Tensile properties, namely the elastic modulus, tensile strength, percent of elongation at yield and at the break were determined for the pure components and blends. The results are connected to the respective phase diagrams and demonstrate that blending makes property manipulation possible. Blends for which the mechanical properties are better than those of pure EPs can be obtained.

Orientador: Vivaldo Silveira Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-08T21:44:28Z (GMT). No. of bitstreams: 1 MonzonDavila_LenaSoledad_M.pdf: 1297499 bytes, checksum: 0150b5616aa8630cf25a2830c9e27b00 (MD5) Previous issue date: 2007 / Resumo: As propriedades termofisicas dos alimentos são requeridas para o cálculo de tempo de processamento em projetos de equipamentos para a indústria de alimentos. Os processos de congelamento exigem dados precisos das propriedades térmicas do produto, tais como condutividade térmica, fração de gelo, calor específico e entalpia. A necessidade do conhecimento do comportamento destas propriedades tem levado ao desenvolvimento de alguns modelos matemáticos para suas predições. A condutividade térmica dos alimentos é uma propriedade fortemente dependente da composição química e da temperatura do alimento. Neste trabalho compararam-se os resultados experimentais de condutividade térmica de soluções modelo congeladas em três diferentes velocidades de congelamento, utilizando o método da sonda linear de aquecimento, com os obtidos pelo modelo matemático ¿Maxwell-Eucken¿ ou disperso como função da fração de gelo contida nos alimentos. Foi obtida uma divergência com o modelo por não considerar a velocidade de congelamento. Determinou-se que a condutividade térmica é uma propriedade termofísica diretamente proporcional ao aumento da velocidade de congelamento Os valores de condutividade térmica das amostras foram calculados através da inclinação obtida da regressão linear determinada pelo perfil do logaritmo natural do tempo versus temperatura. Os resultados da condutividade térmica foram correlacionados com as velocidades de congelamento e com a fração de gelo, indicando sua dependência devido à dispersão do gelo no produto / Abstract: The thermophysical properties of foods are required to calculate freezing time in the equipments design for foods industry. Freezing process demand exacts data of product thermal properties, as thermal conductivity, ice fraction, specific heat and enthalpy. The necessity of knowledge of the behavior of these properties has led to development of some mathematical models for their prediction. Thermal conductivity of foods is a property strongly dependent of chemical composition and food temperature. In this work, the experimental thermal conductivity results of model solutions freezing in three different velocities using line source probe method have been compared with the results obtained by the Maxwell-Eucken mathematical model or disperse as a function of ice fraction contained in foods, getting a divergence of the model for not considerer freezing velocities. Model solutions were frozen in three different velocities of freezing. Was determined that the thermal conductivity is a thermophysical property directly proportional to the increase of the freezing velocity. The thermal conductivity values of samples were calculated by the angular coefficient obtained by the linear regression which was determinate by the time natural logarithmic profile versus temperature. The thermal conductivity results were correlated with freezing velocities and ice fraction, indicating its dependence due to ice dispersion in the product / Mestrado / Mestre em Engenharia de Alimentos

No description available.

Recent global efforts have focused on developing new lightweight alloys specifically designed for high-pressure die casting (HPDC) processes, aiming to achieve the lightweight of electrified vehicles. HPDC offers a distinct advantage by allowing the production of neat-net-shape automotive components, minimizing the need for further processing. An inherent characteristic of HPDC is its rapid cooling rates, making the understanding and characterization of the thermophysical properties of these newly developed lightweight alloys under high cooling rates a must. These properties have a significant effect on controlling the HPDC process and developing suitable filling and solidification models to simulate the HPDC process intricacies for commercial production adaptation. The thermophysical properties of these alloys are shown to exhibit considerable variability with temperature, particularly under rapid solidification conditions, like in HPDC. Hence, an essential step in developing such alloys is to thoroughly investigate the variation of their thermophysical properties with temperature under high cooling rates. To fulfill such a need, an experimental setup has been developed to allow the solidification of molten metal samples under varying cooling rates using a set of impinging water jets. An inverse heat transfer algorithm has been developed to estimate the thermal conductivity and thermal diffusivity as a function of the temperature of the solidifying samples under high cooling rates. To validate the accuracy of the inverse heat transfer algorithm and the experimental methodology, a set of experiments has been carried out using pure Tin, which is a well-characterized material. Its thermal diffusivity and thermal conductivity are readily available in the literature. The estimated thermal diffusivity and thermal conductivity of Tin have been compared with the published data. The estimated thermal diffusivity and conductivity of the solid phase were in good agreement with the published values. A maximum deviation ranging from +10.1% to -3.47% was observed in the estimated thermal diffusivity. The maximum deviation in the estimated thermal conductivity was between +7.8% and -13.6%. Higher deviations have been observed in the estimated thermal diffusivity and conductivity of the liquid phase with deviations in the range of +33.71% to -4.86% and +0.76% to 26.53%, respectively. The higher deviations observed for the liquid phase might be attributed due to the natural convection that developed in the tested liquid sample. The effect of natural convection was examined using a set of numerical simulations that confirmed the existence of a convection-induced movement within the liquid phase. A sensitivity analysis was carried out to examine the impact of the accuracy of thermocouple positions and the effect of temperature sensing accuracy on the estimated thermal properties. / Thesis / Master of Applied Science (MASc) / An inverse heat transfer algorithm along with an experimental setup has been developed to estimate the temperature-dependant thermophysical properties during solidification of metallic alloys under high cooling rates. To verify the accuracy of the developed algorithm and the experimental setup the estimated thermal conductivity and diffusivity of pure Tin have been compared with data available in the literature. The results showed reasonable agreement.

The temperature and moisture content of biomass feedstocks both play a critical role in minimizing storage and transportation costs, achieving effective bioconversion, and developing relevant postharvest quality models. Hence, this study characterizes the heat and mass transfer occurring within baled switchgrass through the development of a mathematical model describing the relevant thermal and physical properties of this specific substrate. This mathematical model accounts for the effect of internal heat generation and temperature-induced free convection within the material in order to improve prediction accuracy. Inclusion of these terms is considered novel in terms of similar biomass models. Two disparate length scales, characterizing both the overall bale structure (global domain) and the individual stems (local domain), are considered with different physical processes occurring on each scale. Material and fluid properties were based on the results of hydraulic conductivity experiments, moisture measurements and thermal analyses that were performed using the constant head method, TDR-based sensors and dual thermal probes, respectively. The unique contributions made by each of these components are also discussed in terms of their particular application within various storage and bioconversion operations. Model validation was performed with rectangular bales of switchgrass (102 x 46 x 36 cm3) stored in an environmental chamber with and without partial insulation to control directional heat transfer. Bale temperatures generally exhibited the same trend as ambient air; although initial periods of microbial growth and heat generation were observed. Moisture content uniformly declined during storage, thereby contributing to minimal heat generation in the latter phases of storage. The mathematical model agreed closely with experimental data for low moisture content levels in terms of describing the temperature and moisture distribution within the material. The inclusion of internal heat generation was found to be necessary for improving the prediction accuracy of the model; particularly in the initial stage of storage. However, the effects of natural convection exhibited minimal contribution to the heat transfer as conduction was observed as the predominate mechanism occurring throughout storage. The results of this study and the newly developed model are expected to enable the maintenance of baled biomass quality during storage and/or high-solids bioconversion.

A l'heure où chacun débat sur la protection de l'environnement et les diminutions de la consommation énergétique, de nouveaux matériaux apparaissent sur le marché. Les matériaux à changement de phase (MCP) présentent un avantage et une technologie qui serait avantageuse tant sur le plan écologique qu'économique. Ils peuvent apporter des avantages compétitifs (baisse de la consommation d'énergie, gain du confort dans la vie sociale, refroidissement de packaging électronique….etc). Les enjeux écologiques mondiaux donnent plus de légitimité et intérêt à l'utilisation des matériaux à changement de phase (MCP) dans plusieurs domaines (les biomatériaux, le bâtiment, les semi-conducteurs, composites…). Ce travail vise à mettre au point l'intégration de Matériaux à Changement de Phase (MCP) encapsulés/ou non encapsulés dans une matrice de polymère renforcée par des charges conductrices/ou non conductrices. La matrice peut être un thermoplastique ou un thermodurcissable. Le but est d'augmenter la conductivité effective et la vitesse de stockage/restitution de l'énergie sous forme de chaleur latente. La maîtrise du comportement thermique de ces matériaux passe par l'analyse fine de leurs propriétés thermophysiques. Il est donc indispensable de disposer d'outils expérimentaux adaptés pour caractériser ces matériaux. Nous avons donc fabriqué des échantillons « MCP » et conçu une plaque chaude gardée transitoire (PCGT), instrumentée de capteurs de température et de flux placés sur les deux faces de l'échantillon pour qu'ils soient sensibles aux variations des conditions aux limites thermiques contrôlées. La réponse thermique de ces échantillons à un cycle thermique de stockage-déstockage est présentée puis analysée. Les paramètres mesurés sont les conductivités thermiques et les chaleurs massiques dans les états solides et liquides, la température et la chaleur latente de changement de phase. Ces mesures fluxmétriques sont une source de données expérimentales très intéressante qui viennent compléter nos mesures calorimétriques de DSC / Pas de résumé en anglais

Accurate thermophysical property data are crucial for designing efficient chemical processes. For this reason, the Design Institute for Physical Properties (DIPPR 801) provides evaluated experimental data and prediction of various thermophysical properties. The critical temperature (Tc), critical density (ρc), critical pressure (Pc), critical compressibility factor (Zc), and normal boiling point (Tb) are important constants to check for thermodynamic consistency and to estimate other properties. The n-alkane family is of primary interest because it is generally assumed that other families of compounds behave similarly to the n-alkane family with increasing chain-length. Unfortunately, due to thermal decomposition, experimental measurements of Tc, ρc, and Pc for large n-alkanes are scarce and potentially unreliable. For this reason, molecular simulation is an attractive alternative for estimating the critical constants. However, molecular simulation has often been viewed as a tool that is limited to providing qualitative insight. One key reason for this perceived weakness is the difficulty in quantifying the uncertainty of the simulation results. This research focuses on a systematic top-down approach to quantifying the uncertainty in Gibbs Ensemble Monte Carlo (GEMC) simulations for large n-alkanes. We implemented four different methods in order to obtain quantitatively reliable molecular simulation results. First, we followed a rigorous statistical analysis to assign the uncertainty of the critical constants when obtained from GEMC. Second, we developed an improved method for predicting Pc with the standard force field models in the literature. Third, we implemented an experimental design to reduce the uncertainty associated with Tc, ρc, Pc, and Zc. Finally, we quantified the uncertainty associated with the Lennard-Jones 12-6 potential parameters. This research demonstrates how uncertainty quantification renders molecular simulation a quantitative tool for thermophysical property evaluation. Specifically, by quantifying and reducing the uncertainty associated with molecular simulation results, we were able to discern between different experimental data sets and prediction models for the critical constants. In this regard, our results enabled the development of improved prediction models for Tc, ρc, Pc, and Zc for large n-alkanes. In addition, we developed a new Tb prediction model in order to ensure thermodynamic consistency between Tc, Pc, and Tb.

This study aims to simulate a vapor compression refrigeration cycle, working with either butane (R-600) or isobutane (R-600a). For this purpose a computer program is written to design a household refrigerator, by modeling a steady-state, vapor compression cycle, with user defined input data. Each refrigerator component can be designed separately, as well as parts of a single refrigeration system in the program. In order to determine the refrigerant thermophysical properties at different states, least squares polynomial equations for different properties of R-600 and R-600a have been developed. Computer program is used for refrigeration cycle analysis, variable speed compressor design and calculating coefficient of performance (COP) and irreversibility of the cycle. Sample-preliminary designs have been carried out for different refrigeration loads, room and cold space temperatures with the program, to compare the performance characteristics of the refrigerants. Designs have been performed at different refrigeration loads, room and cold space temperatures. It is observed that for the same conditions R-600 has slightly better performance characteristics than those of R-600a.

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-11-05T14:38:58Z No. of bitstreams: 1 JOSÉ CARLOS FERREIRA - TESE (PPGEP) 2011.pdf: 2583715 bytes, checksum: 354f3d59e0d3399d607fa4a93fbde40a (MD5) / Made available in DSpace on 2018-11-05T14:38:58Z (GMT). No. of bitstreams: 1 JOSÉ CARLOS FERREIRA - TESE (PPGEP) 2011.pdf: 2583715 bytes, checksum: 354f3d59e0d3399d607fa4a93fbde40a (MD5) Previous issue date: 2011-08-05 / Capes / O presente trabalho tem, como objetivo, propor um novo equipamento para obtenção do extrato de soja e desenvolver um novo produto alimentício elaborado com polpa de umbu, extrato de soja e rapadura, de alta qualidade protéica e energética, para suprir as carências nutritivas essenciais da população de baixa renda, principalmente para merenda escolar. O estudo foi dividido em quatro capítulos. No Capítulo 1 se avaliaram o processo de obtenção do extrato de soja com diferentes proporções de água:soja (1:8, 1:10 e 1:12), e o preparo da umbuzada com diferentes concentrações de polpa de umbu (30, 40 e 50%). Avaliaram-se também as características físico-químicas (proteínas, carboidratos, lipídios, pH, acidez total titulável, cinzas, teor de água e valor calórico), termofísicas (condutividades térmica, difusividade térmica, massa específica e calor específico), as propriedades sensoriais (cor, aroma e sabor) do extrato de soja, polpa de umbu e das formulações de umbuzada. No Capítulo 2 estudou-se o comportamento reológico (10, 20, 30 e 40 oC) do extrato de soja, da polpa de umbu e das formulações da umbuzada e se avaliou dentre os modelos de Ostwald-de-Waelle e Casson qual apresentava o comportamento reológico. No Capítulo 3 foram estudadas a cinética de congelamento e o efeito das condições de congelamento sobre as características físico-químicas, sensoriais e microbiológicas das formulações de umbuzada. Ademais, avaliaram-se as formulações da umbuzada em condições de armazenamento nas temperaturas de (-20 oC, a -170 oC até -50 oC em vapor de nitrogênio líquido e a -196 oC até - 50 oC por imersão em nitrogênio líquido). No Capítulo 4 estudou-se a cinética de secagem por liofilização das formulações de umbuzada congeladas em três condições (-20 oC e até -50 oC em vapor e por imersão em nitrogênio líquido) e se avaliou dentre os modelos de Cavalcanti Mata, Page e Midilli, qual representa o comportamento das curvas de secagem com precisão e se quantificou o efeito das temperaturas de congelamento e do percentual de polpa de umbu nas características físico-químicas e sensoriais da umbuzada liofilizada. Com base nos resultados obtidos verificou-se que o extrato de soja na proporção soja:água de 1:8 apresentou as melhores características físicoquímicas e sensoriais. A condutividade térmica e a difusividade térmica diminuem e a massa específica aumenta com a elevação da concentração de polpa de umbu. Os modelos de Ostwalt-de-waelle e Casson foram, de maneira geral, os que melhor representaram o comportamento reológico do extrato de soja, da polpa de umbu e das formulações nas temperaturas estudadas. O congelamento até -50 oC por imersão em nitrogênio líquido, apresentou o menor tempo de congelamento. A difusividade efetiva média aumentou de acordo com a ordem do método de congelamento apresentada: -20 oC, a 50 oC em vapor de nitrogênio e a 50 oC por imersão em nitrogênio líquido. A formulação com 50% de polpa de umbu apresentou a maior taxa de secagem por liofilização e o modelo de Cavalcanti Matta foi o que melhor representou o comportamento das curvas de secagem por liofilização. / The present work has the aim to propose a new device to get the soybean extract and develop a new food product made with umbu pulp, soymilk and brown sugar, highquality protein and energetic, to supply the main nutritional needs of low-income population, especially for school lunches. The study was divided into four chapters. In Chapter 1 we evaluated the process of obtaining the soybean extract with different proportions of water: soybean (1:8, 1:10 and 1:12), the preparation of umbuzada with different concentrations of umbu pulp (30, 40 and 50%). Still, we evaluated the physico-chemical characteristic (protein, carbohydrates, lipids, pH, total acidity, ash, moisture content and calorific value), thermophysical (thermal conductivity, thermal diffusivity, density and specific heat), the sensory properties (color aroma and flavor) of soymilk, umbu’s pulp, umbuzada’s formulations. In Chapter 2 we studied the Rheological behavior (10, 20, 30 and 40 °C) of the soymilk of umbu’s pulp and umbuzada’s formulations and it was evaluated from the model Ostwald-Waelle and Casson which represented the rheological behavior. In Chapter 3 we studied the freezing kinetics and the effect of freezing conditions on the physico-chemical characteristic, sensory and microbiological umbuzada’s formulations. Moreover, the formulations were evaluated in the umbuzada storage conditions at temperatures of (-20 °C, the -170 °C to -50 °C in nitrogen steam liquid and -196 °C to -50 °C by immersion in liquid nitrogen). In Chapter 4, we studied the kinetics of drying by lyophilization umbuzada’s formulations frozen in three conditions (-20 °C and -50 °C in steam and immersion in liquid nitrogen), they were evaluated from the models Cavalcanti Mata, Page and Midilli which represents the behavior of the drying curves with precision, and quantified the effect of freezing temperatures and the percentage of umbu’s pulp in physico-chemical and sensory umbuzada lyophilized. Based on the results obtained the soy extract in proportion soybean: water 1:8 showed better physico-chemical and sensory. The thermal conductivity and thermal diffusivity decreases and density increases with concentration increasing of umbu’s pulp. Models Ostwalt-of-Waelle and Casson were, in general, those which better represent the behavior rheology of the soy extract, the umbu’s formulations and temperatures studied. Freezing to -50 °C by immersion in liquid nitrogen had the lowest freezing time. The average effective diffusivity increased according to the order of presented freezing method: -20 °C to 50 °C in nitrogen steam and 50 °C by immersion in liquid nitrogen. The formulation with 50% umbu’s pulp show the highest rate of drying by lyophilization and Cavalcanti Mata model was the one that best represented the behavior of drying curves by lyophilization.

Made available in DSpace on 2015-05-08T14:59:32Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2230755 bytes, checksum: ca3daa0f19b4271abeb34495fd22c22f (MD5) Previous issue date: 2011-04-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The analysis of the properties of heat and mass transfer in foods has been studied for many researchers due to their need for knowledge to feed the codes of optimization calculations and equipment design involving the addition and removal of energy. This work deals with the solution of an inverse problem of parameter estimation to estimate the thermal diffusivity and thermal conductivity of a sample of acerola jam. The direct problem is solved numerically using finite differences and the system of algebraic equations arising from the method is solved by explicit method. The experimental transient temperature profile required for the solution of the inverse problem is obtained by a thermal pulse method, specifically, via flash method. The experimental procedure consists of submitting a sample of acerola jelly confined in a cylindrical cavity with a thermal disturbance of short duration on one side (front) and measure the transient temperature evolution on the other side (back side). The acerola jelly was specially produced and analyzed physical and chemical for this purpose. For the thermal disturbance of the sample we used a device called a micro-flash, LFA model 457, manufactured by Netzsch. The pulse of short duration is from a power system that releases an energy equivalent to 15 joules per pulse and records the evolution of temperature using an infrared sensor, type ISB. This equipament has a system for generating laser pulse. The results are shown in terms of thermal diffusivity and thermal conductivity and are compared with the values available in literature for similar products. The values found for the thermal diffusivity of 0,121 to 0,148 mm2s-1 and the thermal conductivity of 0,372 to 0,497Wm-1 are in agreement with the values found by other techniques. / A estimação das propriedades termodinâmicas e de transportes tem sido objeto de estudo de diversos pesquisadores devido à necessidade de seu conhecimento para alimentar os códigos de cálculos de otimização e projetos de equipamentos que envolvam adição e remoção de energia. Esse trabalho trata da solução de um problema inverso de estimação de parâmetros para estimar a difusividade térmica e a condutividade térmica de uma amostra de geléia de acerola. O problema direto é resolvido numericamente utilizando diferenças finitas e o sistema de equações algébricas advindo da aplicação do método é resolvido pelo método explicito. O perfil de temperatura transiente experimental necessário para a solução do problema inverso é obtido através de um método de pulso térmico, especificamente, via método flash. O procedimento experimental consiste de submeter uma amostra de geléia de acerola confinada em uma cavidade cilíndrica a uma perturbação térmica de curta duração em uma das faces (anterior) e medir a evolução da temperatura transiente na outra face (face posterior). A geléia de acerola foi especialmente produzida e analisada físico-quimicamente com essa finalidade. Para a perturbação térmica da amostra foi utilizado um dispositivo, denominado de micro-flash, modelo LFA 457, fabricado pela Netzsch. O pulso de curta duração é originário de um sistema de potencia que libera uma energia equivalente a 15 Joules por pulso e registra a evolução da temperatura através de um sensor infravermelho, tipo ISb. Esse equipamento dispõe de um sistema de geração de pulso laser. Os resultados são mostrados em termos da difusividade térmica e da condutividade térmica e são comparados com os valores disponíveis na literatura para produtos da mesma natureza. Os valores encontrados para a difusividade térmica de 0,121 à 0,148 mm2s-1 e para a condutividade térmica de 0,372 à 0,497Wm-1°C-1 estão em acordo com os valores encontrados por outras técnicas.