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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Proposta de método para avaliação do processo de extração de sucos cítricos

Kharfan, Daniela 30 August 2011 (has links)
Made available in DSpace on 2016-06-02T19:51:53Z (GMT). No. of bitstreams: 1 4027.pdf: 1690749 bytes, checksum: 8d859783d2c99e52f4016543ef37c8dd (MD5) Previous issue date: 2011-08-30 / For almost one century, citrus chain has been one of the most important agribusiness for Brazil. Brazil is the largest world orange producer and the largest orange juice exporter, responsible for almost 90% of the worldwide orange juice exportations. Doubtless one of the most important Brazilian sectors, citrus is responsible for a huge percentage of the agribusiness exportations (around USD 1,5bilion/year) and one of the economy motors of the central regions of the State of São Paulo. Over this period, many changes occurred and are still going on into the national and international scenarios. Also, in the XXI century changes have being happened more quick and intense: great fruit and orange juice price oscillations, influence of exchange variation, the 2008 economical crisis, influence of climate conditions and incidence of new diseases, besides demand variations regarding volume and type of product (advent of NFC Not From Concentrate or single strength juice). Citrus processing industry represents a fundamental key role in the whole chain, to achieve new frontiers, putting the Brazilian product into the 5 continents, leveraging exportations to almost 1,300 k/tons of juice exported annually. To guarantee competitiveness in the business, processors have searched continuous improvement on processes, equipment, management techniques as well as quality standards of their products, in order to meet the demands of the market that, year by year, have become more discerning and demanding. There is also the need of continuous improvement and adjustment of the Research & Development techniques for equipment applied to industry, to attend the new parameters. Performance tests of citrus juice equipment are totally important to: evaluate productive process efficiency, investment definition, meet customer s standards and represent a point that impacts the strategic corporate decisions. The purpose of this master s degree dissertation is to propose a method for evaluating the technical-economic stage of citrus juice extraction. The study aims the juice extraction process introduced in the citrus juice extraction chain. For this, it was performed a review of literature and a case study in the segment of citrus juice processing. The research approach used is qualitative and quantitative, using already existent data, from empirical studies conducted in the sector. This work aims to structure and propose a method for the process of citrus juice comparative tests, and the performance evaluation of the extraction system, considering the higher number of variables and ensuring all necessary and sufficient data for decisionmaking. As academic contribution, this work aims to bring an empirical example improvement of food industry equipment, using experimental techniques and data analysis in a specific juice extraction situation, whose results are used for tracking their productive processes, monitoring and improving performance and decision-making regarding changes and investments. / A cadeia citrícola, ao longo de quase um século de existência no Brasil, tem se mostrado uma das mais importantes no agronegócio, visto que o Brasil é o maior produtor mundial de laranjas e o maior exportador de suco cítrico com quase 90% das exportações mundiais. É, sem dúvida, um dos setores mais importantes da economina brasileira, responsável por uma parcela generosa das exportações do agronegócio (cerca de US$ 1,5 bilhões / ano) e um dos motores da economia da região centro do Estado de São Paulo. Ao longo deste período, muitas mudanças ocorreram e continuam acontencendo no cenário nacional e internacional, e no século XXI as mudanças têm se tornado mais rápidas e intensas: grandes oscilações nos preços da fruta e do suco de laranja, influência da variação cambial e da crise econômica de 2008, influência das condições climáticas e incidência de novas doenças, além de variações na demanda no que se refere ao volume e tipo de produto (advento do NFC Not From Concentrate ou suco integral). Nesta cadeia, a indústria de processamento dos cítricos tem papel fundamental no avanço das fronteiras, colocando o produto brasileiro nos cinco continentes, alavancando as exportações com quase um milhão e trezentas mil toneladas de suco exportado anualmente. Para garantir a competitividade no negócio, as indústrias têm buscado melhorias contínuas nos seus processos, equipamentos, técnicas de gestão e também nos padrões de qualidade dos seus produtos, a fim de atender às exigências do mercado consumidor que tem se tornado, a cada ano, mais criterioso e exigente. A fim de atender estes novos parâmetros, há, também, uma necessidade de melhoria contínua e adequação das técnicas de Pesquisa e Desenvolvimento para os equipamentos aplicados na indústria. A realização de testes de desempenho dos equipamentos de extração de sucos cítricos é de fundamental importância na avaliação da eficiência do processo produtivo, definição de investimentos, atendimento aos padrões de qualidade dos clientes, representando um ponto que causa impacto nas decisões estratégicas das empresas. Nesse sentido, esta dissertação de mestrado tem como objetivo a proposição de um método para a avaliação técnica-econômica da etapa de extração de sucos cítricos. O objeto de estudo, inserido na cadeia de produção de sucos cítricos, é o processo de extração de sucos. Para a realização deste trabalho, foi feita uma revisão bibliográfica e um estudo de caso no segmento de processamento de sucos cítricos. A abordagem de pesquisa utilizada é a qualitativa e quantitativa, com a utilização de dados já existentes da literatura e dados de estudos práticos realizados neste setor. Espera-se com este trabalho a estruturação e proposição de um método para o processo de realização de testes comparativos de extração de suco cítrico e a avaliação do desempenho deste sistema de extração, de forma que considere o maior número de variáveis do processo e garanta a obtenção de dados necessários e suficientes para tomadas de decisão. Como uma contribuição acadêmica, espera-se que o trabalho proposto traga um exemplo prático de melhoria no segmento de equipamentos para a indústria de alimentos por meio do uso de técnicas de experimentação e análise de dados em uma situação específica de extração de suco, cujos resultados são utilizados para acompanhamento de seus processos produtivos, monitoramento e aprimoramento de desempenho e tomada de decisão de modificações e investimentos.
2

Development of evaluation tools as an approach to pre-design district energy systems : Qualitative modeling and performance simulation using OpenModelica

Faramarzi, Ghazal, Torestam, Malin January 2020 (has links)
Cities and districts contribute to a large fraction of the total energy consumption in Sweden. The residential- and service sector accounted for almost 40% of the total energy consumption in 2018. The increasing urbanization also puts more importance on the energy supply, distribution and consumption in these areas. One way of planning an energy system in urban areas is to have integrated energy systems where synergies between different technologies and energy carriers are utilized. Such a solution can increase the flexibility of the energy system and thus help integrate more intermittent renewable energy sources. The aim of this study was to suggest tools for planning energy systems in districts. This was done by performing a literature review regarding the design of energy systems and the identification of barriers and opportunities for the integration of different production- and distribution technologies. The focus was on systems for heating, cooling and electricity. The proposed tools are three Excel-based modules. The first module is a qualitative model that presents the reviewed technologies and their connections. It also includes synergies between different energy carriers and sectors for consumption and production. The second module is qualitative model related to market mechanisms, juridical, organizational and institutional aspects. The third module is a table containing the barriers and opportunities. Furthermore, relevant stakeholders are identified to be district heating companies, building owners, joint associations, municipalities, district cooling companies and photovoltaic plant owners. The proposed tools can be used in the first stage of planning when the technologies are selected. To show how the suggested tools can be applied, a case study was performed. The study case is a district being planned in Stockholm, Sweden. For the analysis, a model for a hypothetical heating system was required. Two models were developed for the heat supply system using the modelling environment OpenModelica. The main objective of the case study was to compare the techno-economic and environmental performance of different scenarios. Three different scenarios were considered for covering the total heating demand in the district. In the first scenario the total heating demand is covered only by local heat pumps. In the second scenario the space heating demand is covered by heat pump(s) coupled with a thermal energy storage (hot water tank). An electric boiler is used as backup. In the third scenario, the electric boiler is replaced by district heating as backup. A sensitivity analysis was included for different numbers of heat pumps and different sizes of thermal energy storage in the two last scenarios. The economic and environmental results in this study were strongly dependent on the assumptions regarding prices and emission factors. The result of the case study indicates that the third scenario causes the lowest CO2 emissions. An increased size of the thermal energy storage causes a higher compressor electricity consumption thus more emissions. However the total emissions from the system depends on the backup component. For this result, the emission factor related to Swedish electricity mix and the emission factor stated by a district heating company in Stockholm was used. The cheapest alternative in terms of annual operational cost of energy is the first scenario with only heat pumps. However, from the scenarios which also includes thermal energy storage, the second scenario with three heat pumps and a 100 m3 large thermal energy storage, presents the lowest cost. This system design in scenario 2 is only 0.6% more expensive than the first scenario. For the energy prices, the assumption for electricity is based on hourly values from Nordpol and for heat, the values presented in a normal price list from a district heating company is assumed. Regarding the technical performance of the system the result indicates that the contribution from the thermal energy storage as it is modelled in this case study is not significant on anannual basis. However it is observed that a larger thermal energy storage unit covers a higher fraction of the power demand during the hours it is utilized. / Städer och stadsdelar står för en stor del av totala energikonsumtionen i Sverige. Bostads- och servicesektor stod för ungefär 40% av totala energikonsumtionen under 2018. Den ökande urbaniseringen lägger också mer vikt vid energiproduktion, distribution och konsumtionen i dessa områden. Ett alternativ för planering av energisystem i urbana områden är att ha integrerade energisystem där synergier mellan olika teknologier och energibärare kan utnyttjas. Den typen av system skulle kunna öka flexibiliteten i energisystemet och därför förenkla integrering av oförutsägbara förnybara energikällor. Syftet med denna studie var att föreslå verktyg för planering av energisystem i stadsdelar. Detta gjordes genom en litteraturstudie angående utformningen av olika energisystem samt identifiera hinder och möjligheter för att integrera olika produktions- och distributions teknologier. Fokus låg på systemen för värme, kyla och elektricitet. Det föreslagna verktygen är tre Excel baserade moduler. Den första modulen är en qualitative modell som presenterar de studerade teknologier och deras kopplingar. Den innehåller också synergier mellan de olika energibärarna och konsumtions- och produktionssektorn. Den andra modulen är en qualitative modell, men relaterad till marknad mekanismer, juridiska, organisatoriska och institutionella aspekter. Den tredje modulen är en tabell som beskriver hinder och möjligheter för några av teknologierna. Utöver det de relevanta aktörerna identifierades. För värme-, kyla- och elektricitet marknaden är de fjärrvärmeföretagen, fastighetsägare, samfälligheter, kommuner, fjärrkyla företagen, solcells ägare. De föreslagna verktyget kan användas för planering av energisystem i ett första skede när teknologier ska väljas.  En fallstudie genomfördes för att visa hur det föreslagna verktyget kan användas. Fallstudien en stadsdel som planeras i Stockholm, Sverige. För att genomföra en analys behövdes en modell för ett hypotetiskt värmesystem. Två modeller utvecklades för värmesystemet genom att använda modelleringsmiljön OpenModelica. Det huvudsakliga målet med fallstudien var att jämföra den teknoekonomiska- och miljöinriktade prestandan för olika scenarierna. Tre olika scenarier övervägdes för att täcka totala värmebehovet i stadsdelen. I det första scenariot täcks det totala värmebehovet endast av lokala värmepumpar. I andra scenariot täcks värmebehovet för uppvärmning av värmepump(ar) kopplade till en värmelagrings komponent (ackumulatortank). En elpanna användes för reserveffekt. I tredje scenariot är elpannan ersatt av fjärrvärme. En känslighetsanalys var utförd för olika antal värmepumpar kopplade till olika storlekar av värmelagrings-komponenten i de två sista scenarierna. De ekonomiska och miljörelaterade resultatet i den här studien är starkt beroende av antaganden gällande priser och utsläppsfaktorer. Resultatet indikerar att det tredje scenariot har de lägsta CO2 utsläppen. Ökad värmelagringsstorlek bidrar till att värmepumpen förbrukar mer elektricitet och därför ökar de relaterade utsläppen. Däremot beror de totala utsläppen i systemet på vilken reservkraft som används. För dessa resultat användes utsläppsfaktorn för svensk elmix samt utsläppsfaktorn från ett fjärrvärme företag i Stockholm. Den billigaste alternativet gällande årlig driftsenergikostnad är det första scenariot med endast värmepumpar. Däremot, bland de scenarion som innehåller värmelagring, har det andra scenariot med tre värmepumpar och 100m3 stor värmelagringsenhet den lägsta kostnaden. Detta system är endast 0.6% dyrare än det första scenariot. För energipriser har timvärden från Nordpol antagits för elektricitet och för värme har normalprislistan från ett fjärrvärmebolag i Stockholm antagits. Angående den tekniska systemprestandan, indikerar resultatet att bidraget från värmelagringsenheten som den är modellerad i den här fallstudien inte är signifikant på årsbasis. Det observeras emellertid att en större värmelagringsenhet täcker en större andel av effektbehovet under de timmar som enheten används.

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