Добірка наукової літератури з теми "Thermal propertie"

Through screen-printing technology, we prepared heater which is used for planar oxygen sensor with YSZ solid electrolyte, alumina insulating layer and platinum(Pt) paste, then sintered at different temperatures.Analysis the properties of Pt electrode through aging time test and thermal shock test. The results show that 1100°C is the best sintering temperature for Pt electrode.Resistance and surface morphology of Pt electrode changed obviously with aging time increasing and 100 times thermal shock is not enough to affect the morphology of electrode and the change of resistance has no regularity.

With the rapid development of automobile industry, automobile panel material has also gained great attention, the IF steel has got more and more applications in automobile panel production for its excellent deep drawing propertie s, such as, high strain ratio, high extensibility, high yield ratio, etc. In this paper, through the analysis of thermal simulation results and microstructure of IF steel, we studied the influences of microstructure changes on IF steel with different deformation parameters, obtained the influence laws of the deformation parameters on deformation resistanc e of IF steel. So there is a certain directive significance to control the rolling process of IF steel in the actual production of IF steel.

The thermal properties of soursop seeds and kernels were determined as a function of moisture content, ranged from 8.0 to 32.5% (d.b.). Three primary thermal properties: specific heat capacity, thermal conductivity and thermal diffusivity were determined using Dual-Needle SH-1 sensors in KD2-PRO thermal analyser. The obtained results shown that specific heat capacity of seeds and kernels increased linearly from 768 to 2,131 J/kg/K and from 1,137 to 1,438 J/kg/K, respectively. Seed thermal conductivity increased linearly from 0.075 to 0.550 W/m/K while it increased polynomially from 0.153 to 0.245 W/m/K for kernel. Thermal diffusivity of both seeds and kernels increased linearly from 0.119 to 0.262 m²/s and 0.120 to 0.256 m²/s, respectively. Analysis of variance results showed that the moisture content has a significant effect on thermal properties (p ≤ 0.05). These values indicated the ability of the material to retain heat which enhances oil recovery and can be used in the design of machine and selection of suitable methods for their handling and processing.

Acylated low molecular weight chitosans (LChA) were prepared from nucleophilic acylation of chitosan using acid anhydrides of short and medium chain length (4 - 10) to study the response of applied heat as a function of acyl chain length. Thermogravimetric analysis (TGA) revealed the decomposition of LChA consisted of glucosamine and acyl-glucosamine units around 141 - 151and#176;C to 400 - 410and#176;C. Both TGA and differential scanning calorimetry (DSC) analyses indicated that the introduction of acyl groups disrupted the hydrogen bonding of chitosan, the effect was more prominent as the degree of substitution and chain length of LChA increased. Grafting of acyl chains lowered the kinematic viscosity of LChA as the disruption of hydrogen bonding led to decreased hydrodynamic volume. Field emission scanning electron micrographs showed that LChA with longer chains having larger particle size due to bigger occupancy volume of acyl chains during spray drying.

In this study, some new chitosan materials were synthesized by the grafting of chitosan with the monomers such as 1-vinylimidazole (VIM), methacrylamide (MAm) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). First of all, chitosan methacrylate was prepared by esterification of primary -OH group with methacryloyl chloride a 25.13% yield by mole. The monomers were grafted into chitosan methacrylate via free radical polymerization using 2,2and#39;-Azobisisobutyronitrile as an initiator in N,N-dimethylformamide. The graft copolymers were characterized by FT-IR spectra and elemental analysis. Thermal stabilities of the graft copolymers were determined by TGA (thermo gravimetric analysis) method. The synthesized chitosan methacrylate and its graft copolymers were tested for their antimicrobial activity against bacteria and yeast.

Orientador: Flavia Maria Netto
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-08T22:07:21Z (GMT). No. of bitstreams: 1 Diniz_AdrianaCeciliaPinto_D.pdf: 3167091 bytes, checksum: 9297804acc866f90492faf9a5227fad2 (MD5) Previous issue date: 2007
Resumo: Em algumas aplicações em alimentos, a indução da geleificação a temperaturas altas pode ser indesejável. Alguns produtos de soja quando submetidos ao tratamento térmico, mesmo que moderado, desenvolvem sabores e aromas não desejáveis, limitando sua aplicação. A produção de géis a frio envolve essencialmente duas etapas: a formação de uma dispersão estável de agregados de proteína obtida após o aquecimento da solução protéica e a indução da geleificação por redução do pH ou adição de sal. Ao contrário da geleificação induzida pelo calor, no processo de geleificação a frio a etapa de ativação da proteína, a desnaturação térmica, não ocorre simultaneamente às etapas de agregação e geleificação, permitindo determinar as propriedades dos agregados após o aquecimento e as propriedades finais do gel. Embora géis termicamente formados de proteínas de soja tenham sido extensivamente estudados, pouco se conhece sobre a capacidade das proteínas de soja de formarem gel a frio. O presente estudo investigou o efeito do tratamento térmico na fase de produção do isolado protéico de soja (IPS) e o efeito da adição de CaCl2 na formação a frio de estrutura tipo gel de IPS. IPS foi obtido a partir de farinha desengordurada de soja comercial, e, após a etapa de neutralização, tratado a 60 ou 80oC por 15 ou 30 min., variando-se a concentração protéica (3 e 5%), para obtenção de isolados com agregados de diferentes propriedades físico-químicas. Géis foram obtidos a frio a partir de dispersões com 12 e 14% de proteína (p/p), com e sem a adição de CaCl2 (5 e 15 mM). A desnaturação protéica e agregação foram avaliadas por análises de calorimetria diferencial de varredura (CDV), turbidez, solubilidade em água, sulfidrila livre, hidrofobicidade superficial e cromatografia líquida de alta eficiência de exclusão molecular. Os resultados indicaram desnaturação parcial, maior grau de agregação e aumento da massa molar dos agregados com o incremento da concentração da proteína no tratamento prévio dos IPSs. Os isolados não tratado termicamente e o tratado a 60ºC não formaram gel em nenhuma das condições experimentais utilizadas, enquanto para os IPSs tratados a 80ºC, os valores de G¿, G¿¿ e tan d foram característicos de um sólido viscoelástico, sugerindo a formação de uma matriz tridimensional estável, independente da adição de CaCl2. Os géis protéicos de soja induzidos a frio sem a presença de sal foram mais translúcidos, de estrutura menos porosa e maior capacidade de retenção de água (91,9 ¿ 82,5%) do que os obtidos com 15 mM de CaCl2. Os géis formados pela adição de 5 e 15 mM de CaCl2 foram mais opacos e consistentes do que os géis sem adição de sal. Porém, os géis formados pela adição de 15 mM CaCl2 foram mais esbranquiçados, indicando a formação de grandes agregados e com menor capacidade de retenção de água (51,2 ¿ 76,1%). Os resultados mostraram que os géis formados a frio dos IPSs tratados termicamente apresentaram características macroscópicas diferentes, atribuídas ao tipo de agregado formado na etapa de aquecimento e à quantidade de CaCl2 adicionada posteriormente. Por sua vez, o tipo de agregado formado na etapa de aquecimento teve influência principalmente da concentração de proteína e da temperatura de aquecimento. A adição de CaCl2 não foi determinante para a formação do gel, mas teve um importante papel em sua estruturação. Concluiu-se que a manipulação das condições térmicas pode conduzir à formação de agregados e géis de proteínas de soja com propriedades físico-químicas desejáveis
Abstract: The induction of gelation by high temperatures can be undesirable in some food applications. When submitted to the thermal treatment, that even moderate, some products of soy may develop not desirable flavors and aromas, limiting its application. The preparation of protein gels using cold-gelation consists of two steps: a stable dispersion of protein aggregation is obtained after heating of a solution of native proteins and gelation induced by lowering the pH or by adding salt. In contrast with the heatinduced gelation, the stage of activation of the protein in the cold-gelation process is previous to the stages of aggregation and gelation, what it allows to determine the properties of aggregates after heating and thereby control final gels properties. Although heat-induced gelation of soy protein has been extensively studied, little is known about the capacity of soy protein to form cold-set gel. The present study has investigated the effects that heat-treatment during soy protein isolates preparations (SPI) in the cold-set gelation by the addition of CaCl2. SPI was obtained from soy defatted flour and heated at 60 or 80°C after the neutralization step, followed of freeze-dried. Protein concentrations of 3 and 5% and heating times of 15 and 30 min were used in order to obtain aggregates with different physical properties. Cold-set gels were obtained from 12 and 14 % (w/w) of protein dispersions, with or without CaCl2 addition (5 and 15 mM). Denaturation followed by aggregation was verified by differential scanning calorimetry (DSC), turbidity, water solubility, free sulfhydryl groups (SH), superficial hydrophobicity and size exclusion-high performance liquid chromatography (SE-HPLC). The results indicated higher aggregation degree and increased molar mass of aggregates when the protein concentration was enhanced to 5% in the pre-heating of the SPIs. The isolates without heat-treatment and the isolates heated at 60°C did not form gels in any of the experimental conditions utilized, while for the IPSs heated at 80ºC, the values of G¿, G¿¿ and tan d were characteristic of a viscous-elastic solid, suggesting the formation of a stable three-dimensional matrix, independent of CaCl2 addition. The cold-induced soy protein gels without the presence of salt were more translucent and with lower porous structure and higher water retention capacity (91.9 - 82.5%), than those obtained with 15 mM of CaCl2. The gels obtained by 5 and 15 mM of CaCl2 addition were opaque and more consistent that gels without the presence of salt. However, gels obtained by 15 mM of CaCl2 were whitened, indicating the formation of large aggregates with lower water retention capacity (51.2 - 76.1%). The results showed that the cold-set gels formed from heat treated SPIs exhibited different macroscopic characteristics, attributable to the type of aggregate formed in the heating step and to the quantity of posterior addition of CaCl2. At the same time, the type of aggregate formed in the heating step was mainly influenced by protein concentration and denaturation degree. The CaCl2 addition was not determining for gel formation but has an important role on his structure. It was concluded that manipulation of thermal conditions can lead to aggregates and soy protein isolate cold-set gels formation with desirable physicalchemical properties
Doutorado
Nutrição Experimental e Aplicada à Tecnologia de Alimentos
Doutor em Alimentos e Nutrição

Fuel cells are the direct energy conversion devices which convert the chemical energy of a fuel to electrical energy with much greater efficiency than conventional devices. Solid Oxide Fuel Cell (SOFC) is one of the various types of available fuel cells; wherein the major components are made of inherently brittle ceramics. Planar SOFC have the advantages of high power density and design flexibility over its counterpart tubular configuration. However, structural integrity, mechanical reliability, and durability are of great concern for commercial applications of these cells. The stress distribution in a cell is a function of geometry of fuel cell, temperature distribution, external mechanical loading and a mismatch of thermo-mechanical properties of the materials in contact. The mismatch of coefficient of thermal expansion and elastic moduli of the materials in direct contact results in the evolution of thermal stresses in the positive electrode/electrolyte/negative electrode (PEN) assembly during manufacturing and operating conditions (repeated start up and shut down steps) as well. It has long been realized and demonstrated that the durability and reliability of SOFCs is not only determined by the degradation in electrochemical performance but also by the ability of its component materials to withstand the thermal stresses. In the present work, an attempt has been made to evaluate the thermal stresses as a function of thermal and mechanical properties of the component materials assuming contribution from other factors such as thermal gradient, mechanical loading and in-service loading conditions is insignificant. Materials used in the present study include the state of art anode (Ni-YSZ), electrolyte(YSZ) and cathode materials(LM and LSM) of high temperature SOFC and also the ones being suggested for intermediate temperature SOFC Ni-SCZ as an anode, GDC and SCZ as electrolyte and LSCF as the cathode. Variation of thermo-mechanical properties namely coefficient of thermal expansion, and elastic and shear moduli were studied using thermo-mechanical analyzer and resonant ultrasound spectroscope respectively in 25-900°C temperature range. A non-linear variation in elastic and shear moduli- indicative of the structural changes in the studied temperature range was observed for most of the above mentioned materials. Coefficient of thermal expansion (CTE) was also found to increase non-linearly with temperature and sensitive to the phase transformations occurring in the materials. Above a certain temperature (high temperature region- above 600°C), a significant contribution from chemical expansion of the materials was also observed. In order to determine thermal stress distribution in the positive electrode, electrolyte, negative electrode (PEN) assembly, CTE and elastic and shear moduli of the component materials were incorporated in finite element analysis at temperature of concern. For the finite element analysis, anode supported configuration of PEN assembly (of 100mm x 100mm) was considered with 1mm thick anode, 10μm electrolyte and 30μm cathode. The results have indicated that cathode and anode layer adjacent to cathode/electrolyte and electrolyte/anode interface respectively are subjected to tensile stresses at the operating temperature of HT-SOFC (900°C) and IT-SOFC (600°C). However, the magnitude of stresses is much higher in the former case (500MPa tensile stress in cathode layer) when compared with the stress level in IT-SOFC (178MPa tensile stress in cathode layer). These high stresses might have been resulted from the higher CTE of cathode when compared with the adjacent electrolyte. However, it is worth mentioning here that in the present work, we have not considered any contribution from the residual stresses arising from fabrication and the stress relaxation from softening of the glass sealant.

La technologie de pulvérisation magnétron par impulsions de haute puissance (HiPIMS) a été développée et est considérée comme une méthode efficace pour la préparation des films. La technologie HiPIMS permet une bien plus grande flexibilité pour ajuster la structure et les performances du film, conduisant à des films avec des propriétés uniques qui sont souvent irréalisables dans les autres approches PVD. Cependant, le mécanisme sous-jacent du plasma pour soutenir la croissance du film impliqué est actuellement flou. De plus, la technologie HiPIMS est limitée au laboratoire, de nombreux films aux propriétés souhaitables n'ont pas été explorés dans le cadre de la pulvérisation HiPIMS. Dans ce travail, (i) le l’origine de la structure cohérente du plasma haute densité (les « spokes ») dans la décharge HiPIMS et (ii) comment la structure et les propriétés des films de TaC/a-C:H et HfC/a-C:H sont gérées par HiPIMS ont été étudiés. Dans l'étude du mécanisme de formation des « spokes », basée sur la relation de dispersion du plasma HiPIMS et l'évolution du couplage entre deux ondes azimutales, un modèle d'onde induit par couplage a été proposé. Dans l'étude des films TaC/a-C:H et HfC/a-C:H, les états des liaisons chimiques, la structure, la morphologie, les propriétés mécaniques et tribologiques, la stabilité thermique ainsi que la résistance à l'oxydation des films ont été étudiés. En comparaison avec ces films déposés par pulvérisation magnétron DC, il est démontré que la technologie HiPIMS permet une stratégie potentielle pour préparer des films TaC/a-C:H et HfC/a-C:H plus performants en termes de dureté, de coefficient de frottement et de résistance à l'usure, de résistance à l'oxydation et de stabilité thermique en modulant l'état de liaison chimique et la structure nanocomposite des films à travers un plasma réactif
High Power Impulse Magnetron Sputtering technology (HiPIMS) has been developed and considered as an effective method for film preparation. HiPIMS technology allows for much greater flexibility for manipulating film structure and performance, leading to films with unique properties that are often unachievable in the other PVD approaches. However, the underlying plasma mechanism for supporting film growth is currently blurred. Moreover, HiPIMS technology is still stationed in the laboratory, many films with desirable properties have not been explored under HiPIMS framework. In this work, (i) the driven mechanism of high density plasma coherent structure (i.e., spokes) in the HiPIMS discharge and (ii) how the structure and properties of the TaC/a-C:H and HfC/a-C:H films are regulated by HiPIMS were investigated. For the driven mechanism of spokes, based on the dispersion relationship of HiPIMS plasma and the evolution of the coupling between two azimuthal waves, the coupling-induced wave model was proposed. For the TaC/a-C:H and HfC/a-C:H films, the chemical bond states, structure, morphology, mechanical and tribological properties, thermal stability as well as oxidation resistance of the films were investigated. By comparison with DC deposited films, it is demonstrated that HiPIMS technology provides a potential strategy for preparing higher performance TaC/a-C:H and HfC/a-C:H films in terms of hardness, friction coefficient and wear resistance, oxidation resistance and thermal stability by modulating the chemical bonding state and nanocomposite structure of the films through HiPIMS reactive plasma

This thesis investigated the physical properties of the macrolide antibiotics: Erythromycin dihydrate (EM-DH), Roxithromycin monohydrate (RM-MH) and Azithromycin dihydrate (AZM-DH). The abovementioned hydrate compounds were investigated in terms of the hydrate-anhydrate crystal structure stability, dehydration and observed polymorphism under controlled temperature heating programs. Identified hydrate and anhydrate polymorphs were subjected to physical stability testing during controlled storage. EM-DH was characterized by thermal analysis (DSC, TGA), X-ray diffraction, FTIR and microscopy. Dehydration of EM-DH at temperatures of 100, 157 and 200°C (followed by supercooling to 25°C) produced the form (I) anhydrate (Tm =142.9°C), form (II) anhydrate (Tm = 184.7°C ) and amorph (II) (Tg = 118°C) respectively. The attempts to produce amorph (I) from melting (in vicinity of form (I) melt over temperature range 133°C to 144°C) and supercooling was unsuccessful due to the high crystallization tendency of the form (I) melt. Brief humidity exposure and controlled temperature (40°C)/ humidity storage for 4 days (0-96% RH) revealed hygroscopic behaviour for the anhydrate crystal (forms (I) and (II)) and amorph (II) forms. Form (II) converted to a nonstoichiometric hydrate where extent of water vapour absorption increased with increased storage humidity (2.1% absorbed moisture from recorded TGA at 96% RH). Amorph (II) exhibited similar trends but with greater water absorption of 4.7% (recorded with TGA) at 96% RH. The pulverization and sieving process of amorph (II) (at normal environmental conditions) was accompanied by some water vapour absorption (1.1%). A slightly lower absorbed moisture content of 3.3% (from TGA) after controlled 4 days storage at 40°C/ 96% RH was recorded. This suggested some physical instability (crystallization tendency) of amorph (II) after pulverization. The thermally induced dehydration of RM-MH by DSC-TG was evaluated structurally (SCXRD), morphologically (microscopy) and by kinetic analysis. Various kinetic analysis approaches were employed (advanced, approximation based integral and differential kinetic analysis methods) in order to obtain reliable dehydration kinetic parameters. The crystal structure was little affected by dehydration as most H-bonds were intramolecular and not integral to the crystal structure stability. Kinetic parameters from thermally stimulated dehydration indicated a multidimensional diffusion based mechanism, due to the escape of water from interlinked voids in crystal. The hygroscopicity of the forms RM-MH, Roxithromycin-anhydrate and amorph glass (Tg = 81.4°C) were investigated. Roxithromycinanhydrate (crystalline) converted readily to RM-MH which were found to be compositionally stable over the humidity range 43-96%RH. Amorphous glass exhibited increased water vapour absorption with increasing storage humidity (40°C/ 0-96% RH). TG analysis suggested a moisture content of 3.5% at 96% RH after 4 storage days. DSC and powder XRD analysis of stored pulverised amorphous glass indicated some physical instability due to water induced crystallization. Commercial AZM-DH and its modifications were characterized by thermal analysis (DSC, TGA), SC-XRD and microscopy. Thermally stimulated dehydration of AZM-DH occurred in a two-step process over different temperature ranges. This was attributed to different bonding environments for coordinated waters which were also verified from the crystal structure. Dehydration activation energies for thermally stimulated dehydration were however similar for both loss steps. This was attributed to similarities in the mode of H- bonding. Different forms of AZM were prepared by programmed temperature heating and cooling of AZM-DH. The prepared forms included amorphous glass (melt supercooling), amorphous powder (prepared below crystalline melting temperature), crystalline anhydrate and crystalline partial dehydrate. Humidity exposure indicated hygroscopic behaviour for the amorphous, crystalline anhydrate and crystalline partial dehydrate modifications. Both the crystalline anhydrate and partial dehydrate modifications converted to the stoichiometric dihydrate form (AZM-DH) at normal environmental conditions at ambient temperature. Both the amorph glass and amorph powder exhibited increased moisture absorption with increased humidity exposure. TG analysis of the pulverised amorph glass indicated a moisture content of 5.1% at 96% RH after 4 storage days. The absence of crystalline melt in DSC and presence of Tg (106.9°C) indicated the sample remained amorphous after pulverisation and storage for 4 days at 40°C/ 96% RH.

The subject of the present Ph.D. thesis is constituted by the development and application of innovative modeling techniques for the representation of the thermophysical properties of fluids. The thermophysical properties are divided into thermodynamic properties, related to states of thermodynamic equilibrium and to transformation processes between two equilibrium conditions, and transport properties, concerning systems in a non-uniform state and then affected by transport phenomena; among these, thermal conductivity has been here considered. The knowledge of the thermophysical properties of pure fluids and mixtures is an absolutely crucial need for the design and the optimization of any equipment in the process industry. The thermophysical properties have to be known in dependence on the controlling variables with a precision as high as possible: errors in the values of the required properties can propagate throughout the entire calculation with amplification effects, yielding wrong design and driving away from the optimal operating conditions. The purpose of this thesis work is to set up modeling techniques able to represent the thermophysical properties with a precision comparable with the experimental uncertainty of the experimental measurements of the properties themselves reducing at the same time the required experimental effort. The proposed modeling techniques are based on a heuristic approach, that get the functional representation of a physical dependence directly from a properly organized data base; the effectiveness of the developed heuristic techniques is fundamentally based on the use of the artificial neural network, which have the characteristic of universal function approximators. The development and application of a heuristic modeling technique to produce equations of state (EoS) in the fundamental form for the representation of thermodynamic properties of pure fluids and mixture are presented in the first part of this thesis work. The modeling technique here proposed for the representation of the thermodynamic properties is based on the extended corresponding states (ECS) principle. The basic idea of the ECS model consists in the distortion of the independent variables of the EoS of the reference fluid to transform it into the EoS of the interest fluid. If the simple two-parameter corresponding states principle should work exactly, no tuning distortion would be necessary; since this is not the case, two tuning functions, indicated as shape functions, are then individually required to exactly match the ECS model with a known thermodynamic surface of the interest fluid. The basic requirements of the ECS technique are the fulfillment of a conformality condition between the reference and the target fluid, and the availability of an accurate equation of state in terms of Helmholtz energy for the reference fluid. In the case that either the conformality condition is not verified among the fluids of a same family or no component of the family, whose fluids are supposed to share a conformality condition, disposes of a DEoS, the discussed ECS method cannot in general be effectually applied. In the model proposed in this thesis the ‘correction’ through the variables distortion is performed on a simple EoS representing, even if roughly, the target fluid itself. In other words a simple EoS for the same target fluid is the starting point for the development of a DEoS through the variables distortion, avoiding in this way any problem about the conformality condition fulfillment. It would be then no more necessary to dispose of a ‘reference fluid’, following the classical interpretation of the ECS theory, but rather of only a ‘reference equation’, whose precision is enhanced, or ‘extended’, through the application of the shape functions. Hence the name of extended equation of state (EEoS) chosen to indicate this new modeling method. The shape functions have to be regressed forcing the model to represent known values of experimentally accessible thermodynamic quantities; in the present model their functional formulation is heuristically obtained applying a multilayer feed-forward neural network (MLFN) as universal function approximator. The new approach is constituted by a general fitting procedure in which a mathematical form of the surface has to be ‘spread’ on known values of it and of its derivatives, overcoming the problems presented by the two traditional ECS approaches, i.e., the local solution and the continuous solution. The proposed modeling technique comes from the combination of the EEoS method with the neural networks and then it can be concisely indicated as EEoS-NN model. The EEoS-NN model allows to obtain for the fluid of interest a DEoS in the default fundamental form which allows to calculate any thermodynamic quantity through mathematical derivations only. In order to set up the method and to test its potentialities, data generated from a DEoS for each target fluid are used instead of experimental data, so that the model performances are not hindered by error noise and uneven data distribution. Moving from generated data, the capability of the proposed method has been verified both for pure fluids and for mixtures. A group of pure alkanes, haloalkanes, and strongly polar substances has been considered; the results obtained for these fluids are very promising. The same is valid for the five binary mixtures and two ternary mixtures of haloalkanes here studied. In the case of pure fluids it has been also verified that slightly more than 100 density points evenly distributed in the pressure-density-temperature plane and with low experimental error can be a sufficient input for the model development, allowing to reduce the experimental efforts. The promising performances for the proposed model based on generated data leads to the possibility to reliably develop DEoSs in the EEoS-NN format directly from experimental data. The EEoS-NN technique was then applied to draw DEoSs for the pure fluids sulfur hexafluoride (SF6) and 2-propanol (iC3H8O) directly from the available data sets of the target fluids. The DEoS for SF6 is valid for the liquid, vapor and supercritical region in the ranges from the triple-point temperature at about 223.6 K up to 625 K and for pressures up to 60 MPa, with the exclusion of a region close to the critical point in case of caloric property calculation. The representation of the available experimental data is satisfactory for all the considered properties; in fact the deviations of the equation from the data are comparable with the ascribed uncertainties of the experimental sources. One of the advantages of the EEoS-NN method, shown for the fluid sulfur hexafluoride, is that the data set on which to base the regression procedure can include only density and coexistence values, getting in the meantime a satisfactory performance also for the other properties. The DEoS for iC3H8O is valid for the liquid, vapor and supercritical region for temperatures from 280 up to 600 K and for pressures up to 50 MPa. Due to the substantial lack of data in the near critical region and the non-specialization of this DEoS in representing such region very close to the critical point the present equation is not suggested to be used within a region very close to the critical point. The representation of the available experimental data is satisfactory for all the considered properties; in fact the deviations of the equation from the data are comparable with the realistic uncertainties of the experimental sources for this fluid. The results obtained for the fluid 2-propanol demonstrate that the EEoS-NN modeling method is completely reliable to develop highly effective DEoSs even if the experimental data situation for the fluid is not completely favorable. This aspect is particularly valuable in the case a DEoS is required for engineering applications where the economy of the experimental effort and the representation accuracy have to be met through a suitable compromise. The pointed out features make the EEoS-NN technique a useful tool for the process analysis and optimization. To prove the potential of the cited technique as a tool to study real processes typical of the chemical industry the system propylene + 2-propanol + water has been chosen as an exemplification case. The objective is therefore to investigate the possibility to use the EEoS-NN technique to study the energetic optimization of the extraction process of 2-propanol from aqueous solutions using propylene as solvent. This system has been chosen after a screening of the literature data because it seems to present a favorable phase equilibrium behavior for an extraction operation. Furthermore, the propylene + 2-propanol + water system is thermodynamically strongly deviating from ideal behavior due to several causes as the strong polarity of the components, their association behavior, etc., which increases a lot the difficulties of a complete and accurate thermodynamic representation. For such a reason the set up of a DEoS for this system is an interesting challenge from a scientific point of view, being the first case in which a dedicated equation of state is developed for a strongly deviating ternary mixture. The experimental data available from the literature for the ternary mixture are vapor-liquid equilibrium (VLE) and liquid-liquid equilibrium (LLE). In order to set up a semi-predictive thermodynamic model of the ternary mixture to study its phase behavior, vapor-liquid-liquid equilibrium (VLLE) measurements have been performed. Excess enthalpy measurements have also been carried out for the ternary mixture and for the 2-propanol + water binary mixture in order to obtain a good temperature dependence in the semi-predictive model, constituted of a Peng-Robinson cubic EoS with Wong-Sandler mixing rules and a modified UNIQUAC model to represent the excess Gibbs energy. This model has been used to investigate the phase equilibrium behavior of the ternary mixture from a qualitative point of view. This is a necessary preliminary step to efficiently plan an experimental campaign of measurements suitable to set up a DEoS of the ternary mixture in the EEoS-NN format. The chosen range of interest for the extraction operation is from about 300 to 350 K in temperature, up to 10 MPa in pressure and it extends up to the pure fluids in composition. The properties to be measured in the selected range in order to set up the DEoS are density and phase equilibria. Some isobaric heat capacity measurements are also required to validate the model capability to correctly predict the caloric properties in the range of interest. Density data have been produced using a vibrating tube densimeter (VTD) for the pure 2-propanol, for the propylene + 2-propanol mixture, for the 2-propanol + water mixture and for the propylene + 2-propanol + water mixture. Bubble pressure data were also determined using the VTD for the propylene + 2-propanol mixture and for the propylene + 2-propanol + water mixture. At present the experimental work is still in progress and phase equilibrium and isobaric heat capacity data have to be carried out. This experimental work, together with the development of a DEoS for the propylene + 2-propanol + water mixture, will constitute the extension of this thesis work. Once a thermodynamic model in EEoS-NN format will be obtained, it will be possible to link it with a process simulator, studying the better operative conditions for the 2-propanol extraction process. The development and application of a heuristic modeling technique to produce dedicated equations for the representation of the thermal conductivity of pure fluids is presented in the second part of this thesis work. The proposed model is based on the ECS principle, but the shape functions are got in a continuous analytical form expressed by a universal function approximator, i.e. a neural network, through regression of thermal conductivity data. This innovative approach, named ECS-NN, allows to overcome the problems in obtaining the scale factors presented by the two traditional ECS approaches for transport properties, i.e., the local solution and the continuous solution. The potentiality of the ECS-NN modeling technique for thermal conductivity has been shown with application to both values generated from existing models and experimental values. Assuming R134a as reference fluid, two dedicated thermal conductivity equations have been regressed for carbon dioxide and R152a from the available experimental data. The obtained results are very encouraging; in fact the proposed technique yields thermal conductivity equations that represent the experimental values in the liquid, vapor and supercritical regions within their experimental accuracy; moreover, the method is able to satisfactorily model the strong critical enhancement of thermal conductivity in the near-critical region. The performance change of the model has been studied varying the number of experimental data in the training procedure, showing that about two hundred data points, regularly distributed on the thermal conductivity-temperature-density surface of the target fluid, are sufficient to draw a very precise equation, with evident saving of experimental efforts. Summarizing, the present Ph.D. thesis has shown the effectiveness of the application of heuristic techniques to both thermodynamic and transport property modeling, as a valid alternative to the techniques that are at present adopted. The proposed methods, exploiting the prediction capability of the neural networks, allow to reduce the experimental effort, yielding at the same time equations representing the data within their experimental uncertainties. This feature makes the developed methods suitable tools for the design and optimization of unit operations of the industrial processes.
L’argomento di questa tesi di Dottorato è lo sviluppo e l’applicazione di tecniche modellistiche innovative per la rappresentazione di proprietà termofisiche di fluidi. Le proprietà termofisiche sono divise in proprietà termodinamiche, riguardanti stati di equilibrio termodinamico e processi di trasformazione tra due condizioni di equilibrio, e proprietà di trasporto, riguardanti sistemi in stato non uniforme e quindi caratterizzate da fenomeni di trasporto; tra queste è stata qui trattata la conduttività termica. La conoscenza delle proprietà termofisiche di fluidi puri e miscele è un requisito assolutamente fondamentale nella progettazione ed ottimizzazione di qualsiasi apparecchiatura nell’industria di processo. Le proprietà termofisiche devono essere conosciute in dipendenza delle variabili controllanti con una precisione il più elevata possibile: errori nel valore delle proprietà richieste possono propagarsi attraverso l’intero calcolo amplificandosi, dando luogo ad una progettazione scorretta ed allontanando dalle condizioni operative ottimali. Lo scopo di questa tesi è lo sviluppo di tecniche modellistiche capaci di rappresentare le proprietà termofisiche con un’accuratezza comparabile con l’incertezza sperimentale delle misure stesse, riducendo allo stesso tempo il lavoro sperimentale. Le tecniche modellistiche proposte sono basate su un approccio euristico, che deriva la rappresentazione funzionale di una dipendenza fisica direttamente da una appropriata base di dati; l’efficacia delle tecniche euristiche sviluppate è basata sull’utilizzo delle reti neurali artificiali, che hanno la caratteristica di essere approssimatori universali di funzione. Lo sviluppo e l’applicazione di tecniche modellistiche di natura euristica atte a produrre equazioni di stato (EoS) in forma fondamentale per la rappresentazione delle proprietà termodinamiche di fluidi puri e miscele sono trattati nella prima parte di questa tesi. La tecnica modellistica qui proposta per la rappresentazione delle proprietà termodinamiche è basata sul principio degli stati corrispondenti estesi (ECS). L’idea alla base del modello ECS consiste nella distorsione delle variabili indipendenti della EoS del fluido di riferimento trasformandola nella EoS del fluido di interesse. Se il principio degli stati corrispondenti a due parametri fosse esatto non sarebbero necessari aggiustamenti delle variabili indipendenti, ma poiché questo non è verificato sono richieste due funzioni distorcenti, chiamate shape function, per far corrispondere il modello ECS con una superficie termodinamica nota del fluido d’interesse. Per l’applicazione della tecnica ECS deve essere verificata la condizione di conformality tra il fluido di riferimento ed il fluido target, e l’esistenza di un’accurata equazione di stato espressa in forma di energia libera di Helmholtz per il fluido di riferimento. Nel caso in cui la condizione di conformality tra i fluidi non sia verificata, o nessun fluido della famiglia che si suppone presenti una condizione di conformality con il fluido di interesse disponga di una DEoS, il metodo ECS non può essere applicato efficacemente. Nel modello presentato in questa tesi la ‘correzione’ ottenuta attraverso la distorsione delle variabili è applicata ad un’equazione semplice che rappresenta, anche se approssimativamente, lo stesso fluido target. In altre parole, una EoS semplice per il fluido target stesso è il punto di partenza per lo sviluppo di una DEoS per mezzo della distorsione delle variabili, evitando in questo modo il vincolo costituito dalla necessità di soddisfare la condizione di conformality. Non è più quindi necessario disporre di un ‘fluido di riferimento’, come nell’interpretazione classica della teoria ECS, ma piuttosto solo di una ‘equazione di riferimento’, la cui precisione è aumentata, o ‘estesa’, per mezzo dell’applicazione delle shape function. Di qui deriva il nome di extended equation of state (EEoS) scelto per indicare questa nuova tecnica modellistica. Le shape function devono essere regredite forzando il modello a rappresentare valori noti delle grandezze termodinamiche sperimentalmente accessibili; nel modello proposto la loro forma funzionale è ottenuta in modo euristico utilizzando una multilayer feed-forward neural network (MLFN) come approssimatore universale di funzione. La nuova tecnica è costituita da una procedura di fitting in cui la forma matematica della superficie di deve essere ‘spalmata’ su valori noti della stessa e delle sue derivate, superando i problemi che derivano dai due approcci ECS convenzionali, cioè la local solution e la continuous solution. La tecnica modellistica proposta deriva dalla combinazione del metodo EEoS con le reti neurali ed è quindi brevemente indicata come EEoS-NN. Il modello EEoS-NN permette di ottenere per il fluido di interesse una DEoS in forma fondamentale che consente di calcolare ogni proprietà termodinamica attraverso il solo utilizzo di operazioni di derivazione. Allo scopo di mettere a punto il metodo e di testare le sue potenzialità, sono stati scelti alcuni fluidi target per i quali sono stati utilizzati valori generati da una DEoS preesistente al posto dei dati sperimentali, in modo tale che la performance del modello non sia compromessa dall’error noise e dalla distribuzione irregolare dei dati. Utilizzando dati generati la performance del modello è stata verificata per fluidi puri e per miscele. E’ stato considerato un gruppo di fluidi puri comprendenti alcani, aloalcani, e sostanze fortemente polari; in ogni caso i risultati ottenuti sono molto promettenti. La stessa considerazione può essere fatta per le cinque miscele binarie e le due miscele ternarie di aloalcani studiate. Nel caso di fluidi puri è stato anche verificato che un numero poco superiore a 100 punti di densità regolarmente distribuiti sul piano pressione-densità-temperatura e caratterizzati da un basso errore sperimentale possono essere un input sufficiente per lo sviluppo del modello, permettendo di ridurre il lavoro sperimentale usualmente necessario per l’ottenimento di una DEoS. Le promettenti prestazioni ottenute della tecnica modellistica applicata ai dati generati conducono alla possibilità di mettere a punto delle DEoS in forma EEoS-NN utilizzando direttamente dati sperimentali. La tecnica EEoS-NN è stata quindi utilizzata per produrre la DEoS per i fluidi puri esafluoruro di zolfo (SF6) e 2-propanolo (iC3H8O) direttamente dai dati sperimentali dei due fluidi. La DEoS per il fluido SF6 è valida nel liquido, vapore e supercritico dalla temperatura del punto triplo, a circa 223.6 K, fino a 625 K e per pressioni fino a 60 MPa, con l’esclusione della regione prossima al punto critico nel caso delle proprietà caloriche. La precisione con cui il modello rappresenta i dati è da considerarsi soddisfacente per tutte le proprietà termodinamiche, infatti le deviazioni dell’equazione dai dati sono confrontabili con l’incertezza attribuita alle fonti sperimentali. Uno dei vantaggi del metodo EEoS-NN, evidenziato nell’applicazione al fluido esafluoruro di zolfo, è che la procedura di regressione della DEoS può essere basata su una base dati comprendente solo valori di densità e coesistenza, ottenendo allo stesso tempo una rappresentazione accurata anche delle altre proprietà. La DEoS per il fluido iC3H8O è valida nel liquido, vapore e supercritico per temperature da 280 a 600 K e per pressioni fino a 50 MPa. A causa della mancanza di dati nella regione prossima al punto critico e della non-specializzazione della forma funzionale di questa DEoS nella rappresentazione delle proprietà termodinamiche nelle immediate vicinanze del punto critico l’utilizzo della presente equazione è sconsigliato nella suddetta regione. La rappresentazione delle proprietà termodinamiche è soddisfacente per tutte le proprietà considerate, infatti le deviazioni dell’equazione dai dati sono confrontabili con i valori realisticamente attribuibili alle fonti sperimentali. I risultati ottenuti per il fluido 2-propanolo dimostrano che il metodo modellistico EEoS-NN è completamente affidabile per lo sviluppo di equazioni di stato dedicate anche nella condizione non favorevole in cui i dati sperimentali presentano una scarsa qualità. Questo aspetto è particolarmente importante nel caso in cui una DEoS sia necessaria per applicazioni ingegneristiche, dove deve essere raggiunto un compromesso tra l’economia del lavoro sperimentale e l’accuratezza della rappresentazione delle proprietà termodinamiche. Le caratteristiche evidenziate fanno della tecnica EEoS-NN uno strumento utile per la progettazione e l’ottimizzazione dei processi. Il sistema propilene + 2-propanolo + acqua è stato scelto come caso esemplificativo per provare le potenzialità della tecnica EEoS-NN per l’analisi di processi reali tipici dell’industria chimica. L’obiettivo è perciò indagare la possibilità di utilizzare la tecnica EEoS-NN per studiare l’ottimizzare dal punto di vista energetico del processo di estrazione del fluido 2-propanolo da soluzioni acquose utilizzando il propilene come solvente. Questo sistema è stato scelto dopo uno screening dei dati disponibili in letteratura poiché sembra presentare un andamento degli equilibri di fase adatto per un’operazione di estrazione. Inoltre il sistema propilene + 2-propanolo + acqua presenta un comportamento termodinamico fortemente deviante dall’idealità a causa della forte polarità dei componenti e del loro comportamento associante, aumentando le difficoltà per l’ottenimento di un modello che rappresenti accuratamente le proprietà termodinamiche. Per questo motivo la realizzazione di una DEoS per questo sistema è una sfida interessante dal punto di vista scientifico, infatti esso è il primo caso in cui viene realizzata un’equazione di stato dedicata per una miscela ternaria fortemente deviante. I dati sperimentali disponibili in letteratura per la miscela ternaria sono di equilibrio vapore-liquido (VLE) e di equilibrio liquido-liquido vapore (LLE). Allo scopo di ottenere un modello termodinamico semi-predittivo per la miscela ternaria per studiarne l’equilibrio di fase, sono state effettuate anche misure di equilibrio vapore-liquido-liquido (VLLE). Inoltre, sono state misurate le entalpie di eccesso per la miscela ternaria e per la miscela binaria 2-propanolo + acqua al fine di ottenere una buona rappresentazione della dipendenza dalla temperatura nel modello semi-predittivo, costituito da una EoS cubica di tipo Peng-Robinson, con regole di miscela di tipo Wong-Sandler e un modello UNIQUAC modificato per la rappresentazione della energia libera di Gibbs. Questo modello è stato utilizzato per investigare l’equilibrio di fase della miscela ternaria da un punto di vista qualitativo, step preliminare necessario per pianificare efficientemente una campagna di misure sperimentali adatte ad ottenere una DEoS nel formato EEoS-NN per la miscela. Il range di interesse scelto per il processo di estrazione è circa da 300 a 350 K in temperatura, fino a 10 MPa in pressione e si estende fino ai fluidi puri in composizione. Le proprietà che devono essere misurate in questo range al fine di regredire una DEoS sono densità ed equilibri di fase. Sono inoltre richieste alcune misure di calore specifico a pressione costante per valicare la capacità del modello di rappresentare in modo predittivo le proprietà caloriche nel range di interesse. Il range di interesse per la composizione si estende fino ai fluidi puri. Utilizzando un densimetro a tubo vibrante (VTD) sono state effettuate misure di densità per il fluido puro 2-propanolo, per la miscela propilene + 2-propanolo, per la miscela 2-propanolo + acqua e per la miscela propilene + 2-propanolo + acqua. Ad oggi l’attività sperimentale è ancora in corso, e devono essere effettuate misure di equilibrio di fase e di calore specifico a pressione costante. Questo lavoro sperimentale, insieme alla regressione di una DEoS per la miscela propilene + 2-propanolo + acqua, costituirà il proseguimento di questo lavoro di tesi. Una volta che un modello termodinamico in forma EEoS-NN sarà stato ottenuto, sarà possibile integrarlo in un simulatore di processo, permettendo quindi lo studio delle condizioni operative migliori per il processo di estrazione del fluido 2-propanolo. Lo sviluppo e l’applicazione di tecniche modellistiche di natura euristica atte a produrre equazioni dedicate per la rappresentazione della conduttività termica di fluidi puri sono trattati nella seconda parte di questa tesi. Il modello proposto è basato sul principio ECS, ma le shape functions sono prodotte in una forma analitica continua espressa attraverso un approssimatore universale di funzione, anche in questo caso una rete neurale, attraverso la regressione di dati di conduttività termica. Questo approccio innovativo, denominato ECS-NN, permette di superare i problemi che derivano dai due approcci ECS convenzionali, cioè la local solution e la continuous solution. Le potenzialità della tecnica modellistica ECS-NN per la conduttività termica sono state dimostrate con l’applicazione sia a dati generati da modelli preesistenti, sia a dati sperimentali. Assumendo R134a come fluido di riferimento, sono state ottenute equazioni dedicate di conduttività termica per l’anidride carbonica e per il fluido R152a basate sulle misure sperimentali disponibili in letteratura. I risultati ottenuti sono incoraggianti, infatti la tecnica proposta permette di ottenere equazioni dedicate di conduttività termica che rappresentano i valori sperimentali nelle regioni del liquido, vapore e supercritico con un’accuratezza confrontabile con la loro l’incertezza sperimentale dei dati stessi; inoltre il metodo è adatto alla rappresentazione dell’elevato critical enhancement della superficie di conduttività termica nella regione prossima al punto critico. La variazione della performance del modello è stata studiata variando il numero di dati sperimentali nella procedura di training, mostrando che circa duecento punti, regolarmente distribuiti sulla superficie conduttività termica-temperatura-densità del fluido target, sono sufficienti a ricavare un’equazione molto precisa, con notevole riduzione del lavoro sperimentale. Riassumendo, questa tesi di Dottorato ha mostrato l’efficacia dell’applicazione di tecniche euristiche come valida alternativa alle tecniche attualmente utilizzate per la rappresentazione sia delle proprietà termodinamiche sia delle proprietà di trasporto. I metodo proposti, sfruttando la capacità predittiva delle reti neurali, permettono di ridurre il lavoro sperimentale, producendo allo stesso tempo equazioni in grado di rappresentare i dati con un’accuratezza all’interno della loro incertezza sperimentale. Questa caratteristica fa si che le tecniche sviluppate possano essere considerate strumenti adatti per la progettazione e l’ottimizzazione di operazioni unitarie di processi industriali.

Abstract This book chapter outlines the extraction and purification, physiochemical properties (i.e. biochemical characteristics, amylose and amylopectin content), structural properties (i.e. granule morphology, XRD and starch crystallinity, structure of amylose and amylopectin), functional properties (i.e. swelling pattern and solubility, viscosity, rheological property, retrogradation), thermal properties (i.e. DSC), and digestibility of sweet potatoes.

New data for thermophysical properties of materials are being discovered and measured routinely throughout the world, but sometimes conflicts exist in the published data from various sources. We introduce an online thermal properties database intended for use as a repository for experimentally obtained thermophysical properties of materials by researchers across the globe. This online database is a part of www.thermalhub.org, which is a NSF-funded cyber infrastructure initiative aimed at serving the global heat transfer community. The relevant details associated with an experiment, such as the material type and composition, the thermophysical property measured, the test methods employed, the test conditions of the experiment, the results of the experiments, the uncertainty associated with the experimental results, and the literature where the results are published, are included as fields in the online database. It is known that one thermophysical property can be tested by various methods whose results may differ. Similarly, one thermophysical property can be experimentally measured under varying test conditions to produce different results.

The performance of a nonlinear device may be significantly altered by thermal effects. The heat generated by the absorption of power from the switching laser can induce thermal index changes which may overwhelm the photonic index changes. Here a model of these thermal effects is presented, and expressions for the relationship of thermal to photonic index changes are derived. Previous workers have considered heating due to a single pulse.1 Our treatment snows that, for the appropriate material and device parameter ranges, cumulative thermal build-up will be important in the envisioned high-data-rate systems. Using these results, we compare the potential performance characteristics of various materials, including experimental heavy-metal glasses which show large nonlinear effects.

Abstract The thermo-mechanical properties of a thermal barrier bond coat (BC) play an important role in governing the life-time of a coating system. The presented work aims to determine these properties for NiCoCrAlY coatings sprayed on Hastelloy X substrates sprayed under different process conditions. Temperature dependent Young’s modulus values are determined for both Atmospheric Plasma Sprayed (APS) and HVOF sprayed coatings using the four-point bending test. Particular attention is paid to microstructure-property relationships during heating. Young´s modulus was determined up to 950°C and evaluated for coatings loaded in both tension and compression. Results are discussed in the context of the effect of feedstock material, process conditions and microstructure characteristics. The methods and results presented are attractive, particularly for the thermal spray industry, since these properties are a prerequisite when the BC is to be considered in component design.

The aim of this technical report is to provide a large collection of the main thermos-physical properties of various common construction materials and materials composing the elements inside the indoor environment of residential and office buildings. The Excel file enclosed with this document can be easily used to find thermal properties of materials for building energy and indoor environment simulation or to analyze experimental data. Note: A more recent version of that report and database are available at: https://vbn.aau.dk/en/publications/thermal-properties-of-building-materials-review-and-database

The environmental phenomenological properties responsible for the thermal variability evident in the use of thermal infrared (IR) sensor systems is not well understood. The research objective of this work is to understand the environmental and climatological properties contributing to the temporal and spatial thermal variance of soils. We recorded thermal images of surface temperature of soil as well as several meteorological properties such as weather condition and solar irradiance of loamy soil located at the Cold Regions Research and Engineering Lab (CRREL) facility. We assessed sensor performance by analyzing how recorded meteorological properties affected the spatial structure by observing statistical differences in spatial autocorrelation and dependence parameter estimates.

This Subtask aims to have reliable thermal analysis methods/protocols and procedures for the characterization of aterial and reaction properties for sorption and chemical reactions of thermal energy storage (TES) applications. One goal is an inventory of already standardized measurement procedures for TCM as well as of needed characterization procedures.