Graphical weibull analysis of repairable systems

A graphical method is given for the analysis of repairable systems failing according to a Weilbull process. The integrated hazard rate is plotted in a logarithmic co-ordinate system. If the process is of Weibull type the observed data will be located around a straight line. The plot provides estimates of the parameters. The graphical procedure is completed by confidence bands and variation bands built either around the observed failure numbers at fixed time or vice versa.     

Reliability analysis of utility and stand-by electric power systems under uncertainty

The persistent and transient-cause forced outages and interruptions of utility power systems are subject to two kinds of uncertainties; the exact time of occurrence of outages is not known and the pdf of outage times is partially known or unknown. This paper obtains the utility and stand-by electric power system reliability by using Bayesian adaptive techniques. Cases of perfect switching, imperfect switching and idling stand-by are given.     

Optimal design of cogeneration system based on exergoenvironmental analysis

In this article, a new procedure was introduced for the optimal design of utility system in process industries. This method was based on the development of the R-curve concept and a new cogeneration targeting through estimating costs, environmental impacts, exergoeconomic, and exergoenvironmental analyses. In the exergoenvironmental analysis, the environmental impacts obtained by life cycle assessment are apportioned to the exergy streams pointing out the main system components with the highest environmental impact and possible improvements associated with these components. Moreover, exergoenvironmental variables are calculated, and an exergoenvironmental evaluation is carried out. In this regard, correlations for estimating the environmental impacts of cogeneration system have been introduced. In addition, the powerful and accurate cogeneration targeting method was applied. Also, the new graphic representations have been proposed. These curves are based on cost estimation, environmental impacts, and exergoenvironmental analysis. In addition, the optimal design of site utility was carried out in Iran LNG cogeneration plant, in which the usefulness of this method was clearly demonstrated.     

New type steam turbine for cogeneration

本文论述了供热汽轮机利用冷源节能增效原理;提出“NCB”新型供热汽轮机,其供热能力、热效率和发电功率均有大幅度提高;并以300MW供热汽轮机为例进行比较,供热能力提高30％,达到最大,热效率提高12 ％,供热高峰时发电功率可增加15 MW     

Performance analysis of a combined vapor compression cycle and ejector cycle for refrigeration cogeneration

A hybrid vapor compression refrigeration (HVCR) system, which combines a vapor compression refrigeration (VCR) system and an ejector refrigeration (ER) system, was developed. The waste heat energy from the gas cooler in the VCR system is applied as driven source towards ER system.Thermodynamic investigations on the performance of the HVCR system, using CO₂ as a refrigerant, are performed with energetic and exergetic methods, and the comparative analyses with the VCR system are conducted. Comprehensive effects of key operating parameters on the system performance are also studied. The results indicate that for the same cooling capacity, the coefficient of performance (COP) of the HVCR system shows 25% higher COP and the total mechanical power consumption is reduced by 20% than that of conventional VCR system, respectively. The performance characteristics of the proposed cycle show its application potential in cooling and air-conditioning.     

Multi-objective optimization of process cogeneration systems with economic, environmental, and social tradeoffs

Process cogeneration is an effective strategy for exploiting the positive aspects of combined heat and power in the process industry. Traditionally, decisions for process cogeneration have been based mostly on economic criteria. With the growing interest in sustainability issues, there is need to consider economic, environmental, and social aspects of cogeneration. The objective of this article is to develop an optimization framework for the design of process cogeneration systems with economic, environmental, and social aspects. Process integration is used as the coordinating framework for the optimization formulation. First, heat integration is carried out to identify the heating utility requirements. Then, a multi-header steam system is designed and optimized for inlet steam characteristics and their impact on power, fixed and operating costs, greenhouse gas emissions, and jobs. A genetic algorithm is developed to solve the optimization problem. Multi-objective tradeoffs between the economic, environmental, and social aspects are studied through Pareto tradeoffs. A case study is solved to illustrate the applicability of the proposed procedure.     

Graphical fault tree analysis for fatal falls in the construction industry

The current study applied a fault tree analysis to represent the causal relationships among events and causes that contributed to fatal falls in the construction industry. Four hundred and eleven work-related fatalities in the Taiwanese construction industry were analyzed in terms of age, gender, experience, falling site, falling height, company size, and the causes for each fatality. Given that most fatal accidents involve multiple events, the current study coded up to a maximum of three causes for each fall fatality. After the Boolean algebra and minimal cut set analyses, accident causes associated with each falling site can be presented as a fault tree to provide an overview of the basic causes, which could trigger fall fatalities in the construction industry. Graphical icons were designed for each falling site along with the associated accident causes to illustrate the fault tree in a graphical manner. A graphical fault tree can improve inter-disciplinary discussion of risk management and the communication of accident causation to first line supervisors.     

Materials selection and multi-attribute utility analysis

Summary Multi-attribute utility analysis (MAUA) has emerged as a powerful tool for materials selection and evaluation. An operations research technique, MAUA has been used in a wide range of engineering areas, of which materials science and engineering is one of the more recent. Utility analysis affords a rational method of materials selection which avoids many of the fundamental logical difficulties of many widely used alternative approaches. However, MAUA has traditionally been used in materials selection problems only, in which there is certainty regarding the attribute levels of the alternatives. For many new technologies this is not the case. Another operations research technique, subjective probability assessment (SPA), can be used to address this issue. SPA makes it possible to measure a probabilistic distribution describing the confidence of the decision maker in the levels of attributes for which there is a high degree of uncertainty. These probability distributions can be used in conjunction with MAUA to provide a consistent framework for making materials selection decisions. Furthermore, the use of these techniques extends beyond the problem of materials selection into the more speculative areas of materials competitiveness and market demand in cases involving new, unproven technologies.     

Reliability analysis techniques for mechanical systems

This paper discusses the application of known system reliability analysis techniques and identifies problems encountered in the practical implementation of these methods, revealing that no single technique is sufficient or even feasible in the case of complex mechanical systems. A new functional analysis method as well as a (new) criticality quantitative approach and failure mechanism analysis are presented and used to analyse an aircraft fuel system. A rigorous and detailed FMECA is still required. Besides its main function it will supply much of the valuable information for many other techniques.     

Optimization analysis for recycle-oriented manufacturing systems

Recycling has been recently recognized as one of effective tools for solving environmental problems. In this respect present and future manufacturing systems should take the recycling of materials used into consideration. This paper points out the issues contained in such a recycle-oriented manufacturing system, then the basic parts-flow in the product's life cycle is clarified by taking account of re-use and re-production of the parts contained in the product. A model is constructed to maximize two measures of performance—total profit and recycling rate. This is solved by goal programming. Finally, a numerical example is used to demonstrate the effectiveness of the model proposed.     

Process integration of solid oxide fuel cells with process utility systems

In the process industry, a utility system is one of the main energy consumption and pollution emission sources. Significant progresses have been made in the chemical industry to improve the efficiency and reduce the emissions of utility systems. However, few efforts have been made in investigating the possibility and strategy of incorporating new energy conversion devices such as fuel cells into industrial energy systems. The article presented focuses on systematic integration of fuel cells and industrial energy systems. A steady-state model of an indirect internal reforming solid oxide fuel cell (IIR-SOFC) system has been developed to estimate its thermodynamic and electrochemical properties and to optimise system performance. The model is then applied to the integration study of SOFCs into utility systems. Different process integration options are investigated and evaluated. Case studies show significant benefits of energy efficiency improvement and emission reductions by incorporating fuel cells into industrial utility systems.     

Graphical methods for production control

Three graphical method families are investigated and compared in terms of their representability in production control problems. The confrontation put PERT networks and their extensions in GANs before the same comparison basis as Petri nets and the new GRAI nets suggested by one of the authors.     

Investment risk analysis with a simple utility function

This study suggests an approach to investment risk analysis which provides a useful complement to more detailed analyses. The analyst specifies an appropriate distribution of cash flows and associated utility function from one of the four models suggested. Next, the risk adjusted present value of the investment stream is calculated using the simplified procedure outlined in the paper. Sensitivity analysis is then performed on the results to determine whether a more extensive analysis of the decision maker's risk preferences is called for.     

Investigation on gradient thermal cycle for power and refrigeration cogeneration

In order to improve energy utilization efficiency of low grade heat, a novel gradient thermal cycle for power and refrigeration cogeneration is proposed. The cycle is cascaded with two stages based on different thermal driven temperature. The first stage is pumpless Organic Rankine Cycle (PRC) while the second stage is two-stage sorption refrigerator. R245fa is selected as the working fluid of PRC, whereas CaCl₂-BaCl₂-NH₃ working pair is chosen for two-stage sorption refrigerator. Different heat source temperatures from 80°C to 95°C are adopted for analysis and comparison. Results indicate that the highest average power output and cooling effect are able to reach 204 W and 0.91 kW under the condition of 95°C heat source temperature and 10°C refrigeration temperature. For different heat source temperatures, total energy and exergy efficiency of the gradient thermal cycle for power and refrigeration cogeneration range from 9.49% to 9.9% and 10.9% to 11.8%, respectively. For gradient thermal cycle exergy efficiency of heat utilization ranges from 24% to 18.8% which is 126.5% and 70.9% higher than the PRC and two-stage sorption refrigerator, respectively, when the heat source temperature is 80°C.     

Utilizing spatial information systems for non-spatial-data analysis

Recent advances in the power and capabilities of personal computers have brought the algorithms and representational methods of Geographic Information Systems (GIS) to the desktop. Information that has relationships between elements may be represented spatially, especially if some distance metric can be brought to bear. This paper discusses information cartography, the use of spatial methods for the display of non-Geographic data. This revised version was published online in June 2006 with corrections to the Cover Date.