotic production is described by a drifted Brownian motion, and the cycle time is evaluated by using the first passage time theory of a Wiener process to a boundary. The proposed method estimates the right efforts required to reach Six Sigma goals.     

包含五种循环的普适定常流内可逆制冷循环最优性能

用有限时间热力学方法分析了一类普适定常流内可逆制冷机循环,导出了存在传热损失时,由一个吸热过程、一个放热过程和两个绝热过程组成的一类普适的定常流内可逆制冷机循环的制冷率、制冷系数、(火用)损失率、(火用)输出率和生态学性能,并由数值计算分析了循环过程对循环性能的影响特点.所得结果包含了内可逆Carnot、Diesel、Otto、Atkinson和Brayton制冷循环的特性.     

Low cycle fatigue behaviour of cast nickel-base superalloy IN738LC at room temperature

The cyclic stress/strain response and the low cycle fatigue life of cast nickel-base superalloy IN738LC were studied. Fully reversed strain-controlled tests were performed at room temperature and at two different strain rates. Optical and electron microscopy were used to study the processes of deformation and cracking during cycling. A power-law relationship between life-time and total (plastic as well as elastic) strain range was obtained, which is not influenced by the strain rate and by the frequency. Cracking was generally initiated at the surface microporosities and propagated along interdendritic paths. During cyclic deformation, only cyclic hardening occurred at room temperature.     

全生命周期产品和过程模型集成技术研究

制造业的产品和过程集成技术体现在各个不同的层面,为此,研究了全生命周期产品和过程模型的集成技术。采用面向对象方法,构建全生命周期虚拟产品模型,对全生命周期的产品信息进行表达,并对全生命周期的涵义进行阐述。虚拟产品模型由实体对象和联系对象组成,它是一个动态模型,在产品全生命周期中不断进化。通过面向对象Petri网模型(OPN),描述产品全生命周期的各种过程。在虚拟产品模型和OPN模型的基础上重点讨论产品模型和过程模型的集成技术,并结合实例进行研究。产品和过程模型集成为产品信息的重用和追溯提供支持。     

液氮发动机循环分析

新型零排放液氮发动机存在朗肯循环和布雷顿循环两种做功循环方式,为了了解两种循环方式对液氮发动机匹配设计的要求,基于有限时间热力学理论,对比了两种循环对液氮发动机输出功率的影响,研究了液氮发动机在变温热源和恒温冷源之间朗肯循环和布雷顿循环的性能,着重分析了导热率对循环性能及输出功率的影响,为液氮发动机换热器的匹配提供依据.得出换热器的热导率和热容率的匹配决定朗肯循环的最佳循环功率,而与朗肯循环相比布雷顿循环能更好的实现发动机的功率特性的结论.     

Life cycle assessment framework for asphalt pavements: methods to calculate and allocate energy of binder and additives

The construction, maintenance and disposal of asphalt pavements may lead to considerable environmental impacts, in terms of energy use and emissions during the life of the pavement. In order to enable quantification of the potential environmental impacts due to construction, maintenance and disposal of roads, an open life cycle assessment (LCA) framework for the asphalt pavements is presented in this paper. Emphasis was placed on the calculation and allocation of energy used for binder and additives at the project level. It was concluded from this study that when progressing from LCA to its corresponding life cycle cost, the feedstock energy of the binder becomes highly relevant as the cost of the binder will be reflected in its alternative value as fuel. Regarding additives like wax, a framework for energy allocation was suggested. The suggested project level LCA framework was demonstrated in a limited case study of a Swedish asphalt pavement. It was concluded that the asphalt production and transporting materials were the two most energy-consuming processes, emitting most greenhouse gases depending on the fuel type and electricity mix.     

Three-dimensional process cycle simulation of composite parts manufactured by resin transfer molding

A process cycle of resin transfer molding (RTM) consists of two sequential stages, i.e. filling and curing stages. These two stages are interrelated in non-isothermal processes so that the curing stage is dominated by the resin flow as well as temperature and conversion distributions during the filling stage. Therefore, it is necessary to take into account both filling and curing stages to analyze the process cycle accurately. In this paper, a full three-dimensional process cycle simulation of RTM is performed. Full three-dimensional analysis is necessary for thick parts or parts having complex shape. A computer code is developed based on the control volume/finite element method (CV/FEM). The resulting computer code can provide information regarding flow progression and pressure field during mold filling; and temperature distribution and degree of cure distribution for a process cycle. The computer code can also be used for process cycle simulation of composite structures with complex geometry and with various molding strategies including switching injection strategy, multiple gate injection strategy and variable mold wall temperature. Numerical examples provided in the present work show the capabilities of the computer code in analyzing the process cycle.