This work was concerned with the determination of mass transfer and kinetic parameters of ozone reactions with four organic compounds from different families, namely reactive dye RO16, triclocarban, naphthalene and methanol. In order to understand the mechanisms of ozone reactions with the organic pollutants, a radical scavenger (t-butanol) was used and the pH was varied from 2 to 9. Ozone solubility (CAL*) is an important parameter that affects both mass transfer rates and chemical reaction kinetics. In order to determine accurate values of the CAL* in the current work, a set of experiments were devised and a correlation between CAL* and the gas phase ozone concentration of the form CAL*(mol/L) = 0.0456 CO3 (g/m3 NTP) was obtained at 20°C. This work has also revealed that t-butanol did not only inhibit hydroxyl radical reactions but also increased mass transfer due to it increasing the specific surface area (aL). Values of the aL were determined to be 2.7 and 3.5 m2/m3 in the absence and presence of t-butanol respectively. It was noticed that the volumetric mass transfer coefficient (kLa) has increased following the addition of t-butanol. Ozone decomposition was studied at pH values of 2 to 9 in a 500 mL reactor initially saturated with ozone. Ozone decomposition was found to follow a second order reaction at pH values less than 7 whilst it was first order at pH 9. When the t-butanol was added, the decomposition of ozone progressed at a lower reaction order of 1.5 for pH values less than 7 and at the same order without t-butanol at pH 9. Ozone decomposition was found significant at high pHs due to high hydroxide ion concentration, which promotes ozone decomposition at high pHs. The reaction rate constant (k) of RO16 ozonation in the absence of t-butanol was determined. The result suggests that RO16 degradation occurs solely by molecular ozone and indirect reactions by radicals are insignificant. The chemical reaction of triclocarban with ozone was found to follow second order reaction kinetics. The degradation of naphthalene using the liquid/gas-ozone (LGO) system was studied. This result showed that hydroxyl radicals seemed to have limited effect on naphthalene degradation which was also observed when a radical scavenger (t-butanol) was used. Reaction rate constants were calculated and were found around 100 times higher than values reported in the literature due to differences in experimental conditions. From the results of the experimental investigation on the degradation of methanol by ozone it was found that the rate constant (k) of the degradation reaction increased at pH 9. The reaction stoichiometry was found to have a value of 1 mol/mol. The two steps of the liquid/solid-ozone (LSO) system were studied on beds of silica gel and a zeolitic material (D915) and the ozone adsorption process was modeled and found that particle rate controls ozone adsorption step but liquid rate controls the water treatment step. Ozone desorption with pure deionised water was studied. The water flow rate was found to accelerate the desorption rates but pH was found to decrease the desorption rates. In contrast, the effect of pH was insignificant in the presence of t-butanol. Determination of the adsorption isotherms for RO16, naphthalene and methanol revealed that RO16 did not exhibit adsorption on silica gel, but both naphthalene and methanol showed adsorption on D915 described by Langmuir model.

The mass transfer area of nine structured packings was measured as a function of liquid load, surface tension, liquid viscosity, and gas rate in a 0.427 m (16.8 in) ID column via absorption of CO₂ from air into 0.1 mol/L NaOH. Surface tension was decreased from 72 to 30 mN/m via the addition of a surfactant (TERGITOL[trademark] NP-7). Viscosity was varied from 1 to 15 mPa·s using poly(ethylene oxide) (POLYOX[trademark] WSR N750). A wetted-wall column was used to verify the kinetics of these systems. Literature model predictions matched the wetted-wall column data within 10%. These models were applied in the interpretation of the packing results. The packing mass transfer area was most strongly dictated by geometric area (125 to 500 m²/m³) and liquid load (2.5 to 75 m³/m²·h or 1 to 30 gpm/ft²). A reduction in surface tension enhanced the effective area. The difference was more pronounced for the finer (higher surface area) packings (15 to 20%) than for the coarser ones (10%). Gas velocity (0.6 to 2.3 m/s), liquid viscosity, and channel configuration (45° vs. 60° or smoothed element interfaces) had no appreciable impact on the area. Surface texture (embossing) increased the area by 10% at most. The ratio of effective area to specific area (a[subscript e]/a[subscript p]) was correlated within limits of ±13% for the experimental database: [mathematical formula]. This area model is believed to offer better predictive accuracy than the alternatives in the literature, particularly under aqueous conditions. Supplementary hydraulic measurements were obtained. The channel configuration significantly impacted the pressure drop. For a 45°-to-60° inclination change, pressure drop decreased by more than a factor of two and capacity expanded by 20%. Upwards of a two-fold increase in hold-up was observed from 1 to 15 mPa·s. Liquid load strongly affected both pressure drop and hold-up, increasing them by several-fold over the operational range. An economic analysis of an absorber in a CO₂ capture process was performed. Mellapak[trademark] 250X yielded the most favorable economics of the investigated packings. The minimum cost for a 7 m MEA system was around $5-7/tonne CO₂ removed for capacities in the 100 to 800 MW range. / text

The goal of this research is to realize the advantages of declarative modeling for complex physical systems that involve both advection and diffusion to varying degrees in multiple domains. This occurs, for example, in chemical devices such as fuel cells. The declarative or equation-based modeling approach can provide computational advantages and is compatible with physics-based, object-oriented representations. However, there is no generally accepted method of representing coupled advection and diffusion in a declarative modeling framework. This work develops, justifies, and implements a new upstream discretization scheme for mixed advective and diffusive flows that is well-suited for declarative models. The discretization scheme yields a gradual transition from pure diffusion to pure advection without switching events or nonlinear systems of equations. Transport equations are established in a manner that ensures the conservation of material, momentum, and energy at each interface and in each control volume. The approach is multi-dimensional and resolved down to the species level, with conservation equations for each species in each phase. The framework is applicable to solids, liquids, gases, and charged particles. Interactions among species are described as exchange processes which are diffusive if the interaction is inert or advective if it involves chemical reactions or phase change. The equations are implemented in a highly modular and reconfigurable manner using the Modelica language. A wide range of examples are demonstrated—from basic models of electrical conduction and evaporation to a comprehensive model of a proton exchange membrane fuel cell (PEMFC). Several versions of the PEMFC model are simulated under various conditions including polarization tests and a cyclical electrical load. The model is shown to describe processes such as electro-osmotic drag and liquid pore saturation. It can be scaled in complexity from 4000 to 32,000 equations, resulting in a simulation times from 0.2 to 19 s depending on the level of detail. The most complex example is a seven-layer cell with six segments along the length of the channel. The model library is thoroughly documented and made available as a free, open-source software package.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Donghai Wang / Sweet sorghum accumulates high concentrations of fermentable sugars in the stem, produces significant amount of starch in the grain (panicle) and has shown to be a promising energy feedstock. Sweet sorghum has a short growing season so adding it to the sugar cane system would be good. The overall goal of this dissertation is to enhance the attractiveness of biofuel production from sweet sorghum to fully utilize fermentable sugars in the juice, starch in the panicle and structural carbohydrates in the stalk for high efficiency and low-cost ethanol production. Sweet sorghum juice was incorporated into the dry-grind process which increased ethanol yield by 28% increase of ethanol yield compared to the conventional ethanol method and decreased enzymatic hydrolysis time by 30 minutes. A very high gravity fermentation technique was applied using sweet sorghum juice and sorghum grain yielded 20.25% (v/v) of ethanol and 96% fermentation efficiency. Response surface methodology was applied in order to optimize diffusion conditions and to explore effects of diffusion time, diffusion temperature, and ratio of sweet sorghum biomass to grain on starch-to-sugar efficiency and total sugar recovery from sweet sorghum. Starch hydrolysis efficiency and sugar recovery efficiency of 96 and 98.5% were achieved, respectively, at an optimized diffusion condition of 115 minutes, 95 °C, and 22% grain loading. Extraction kinetics based on the optimized diffusion parameters were developed to describe the mass transfer of sugars in sweet sorghum biomass during the diffusion process. Ethanol obtained from fermented extracted sugars treated with granular starch hydrolyzing enzyme and those with traditional enzymes were comparable (14.5 – 14.6% v/v). Ethanol efficiencies also ranged from 88.92 –92.02%.

Microneedle is a promising technique for delivering high molecular weight drugs across skin. The microneedles can offer a number of benefits over other drug delivery methods. For example, the drugs only diffuse over a short distance before reaching the blood circulation which enhances the absorption of drugs by the tissue. However, the drug transport behaviour in skin is affected by a complex interplay of many parameters (e.g., microneedle geometries, permeability across skin, etc). In this thesis, many aspects of the microneedle field were examined. A mathematical model for drug transport from microneedle systems into skin was developed. Issues such as microneedle penetration, surface area of the microneedle arrays, etc. were investigated. This work helped us to focus into optimizing the design of microneedles by developing an in-house algorithm to enhance the performance of transdermal drug delivery using microneedles. Following the development of this algorithm, the influence of skin thickness with its classification (i.e., age group, race, etc.) on drug permeability across skin was studied. Attention was then given to determine the effective permeability (Peff) and the effective skin thickness (Heff) for various solid microneedle models. The outcome of this research allowed us to study the influence of microneedle dimensions on the drug concentration in blood (Cb). Furthermore, the 'pattern' (shape) of the microneedles array (i.e., square or rectangular) and the 'distribution' (arrangement) of the microneedles inside an array (i.e., triangular or diamond) were investigated to identify the optimum microneedle models. Finally, the effect of skin metabolism on both the patch (without microneedles) and the microneedle arrays on drug intake were examined.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / Donghai Wang / Sweet sorghum accumulates high concentrations of fermentable sugars in the stem, produces significant amount of starch in the grain (panicle) and has shown to be a promising energy feedstock. Sweet sorghum has a short growing season so adding it to the sugar cane system would be good. The overall goal of this dissertation is to enhance the attractiveness of biofuel production from sweet sorghum to fully utilize fermentable sugars in the juice, starch in the panicle and structural carbohydrates in the stalk for high efficiency and low-cost ethanol production. Sweet sorghum juice was incorporated into the dry-grind process which achieved 28% increase of ethanol yield compared to the conventional ethanol method and decreased enzymatic hydrolysis time by 30 minutes. A very high gravity fermentation technique was applied using sweet sorghum juice and sorghum grain yielded 20.25% (v/v) of ethanol and 96% fermentation efficiency. Response surface methodology was applied in order to optimize diffusion conditions and to explore effects of diffusion time, diffusion temperature, and ratio of sweet sorghum biomass to grain on starch-to-sugar efficiency and total sugar recovery from sweet sorghum. Starch hydrolysis efficiency and sugar recovery efficiency of 96 and 98.5% were achieved, respectively, at an optimized diffusion condition of 115 minutes, 95 °C, and 22% grain loading. Extraction kinetics based on the optimized diffusion parameters were developed to describe the mass transfer of sugars in sweet sorghum biomass during the diffusion process. Ethanol obtained from fermented extracted sugars treated with granular starch hydrolyzing enzyme and those with traditional enzymes were comparable (14.5 – 14.6% v/v). Ethanol efficiencies also ranged from 88.92 –92.02%.

A bench-scale, sweeping gas, flat-sheet Membrane Distillation (MD) unit was used to assess the importance of membrane architecture and operational variables to distillate production rate. Sweeping gas membrane distillation (SGMD) was simulated for various membrane characteristics (material, pore size, porosity and thickness), spacer dimensions and operating conditions (influent brine temperature, sweep gas flow rate and brine flow rate) based on coupled mass and energy balances. Model calibration was carried out using four membranes that differed in terms of material selection, effective pore size, thickness and porosity. Membrane tortuosity was the lone fitting parameter. Distillate fluxes and temperature profiles from experiments matched simulations over a wide range of operating conditions. Limitations to distillate production were then investigated via simulations, noting implications for MD design and operation. Under the majority of conditions investigated, membrane resistance to mass transport provided the primary limitation to water purification rate. The nominal or effective membrane pore size and the lumped parameter epsilon/delta tau (porosity divided by the product of membrane tortuosity and thickness) were primary determinants of membrane resistance to mass transport. Resistance to Knudsen diffusion dominated membrane resistance at pore diameters <0.3 mu m. At larger pore sizes, a combination of resistances to intra-pore molecular diffusion and convection across the gas-phase boundary layer determined mass transport resistance. Findings are restricted to the module design flow regimes considered in the modeling effort. Nevertheless, the value of performance simulation to membrane distillation design and operation is well illustrated.

Tidally-induced head fluctuation is a natural phenomenon in coastal regions. The discharge of groundwater through sediments will occur anywhere that the aquifer is hydraulically connected to a surface water body and the time averaged tidally-influenced water level in the aquifer is higher than sea level, and almost all coastal regions are subject to such flow. With the development of coastal areas, the discharge of groundwater contaminants into tidally affected coastal water bodies has become a significant problem. Biota that live in the benthic region are known to be sensitive to the concentration of discharging anthropogenic chemical compounds. Thus the contaminant concentration entering the benthos is of very significant practical importance and its study is the focus of this dissertation. An investigation of the effect of tides on the concentration of groundwater contaminants discharging to a surface water body is studied using a one-dimensional homogeneous sand column. Results of the experiment are confirmed using a three-dimensional heterogeneous groundwater tank model. A constant water level is imposed upgradient, and the downgradient water level is controlled by a wave generator that controls the hydraulic head to mimic a 12 hour tidal fluctuation. The experimental results demonstrate that the tidal fluctuations in the downgradient reservoir result in a decrease in average contaminant concentration at the point of groundwater discharge to the surface-water body. The further upstream the well is located, the smaller the amplitude of the concentration oscillation. In addition, upstream migration of concentration oscillations is observed in spite of a net downgradient flow. Fourier analysis suggests that the dominant frequency of the peaks of pressure and chemical data at different locations along the length of the column is identically two cycles per day and that the amplitudes of the concentration oscillations increase with time at measurement locations at the upstream responding probes. As the classical groundwater flow and transport model cannot reproduce the phenomena we observed, an innovative multi-mobility model, is proposed with one highly mobile liquid phase, one less mobile liquid phase and a solid phase. Averaging theory is applied to develop the mass conservation equation from the microscale to the macroscale and facilitate the reduction of dimensionality to obtain one-dimensional governing equations with closure relations. A new finite volume method is utilized to solve the resulting equations. The simulation confirms the existence of the enhanced tidally-induced mixing process.

O processo estudado utilizou tubos cerâmicos porosos fabricados predominantemente com alumina e produzidos pela técnica da colagem de barbotina e sinterizados a temperaturas próximas a 1450 graus Celsius, para seleção de uma temperatura. O meio micro poroso foi caracterizado pela técnica de porosimetria por intrusão de mercúrio, apresentando tamanho médio de poro de 0,5 'mü'm. Os tubos foram submetidos à impregnação com solução de citrato de zircônio (precursor) por capilaridade. Posteriormente, os tubos foram calcinados e tratados termicamente até 600 e 900 graus Celsius, com o objetivo de eliminar componentes orgânicos voláteis e transformar o precursor no óxido metálico. A impregnação foi realizada em diferentes proporções e os tubos microporosos foram testados na bancada de micro-filtração, onde foram variados parâmetros fluidodinâmicos do processo (Reynolds e pressão transmembrana) e analisada as propriedades físico-químicas do volume de permeado, através de medidas da concentração de carbono orgânico total (TOC), condutividade elétrica, pH e a caracterização da mistura (concentrado) através de microscopia óptica. O meio micro poroso impregnado foi caracterizado por microscopia eletrônica de varredura (MEV), para analisar a morfologia do material impregnado e sua composição qualitativa. Os resultados do fluxo de permeado foram analisados e observou-se que os melhores resultados quanto ao fluxo transmembrana foram obtidos para o tubo impregnado a 900 graus Celsius. O tubo impregnado a 600 graus Celsius apresentou melhor desempenho relativo à desemulsificação, por apresentar menores valores de TOC. Em relação ao processo de transferência de massa, o tubo impregnado 900 graus Celsius obteve maiores valores de Sherwood, portanto a temperatura após impregnação influenciou no transporte de massa durante o processo de separação. A retenção da fase óleo analisada através de medidas de TOC foi de até 99%. / The studied process used porous ceramic tubes manufactured predominantly with alumina and produced by the technique of the collage with barbotina and sintered to close temperatures for 1450 Celsius degrees, for selection of a temperature. The microporous enviroment was characterized by mercury porosimetry, presenting medium size of pore of 0,5 'mü'm. The tubes were submitted to the impregnation with solution of citrate of zirconium (precursory) by capillarity. Later on, the tubes were burned and thermally treated up to 600 and 900 Celsius degrees, with the objective of to eliminate volatile organic components and to transform the precursory in the metallic oxide. The impregnation was accomplished in different proportions and the microporous tubes were tested in apparatus of microfiltration process, where were varied fluid dynamics parameters of the process (Reynolds and transmembrane pressure) and analyzed the physical-chemical properties of the volume of permeated, through measures of the concentration of total organic carbon (TOC), electric conductivity, pH and the characterization of the mixture (concentrated) through optical microscopy. The enviroment impregnated microporous was characterized by scanning eletronic microscopy (SEM), to analyze the morphology of the impregnated material and its qualitative composition. The results of the flow of having permeated were analyzed and it was observed that the best results with relationship to the transmembrane flux were obtained for the tube impregnated for 900 Celsius degrees. The tube impregnated for 600 Celsius degrees presented better relative acting to the demulsifying, for presenting smaller values of TOC. In relation to the process of mass transfer, the impregnated tube 900 Celsius degrees obtained larger values of Sherwood, therefore the temperature after impregnation influenced in the mass transport during the separation process. The retention of the phase oil analyzed through measures of TOC was of up to 99%.

A tecnologia de evaporação por filme descendente pode ser empregada em diferentes aplicações como processos químicos, petroquímicos, dessalinização de água, ciclos de refrigeração por absorção, OTEC Ocean termal energy conversion primer, só para mencionar alguns. No entanto, esta tecnologia tem demandado númerosos estudos devido a que ainda não é totalmente bem entendida, inclusive certos fenômenos básicos como são os problemas de distribuição do líquido, comportamento da espessura do filme e, sua transferência simultânea de calor e massa, sendo sujeito a vários estudos tanto numéricos quanto experimentais. Este trabalho foi focado no estudo da transferência simultânea de calor e massa, espessura do filme a os problemas de distribuição na vaporização de filme de água sobre tubos. Para isto, foi construída uma bancada de teste experimental, disponível para mensurar as seguintes variáveis; (a) temperatura da superfície dos tubos evaporadores, (b) espessura do filme descendente, (c) vazões mássicas, (d) potência elétrica fornecida aos tubos evaporadores, e (e) registro fotográfico infravermelho. O presente trabalho foi estruturado em dois aspectos principais; (1) avaliação do coeficiente de transferência de calor e massa, e (2) medição da espessura do filme descendente. Para os dois casos foram analisados os mecanismos de transferência de calor: sensível e latente. Para o primeiro ponto foram calculados os coeficientes local e médio de transferência de calor. No último ponto, usou-se um mecanismo formado por um micrômetro de elevada precisão aliado a um sistema elétrico para mensurar a espessura do filme líquido, sendo comparada com a teoria de Nusselt. Encontrou-se que há uma forte dependência da transferência de calor e massa com a espessura do filme descendente para a região laminar de Reynolds ente 160 a 950, implicando uma diminuição da taxa de transferência de calor com o aumento do Reynolds, já que a espessura de filme impôs uma maior resistência térmica. Além disso, avaliou-se o sistema de medição da espessura do filme com 25% de divergência da teórica de Nusselt. / Falling film evaporation technology can be used in different applications such as water desalination, refrigeration and ar-conditioning absorption cycles, OTEC (ocean thermal energy conversion primer), petrochemical and chemical process industries. This technology still demands númerous studies due to the lack of a complete understanding, even some basic phenomena such as the liquid distribution problem, liquid film thickness behavior and the heat and mass transfer coefficients are subject of intense experimental and numerical studies. This work has analyzed experimentally the heat and mass transfer coefficient, falling film thickness and the distribution system in water vaporization over tubes. For that, it was built an experimental setup, which has been measured the following; (a) tube wall temperature, (b) falling film thickness, (c) mass flow rate, (d) electrical power supplied to the evaporator tube, (e) infrared images. The present work has been structured in two mean aspects; (1) heat and mass transfer coefficient evaluation, and 2) falling film thickness measurement. In both topics, the two heat transfer mechanisms were analyzed: sensible and latent heat transfer. For the first topic, it has been analyzed the local and the overall heat transfer. For the second part, the method used a novel mechanical configuration (leverage effect), which improves the micrometer reading with more precision to obtain the film thickness, which was compared with the Nusselt theory. The experimental data showed that there is a strong dependence between the heat and mass transfer coefficient with the film thickness in the laminar region (Reynolds between 160 e 950), implying a decreasing of the heat transfer rate when the Reynolds increased, due to that the film thickness imposes a greater thermal resistance. Moreover, the study found the film thickness with a divergence of 25 % when it was compared with the theoretical Nusselt film thickness.