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Total Annual Cost (total + annual_cost)

Distribution by Scientific Domains

Chemistry	42%
Medical Sciences	28%
Engineering	28%

Selected Abstracts

Automatic design of conventional distillation column sequence by genetic algorithm

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
Ramin Bozorgmehry Boozarjomehry
Abstract Synthesis of the optimum conventional (with non-sharp separations) distillation column sequence (DCS) is a challenging problem, in the field of chemical process design and optimization, due to its huge search space and combinatorial nature. In this paper, a novel procedure for the synthesis of optimum Conventional Distillation Column Sequence is proposed. The proposed method is based on evolutionary algorithms. The main criterion used to screen alternative DCS's is the Total Annual Cost (TAC). In order to estimate the TAC of each DCS alternative all columns that exist in the DCS are designed using short-cut methods. The performance of the proposed method and other alternatives are compared based on the results obtained for four standard benchmark problems used by researchers working in this area. Based on the results of the comparison, the proposed method outperforms the other methods and is also more flexible than other existing methods. La synthèse de la séquence de colonne de distillation (SCD) traditionnelle optimale (caractérisée par des séparations non tranchantes) représente un problème difficile à régler, dans le domaine de la conception et de l'optimisation de procédés chimiques, en raison de son immense espace de recherche et de sa nature combinatoire. Ce document propose une procédure nouvelle en vue de la synthèse de la séquence de colonne de distillation traditionnelle optimale. La méthode proposée est fondée sur des algorithmes évolutionnistes. Le critère principal utilisé pour présélectionner les autres possibilités de SCD est le coût total annuel (CTA). Pour estimer le CTA de chaque option de SCD, toutes les colonnes qui existent dans la SCD sont conçues en utilisant des méthodes abrégées. On compare ensuite le rendement de la méthode proposée et des autres possibilités en s'appuyant sur les résultats obtenus dans le cadre de quatre problèmes d'évaluation standard utilisés par les chercheurs oeuvrant dans ce domaine. En s'appuyant sur les résultats de la comparaison, la méthode proposée donne un meilleur rendement que les autres méthodes et est également plus souple que les autres méthodes qui existent. [source]

European comparison of costs and quality in the prevention of secondary complications in Type 2 diabetes mellitus (2000,2001)

DIABETIC MEDICINE, Issue 7 2002
A. Gandjour
Abstract Aims To compare the out-patient costs and process quality of preventing secondary complications in patients with Type 2 diabetes mellitus in France, Germany, Italy, The Netherlands, Sweden, Switzerland, and the UK. Methods A total of 188 European physician practices assessed annual services for one hypothetical average patient (cost evaluation) and 178 practices reported retrospective data on one or two real patients (quality evaluation) in 2000/2001. In countries with a detailed fee-for-service schedule (Germany, Italy, and Switzerland) reimbursement fees were used to approximate costs. These fee-for-service schedules were also used to develop index (average) fees for all countries, in order to measure resource utilization. The following process quality indicators were evaluated: control of HbA1c; control of lipids; urine test for (micro)albuminuria; control of blood pressure; foot examination; neurological examination; eye examination; and patient education. For each country an average quality rating was calculated by weighting the response to each quality indicator with the level of scientific evidence. Results Average quality ratings ranged from 0.40 in The Netherlands to 0.62 in the UK (0 = lowest rating; 1 = highest rating). Total annual costs for secondary prevention were higher in Switzerland than in Germany and Italy (EUR475, EUR381, and EUR283, respectively). Resource utilization was highest in Germany and lowest in the UK. Conclusions The overall quality of preventive services documented was found to be poor in the seven European countries studied. The UK rated as both the most effective and the most efficient country in providing secondary prevention in Type 2 diabetes. [source]

The economic costs of dementia in Korea, 2002

INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 8 2006
Guk-Hee Suh
Abstract Objective To estimate the economic costs of dementia in 2002 using an economic evaluation model for dementia care. Methods Data were from the Korea National Survey of the Long-Term Care Need (LTC survey) (n,=,5058), two prospective 1-year studies [one clinical trial (n,=,234), one naturalistic community cohort study (n,=,107)], and two epidemiologic community studies for prevalence of dementia (n,=,1037,+,1481). Daily costs and proportions of different levels of institutional service provided were collected from the LTC survey. Resource use in the community included health care services, social care services, out-of-pocket purchase for self-support, caregiver time and missed work of caregiver. Costs in community were calculated based on resource utilization multiplied by the unit costs for each resource. Results Total annual costs of dementia were estimated to be over 2.4 billion US$ for 272,000 dementia sufferers. Costs in community represent 96% of the total annual costs, while costs of informal care and missed work of caregivers were 1.3 billion US$, or 55% of total annual cost. Average annual costs of full time care (FTC) and pre-FTC in community LTC were 44,121 US$ and 13,273 US$ per person, whereas cost per patient who did not need community LTC was 3986 US$. Conclusion Given that the number of dementia sufferers is projected to increase in the near future and that larger part of the costs are subsidized by the government, the economic and social costs of dementia is significant not only for dementia sufferers and their caregivers, but also for society. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Baghouse system design based on economic optimization

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2000
Antonio C. Caputo
In this paper a method is described for using economic optimization in the design of baghouse systems. That is, for a given emission control problem, the total filtration surface area, the overall pressure drop, fabric material effects, and the cleaning cycle frequency, may all be evaluated simultaneously. In fact, as baghouse design parameters affect capital and operating expenses in interrelated and counteracting manners, a minimum total cost may be searched defining the best arrangement of dust collection devices. With this in mind, detailed cost functions have been developed with the aim of providing an overall economic model. As a result, a discounted total annual cost has been obtained that may be minimized by allowing for optimal baghouse characterization. Finally, in order to highlight the capabilities of the proposed methodology, some optimized solutions are also presented, which consider the economic impact of both bag materials and dust properties. [source]

Thermoeconomic optimization for a finned-tube evaporator configuration of a roof-top bus air-conditioning system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2008
M. Khamis Mansour
Abstract This paper presents a methodology of a design optimization technique that can be useful in assessing the best configuration of a finned-tube evaporator, using a thermoeconomic approach. The assessment has been carried out on a direct expansion finned-tube evaporator of a vapor compression cycle for a roof-top bus air-conditioning (AC) system at a specified cooling capacity. The methodology has been conducted by studying the effect of some operational and geometrical design parameters for the evaporator on the entire cycle exergy destruction or irreversibility, AC system coefficient of performance (COP), and total annual cost. The heat exchangers for the bus AC system are featured by a very compact frontal area due to the stringent space limitations and structure standard for the system installation. Therefore, the current study also takes in its account the effect of the variation of the design parameters on the evaporator frontal area. The irreversibility due to heat transfer across the stream-to-stream temperature difference and due to frictional pressure drops is calculated as a function of the design parameters. A cost function is introduced, defined as the sum of two contributions, the investment expense of the evaporator material and the system compressor, and the operational expense of AC system that is usually driven by an auxiliary engine or coupled with the main bus engine. The optimal trade-off between investment and operating cost is, therefore, investigated. A numerical example is discussed, in which a comparison between the commercial evaporator design and optimal design configuration has been presented in terms of the system COP and evaporator material cost. The results show that a significant improvement can be obtained for the optimal evaporator design compared with that of the commercial finned-tube evaporator that is designed based on the conventional values of the design parameters. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Thermoeconomic optimization of the geometry of an air conditioning precooling air reheater dehumidifier

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2006
Rahim K. Jassim
Abstract Exergy method of optimization for the geometrical parameters of an air conditioning precooling air reheater with turbulent flow is developed in this paper. The method is based on exergy, economic analysis and optimization theory. As there are humid air streams involved in the heat transfer process, then there are irreversibilities or exergy destruction, which is due to pressure losses, temperature difference and specific humidity gradient. These principle components of total irreversibility are not independent and there is a trade-off between them. Therefore, the purpose of this research paper is to study the effect of the geometry and the specific humidity of the two streams on the irreversibilities of a crossflow precooling air reheater dehumidifier. Also, the optimum balance between the three components of irreversibility is determined thereby giving the optimum solution for heat exchanger area. The total cost function is expressed on an annualized basis of the sum of the precooler capital cost and the running cost attributable to the precooler irreversibility. This total cost function is optimized in this paper according to the optimum heat transfer area and the total irreversibilities. Two optimum heat transfer areas were found for minimum total irreversibility and minimum total annual cost for a specific example. Finally, the relations between the typical operational variables such as heat transfer area, Reynolds numbers and the total annual cost for the precooler is developed and presented in graphs, which allow the calculation of the optimal heat transfer area, which gives the optimum irreversibility and minimum total annual cost. Copyright © 2005 John Wiley & Sons, Ltd. [source]

The economic costs of dementia in Korea, 2002

On the appropriate modeling of process plant water systems

AICHE JOURNAL, Issue 3 2010
Débora C. Faria
Abstract The definition of the water/wastewater allocation problem is discussed as it was originally defined by Takama et al.1 how this concept was modified, and sometimes simplified, through time, as well as additional issues that is believed are still not properly addressed. A few attempts are reviewed where parts are pointed out, and the addition of water pretreatment units are discussed, and further investigation in to the impact that proper modeling has on predictions of freshwater consumption, total annual cost and zero discharge cycles. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

A property-based optimization of direct recycle networks and wastewater treatment processes

AICHE JOURNAL, Issue 9 2009
José María Ponce-Ortega
Abstract This article presents a mathematical programming approach to optimize direct recycle-reuse networks together with wastewater treatment processes in order to satisfy a given set of environmental regulations. A disjunctive programming formulation is developed to optimize the recycle/reuse of process streams to units and the performance of wastewater treatment units. In addition to composition-based constraints, the formulation also incorporates in-plant property constraints as well as properties impacting the environment toxicity, ThOD, pH, color, and odor. The MINLP model is used to minimize the total annual cost of the system, which includes the cost for the fresh sources, the piping cost for the process integration and the waste stream treatment cost. An example problem is used to show the application of the proposed model. The results show that the simultaneous optimization of a recycle network and waste treatment process yields significant savings with respect to a commonly-used sequential optimization strategy. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Cost analysis of proton exchange membrane fuel cell systems

AICHE JOURNAL, Issue 7 2008
Ai-Jen Hung
Abstract Tradeoff between capital cost and the operating cost can be seen in the design of proton exchange membrane fuel cell systems. The polarization curve indicates that operating in the region of lower current densities implies less operating cost (hydrogen fuel) and higher capital cost (larger membrane electrode assembly area). The opposite effects are observed when one operates in the region of higher current densities. Therefore, an appropriate design should take both factors into account and the optimality depends on the corresponding costs of hydrogen and membrane area. An analytical cost model is constructed to describe such an economic balance in a proton exchange membrane fuel cell system. The objective function of the optimization is the total annual cost. Six scenarios are used to illustrate the optimal design based on the total annual cost as cost and materials factors fluctuate. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source]

Design of reactive distillations for acetic acid esterification

AICHE JOURNAL, Issue 6 2005
Yeong-Tarng Tang
Abstract The reactive distillation provides an attractive alternative for reaction/separation processes with reversible reactions, especially for etherification and esterification. The discrete nature of chemical species and the complexity of phase equilibria seem to cloud the picture in understanding reactive distillation. The esterifications of acetic acid with five different alcohols, ranging from C1 to C5, are studied. First, qualitative relationships between macroscopic process flowsheet and microscopic phase equilibria are established, and the process flowsheets are classified into type I, II, and III for these five systems. Next, a systematic design procedure is devised to optimize the design, based on the total annual cost (TAC) and dominant design variables are identified for different flowsheets. Once quantitative design is available, process characteristic are analyzed and potential problems in process operation are identified. Finally, the economic potentials of these three different flowsheets are explored and explanations are given. The results clearly indicate that it is possible to systemize the design of reactive distillation by qualitatively generating flowsheet from phase equilibria and by quantitatively completing the process flow diagram from a sequential design procedure. Moreover, some of the flowsheets presented in this work cannot be found elsewhere in the open literature. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]

Dividing Wall Distillation Columns: Optimization and Control Properties

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2008
F. I. Gómez-Castro
Abstract The optimal design of dividing wall columns is a non-linear and multivariable problem, and the objective function used as optimization criterion is generally non-convex with several local optimums. Considering this fact, in this paper, we studied the design of dividing wall columns using as a design tool, a multi-objective genetic algorithm with restrictions, written in MatlabTM and using the process simulator Aspen PlusTM for the evaluation of the objective function. Numerical performance of this method has been tested in the design of columns with one or two dividing walls and with several mixtures to test the effect of the relative volatilities of the feed mixtures on energy consumption, second law efficiency, total annual cost, and theoretical control properties. In general, the numerical performance shows that this method appears to be robust and suitable for the design of sequences with dividing walls. [source]