Methane-air, ethane-air, and n-heptane-air over-ventilated co-flow laminar diffusion flames were studied up to pressures of 2.03, 1.52, and 0.51 MPa, respectively, to determine the effect of pressure on flame shape, soot concentration, and temperature. A spectral soot emission optical diagnostic method was used to obtain the spatially resolved soot formation and temperature data. In all cases, soot formation was enhanced by pressure, but the pressure sensitivity decreased as pressure was increased. The maximum fuel carbon conversion to soot, ηmax, was approximated by a power law dependence with the pressure exponent of 0.92 between 0.51 and 1.01 MPa, and 0.68 between 1.01 and 2.03 MPa with ηmax=9.5% at 2.03 MPa for methane-air flames. For ethane-air flames, the pressure exponent was 1.57 between 0.20 and 0.51 MPa, 1.08 between 0.51 and 1.01 MPa, and 0.58 between 1.01 and 1.52 MPa where ηmax=23% at 1.52 MPa. For nitrogen-diluted n-heptane-air flames, ηmax=6.5% at 0.51 MPa.

El objetivo de la tesis fue evaluar la aptitud tecnológica de la leche tratada por ultra alta presión homogenización (UHPH) como alternativa a la pasteurización en el tratamiento de higienización de la leche para la obtención de queso fresco. Dicho objetivo se llevó a cabo mediante (a) la determinación de las condiciones óptimas de presión y temperatura, estudiando los efectos de la UHPH en las propiedades de coagulación, (b) la identificación de cambios a nivel de las interacciones proteicas de la cuajada así como de la composición proteica de la membrana del glóbulo graso, (c) la evaluación de la aptitud quesera de la leche produciendo quesos frescos a escala piloto, (d) la determinación de la vida útil mediante el seguimiento de la evolución durante la conservación en refrigeración de la microbiota, composición y bioquímica de los quesos, (e) la evaluación de la textura, reología, microstructura y color de los quesos así como la aceptabilidad en su consumo mediante un análisis sensorial.La utilización de la UHPH con una sola etapa y presiones superiores a 200 MPa resultó en una mejora de las propiedades de coagulación. Las condiciones óptimas de tratamiento fueron establecidas como 300 MPa y 30 ºC. La UHPH favoreció las uniones vía calcio de las caseínas y las interacciones hidrofóbicas tanto de caseínas como de proteínas del suero en la cuajada, inhibiendo las interacciones vía puentes de hidrógeno. Al reducir significativamente el tamaño de los glóbulos grasos, la UHPH provocó la adsorción de proteínas de la leche a nivel de la membrana de los glóbulos grasos. La UHPH empeoró en cierta medida el corte de la cuajada produciéndose más finos de quesería por desmenuzado de los granos de cuaja e insuficiente cohesión de los granos. Los quesos frescos producidos con leche tratada por UHPH presentaron mayor vida útil (19 vs. 13 días). El crecimiento de lactococos fue potenciado durante los primeros días de la conservación. Por lo contrario, no se detectaron lactobacilos durante todo el período de almacenamiento. El crecimiento de levaduras y hongos fue parcialmente inhibido resultando en recuentos más bajos al final de la vida útil de los quesos. Durante el almacenamiento, los quesos producidos con leche tratada por UHPH presentaron menor desuerado que aquellos producidos con leches tratadas convencionalmente, resultando en contenidos más altos de humedad y sal. Aunque no se observaron diferencias en el contenido en grasa y proteínas, los quesos UHPH presentaron niveles más bajos de proteólisis y lipólisis. Así mismo, los perfiles en ácidos grasos libres fueron significativamente diferentes. La oxidación lipídica, detectada como el mayor inconveniente, resultó en un gran número de compuestos volátiles tales como aldehídos y cetonas cuya presencia explicó la aparición de flavores defectuosos detectados por algunos de los catadores. Finalmente, la UHPH resultó en quesos más firmes, menos deformables, con menor sensación acuosa en boca y más blancos. Estos cambios podrían atribuirse a los efectos de la UHPH en los glóbulos grasos. A excepción de la escasa sensación acuosa en boca, los catadores calificaron como mejores las características estructurales de los quesos frescos.En conclusión, los resultados obtenidos revelaron que la UHPH es una tecnología prometedora para el tratamiento de la leche de quesería ya que puede alargar la vida útil y mejorar algunas de las características tales como la textura y la microestructura de los quesos frescos. Al solventar los problemas de oxidación mediante la modificación de algunas piezas metálicas del equipo, se espera obtener quesos frescos con una calidad en el sabor similar o incluso superior a la de los quesos producidos con leche tratada convencionalmente. / Among the emerging technologies for minimal food-processing, ultra-high pressure homogenisation (UHPH) is a promising technology for liquid foods such as milk owing to the fact that (a) it is a continuous process, (b) it performs two separated processes at once, i.e., pasteurisation and homogenisation, (c) it can deal with volumes usual at pilot-scale with a view to go for larger volumes such as those at production-scale, (d) it can provoke high temperatures but at such a short time that heat effect can be minimised, and finally, (e) it requires the same equipments as a common homogeniser. UHPH, as a food technology alternative to conventional heat-treatments, is currently investigated in a wide range of liquid foods. Research not only aims at evaluating the effects on the liquid food itself but also on the capacity in obtaining manufactured products and the quality of the final products. The present thesis aimed at assessing the suitability of UHPH as an alternative to conventional processes for the manufacture of starter-free fresh cheeses through (a) determination of optimal pressure and temperature conditions for cheese production, by studying the effects of UHPH on the rennet coagulation properties, (b) identification of changes at the nature of protein interactions and the protein composition of the milk fat globule membrane (MFGM), in order to better understand the overall effect of UHPH on the coagulation and cheese-making properties of milk, (c) evaluation of the suitability of UHPH-treated milk for the manufacture of fresh cheeses, by producing starter-free fresh cheeses at a pilot-scale, (d) determination of the shelf life of produced cheeses, by following their microbiological, compositional and biochemical evolution during cold storage, (e) evaluation of the texture, rheology, microstructure and colour of produced cheeses, and their aptness for consumption through a sensory analysis.Rennet coagulation properties of milk were enhanced by single-stage UHPH over 200 MPa, and optimal UHPH conditions were set to 300 MPa and 30 ºC. UHPH increased calcium-bonding of caseins within curds, impaired hydrogen bonding and favoured hydrophobic interactions. Moreover, by greatly reducing milk fat globule size, UHPH provoked the adsorption of milk proteins onto the MFGM. UHPH impaired in some extent curd cutting due to crumbling, improper matting and poor grain cohesion. Cheeses from UHPH-treated milk showed longer microbiological shelf life (19 vs. 13 days). Lactococci growth was enhanced at an early stage of the storage period but lactobacilli were not detected. The growth of yeasts and moulds was partly inhibited resulting in lower counts at the end of their shelf life. During storage, UHPH cheeses expelled less whey than those from conventionally treated, resulting in higher moisture and salt contents. Although fat and protein contents on a dry basis were not affected, lower levels of proteolysis and lipolysis were observed. Moreover, free fatty acid profiles greatly differed. Oxidation was found to be the major drawback resulting in a great number of volatile compounds, e.g., aldehydes and ketones, which presence explained off-flavours detected by some panellists. Finally, UHPH treatment of milk resulted in firmer, less deformable, with lower water-mouth feeling, and whiter fresh cheeses. Such changes could be attributed to the effects on the fat globules. Except for the dry mouth-feeling, the sensory panel described the structural attributes of cheeses from UHPH-treated milk as their best characteristics.In conclusion, these results show that UHPH is a promising technology as treatment of milk for the manufacture of fresh cheese by increasing their shelf life and improving some of their characteristics such as texture and microstructure. By solving the oxidation problems through the modification of some metal pieces of the UHPH equipment, fresh cheeses with similar or even higher flavour quality are expected to be obtained with UHPH-treated milk than with conventionally treated milk.

A growing interest in the strengths of several interactions that play important structural roles in biochemical systems has been building over the past couple decades. The binding energies and entropies of formation of the clusters of several protonated amino acids and nucleic acid bases with methanol have been measured using High Pressure Mass Spectrometry. The results generally show that binding energy decreases when the proton affinity difference between the alcohol and amino acid is increased. The structures and energies of various alcohol stabilized conformers of these protonated biomolecules were computed using ab initio calculations at the MP2(Full)/6‐311++g(2d,2p) level of theory. The enthalpies of formation of the lowest energy conformers of the proton‐bound clusters between the alcohols and amino acids or peptides match very closely with the experimental values, indicating that protonation and subsequent methanol attachment occurs primarily at the terminal amine functionality. The methanol stabilized protonated nucleic acid bases have energies that match closely with a more entropically favourable conformation of the cluster, hence yielding less negative enthalpy changes experimentally. The effect of alcohol size on binding energy was also monitored through measurements of enthalpies and entropies of formation for the clusters of protonated diglycine with several alcohols. The binding energy between protonated diglycine and benzene was also measured, yielding a measurable cation‐π interaction of over 20 kcal mol‐1, a comparable value to typical strong hydrogen bonds.

A growing interest in the strengths of several interactions that play important structural roles in biochemical systems has been building over the past couple decades. The binding energies and entropies of formation of the clusters of several protonated amino acids and nucleic acid bases with methanol have been measured using High Pressure Mass Spectrometry. The results generally show that binding energy decreases when the proton affinity difference between the alcohol and amino acid is increased. The structures and energies of various alcohol stabilized conformers of these protonated biomolecules were computed using ab initio calculations at the MP2(Full)/6‐311++g(2d,2p) level of theory. The enthalpies of formation of the lowest energy conformers of the proton‐bound clusters between the alcohols and amino acids or peptides match very closely with the experimental values, indicating that protonation and subsequent methanol attachment occurs primarily at the terminal amine functionality. The methanol stabilized protonated nucleic acid bases have energies that match closely with a more entropically favourable conformation of the cluster, hence yielding less negative enthalpy changes experimentally. The effect of alcohol size on binding energy was also monitored through measurements of enthalpies and entropies of formation for the clusters of protonated diglycine with several alcohols. The binding energy between protonated diglycine and benzene was also measured, yielding a measurable cation‐π interaction of over 20 kcal mol‐1, a comparable value to typical strong hydrogen bonds.

Solvent selection is an important factor in chemical process efficiency, profitability, and environmental impact. Prediction of solvent phase behavior will allow for the identification of novel solvent systems that could offer some economic or environmental advantage. A modified cohesive energy density model is used to predict the solid-liquid-equilibria for multifunctional solids in pure and mixed solvents for rapid identification of process solvents for design of crystallization processes. Some solubility data at several temperatures are also measured to further test the general applicability of the model. Gas-expanded liquids have potential environmentally advantageous applications as pressure tunable solvents for homogeneous and heterogeneous catalytic reactions and as novel solvent media for anti-solvent crystallizations. The phase behavior of some carbon dioxide/organic binary systems is measured to provide basic process design information. Solvent selection is also an important factor in the anti-solvent precipitation of solid compounds. The influence of organic solvent on the solid-liquid equilibria for two solid pharmaceutical compounds in several carbon dioxide expanded solvents is explored. A novel solvent system is also developed that allows for homogeneous catalytic reaction and subsequent catalyst sequestration by using carbon dioxide as a miscibility switch. The fundamental biphasic solution behavior of some polar organics with water and carbon dioxide are investigated.

Natural gas is the primary fuel used in industrial gas turbines for power generation. Hydrocarbon blends of methane, ethane, and propane make up a large portion of natural gas and it has been shown that dimethyl ether can be used as a supplement or in its pure form for gas turbine combustion. Because of this, a fundamental understanding of the physical characteristics such as the laminar flame speed is necessary, especially at elevated pressures to have the most relevance to the gas turbine industry. This thesis discusses the equations governing premixed laminar flames, historical methods used to measure the laminar flame speed, the experimental device used in this study, the procedure for converting the measured data into the flame speed, the results of the measurements, and a discussion of the results. The results presented in this thesis include the flame speeds for binary blends of methane, ethane, propane, and dimethyl ether performed at elevated pressures, up to 10-atm initial pressure, using a spherically expanding flame in a constant-volume vessel. Also included in this thesis is a comparison between the experimental measurements and four chemical kinetic models. The C4 mechanism, developed in part through collaboration between the National University of Ireland Galway and Texas A&M, was improved using the data presented herein, showing good agreement for all cases. The effect of blending ethane, propane, and dimethyl ether with methane in binary form is emphasized in this study, with the resulting Markstein length, Lewis number (Le), and flame stability characterized and discussed. It was noticed in this study, as well as in other studies, that the critical radius of the flame typically decreased as the Le decreased, and that the critical radius of the flame increased as the Le increased. Also, a rigorous uncertainty analysis has been performed, showing a range of 0.3 cm/s to 3.5 cm/s depending on equivalence ratio and initial pressure.

Gas viscosity is one of the gas properties that is vital to petroleum engineering. Its role in the oil and gas production and transportation is indicated by its contribution in the resistance to the flow of a fluid both in porous media and pipes. Although viscosity of some pure components such as methane, ethane, propane, butane, nitrogen, carbon dioxide and binary mixtures of these components at low-intermediate pressure and temperature had been studied intensively and been understood thoroughly, very few investigations were performed on viscosity of naturally occurring gases, especially gas condensates at low-intermediate pressure and temperature, even fewer lab data were published. No gas viscosity data at high pressures and high temperatures (HPHT) is available. Therefore this gap in the oil industry still needs to be filled. Gas viscosity at HPHT becomes crucial to modern oil industry as exploration and production move to deep formation or deep water where HPHT is not uncommon. Therefore, any hydrocarbon encountered there is more gas than oil due to the chemical reaction causing oil to transfer to gas as temperature increases. We need gas viscosity to optimize production rate for production system, estimate reserves, model gas injection, design drilling fluid, and monitor gas movement in well control. Current gas viscosity correlations are derived using measured data at low-moderate pressures and temperatures, and then extrapolated to HPHT. No measured gas viscosities at HPHT are available so far. The validities of these correlations for gas viscosity at HPHT are doubted due to lack of experimental data. In this study, four types of viscometers are evaluated and their advantages and disadvantages are listed. The falling body viscometer is used to measure gas viscosity at a pressure range of 3000 to 25000 psi and a temperature range of 100 to 415 oF. Nitrogen viscosity is measured to take into account of the fact that the concentration of nonhydrocarbons increase drastically in HPHT reservoir. More nitrogen is found as we move to HPHT reservoirs. High concentration nitrogen in natural gas affects not only the heat value of natural gas, but also gas viscosity which is critical to petroleum engineering. Nitrogen is also one of common inject gases in gas injection projects, thus an accurate estimation of its viscosity is vital to analyze reservoir performance. Then methane viscosity is measured to honor that hydrocarbon in HPHT which is almost pure methane. From our experiments, we found that while the Lee-Gonzalez-Eakin correlation estimates gas viscosity at a low-moderate pressure and temperature accurately, it cannot give good match of gas viscosity at HPHT. Apparently, current correlations need to be modified to predict gas viscosity at HPHT. New correlations constructed for HPHT conditions based on our experiment data give more confidence on gas viscosity.

No description available.

An industrial Fourier transform infrared (FTIR) milk analyser has been adapted for the proximate analysis of fresh or cooked meat and meat products. Stable freeze-dried samples of ground beef and bologna were prepared for the calibration of an FTIR spectrometer equipped with a 37-mum transmission cell maintained at a constant temperature of 65°C and were analysed for fat, protein, moisture, and ash by the official methods of analysis of the Association of Official Analytical Chemists (AOAC) prior to instrumental measurement. The requirement to prepare a "milk-like" emulsion of meat for FTIR analysis led to the development of two prototype high-pressure homogenizers specifically designed to produce analytical volumes of emulsions in which the largest residual colloids present in suspension would have dimensions smaller than 1 mum. Emulsified samples were examined by transmission electron microscopy and laser light scattering spectroscopy to determine the size distribution of fat globules and the dimensions of the residual insoluble fragments of protein. / "Milk-like" emulsions of meat passed three times through a high-pressure homogenizer operating at 20,000 psi (138 MPa) had an average fat globule diameter of less than 320 nm. Also, the use of high-pressure homogenization eliminated the need to filter out insoluble proteins from connective tissues prior to the infrared analysis, resulting in a more accurate determination of the protein content in the meat samples. The results of validation studies conducted with both fresh and freeze-dried samples demonstrated that it is possible to analyse meat samples simultaneously for fat, protein, carbohydrates and moisture with good accuracy in approximately 7½; minutes per sample employing existing FTIR instrumentation used for the routine analysis of milk and dairy products.

The first goal of this thesis is to validate a detailed co-flow flame soot formation model for high pressure applications. The second goal is to use this detailed model to understand the effect pressure has on soot formation. The third goal is to note any deficiencies in the model, and the fourth is to remedy these issues. The thesis is divided into two research studies. The first study validates the model for high pressure use against ethane-air co-flow diffusion flames from 2 to 15 atm. After validation, the results are used to determine the impact pressure has on the three main soot formation processes. It is determined that the original model could not account for the flame pre-heating effect. The second study addresses this issue by adapting the model to extend below the fuel tube exit plane, and includes conjugate heat transfer (CHT) between the fluid streams and solid fuel tube.