Thesis (Ph. D.)--Columbia University. / Vita. Bibliography: p. 21.

Thesis (Ph. D.)--Columbia University, 1927. / Vita.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Space heating and cooling, as required for chicken poultry farming, is an energy intensive operation. Due to the continuous rise in the prices of fossil fuel, water and electricity, there is a need to develop renewable and sustainable energy systems that minimise the use of fuel or electricity, for heating, and water, for cooling of air. The HYDROSOL (HYDro ROck SOLar) system, developed at Stellenbosch University, is such a renewable energy system that potentially provides a low cost solution. Instead of using conventional gas and electricity heaters for the heating of air during winter, the HYDROSOL system collects solar heat, stores it in a packed bed of rocks and dispatches the heat as required. During hot summer days, when cooling is needed, the rocks are cooled during the night when the ambient temperatures are low and/ or by evaporative cooling by spraying water onto them. During the day, hot air is then cooled when it passes through the colder rocks with minimal water consumption compared to current systems. In this thesis, a prototype of the HYDROSOL system is presented, designed and built for experimental testing. A transient 2-D thermo flow model is developed and presented for the analytical and experimental performance evaluation of this system for solar heating and night air cooling operation. This model is used to conduct a parametric study on HYDROSOL to gain a better understanding of the operation and control of the system. The HYDROSOL concept is intended to be used for heating and cooling of residential buildings, office suites, warehouses, shopping centres, food processing industries e.g. drying of foods, and various agricultural industries e.g. greenhouses. In this thesis, a HYDROSOL system is developed mainly for poultry broiler houses in South Africa focussing on convective dry cooling, charging the rock bed with night-time ambient air, and convective heating, harvesting solar heat during the day, with different modes of operation available. / AFRIKAANSE OPSOMMING: Ruimte verhitting en verkoeling, soos benodig vir hoender pluimvee boerdery, is ‘n energie intensiewe bedryf. As gevolg van die voortdurende styging in fossiel brandstof-, water- en elektrisiteitpryse, het ‘n behoefte ontstaan om hernubare en volhoubare energie-stelsels te ontwikkel wat minder brandstof of elektrisiteit, vir verhitting, en water, vir verkoeling van lug, gebruik. Die HYDROSOL (HYDro ROck SOLar) stelsel, wat ontwikkel is by die Universiteit van Stellenbosch, is ‘n hernubare energie-stelsel wat ‘n potensiële lae koste oplossing bied. In plaas daarvan om konvensionele gas en elektrisiteit verwarmers vir verhitting van lug gedurende die winter te gebruik, maak HYDROSOL gebruik van son warmte, stoor dit in `n gepakte bed van klip en onttrek die warmte soos benodig. Gedurende die warm somer dae wanneer verkoeling benodig word, word die klippe gedurende die nag, met kouer omgewings lug en/of met verdampingsverkoeling, deur water op die klippe te spuit, afgekoel. Gedurende die dag word warm lug afgekoel deur die lug oor die koue klippe te forseer met minimale waterverbruik in vergelyking met huidige stelsels. ‘n Prototipe van die HYDROSOL word voorgestel, ontwerp en gebou vir eksperimentele doeleindes. ‘n 2-D tyd afhanklike termo- vloei model word voorgestel vir die analitiese en eksperimentele verrigting evaluering vir son verhitting en nag lug verkoeling. Hierdie model word gebruik om ‘n parametriese studie te doen om die werking en beheer van HYDROSOL beter te verstaan. Die HYDROSOL stelsel is bedoel om die verwarming en verkoeling vereistes van residensiële geboue, kantoor areas, pakhuise, winkelsentrums, voedsel verwerking nywerhede, soos bv. die droging van voedsel, en verskeie landboubedrywe, soos bv. kweekhuise, te bevredig. In hierdie tesis word ‘n HYDROSOL stelsel, hoofsaaklik vir pluimvee kuikenhuise in Suid- Afrika, ondersoek en fokus op die droë verkoeling, deur die rotsbed te laai gedurende die nag, asook droë- verhitting, wat gebruik maak van son energie gedurende die dag en kan beheer word op verskillende maniere.

L’industrie parapharmaceutique de même que l’industrie cosmétique recherche des alternatives naturelles aux conservateurs synthétiques. Cet intérêt est lié à l’exigence du consommateur et à la volonté de développer des produits innovants éco-conçus. Compte tenu de leurs activités antioxydantes et antimicrobiennes, les huiles essentielles constituent des options intéressantes dont les coûts et impacts organoleptiques doivent cependant être considérés. Dans le cadre de cette thèse, les activités antioxydante et antimicrobienne de combinaisons huile essentielle-hydrolat et huile essentielle-huile essentielle de Lippia alba, Rosmarinus officinalis et Thymus vulgaris ont été évaluées afin d’objectiver leur potentiel de conservateur pour des produits phytothérapeutiques. Initialement, l’impact d’une méthode de distillation utilisant le macérât aqueux de la matière végétale comme source de vapeur a été évalué sur les propriétés physico-chimiques des hydrolats et huiles essentielles de Thymus vulgaris et Rosmarinus officinalis cultivées dans le sud de Bogotá en Colombie. Puis, les distillats et hydrolats ayant présenté une activité biologique significative ainsi que l’huile essentielle de Lippia alba ont été combinés deux à deux. Les activités antiradicalaire et microbicide ont été évaluées respectivement par ABTS et par les méthodes de microdilution et de diffusion en agar. Des résultats biologiques significatifs ont été obtenus pour les combinaisons huile essentielle-huile essentielle tout spécialement dans le cas de la combinaison des huiles essentielles de T. vulgaris et de L. alba avec une diminution de la CI50 de 2,9 (huile essentielle de Thym seule) à 1,4 µL/L ainsi que dans le cas spécifique de la combinaison hydrolat-huile essentielle de Thymus vulgaris avec une CI50 de 2,1 µL/L. De même, cette dernière combinaison a présenté un effet de synergie en diminuant la Concentration Minimale Bactéricide de l’huile essentielle de Thym de 0,4 à 0,1 µL/mL. Les différents résultats sont discutés ainsi que leurs impacts d’un point de vue industriel et thérapeutique. / The parapharmaceutical industry as well as the cosmetics industry is looking for natural alternatives to synthetic preservatives. This interest is linked to the requirement of the consumer and the will to develop eco-designed innovative products. Antioxidant and antimicrobial activities of essential oils are interesting options, however costs and organoleptic impacts should be considered. As part of this thesis, the antioxidant and antimicrobial activities of essential oil-hydrosol and essential oil-essential oil of Lippia alba, Rosmarinus officinalis and Thymus vulgaris were evaluated to objectify their preservative potential for herbal products. Initially, the impact of a distillation method using the aqueous macerate of a part of vegetal material as vapor source was evaluated on the physicochemical properties of hydrosols and essential oils of Thymus vulgaris and Rosmarinus officinalis grown in southern Bogotá Colombia. Then, distillates and hydrosols with significant biological activity as well as the essential oil of Lippia alba were combined by pairs. The antiradical and microbicidal activities were evaluated respectively by ABTS and by the methods of microdilution and agar diffusion. Significant results were obtained with the essential oil-essential oil combinations especially in the case of the combination of essential oils of T. vulgaris and L. alba with a decrease of the IC50 of 2,9 (T. vulgaris essential oil alone) to 1,4 µL/L as well as in the specific case of the T. vulgaris hydrosol and essential oil combination with an IC50 of 2,1 µL/L. Similarly, the latter combination presented a synergy effect by decreasing the Minimal Bactericidal Concentration of the essential oil of Thyme from 0,4 to 0,1µL/mL. The different results are discussed as well as their impacts in both industrial and therapeutic domains.

Les eaux florales sont des matières premières aromatiques issues de la distillation, contenant généralement moins de 1 g/L de composés volatils leur conférant leurs propriétés organoleptiques. Elles sont utilisées principalement en industrie agroalimentaire et cosmétique. Elles sont sujettes à des problèmes d’instabilité microbienne incompatibles avec leurs applications. Ces microorganismes, leurs dynamiques, ainsi que les nutriments disponibles nécessaires à leur croissance restent mal connus. Les eaux florales sont actuellement stabilisées par ajout de conservateurs dont certains sont controversés et visent à être retirés du marché. De plus, leur efficacité dans les eaux florales n’a pas été évaluée.L’objectif de cette thèse est d’apporter une meilleure connaissance de la composition des eaux florales et de ses contaminants afin de proposer une méthode de stabilisation adaptée.La composition en huile essentielle et le microbiote de 22 échantillons d’eau de fleur d’oranger (Citrus aurantium L. ssp. amara L.) et de rose (Rosa damascena Miller et Rosa centifolia L.), provenant de différents producteurs autour du bassin méditerranéen, ont été analysés afin de déterminer les facteurs responsables de leur altération. Bien que les composés volatils soient connus pour leurs propriétés antimicrobiennes, leurs concentrations dans les hydrolats ne sont pas suffisantes pour assurer la stabilité microbiologique. En plus des composés volatils, les hydrolats contiennent des composés non-volatils tels que des sucres, entraînés vers le distillat par effet de primage ou de moussage pendant la distillation, et pouvant être utilisés comme substrat de croissance par les microorganismes. La population microbienne peut atteindre 106 à 107 UFC/mL en quelques jours à température ambiante et jusqu’à 3 mois à 5°C. Des bactéries environnementales, oligotrophes, et acido-tolérantes, appartenant principalement aux genres Pseudomonas sp. et Burkholderia sp. ont été isolées et identifiées. Parmi ces bactéries, B. vietnamiensis et Novosphingobium capsulatum ont été capables de métaboliser des composés volatiles tels que le géraniol ou l’acétate de 2-phényléthyle pour produire la 6-méthyl-5-heptèn-2-one ou le 2-phényléthanol, et modifier ainsi les propriétés organoleptiques des hydrolats. Enfin, la capacité de croissance de bactéries pathogènes et d’altération dans les hydrolats a été évaluée, et différents conservateurs ont été testés sur les souches capables de se multiplier dans les hydrolats.Une distillation aseptique et un conditionnement stérile permettrait d’assurer la stabilité des hydrolats sans ajout de conservateurs. En l’absence de conditions aseptiques, l’ajout de conservateurs est nécessaire pour assurer la stabilité des hydrolats. / Hydrosols are hydrodistillation products mainly used as food flavoring agents or ingredient in cosmetics. They contain less than 1 g/L of dispersed essential oils giving the organoleptic properties. These are subjected to microbial proliferation that can prevent use due to non-compliance to professional microbiological standards. The microorganisms, their growth dynamics, and the available nutrients in hydrosols remain unknown. Hydrosols can contain few preservatives, but there is no data about their efficiency in hydrosols.The aim of this study was to have a better knowledge on hydrosols composition, their microbiota, and spoilage conditions, in order to propose an adapted stabilization method.The composition in volatile compounds and the microbiota of 22 hydrosol samples of Citrus aurantium L. ssp. amara L. (orange blossom), Rosa damascena Miller (rose D.), and Rosa centifolia L. (rose C.) flowers were analyzed to determine factors responsible for decay. Some non-volatile compounds were likely carried over during distillation by a priming and foaming effect, and could be used as nutrients by microorganisms. Concentrations of volatile compounds in hydrosols are not high enough to prevent microbial proliferation, and bacteria concentrations can reach up to 106 CFU/mL in both hydrosols. The isolated microbial population was composed of oligotrophic Gram-negative bacteria, arranged in four major genera: Pseudomonas sp., Burkholderia cepacia complex, and presumably two new genera belonging to Acetobacteraceae and Rhodospirillaceae. Among those bacteria, Burkholderia vietnamiensis and Novosphingobium capsulatum were able to metabolize volatile compounds, such as geraniol to produce 6-methyl-5-hepten-2-one or geranic acid, or 2-phenylethyl acetate to produce 2-phenylethanol. Finally, the growth potential of a range of bacteria isolated from hydrosols and of pathogenic micro-organisms was evaluated, then the anti-microbial activity in nutrient broth and/or in hydrosols of a range of chemical preservatives authorized for food and cosmetic applications was tested.Additional hurdles such as chemical preservatives or aseptic packaging will be necessary to insure microbial stability.

Neste trabalho, foi investigado o comportamento tribológico dos pares cerâmicos aluminanitreto de silício no deslizamento em água e em uma suspensão de sílica coloidal em água (hidrosol). O objetivo foi verificar a possibilidade de atingir um coeficiente de atrito da ordem de unidades de milésimos, aqui chamado de ultra-baixo coeficiente de atrito (UBCA), verificar se a mudança do meio, de água para hidrosol, diminui o running-in do coeficiente de atrito, e verificar o efeito da variação da rugosidade inicial da alumina no comportamento do atrito. Os ensaios foram realizados na configuração de teste esferasobre- disco, no qual a esfera foi de nitreto de silício e o disco de alumina, sob carga normal de 54 N e velocidade de 1 m/s. A água utilizada nos ensaios foi destilada e deionizada, e a sílica coloidal amorfa, hidrofílica, sem porosidade e de tamanho médio de partícula de 12 nm foi a Aerosil® 200, e o hidrosol foi preparado com pH 8,5 num eletrólito de NaCl de 1 mM. A esfera de nitreto de silício, adquirida comercialmente, e a alumina, sinterizada em laboratório, foram caracterizadas quanto a densidade, as fases foram determinadas por difração de raios X, microscopia eletrônica de varedura (MEV) observada em amostras ceramográficas atacadas. Algumas propriedades mecânicas como dureza, módulo de elasticidade e tenacidade à fratura foram determinadas. Duas condições de rugosidade dos discos de alumina foram utilizadas nos ensaios tribológicos, 350 nm e 10 nm RMS. Em todos os ensaios, em água, em hidrosol e independentemente da rugosidade inicial do disco o coeficiente de atrito no regime permanente apresentou pequena dispersão de valores de 0,002 a 0,006, e não foi possível estabelecer diferença entre elas. A menor rugosidade do disco de alumina acarretou menor desgaste e menor período de running-in de coeficiente de atrito, tanto em água quanto em hidrosol. Os ensaios em meio de hidrosol acarretaram menor desgaste das cerâmicas e apresentaram menor running-in de coeficiente de atrito, comparados aos ensaios com água. O disco de alumina apresentou menor desgaste do que a esfera de nitreto de silício, em todas as condições estudadas. Com a análise das perdas volumétricas, da rugosidade final das superfícies desgastadas, das curvas de coeficiente de atrito e das espessuras mínimas de filme lubrificante, calculadas com uso de modelo da literatura, foi possível relacionar a diminuição do desgaste e do running-in de coeficiente de atrito em meio de hidrosol, com a presença da sílica na superfície ou próxima dela. / In this work, the tribological behavior of the alumina-silicon nitride couple was investigated under water and hydrosol (colloidal silica suspensions in water) lubricated sliding. The purposes were to study how an ultra-low friction coefficient can be achieved and to analyze the effects of the environment, lubricant and alumina roughness changes on the friction behavior. Ball-on-disk tests with a normal load of 54 N and a sliding speed of 1 m/s were carried out, using a silicon nitride ball and an alumina disk. The water used as lubricant was distilled and deionized. The silica was amorphous colloidal and hydrophilic, without porous and with a 12 nm medium particle diameter, commercially named Aerosil ® 200. The hydrosol was obtained with a pH value of 8,5 and a 1mM NaCl electrolyte. To estimate the minimum film thickness, formed during the lubricated sliding tests, a theory model was used. The commercial silicon nitride balls and the alumina disks, which were conformed and sintered in laboratory, were characterized by density, X-ray diffraction and scanning electron microscopy measurements. The mechanical properties such as hardness, Young modulus and fracture toughness were determined. The friction coefficient values obtained in the steady state regime showed low standard deviations (0,002 to 0,006) under all conditions. A shorter period of running-in was observed with the lower disk roughness, both in water and hydrosol lubrication. The hydrosol lubricated sliding produced a lower wear and friction running-in comparing with the tests under water lubrication. The alumina disk always showed lower wear than the silicon nitride ball. The volume loss, friction coefficients, worn surfaces roughness and minimum film thickness results suggest that the wear and friction coefficient running-in decrease was caused by the presence of silica on the sliding surfaces or on the near surface regions.

Neste trabalho, foi investigado o comportamento tribológico dos pares cerâmicos aluminanitreto de silício no deslizamento em água e em uma suspensão de sílica coloidal em água (hidrosol). O objetivo foi verificar a possibilidade de atingir um coeficiente de atrito da ordem de unidades de milésimos, aqui chamado de ultra-baixo coeficiente de atrito (UBCA), verificar se a mudança do meio, de água para hidrosol, diminui o running-in do coeficiente de atrito, e verificar o efeito da variação da rugosidade inicial da alumina no comportamento do atrito. Os ensaios foram realizados na configuração de teste esferasobre- disco, no qual a esfera foi de nitreto de silício e o disco de alumina, sob carga normal de 54 N e velocidade de 1 m/s. A água utilizada nos ensaios foi destilada e deionizada, e a sílica coloidal amorfa, hidrofílica, sem porosidade e de tamanho médio de partícula de 12 nm foi a Aerosil® 200, e o hidrosol foi preparado com pH 8,5 num eletrólito de NaCl de 1 mM. A esfera de nitreto de silício, adquirida comercialmente, e a alumina, sinterizada em laboratório, foram caracterizadas quanto a densidade, as fases foram determinadas por difração de raios X, microscopia eletrônica de varedura (MEV) observada em amostras ceramográficas atacadas. Algumas propriedades mecânicas como dureza, módulo de elasticidade e tenacidade à fratura foram determinadas. Duas condições de rugosidade dos discos de alumina foram utilizadas nos ensaios tribológicos, 350 nm e 10 nm RMS. Em todos os ensaios, em água, em hidrosol e independentemente da rugosidade inicial do disco o coeficiente de atrito no regime permanente apresentou pequena dispersão de valores de 0,002 a 0,006, e não foi possível estabelecer diferença entre elas. A menor rugosidade do disco de alumina acarretou menor desgaste e menor período de running-in de coeficiente de atrito, tanto em água quanto em hidrosol. Os ensaios em meio de hidrosol acarretaram menor desgaste das cerâmicas e apresentaram menor running-in de coeficiente de atrito, comparados aos ensaios com água. O disco de alumina apresentou menor desgaste do que a esfera de nitreto de silício, em todas as condições estudadas. Com a análise das perdas volumétricas, da rugosidade final das superfícies desgastadas, das curvas de coeficiente de atrito e das espessuras mínimas de filme lubrificante, calculadas com uso de modelo da literatura, foi possível relacionar a diminuição do desgaste e do running-in de coeficiente de atrito em meio de hidrosol, com a presença da sílica na superfície ou próxima dela. / In this work, the tribological behavior of the alumina-silicon nitride couple was investigated under water and hydrosol (colloidal silica suspensions in water) lubricated sliding. The purposes were to study how an ultra-low friction coefficient can be achieved and to analyze the effects of the environment, lubricant and alumina roughness changes on the friction behavior. Ball-on-disk tests with a normal load of 54 N and a sliding speed of 1 m/s were carried out, using a silicon nitride ball and an alumina disk. The water used as lubricant was distilled and deionized. The silica was amorphous colloidal and hydrophilic, without porous and with a 12 nm medium particle diameter, commercially named Aerosil ® 200. The hydrosol was obtained with a pH value of 8,5 and a 1mM NaCl electrolyte. To estimate the minimum film thickness, formed during the lubricated sliding tests, a theory model was used. The commercial silicon nitride balls and the alumina disks, which were conformed and sintered in laboratory, were characterized by density, X-ray diffraction and scanning electron microscopy measurements. The mechanical properties such as hardness, Young modulus and fracture toughness were determined. The friction coefficient values obtained in the steady state regime showed low standard deviations (0,002 to 0,006) under all conditions. A shorter period of running-in was observed with the lower disk roughness, both in water and hydrosol lubrication. The hydrosol lubricated sliding produced a lower wear and friction running-in comparing with the tests under water lubrication. The alumina disk always showed lower wear than the silicon nitride ball. The volume loss, friction coefficients, worn surfaces roughness and minimum film thickness results suggest that the wear and friction coefficient running-in decrease was caused by the presence of silica on the sliding surfaces or on the near surface regions.

No description available.