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Auswahl der wissenschaftlichen Literatur zum Thema „Valor presente expandido“
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Zeitschriftenartikel zum Thema "Valor presente expandido"
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Costa Maldonado Moncada, Julio Ernesto, Leonardo Flor, Viviane Silva und Jonas Pacheco. „Estudo da adição de argila expandida e EPS como agregados na elaboração de concreto leve“. Revista Eletrônica TECCEN 12, Nr. 1 (28.06.2019): 02–07. http://dx.doi.org/10.21727/teccen.v12i1.1849.
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O presente trabalho apresenta uma análise comparativa entre o concreto convencional e o concreto leve com a substituição do agregado graúdo pela argila expandida e poliestireno expandido. Observa-se que o emprego destes elementos em materiais cimentícios viabiliza a redução do peso próprio de estruturas em concreto, assegurando uma minoração econômica no custo total da obra onde for aplicado o concreto leve. Para a realização deste estudo o fator água aglomerante atribuído ao concreto leve foi superior em relação ao traço elaborado para concreto convencional por possuir um agregado poroso. O projeto experimental realizou-se em laboratório à uma temperatura de 24,5°C e humidade relativa do ar de 71%Rh, obedecendo às normas regulamentadoras. O fator de eficiência obtido no concreto leve foi superior em todos os ensaios realizados, no entanto sua resistência mecânica à compressão apresentou um resultado inferior ao concreto convencional, porém ambos os concretos possuem função estrutural que estabelece como um valor mínimo a resistência de 20 MPa de acordo com a NBR 6118:2014. Contudo, observou-se que a adição de argila expandida e poliestireno expandido é viável, pois reduz a massa específica do concreto o que gera um alívio de carregamento nas estruturas reduzindo o custo global da construção. A segurança estrutural mantém-se garantida pelo fator eficiência.
Palavras chaves: concreto, agregado, eficiência
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Nardelli, Paula Moreira, und Marcelo Alvaro da Silva Macedo. „Análise de um projeto agroindustrial utilizando a Teoria de Opções Reais: a opção de adiamento“. Revista de Economia e Sociologia Rural 49, Nr. 4 (Dezember 2011): 941–66. http://dx.doi.org/10.1590/s0103-20032011000400006.
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O objetivo geral deste trabalho é analisar a viabilidade econômicofinanceira de um projeto agroindustrial, através da Teoria de Opções Reais (TOR). A justificativa para utilização da TOR está centrada no fato de que os métodos tradicionais de análise de projetos (VPL e TIR) ignoram duas características importantes: a) a irreversibilidade e b) a possibilidade de adiamento da decisão de investir. Essas características, junto à incerteza sobre o futuro, fazem com que a oportunidade de investimento seja análoga a uma opção financeira. Com o intuito de aplicar estes conceitos, será realizado um estudo de caso, que consiste em um projeto agroindustrial de processamento de frutas, em que se pretende produzir sucos, polpas, geleias, doces e frutas desidratadas. A avaliação pretende demonstrar o valor das flexibilidades operacionais que esse projeto apresenta, como adiar a implementação do mesmo. Para isso, adotou-se a metodologia proposta por Copeland e Antikarov (2001), que adiciona à avaliação tradicional de Fluxo de Caixa Descontado as Opções Reais que o projeto possui. O resultado obtido para o valor presente líquido expandido do projeto, considerando-se as opções reais, para o quarto ano, foi de R$ 891.877,00, aumento de 207% em relação ao valor presente tradicional.
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Herdt, Jeferson Antonio, und Sady Mazzioni. „Distribuição de riquezas e o impacto social do trabalho voluntário das entidades sem finalidade de lucros“. Ágora : revista de divulgação científica 22, Nr. 1 (21.08.2017): 47. http://dx.doi.org/10.24302/agora.v22i1.1422.
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O objetivo do presente estudo é investigar o impacto dos serviços voluntários na formação e distribuição do valor adicionado em uma entidade sem fins lucrativos de Ituporanga – SC. As características de investigação permitem classificá-lo como exploratória e de cunho qualitativo. O ambiente de estudo é o Lar de Idosos Abrigo Mão Amigo (AMA), localizado na cidade de Ituporanga/SC, fundado em 2008 e com início das atividades em 2011. Com o propósito social de acolhimento de idosos desamparados por seus familiares ou até mesmo que por vontade própria do idoso, preferiu viver em abrigo. No tocante a distribuição do valor adicionado, nota-se que o principal grupo de beneficiários são os empregados, isso, devido ao grande número de funcionários necessários para os cuidados com os idosos. Após a mensuração e reconhecimento dos serviços voluntários recebidos, de acordo com as normas contábeis, há um acréscimo de 3,34% no total das receitas da entidade, atribuindo-se a distribuição da riqueza gerada à sociedade e à própria entidade como os beneficiários. A elaboração da demonstração do valor adicionado expandido serve para melhor compreensão da atividade social e econômica das entidades, por considerar em sua elaboração os valores das entradas e saídas sociais, que são recursos não monetários, atribuindo-lhes valores.
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Fujita, Erika, Rogério Lopes Vieites und André José de Campos. „Avaliação enzimática na pós-colheita do maná cubiu tratados com radiação gama“. REVISTA AGRO@MBIENTE ON-LINE 6, Nr. 1 (05.05.2012): 53. http://dx.doi.org/10.18227/1982-8470ragro.v6i1.488.
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Objetivou-se com o presente trabalho avaliar o efeito de diferentes doses de radiação gama e tempos de armazenamento na atividade enzimática de frutos de maná cubiu. Os frutos selecionados foram submetidos a diferentes doses de radiação gama com Co60 (0,0, 0,2, 0,4, 0,6 e 0,8 kGy), embalados em bandejas de poliestireno expandido, cobertos por filme esticável de PVC e armazenados em frigorificado a 10 ± 3°C e 85 ± 5% de UR, sendo avaliados em seis períodos (0, 4, 8, 12, 16 e 20 dias). As variáveis avaliadas foram: atividade enzimática da pectinametilesterase (PME), poligalacturonase (PG), polifenoloxidase (PFO) e peroxidase (POD). Para PG não houve interação entre dose e armazenamento, no dia 16 o valor foi maior com 640,10 UE min-1 g-1 de tecido fresco e a dose 0,8 kGy mostrou o menor alor com 376,37 10 UE min-1 g-1 de tecido fresco. Já a PME no dia 16 e na dose 0,8 kGy, obteve-se os maiores valores do experimento, com 290,74 10 UE min-1 g-1 de tecido fresco. Na PFO, o dia 16 apresentou o valor de 0,26 min-1 g-1 de massa fresca-1. No dia 20 os frutos de todos os tratamentos forneceram os maiores valores de POD durante todo o experimento. Os resultados demonstraram que as diferentes doses de radiação gama não interferiram na atividade das enzimas em estudo.
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Derevetski Trindade, Andrea Possato. „Competencias organizacionales y el desempeño laboral de los líderes de la Iglesia Adventista del Séptimo Día de la ciudad de Campinas, Sao Paulo, Brasil, 2016.“ Revista de Investigación Valor Agregado 5, Nr. 1 (03.03.2020): 40–49. http://dx.doi.org/10.17162/riva.v5i1.1280.
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Actualmente existen, organizaciones las cuales se han tornado altamente competitivas en los últimos años, fundamentado en la coexistencia de grandes identidades quienes generan un empoderamiento definitorio en sus contextos. En consecuencia es necesario considerar que las bases estructurales de las empresas se hallan en su talento humano como eje de producción, en la cual la función de las competencias de cada uno y su desempeño laboral se ven estrechamente ligados al contexto de desarrollo de los mismos, en materia de autorrealización, confort o superación. Ello es aplicable al contexto institucional de la Iglesia Adventista Séptimo Día, caracterizada por promover principios de la cultura cristiana protestante, surgente en el año 1863, a partir del cual se ha expandido con miembros y socios a nivel mundial, lo cual le ha permitido constituir una identidad sólida referente a sus procesos con más de catorce décadas en curso. Con base en estos aspectos, el presente artículo de investigación surgió con el objetivo de analizar la relación existente entre las variables de competencia organizacional y el desempeño laboral en los líderes de la IASD en la ciudad de Campinas; una totalidad muestral de 71 pastores, a quienes se les aplicó una encuesta propuesta contentiva de 13 dimensiones, fundamentadas en las variables de acción de toda organización y su repercusión en los resultados reales de las mismas. Cabe acotar que, se halló un valor adecuado entre las competencias organizacionales y el desempaño laboral de los empleados, siendo esta última variable dependiente de la primera, lo que influye de manera directa en las realidades propias de cada empresa o institución bien consolidada a nivel global.
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Mazzioni, Sady, Sheila Jeane Schulz und Roberto Carlos Klann. „A Demonstração do Valor Adicionado Expandido Aplicada em uma Entidade Sem Fins Lucrativos“. Future Studies Research Journal: Trends and Strategies 6, Nr. 1 (30.07.2014): 83–110. http://dx.doi.org/10.24023/futurejournal/2175-5825/2014.v6i1.152.
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his study poses to investigate the impact of entries of social nature as overlooked by traditional accounting when compiling expanded value added figures, before value added accounting. To this effect, an exploratory qualitative survey was conducted at a non-profit organization located in the State of Santa Catarina, Brazil. The study´s object was Indaial´s Women's Network Against Cancer (SC), an association of social and philanthropic purpose, deemed of both municipal and state public interest. Study results indicate that the value added statement -compiled as of financial information gathered at the researched institution– presents both employees and the government as being the prime beneficiaries of the wealth therein generated. Once both acknowledgement and measurement of volunteer service derived social entries are incorporated, compiled value added figures raise 82.92%. This disclosure approach extends the scope of beneficiaries of generated wealth beyond that of employees and government to include the organization itself - which receives social care program preparation and management services - and society as a whole, the ultimate addressee of services deployed by non-profit entities. One may come to the conclusion that social accounting concepts enable the understanding of both social and economic dynamics of this kind of organization.
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VYTCHIKOV, Yuri S., Mikhail E. SAPAREV und Dar’ya D. KONYaKINA. „OPTIMIZATION OF THE HEAT AND HUMIDITY MODE OF MULTI-LAYER BUILDING ENCLOSING STRUCTURES“. Urban construction and architecture 10, Nr. 4 (05.03.2021): 36–41. http://dx.doi.org/10.17673/vestnik.2020.04.5.
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The article presents a methodology for determining the required resistance to vapor permeation of the outer layer of a multilayer building envelope, based on the condition that there is no condensation of water vapor in it. When deriving the formula, an analytical dependence was used to determine the elasticity of saturated water vapor, obtained by the authors of this article. With the help of the proposed technique, the assessment of the thermal and humidity regime of the outer wall, insulated facade system using thin-walled plaster, as well as layered masonry using expanded polystyrene and basalt plates as insulation was made. The results of the calculation of the indicated external walls are presented, which show that condensation of water vapor is possible in layered masonry. The proposed analytical dependence for determining the maximum allowable resistance to vapor permeation of the outer layer of a multilayer enclosing structure is recommended to be used in engineering calculations of the humidity mode of external enclosures of buildings and structures.
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Souza e Silva, Wagner. „Fotojornalismo e os afetos como valores-notícia“. Discursos Fotograficos 14, Nr. 25 (03.12.2018): 143. http://dx.doi.org/10.5433/1984-7939.2018v14n25p143.
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Expandindo o conceito de valor-notícia, este artigo tem o objetivo de propor mecanismos teóricos para se observar o componente emocional presente na produção da informação. Propõe-se o fotojornalismo como a expressão dos afetos como valores-notícia, tendo em vista não só o apelo emocional que é intrínseco às imagens, mas também a sua circulação potencializada pelas dinâmicas das redes sociais, o que parece reconfigurar a ideia de sensacionalismo na prática jornalística.
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Souza, Samuel Aguiar de Castro e., und Adilson Caldeira. „Renovar o Modelo de Negócios para Sustentar a Competitividade: Uma Experiência no Setor Moveleiro“. Revista Inovação, Projetos e Tecnologias 7, Nr. 2 (01.07.2019): 216–31. http://dx.doi.org/10.5585/iptec.v7i2.15248.
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O presente artigo relata a experiência de um projeto realizado com o objetivo de restabelecer a competitividade de uma empresa brasileira do setor moveleiro e propor estratégias para o seu desenvolvimento, de modo a inovar na oferta de valor aos clientes, mediante a revisão do modelo de negócio. A análise das atuais condições do ambiente competitivo possibilitou um diagnóstico para o delineamento de um novo modelo de negócios, caracterizado pela ampliação da oferta de valor aos clientes por meio da concepção mercadológica de criar valor com os consumidores (market with). Com tal orientação, propôs-se a criação de um marketplace que disponibiliza aos clientes, além dos produtos próprios da empresa, benefícios e produtos complementares, de modo a criar valor para o cliente pela comodidade no ato de compra. O compartilhamento da experiência possibilita expandir o conhecimento e, consequentemente, contribuir para o desenvolvimento de tecnologia de gestão, com potencial de replicação em situações equivalentes.
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Bruni, Adriano Leal, César Valentim de Oliveira Carvalho Júnior, Roberto Brazileiro Paixão, Moreno Figueiredo und José Valdir Garcia da Silva Júnior. „Percepção de Valor e Custeio Alvo: Um Estudo no Segmento de Móveis Planejados“. Revista de Contabilidade da UFBA 2, Nr. 3 (16.01.2008): 35. http://dx.doi.org/10.9771/rc-ufba.v2i3.3267.
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O presente trabalho buscou estudar uma empresa do ramo de móveis planejados com o objetivo de determinar os atributos de valor e o custo alvo da mesma. O estudo de caso foi efetuado na empresa Top Lar, Projetos & Decoração, localizada no bairro da Calçada, Salvador, Bahia. Para atingir aos objetivos de pesquisa propostos, foram utilizados como instrumentos de coleta de dados um questionário e um roteiro de entrevistas para identificação dos atributos de valor atribuídos pelos clientes de micro-empresas de móveis planejados. Os resultados encontrados evidenciam que o custo máximo admissível é superior ao custo estimado pela empresa o que gerou um custo alvo negativo. Este fato amplia a zona de conforto para que o gestor do negócio invista em melhorias para expandir os benefícios agregados ao produto oferecido e aumente o valor percebido pelo cliente, reduzindo sua sensibilidade a preço. Por fim, entende-se que as ferramentas para determinação da percepção de valor e dos índices de valor trazem benefícios importantes para a tomada de decisão e definição da estratégia de formação de preço, redução de custos e maximização dos resultados.
Dissertationen zum Thema "Valor presente expandido"
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Minardi, Andrea Maria Accioly Fonseca. „Teoria de opções aplicada a projetos de investimento“. reponame:Repositório Institucional do FGV, 1996. http://hdl.handle.net/10438/4721.
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Made available in DSpace on 2010-04-20T20:14:40Z (GMT). No. of bitstreams: 0
Previous issue date: 1996-03-28T00:00:00ZApresenta a Teoria de Opções como a melhor abordagem para integrar estratégia e finanças, pois esta considera as flexibilidades gerenciais (opção de postergar investimento, aumentar e contrair escala de produção, abandonar temporária ou definitivamente um projeto, etc.) e opções de crescimento existentes no projeto, assim como estabelece uma política ótima de investimento. Contém uma introdução da Teoria de Opções aplicada a ativos financeiros, mostrando porque é possível se trabalhar com o ambiente neutro ao risco. Realiza uma analogia entre Opções Reais e Opções Financeiras, mostrando algumas limitações para se empregar a Teoria de Opções a projetos de investimento. Apresenta, compara e exemplifica diferentes abordagens numéricas (modelo binomial, integrações numéricas e esquemas de diferenças finitas, etc.) para se quantificar opções reais. Analisa a avaliação de empresas sob a ótica de opções, e cita exemplos onde a aplicação da Teoria de Opções foi fundamental. Realiza considerações e apresenta modelos para lidar com opções múltiplas e estrutura de mercado da indústria.
This dissertation presents Option Pricing Theory as an approach to solve Capital Budgeting problems. The goals of this work are to clarify the applications and limitations of this approach and to provide models and practical principles for quantifying the value of real options. In real life, as the market conditions change, management revises previous strategic considerations, altering investment plans in response to new environment. As the Net Present Value approach cannot properly capture this management's f1exibility, it may undervalue investment opportunities and lead to wrong and not optimal investment decisions. The traditional NPV method should be revamped to consider the value of management's f1exibility: Expanded NPV = Traditional NPV + Value of flexibility Option Pricing Theory is the best approach to capital budgeting problems that have significant operating and strategic options, because it integrates strategy and finance. Investment opportunities are considered as a set of the real options embedded in it (defer a project, expand or contract production scale, abandon, switch inputs and outputs, invest in subsequent projects), having as an underlying asset the gross project value of expected operating cash f1ows. These real options are basically treated analogous to financial options.
Buchteile zum Thema "Valor presente expandido"
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Manescau, Brady, Khaled Chetehouna, Ilyas Sellami, Rachid Nait-Said und Fatiha Zidani. „BLEVE Fireball Effects in a Gas Industry: A Numerical Modeling Applied to the Case of an Algeria Gas Industry“. In Fire Safety and Management Awareness. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.92990.
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This chapter presents the numerical modeling of the BLEVE (Boiling Liquid Expanding Vapor Explosion) thermal effects. The goal is to highlight the possibility to use numerical data in order to estimate the potential damage that would be caused by the BLEVE, based on quantitative risk analysis (QRA). The numerical modeling is carried out using the computational fluid dynamics (CFD) code Fire Dynamics Simulator (FDS) version 6. The BLEVE is defined as a fireball, and in this work, its source is modeled as a vertical release of hot fuel in a short time. Moreover, the fireball dynamics is based on a single-step combustion using an eddy dissipation concept (EDC) model coupled with the default large eddy simulation (LES) turbulence model. Fireball characteristics (diameter, height, heat flux and lifetime) issued from a large-scale experiment are used to demonstrate the ability of FDS to simulate the various steps of the BLEVE phenomenon from ignition up to total burnout. A comparison between BAM (Bundesanstalt für Materialforschung und –prüfung, Allemagne) experiment data and predictions highlights the ability of FDS to model BLEVE effects. From this, a numerical study of the thermal effects of BLEVE in the largest gas field in Algeria was carried out.
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Kandra, Ranju, und Sunil Bajpai. „Wound Dressing Application of Ch/CD Nanocomposite Film“. In Chitin and Chitosan - Physicochemical Properties and Industrial Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95107.
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In this work, carbon dots (CDs), obtained through microwave assisted synthesis from butane tetra carboxylic acid (BTCA), was introduced into chitosan film via simple solvent casting approach. The CDs had an average diameter of 40 to 60 nm as determined by Transmission Electron Microscopy (TEM) analysis. They possessed a zeta potential of −20.2 mV. The X-ray photon spectroscopy (XPS) confirmed presence of carboxylate groups on the surface of carbon dots. The XRD of both the plain sample Ch/CD (0) and carbon dots loaded sample Ch/CD(2) showed two crystalline sharp peaks at 14.6 and 18.1 degree, along with presence of amorphous region also. The moisture absorption data was well fitted on GAB isotherm and the profiles obtained were sigmoidal. The water vapor permeation rates for the sample Ch/CD(0) and Ch/CD(2) were found to be 1758 and 956 g/m2 /day respectively. The film samples Ch/CD(0) and Ch/CD(20 expanded 2.8 and 103 times when immersed in 4% gelatin solution for 4 h. The % hemolysis for the samples Ch/CD(0) and Ch/CD(2) was 2.12 and 1.11 respectively, thus indicating biocompatible nature of the films. In the ex-vivo mucoadhesion study, the maximum detachment force (Fmax) was 88.22 and 46.28 mN for the samples Ch/CD(0) and Ch/CD(2) respectively. Finally, both of the samples, namely Ch/CD (0) and Ch/CD(2) scored “0”, suggesting their non-cell cytotoxic nature.
3
Floudas, Christodoulos A. „Heat Exchanger Network Synthesis“. In Nonlinear and Mixed-Integer Optimization. Oxford University Press, 1995. http://dx.doi.org/10.1093/oso/9780195100563.003.0014.
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This chapter focuses on heat exchanger network synthesis approaches based on optimization methods. Sections 8.1 and 8.2 provide the motivation and problem definition of the HEN synthesis problem. Section 8.3 discusses the targets of minimum utility cost and minimum number of matches. Section 8.4 presents synthesis approaches based on decomposition, while section 8.5 discusses simultaneous approaches. Heat exchanger network HEN synthesis is one of the most studied synthesis/design problems in chemical engineering. This is attributed to the importance of determining energy costs and improving the energy recovery in chemical processes. The comprehensive review of Gundersen and Naess (1988) cited over 200 publications while a substantial annual volume of studies has been performed in the last few years. The HEN synthesis problem, in addition to its great economic importance features a number of key difficulties that are associated with handling: (i) The potentially explosive combinatorial problem for identifying the best pairs of hot and cold streams (i.e., matches) so as to enhance energy recovery; (ii) Forbidden, required, and restricted matches; (iii) The optimal selection of the HEN structure; (iv) Fixed and variable target temperatures; (v) Temperature dependent physical and transport properties; (vi) Different types of streams (e.g., liquid, vapor, and liquid-vapor); and (vii) Different types of heat exchangers (e.g., counter-current, noncounter-current, multistream), mixed materials of construction, and different pressure ratings. It is interesting to note that the extensive research efforts during the last three decades toward addressing these aforementioned difficulties/issues exhibit variations in their objectives and types of approaches which are apparently cyclical. The first approaches during the 1960s and early 1970s treated the HEN synthesis problem as a single task (i.e., no decomposition into sub-tasks). The work of Hwa (1965) who proposed a simplified superstructure which he denoted as composite configuration that was subsequently optimized via separable programming was a key contribution in the early studies, as well as the tree searching algorithms of Pho and Lapidus (1973). Limitations on the theoretical and algorithmic aspects of optimization techniques were, however, the bottleneck in expanding the applicability of the mathematical approaches at that time.
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Graham, Alan. „Cause and Effect Factors Influencing the Composition and Distribution of North American Plant Formations through Late Cretaceous and Cenozoic Time“. In Late Cretaceous and Cenozoic History of North American Vegetation (North of Mexico). Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195113426.003.0005.
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The arrangement of vegetation over the landscape is a product of interactions between the environment, the ecological characteristics of individual organisms, barriers, dispersal potential, epidemic disease, anthropogenic influences, and the partially serendipitous factor of propagule availability. Within the complex of environmental factors, several are of special importance in tracing the history of North American plant communities. They include climate; plate tectonics as a mechanism for orogeny, volcanism, land bridges, and terranes; and catastrophes. Each have numerous interacting subcomponents, feedbacks, and amplifiers, and although constraints of format make it necessary to discuss these separately and sequentially, they are interconnected and pertubation of one affects the entire system. Diagrams summarizing these factors are presented at the end of the following sections. The diagrams are not intended as models for, indeed, the single factor of climate could be expanded into a component so vastly complex that it would be counterproductive to a general summary. Similarly, the hydrological cycle, which involves the largest movement of any substance on Earth, cannot be fully treated because a “systems” view of its role in influencing climate is not available (Chahine, 1992) and the roles of water vapor (a greenhouse gas) and cloud cover are just now being quantified (Cess et al., 1995; Ramanathan et al., 1995). Rather, the diagrams illustrate some of the factors and relationships discussed in the text and serve as a reminder of the complex interactive nature of physical and biotic events. Plants are limited in their ecological amplitude. Several important corollaries follow from this observation; one of the most fundamental is that changes in climate cause extinctions promote evolution, and alter the range and habitats of organisms. Because climate plays a central role in the arrangement of modern communities (Gates, 1993; Kareiva et al., 1993; Woodward, 1987) and in the development and distribution of past assemblages (Brenchley, 1984; Crowley and North, 1991; Hecht, 1985a), reference to some elements of general climatology is necessary for understanding the diversification, radiation, and reshuffling of North American paleocommunities during the Late Cretaceous and Cenozoic.
Konferenzberichte zum Thema "Valor presente expandido"
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Pinhasi, G. A., Y. Dahan, A. Dayan und A. Ullmann. „Modeling of Boiling Liquid Expanding Vapor Explosion (BLEVE): Plane, Cylindrical and Spherical 1D Model“. In ASME 2008 9th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2008. http://dx.doi.org/10.1115/esda2008-59333.
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A 1D plane, cylindrical and spherical numerical model was developed for estimating the thermodynamic and the dynamic state of the boiling liquid during a boiling liquid expanding vapor explosion (BLEVE) event. The model predicts, simultaneously, the flow properties of the expanding two-phase flashing mixture and its surrounding air. The possible presence of a shock wave formed by the fluid expansion through the air is accounted for in the model. Model predictions of the shock wave strengths, in terms of TNT equivalence for the various coordinate systems, were compared against those obtained by simple energy models. As expected, the simple energy models over predicts the shock wave strength. However, the simple model which accounts for the expansion irreversibility, produces results which are closer to current model predictions. For the 1D plane case the model simulates a BLEVE scenario in a tunnel, whereas for the spherical case the more realistic BLEVE scenario in free space is being studied.
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Visser, Frank C. „Basic Considerations for Evaluating Hydraulic Power Recovery of Fluid Streams Expanding With or Without Gas or Vapor Evolution“. In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77055.
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A review of status is presented, discussing hydraulic power recovery of fluid streams expanding with or without gas evolution. Point of departure for the treatise given, is embedded in basic thermodynamics and fluid mechanics. Formulae for estimating isentropic power recovery are derived, which hold asymptotically for low gas to liquid mass fraction. These formulae provide simple means for calculating power recovery with gas evolution, given a certain vapor void fraction. The key element in the entire approach is to attribute the extra power recovery due to gas evolution to the change in density of the fluid stream. The formulae and discussions presented in the paper may assist the (application) engineer in evaluating the effect of vapor evolution with regard to hydraulic performance of hydraulic power recovery turbines. The paper further also discusses the condition of (runaway) overspeed, as this should not be omitted from a review on basic considerations for hydraulic power recovery turbines. Formulae and calculation methods are given for calculating runaway speed, choke flow and time to runaway speed.
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Cai, Qingjun, und Chung-Lung Chen. „A Method of Power Generation From Low Temperature Medium“. In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39556.
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For a long time, how to utilize waste heat to generate electricity has been an interesting and challenging field for energy scientists. This paper presents a new method, ferrofluid power generator (FPG), which takes advantage of waste heat or solar energy to generate electricity in a multiple heating and cooling tube with alternate ferrofluid slug and vapor bubble structures. Based on this method, a new device, a thermomagnetic engine (TME) composed of a straight vacuum tube, a current induced coil, and magnet & ferrofluid slugs (MFS), was designed. Experimental results show that the expanding vapor bubbles push MFSs to generate drastic and continuous oscillating movements under the effect of heat. The pulse voltage signals from the induced coil demonstrate that the TME has a practical structure, potentially higher power generating capacity, and a stable operation.
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Miller, Eric S., Soumya S. Patnaik und Milind A. Jog. „Dynamic Modeling of Vapor Compression Cycles Using a Novel Lagrangian Approach“. In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58303.
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Vapor compression cycles-based systems (VCS) are being adapted for thermal management of modern aircraft. Predicting dynamic behavior is critical to the design and control of these systems, which are likely to experience large dynamic changes in heat load. To meet this demand, a novel Lagrangian method to model the dynamic behavior of vapor compression cycles has been developed. The approach described in this paper considers the basic VCS as 4 fluid sides: one high pressure and one low pressure refrigerant side and external fluids which interact with each respectively. Sides are further divided into some number of material volumes. The model simulates compressible, unsteady flow by allowing each volume to translate and displace other elements, expanding and contracting in response to changes in mass, enthalpy and pressure. At every timestep, heat transfer to each mass element is determined and corresponding changes in thermodynamic properties are evaluated. The model predicts transient system response during normal operation as well as startup mode. Results from a dynamic evaporator simulation are presented and discussed. These results show the low-pressure refrigerant and external fluid response to changes in valve position, external fluid inlet temperature, and refrigerant inlet enthalpy. The conclusion drawn from these results is that the modeling framework described in this paper can reproduce the basic dynamics of a two-phase heat exchanger at a rate less than real time.
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Wu, Tong, Ying Zhou und Tao Qi. „Penetration Jet Impingement Calculation in Engineering Application“. In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67096.
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In the process of nuclear power plant design, Pipe Rupture Hazards Analysis (PRHA) was obliged, including postulated rupture location and configurations, jet impingement effects, compartment pressurization effects, environmental influences, flooding effects, leak-before-break and influence on SSC, etc. The analysis of jet impingement is of great importance; aims at obtaining the jet impingement configuration and the impingement force acting on the target. Jet impingement configuration and force depended on the jet flow properties. A jet discharging from a saturated steam line will accelerate and expand due to the pressure differential, and it will partially condense to a low-moisture wet steam with liquid phase in the form of dispersed, entrained water droplets. A jet discharging from a sub-cooled or saturated hot water line (greater than 100°C) would flash to a low quality wet steam and the flashing would cause the jet diameter to expand very rapidly. These jet flows have a phase change and two-phase flow process; the recommended two-phase flow model that should be used was presented in ANSI/ANS 58.2-1988. However, penetration jet impingement which is often encountered in the PRHA was not introduced. In normal cases, the saturated steam, sub-cooled or saturated hot water (greater than 100°C) expands directly to the surroundings. But for penetration jet impingement, the fluid is first discharged to the narrow annular section formed by the pipe and the penetration, then flows through this area, and finally expands to the surroundings at the open side of the penetration. The penetration expanding jet analysis is much more complicated. A method of determining penetration jet impingement in engineering applications was derived based on the fundamental method presented in ANSI/ANS 58.2-1988, Henry and Fauske model recommended. The simplified method took advantage of the two-phase flow models and equations given by ANSI/ANS 58.2-1988; the jet configuration could be calculated effectively and the target impingement force could be derived using the result presented by these equations simultaneously. The impingement pressure field was defined using the program for different initial states of the postulated pipe rupture — namely sub-cooled and saturated. The pressure distribution along the jet centerline obtained has shown clearly the three regions in ANSI/ANS 58.2-1988. The pressure field has shown that sub-cooled water has a larger zone of influence and saturated vapor has a higher mean impingement pressure as Sub-cooled water was under expanded while saturated vapor has higher enthalpy as it contains more energy.
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Yakovlev, Grigory, Jadvyga Keriene, Anastasiia Gordina, Irina Polyanskikh und Milan Bekmansurov. „Efficient Eco-friendly Composite Fluorine Anhydrite-Based Materials“. In Environmental Engineering. VGTU Technika, 2017. http://dx.doi.org/10.3846/enviro.2017.009.
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The paper presents possible ways of utilizing technogenic waste – fluorine anhydrite – by its use in production of dry mortars and piece goods from lightweight concrete with expanded polystyrene, as a organic filler, for low-rise construc-tion. The developed dry mortars are based on fluorine anhydrite binder and complex modifier comprising curing activator (sulfate or alkaline) and finely dispersed additive. The fluorine anhydrite-based compositions have improved physical and performance characteristics, including the improved strength and average density and reduced water absorption compared to the control composition. The developed lightweight anhydrite polystyrene concrete has the density grade of 700 kg/m3 and good vapor and gas permeability. The concrete is stabile while using and fire safe, because each granule of expanded poly-styrene is coated with anhydrite matrix, and has the strength sufficient for structural and heat insulating slabs and blocks. All mentioned compositions are eco-friendly and are in great demand for low-rise construction. Therefore the manufacturing of these compositions will consume a large amount of technogenic waste and will reduce the environmental load on the region where the waste is located.
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Kandlikar, Satish G. „Heat Transfer Mechanisms During Flow Boiling in Microchannels“. In ASME 2003 1st International Conference on Microchannels and Minichannels. ASMEDC, 2003. http://dx.doi.org/10.1115/icmm2003-1005.
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The forces due to surface tension, inertia, and momentum change during evaporation in microchannel govern the two-phase flow patterns and the heat transfer characteristics during flow boiling. These forces are analyzed in this paper, and two new non-dimensional groups, K1 and K2, relevant to flow boiling phenomenon are derived. These groups are able to represent some of the key flow boiling characteristics, including the CHF. The small hydraulic dimensions of microchannel flow passages present a large frictional pressure drop in single-phase and two-phase flows. In order to keep the pressure drop within limits, the channel lengths are generally shorter and the mass fluxes are generally lower than those with conventional channels (Dh>3 mm). The resulting lower mass fluxes, coupled with small Dh, lead to Reynolds numbers in the range 100–1000. Such low Reynolds numbers are rarely employed for flow boiling in conventional channels. In these low Reynolds number flows, nucleate boiling systematically emerges as the dominant mode of heat transfer. Aided by strong evaporation rates, the bubbles nucleating on the wall grow quickly and fill the entire channel. The contact line between the bubble base and the channel wall surface now becomes the entire perimeter at both ends of the vapor slug. Evaporation occurs at the moving contact line of the expanding vapor slug as well as over the channel wall covered with a thin liquid film surrounding the vapor core. The usual nucleate boiling heat transfer mechanisms, including liquid film evaporation and transient heat conduction in the liquid adjacent to the contact line region, play an important role. The liquid film under the large vapor slug evaporates completely at downstream locations thus presenting a dryout condition periodically with the passage of each large vapor slug. The flow boiling correlation by Kandlikar [1, 2] with (i) the nucleate boiling dominant region equation, and (ii) the laminar flow equation for single-phase all-liquid flow heat transfer coefficient hLO was successful in correlating the available R-134a data for parallel microchannels of 190 μm hydraulic diameter.
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Leskovar, Matjazˇ, und Bosˇtjan Koncˇar. „Simulation of Steam Explosion with a General Purpose CFD Code“. In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89185.
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An ex-vessel steam explosion may occur when during a severe reactor accident the reactor vessel fails and the molten core pours into the water in the reactor cavity. A steam explosion is a fuel coolant interaction process where the heat transfer from the melt to water is so intense and rapid that the timescale for heat transfer is shorter than the timescale for pressure relief. This can lead to the formation of shock waves and production of missiles at later times, during the expansion of the highly pressurized water vapor, that may endanger surrounding structures. In contrast to specialized steam explosion CFD codes, where the steam explosion is modeled on micro-scale using fundamental averaged multiphase flow conservation equations, in the presented approach the steam explosion is modeled in a simplified manner as an expanding high-pressure premixture of dispersed molten fuel, liquid water and vapor. Applying the developed steam explosion model, a comprehensive analysis of the ex-vessel steam explosion in a typical PWR reactor cavity was done using the CFD code CFX-10. At four selected locations, which are of importance for the assessment of the vulnerability of cavity structures, the pressure histories were recorded and the corresponding pressure impulses calculated. The pressure impulses determine the destructive potential of the steam explosion and represent the input for the structural mechanical analysis of the cavity structures. The simulation results show that the pressure impulses depend mainly on the steam explosion energy conversion ratio, whereas the influence of the premixture vapor volume fraction, which is a parameter in our model and determines the maximum steam explosion pressure, is not significant.
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Wilms, Jeffrey, Terry Beck, Christopher M. Sorensen, Mohammad H. Hosni, Steven J. Eckels und Don Tomasi. „Experimental Measurements and Flow Visualization of Water Cavitation Through a Nozzle“. In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-40276.
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A typical refrigeration loop is composed of an evaporator, compressor, condenser, and an expansion valve. There are many possible refrigerants that can be used, but the physical properties of water make it ineffective in the traditional refrigeration loop. But if water could be used it would have many advantages as it is abundant, cheap, and is safe for the environment. As part of development of a new refrigeration loop using water, flow visualization and cavitation of water through nozzles are being investigated. Cavitation is generally defined as creating vapor from liquid, not through adding heat, but by decreasing the pressure. In a converging/ diverging nozzle as the cross sectional area is constricted the velocity of the flow will increase, decreasing the pressure. Therefore, by flowing water through the nozzle it will cavitate. Transforming liquid into gas requires a certain amount of energy, defined as the latent heat. When a liquid is turned to vapor by an increase in the temperature the latent heat is provided by the heat transfer to the system. As no energy is being added in the nozzle to cause the cavitation, the heat to create the vapor comes from the liquid, effectively causes a temperature drop. This article presents results for the flow visualization of the water cavitating as it goes through the nozzle. Under different flow conditions and nozzle geometries the cavitation manifested itself in different formations. When gasses were entrained in the water they formed bubbles, creating a nucleation site and moving through the nozzle, called travelling bubble cavitation. In venturi nozzles the cavitation nucleated off of the wall, forming attached wall cavitation. When water flowed out of an orifice, a turbulent water jet was formed which caused vapor to form around it, causing shear cavitation. When the water was rotated prior to the throat of an orifice, the orifice jet expanded radially and formed swirl cavitation.
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Kornienko, Y. „Zuber-Type Parameter Distributions for Non-Equilibrium Two-Phase Flows: Generalization for Annular Channel and Rod Cluster Geometries“. In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-64755.
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This study presents the main results of the analysis of the previously developed generalized hierarchical closed system of analytical closure relations for the distribution parameters (DPs) Cks (k = f - fluid or g - vapor; s = 0,1,2,3 - mass, energy, momentum) that are used in quasi-one-dimensional form of the conservation laws for mass, momentum and energy in non-equilibrium two-phase flows. The current method has been expanded to account for non-uniform in cross-section profile of void fraction. The main assumptions of the received quadrature relationships for DP are: (a) the use of the drift flux model, (b) the quasi-steady-state approximation, and (c) the power-mode approximations of the local distribution profiles of the variables. These DPs Cks quadrature are expressed in terms of elementary functions, they directly reflect the principle of superposition, generalize and unify not only the Zuber-Findlay method, but also Hancox-Nicoll and Hibiki-Ishii methods. The revealed complementarity properties are particularly useful for the purposes of testing, validating and verifying DPs.