局部反循环打捞装置数值模拟

为了明确常规局部反循环洗井装置在井下形成反循环的机理及其目前洗井效果不理想的原因,解决其在应用过程中碎屑提取率低的问题,采用计算流体力学方法,建立该装置洗井作业时的孔底固液两相流场计算模型,分析液相洗井介质在冲洗碎屑过程中的压力场、速度场分布及湍流特征。模拟计算得出:液相洗井介质的压力、流速及湍动能耗散主要发生在进入孔底流场前的两次出水孔换向过程中,导致其对孔底中部的碎屑冲洗能力不足,部分碎屑滞留在孔底中部。为改善反循环洗井装置的洗井效果,可改进下出水孔的结构,将下出水孔位置适当下移或缩小下出水孔直径,通过增大孔底处洗井介质流速来提升其对碎屑的携带能力。研究结果可为局部反循环打捞装置的优化设计提供参考。     

Design charts for two-phase flashing flow in emergency pressure relief systems

The design charts of this paper apply to the high velocity flow of a boiling liquid and its vapor during two-phase emergency pressure relief events. These charts are used to size relief system components to handle a given minimum relief flow requirement. This flow requirement is determined by computer simulation programs such as that described in [1], or by special-case models [2, 3, 4]. Though intended for use in sizing pressure relief systems, the charts are applicable to high-velocity flashing flow problems.     

The DIERS users group: A forum for development/dissemination of emergency relief system design technology

DIERS was formed in 1976 to develop methods for the design of emergency relief systems capable of handling runaway reactions [1, 2]. Of particular interest at the time were when tow-phase flow venting would occur and the applicability of different methods for sizing emergency relief systems for two-phase, vapor-liquid flashing flow. Approximately $1.6MM was devoted to investigations of two-phase, vapor-liquid onset/disengagement dynamics and the hydrodynamics of emergency relief systems.     

A NEW PERSPECTIVE ON MULTIPLE INTERNAL RATES OF RETURN

The most commonly cited drawback to using the internal rate of return to evaluate deterministic cash flow streams is the possibility of multiple conflicting internal rates, or no internal rate at all. We claim, however, that contrary to current consensus, multiple or nonexistent internal rates are not contradictory, meaningless or invalid as rates of return. There is, moreover, no need to carefully examine a cash flow stream to rule out the possibility of multiple internal rates, or to throw out or ignore “unreasonable” rates. What we show is that when there are multiple (or even complex-valued) internal rates, each has a meaningful interpretation as a rate of return on its own underlying investment stream.It does not matter which rate is used to accept or reject the cash flow stream, as long as one identifies the underlying investment stream as a net investment or net borrowing. When we say it does not matter which rate is used, we mean that regardless of which rate is chosen, the cash-flow acceptance or rejection decision will be the same, and consistent with net present value.     

Hydrodynamic aspects of venting for vessels containing viscous fluids

Nine depressurization experiments for vessels containing water, freon-114 and high viscosity fluids have been analyzed. These experiments were carried out at different plants and provide information about the dependence of the depressurization process on the size of the vessel, the type of vent installed, and the initial conditions. The differences of venting into the atmosphere or venting into a catch tank have been also examined. The accuracy of the two-phase flow model used for the analysis of these experiments has been demonstrated by comparisons with steady state data referring to co-current liquid/vapor flow as well as to batch type of flows, where the liquid phase is stagnant.     

热泵直供采暖两相流毛细管网性能研究

通过在用户自定义程序增加两相流动中质量源项和能量源项的方法,建立了毛细管网内气-液转化的CFD计算模型,对小管径光滑铜管内R22的冷凝性能进行研究。根据CFD模型,计算了不同气相进口流速下R22蒸汽的冷凝过程。得到了压力损失、冷凝系数和流速的关联曲线。对小管径毛细管网辐射末端的设计提供了理论依据,对制冷剂流速选择有一定指导意义。     

An overview of emergency relief system design practice

Cost effective loss prevention requires an optimizing strategy to prevent, moderate (relieve) and contain runaway reactions. Ensuring that an emergency relief system design will either avoid or accommodate two-phase vapor-liquid flow is of particular importance. Use of adiabatic runaway reaction test information in combination with digital computer simulation is a powerful method to design an emergency relief system.     

Measurement of flow resistance of rupture disc devices

Present codes and practices for the design of relief systems in which rupture discs are used are based either on non-typical system configurations or on “rule of thumb” default values of rupture disc flow parameters. There is a need to develop code methods and common practices based on actual relief system configurations, as well as test methods for determining the actual flow resistance of specific rupture disc devices. The methodology reported here is appropriate for these needs.     

基于颗粒动力学的高炉风口焦炭行为仿真研究

焦炭在风口回旋区运动、燃烧,其行为对回旋区的活跃程度产生影响,对高炉起着非常重要的作用,但受到实验手段的限制,难以对其进行直接的测量研究。应用颗粒动力学将焦炭颗粒视作拟流体,采用欧拉双流体理论构建了气固两相流风口回旋区仿真模型,并验证了该模型的正确性。通过该模型分析了回旋区内焦炭的运动规律和燃烧后气体成分的变化,发现风口前端回旋区外围的环形带是焦炭进入回旋区的主要位置;O2浓度沿风口中心线向炉内逐渐降低,CO2浓度先增加后减小至零,CO浓度逐渐增加至稳定。     

任意两相交流电机的统一方程式

任意对称和不对称运行的两相交流电机,根据其电磁物理过程的统一性,应用双旋转磁场理论,分析导出了任意两相交流电机的统一计算方程式。     

Use of DIPPR data in reactive chemical hazard assessment

In the early 1970's AIChE established the concept of Design Institutes. These are cooperative, industrially sponsored research efforts based on getting work done in an area of general interest at low cost to supporters. There are now four active AIChE groups. These are, with date of organization: Design Institute for Physical Property Data (DIPPR), 1978; Research Institute for Food Engineering (RIFE), 1984; Center for Chemical Process Safety (CCPS), 1985; and Center for Waste Reduction Technologies (CWRT), 1989. A fifth, Design Institute for Emergency Relief Systems (DIERS) has completed its work and established a user's group. The subject of this paper, DIPPR, is now in its eleventh year of funded project work. A symposium honoring the completion of DIPPR's tenth year was held in San Francisco in November, 1989. There were 11 papers presented, along with an historical overview. Copies of the 11 papers are available from the Engineering Societies Library in New York City, as Session 40. The papers were published as an AIChE Symposium Series in 1990 [1]. The DIPPR project results that can be used in reactive chemical hazard assessment are highlighted.     

Emergency relief vent sizing for fire emergencies involving liquid-filled atmospheric storage vessels

For large atmospheric vessels the potential occurrence of sufficient liquid swell resulting in two-phase flow is of special importance. Based upon an extension of analytical work it would appear justifiable to ignore two-phase flow effects for non-foamy systems.     

基于支持向量机模型的地铁进站客流量预测

为了更精确地预测短期站点客流量,动态调整城市轨道交通的日常客流方案,采用支持向量机模型对预测地铁客流量。首先,通过对AFC数据分析,利用上周同期进站量、前一天同期进站量、当日前两个时段进站量以及高峰和非高峰时段参数作为模型的输入变量;然后,构造支持向量机预测模型并运用粒子群算法优化模型(PSO-SVM模型),实现地铁站点客流量预测,并进行不同模型预测误差的比较分析;最后,以苏州地铁数据为例,预测汾湖路地铁站的进站客流量。结果表明,优化模型能够有效改善预测误差,预测结果更为准确,证明PSO-SVM方法能有效用于地铁进站客流量的预测研究,为地铁进站客流量预测提供了新的方法。     

LOPA as practiced at a global manufacturing API facility

The standard risk assessment practices used in industry since the OSHA 1910.119 regulation was issued, are to conduct Process Hazard Analyses (PHAs) for hazardous and exothermic (or otherwise high risk) processes. During PHAs, the potential consequences of an undesired event are evaluated along with the safeguards that exist to mitigate the consequences or reduce the frequency of the event. If the PHA team determines that the risk is still not tolerable, additional safeguards are recommended to reach a tolerable level of risk. Typically, a Quantitative Risk Assessment can be completed to evaluate the effectiveness of these existing or newly proposed safeguards. Unfortunately, this is a complex and time-consuming task. The relatively new methodology of Layer of Protection Analysis (LOPA) allows a PHA team to evaluate the effectiveness of safeguards in reducing risk in an efficient yet semiquantitative fashion using some basic assumptions and standard lookup tables. The LOPA methodology can be utilized to evaluate the effectiveness of Safety Instrumented Functions (SIF) (e.g., automated critical interlocks and alarms) to achieve a tolerable risk. The LOPA methodology provides consistency in an approach to risk assessments and communications. It can support an effective mechanical integrity or risk-based maintenance system for critical components of an SIF. This article describes LOPA and includes several scenarios that will provide an overview of how the LOPA methodology is used in a multibatch pharmaceutical facility. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009     

PSM system upgrade in response to an Occupational Safety and Health Administration NEP inspection

This article presents a brief analysis of the Occupational Safety and Health Administration (OSHA) Petroleum Refinery Process Safety Management National Emphasis Program (NEP) citation results as of early 2009. It includes trends distilled from the OSHA inspections performed to date. Recommendations for preparing for PSM NEP level inspections are provided. A proven approach to designing and implementing an upgrade project for OSHA process safety management systems and EPA risk management program is described. The model presented can be targeted to a facility's NEP specific citations or used for a general PSM system effectiveness upgrade. This article includes recommendations for improving PSM as a result of an NEP inspection. The recommendations are for the PSM elements that routinely have major OSHA citations; that is: Operating Procedures, Mechanical Integrity, Process Hazards Analysis, Process Safety Information, Management of Change, and Incident Investigations. © 2009 American Institute of Chemical Engineers Process Saf Prog 2009     

Netzausbauplanung unter Berücksichtigung probabilistischer Einflussgrößen

The present network expansion planning is performed by simulating extreme scenarios in order to proof the security of energy supply. This procedure is associated with high investment costs for equipment which is only needed a few hours per year. Planners have to consider uncertainties and prediction errors for the creation of the extreme scenarios due to the long economic life time of the equipment. The consideration of these influencing factors becomes very complex due to increased utilization of renewable energy sources and frequent changes in the unit commitment of conventional power plants. In contrast to classic load flow methods probabilistic load flow calculation considers the static behaviour of the loads, renewable energies and the power plants instead of only discrete values of nodal powers. These characteristics can be described by probabilistic density functions of load and generation mapped with a probabilistic load flow calculation into a probabilistic density function of the state variables of the energy system (as nodal voltages or line currents). This article presents an overview about existing methods of probabilistic load flow calculations and introduces a newly developed method. The characteristics and the applicability of these methods are verified and the computational burden is analysed exemplarily. Necessary extensions for the mapping of real energy systems and possible approaches for this are presented. The potential and the impact of probabilistic network expansion planning are discussed.     

DISCOUNT RATE VALUE AND CASH FLOW DEFINITION: A NEW RELATIONSHIP AND ITS IMPLICATIONS

This article uses different standpoints to approach the question of the consistency of project valuation methods. It shows that the NPV of a project can be obtained by discounting adjusted operating cash flows at a different rate from the risk-adjusted discount rate which should normally be used. Each of the conventional project valuation methods (standard WACC, equity residual, Arditti-Levy, APV) accordingly corresponds to a specific choice of the discount rate. Thus the convergence of these methods is obvious when the risk-adjusted discount rate integrates a debt ratio equal to the one of the project. Moreover, we obtain the Modigliani-Miller relationship generalized to the case of a project of any duration.     

2006 IIE-EED Business Meeting Minutes

The duration measure of weighted average life has been applied in the capital budgeting literature as a measure of project liquidity. Duration is superior to payback methods because it considers both the timing and present value of the entire cash flow stream. However, the literature is ambivalent on the choice of discount rate in calculating project duration. For duration to properly serve as a project liquidity measure, the internal rate of return should be used to discount future cash flows. Examples show that using the firm's cost of capital to calculate duration fails to measure the time to recover initial project outlays in present value dollars.     

Improved integration of LOPA with HAZOP analyses

Integrating Layer of Protection Analysis (LOPA) with Hazard and Operability Analysis (HAZOP) has many advantages over performing these studies separately. The merits include: fewer actions from the combined effort compared to performing only a HAZOP; team continuity resulting from the combined effort as opposed to two separate teams having possibly differing points of view; and, ultimately, a time and cost savings realized by the combination. This integration defines the risk associated with a given scenario, enabling better decisions that impact business assurance. By using the Center for Chemical Process Safety guidelines to define the independent protection layers upfront, the gray areas can often be reduced or eliminated; thereby enabling a more thorough LOPA. Examples include taking credit if a unit has two independent operators (outside and inside) responding to critical alarms, or taking credit for centralized control rooms that may allow immediate operator interaction and response. This article shows how the guidelines have been used successfully in joint HAZOP/LOPA studies, and describes an initial preparation protocol that can ensure high-quality results. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009     

A Cash Flow Model of Rational Housing Tenure Choice*

This paper develops a model of housing costs in a cash flow framework. The cash flow approach allows both the consumption and investment aspects of tenure choice to be analyzed. By solving the model for the rental flow equivalent to any owning situation, we can determine whether or not a household would buy or rent from an economic perspective. The results are very sensitive to the household's income, the expected duration of occupancy, the mortgage interest rate, and inflation expectations. The results suggest that “rule-of-thumb” generalizations about tenure choice are often ill-founded, and that studies of tenure choice need to explicitly consider the interaction of income, taxes, length of occupancy and expectations.