Fluid dynamic modelling and simulation of circulating fluidized bed reactors: importance of the interface turbulence transfer

The main objective of this work is to analyze the importance of the gas-solid interface transfer of the kinetic energy of the turbulent motion on the accuracy of prediction of the fluid dynamic of Circulating Fluidized Bed (CFB) reactors. CFB reactors are used in a variety of industrial applications related to combustion, incineration and catalytic cracking. In this work a two-dimensional fluid dynamic model for gas-particle flow has been used to compute the porosity, the pressure, and the velocity fields of both phases in 2-D axisymmetrical cylindrical co-ordinates. The fluid dynamic model is based on the two fluid model approach in which both phases are considered to be continuous and fully interpenetrating. CFB processes are essentially turbulent. The model of effective stress on each phase is that of a Newtonian fluid, where the effective gas viscosity was calculated from the standard k-epsilon turbulence model and the transport coefficients of the particulate phase were calculated from the kinetic theory of granular flow (KTGF). This work shows that the turbulence transfer between the phases is very important for a better representation of the fluid dynamics of CFB reactors, especially for systems with internal recirculation and high gradients of particle concentration. Two systems with different characteristics were analyzed. The results were compared with experimental data available in the literature. The results were obtained by using a computer code developed by the authors. The finite volume method with collocated grid, the hybrid interpolation scheme, the false time step strategy and SIMPLEC (Semi-Implicit Method for Pressure Linked Equations - Consistent) algorithm were used to obtain the numerical solution.

Decentralized management of organic household wastes in the Kathmandu Valley using small-scale composting reactors

The sustainable management of municipal solid waste in the Kathmandu Valley has always been a challenging task. Solid waste generation has gone rapidly high in the Kathmandu Valley over the last decade due to booming population and rapid urbaniza-tion. Finding appropriate landfill sites for the disposal of solid wastes generated from the households of the Kathmandu Valley has always been a major problem for Nepalese government. 65 % of total generated wastes from the households of Nepal consist of organic materials. As large fractions of generated household wastes are organic in na-ture, composting can be considered as one of the best sustainable ways to recycle organ-ic wastes generated from the households of Nepal. Model Community Society Development (MCDS), a non-governmental organization of Nepal carried out its small-scale project in five households of the Kathmandu Valley by installing composting reactors. This thesis is based on this small-scale project and has used secondary data provided by MCDS Nepal for carrying out the study. Proper man-agement of organic wastes can be done at household levels through the use of compost-ing reactors. The end product compost can be used as soil conditioners for agricultural purposes such as organic farming, roof-top farming and gardening. The overall average organic waste generation in the Kathmandu Valley is found to be 0,23 kg/person/day and the total amount of organic household wastes generated in the Kathmandu Valley is around 210 Gg/yr. Produced composts from five composting reac-tors contain high amount of moistures but have sufficient amount of nutrients required for the fertility of land and plant growth. Installation of five composting reactors in five households have prevented 2,74 Mg of organic wastes going into the landfills, thus re-ducing 107 kg of methane emissions which is equivalent to 2,7 Mg of carbondioxide.

Application and development of numerical methods for the modelling of innovative gas cooled fission reactors

Innovative gas cooled reactors, such as the pebble bed reactor (PBR) and the gas cooled fast reactor (GFR) offer higher efficiency and new application areas for nuclear energy. Numerical methods were applied and developed to analyse the specific features of these reactor types with fully three dimensional calculation models. In the first part of this thesis, discrete element method (DEM) was used for a physically realistic modelling of the packing of fuel pebbles in PBR geometries and methods were developed for utilising the DEM results in subsequent reactor physics and thermal-hydraulics calculations. In the second part, the flow and heat transfer for a single gas cooled fuel rod of a GFR were investigated with computational fluid dynamics (CFD) methods. An in-house DEM implementation was validated and used for packing simulations, in which the effect of several parameters on the resulting average packing density was investigated. The restitution coefficient was found out to have the most significant effect. The results can be utilised in further work to obtain a pebble bed with a specific packing density. The packing structures of selected pebble beds were also analysed in detail and local variations in the packing density were observed, which should be taken into account especially in the reactor core thermal-hydraulic analyses. Two open source DEM codes were used to produce stochastic pebble bed configurations to add realism and improve the accuracy of criticality calculations performed with the Monte Carlo reactor physics code Serpent. Russian ASTRA criticality experiments were calculated. Pebble beds corresponding to the experimental specifications within measurement uncertainties were produced in DEM simulations and successfully exported into the subsequent reactor physics analysis. With the developed approach, two typical issues in Monte Carlo reactor physics calculations of pebble bed geometries were avoided. A novel method was developed and implemented as a MATLAB code to calculate porosities in the cells of a CFD calculation mesh constructed over a pebble bed obtained from DEM simulations. The code was further developed to distribute power and temperature data accurately between discrete based reactor physics and continuum based thermal-hydraulics models to enable coupled reactor core calculations. The developed method was also found useful for analysing sphere packings in general. CFD calculations were performed to investigate the pressure losses and heat transfer in three dimensional air cooled smooth and rib roughened rod geometries, housed inside a hexagonal flow channel representing a sub-channel of a single fuel rod of a GFR. The CFD geometry represented the test section of the L-STAR experimental facility at Karlsruhe Institute of Technology and the calculation results were compared to the corresponding experimental results. Knowledge was gained of the adequacy of various turbulence models and of the modelling requirements and issues related to the specific application. The obtained pressure loss results were in a relatively good agreement with the experimental data. Heat transfer in the smooth rod geometry was somewhat under predicted, which can partly be explained by unaccounted heat losses and uncertainties. In the rib roughened geometry heat transfer was severely under predicted by the used realisable k − epsilon turbulence model. An additional calculation with a v2 − f turbulence model showed significant improvement in the heat transfer results, which is most likely due to the better performance of the model in separated flow problems. Further investigations are suggested before using CFD to make conclusions of the heat transfer performance of rib roughened GFR fuel rod geometries. It is suggested that the viewpoints of numerical modelling are included in the planning of experiments to ease the challenging model construction and simulations and to avoid introducing additional sources of uncertainties. To facilitate the use of advanced calculation approaches, multi-physical aspects in experiments should also be considered and documented in a reasonable detail.

FABRICAÇÃO DE QUEIJO PETIT SUISSE POR ULTRAFILTRAÇÃO DE LEITE COAGULADO: EFEITO DO TRATAMENTO TÉRMICO DO LEITE NO DESEMPENHO DA MEMBRANA

Leite desnatado coagulado foi ultrafiltrado em membrana tubular cerâmica de 0,08mim com objetivo de avaliar a influência de diferentes tratamentos térmicos do leite sobre o fluxo, o coeficiente de retenção protéico, o coeficiente de retenção de cálcio e o rendimento protéico no processamento de queijo petit suisse. Os tratamentos térmicos utilizados foram 85°C/30min e 72°C/15seg. O efeito do tratamento térmico não foi significativo (p<0,05) na retenção de proteína e cálcio, e no rendimento protéico. Houve aumento significativo do fluxo de permeado durante a ultrafiltração do leite coagulado quando o leite foi submetido ao tratamento térmico menos intenso (72°C/15seg). O tratamento térmico mais intenso pode ter resultado em uma maior atração entre as micelas de caseína e, entre micelas e a superfície da membrana, aumentando a adsorção das proteínas à superfície da membrana, conseqüentemente reduzindo o fluxo de permeado. Também pode ter ocorrido entupimento dos poros da membrana por alfa-lactoalbumina e beta-lactoglobulina desnaturadas, agravando o "fouling".

Conservação de água de coco verde por filtração com membrana

A água de coco verde no interior do fruto é estéril, porém, durante a sua extração e envase, podem ocorrer contaminações microbiológicas e alterações bioquímicas, com perda de qualidade do produto e redução do seu valor comercial. Este trabalho teve como objetivo estudar a conservação da água de coco verde através da microfiltração e da ultrafiltração. Para a microfiltração, foram utilizadas membranas com tamanho de poro de 0,1µm e, para a ultrafiltração, membranas com peso molecular de corte de 100, 50 e 20kDa. A eficiência do processo foi avaliada através do fluxo permeado e da caracterização microbiológica, físico-química, bioquímica e sensorial dos produtos obtidos. Não foi observada variação significativa nos parâmetros físico-químicos analisados. A água de coco filtrada apresentou maior luminosidade e menor turbidez. O teor de proteína na água de coco permeada, medida indireta da concentração de enzimas, foi proporcional à porosidade da membrana. A água de coco ultrafiltrada foi envasada em frascos de plástico e armazenada sob refrigeração por 28 dias, sendo avaliada semanalmente. Durante o período de armazenamento, as amostras avaliadas mantiveram-se com a coloração clara e adequadas ao consumo, atendendo aos padrões exigidos pela legislação. O produto ultrafiltrado obteve boa aceitabilidade sensorial, tendo sido aprovado por 94% dos consumidores.

Fisiologia do transporte de fluidos e solutos atraves da membrana peritoneal

Nesta revisão, são explicados os fenômenos envolvidos nas trocas de fluidos e solutos através da membrana peritoneal, tanto na situação fisiológica quanto no contexto da diálise peritoneal. Para tanto, são utilizados os modelos matemáticos desenvolvidos para estudo do transporte pela membrana, tais como o "Modelo de Poros" e o "Modelo Distributivo". Os ganhos científicos com as pesquisas nesse campo são contemplados e as áreas que merecem pesquisas adicionais também são citadas. Assim, o estado atual do conhecimento fisiológico a respeito dessa modalidade de terapia renal substitutiva, no que se refere aos eventos relacionados à membrana peritoneal, encontra-se sintetizado nesse manuscrito.

Impacto de la orientación proporcionada a padres de niños con enfermedad de membrana hialina : Monterrey, Nuevo León, 1990.

Tesis (Maestría en Enfermería con Especialidad en Salud Comunitaria) UANL

Efecto in vitro de diferentes dosis de Mycobacterium tuberculosis en la expresión de IL-1 de membrana y moléculas HLA-DR en macrófagos humanos

Tesis (Maestría en Ciencias con Especialidad en Inmunología) UANL

Cambios morfológicos en la membrana plasmática del espermatozoide inducidos in vivo por secreciones de endometrio y cérvix humanos

Tesis (Maestría en Ciencias con Especialidad en Biología de la Reproducción) UANL

Morbimortalidad neonatal por enfermedad de membrana hialina en el Hospital Infantil de Monterrey Juan Angel González Escamilla

Tesis (Especialidad en Pediatría)U.A.N.L.

Regeneración tisular guiada en el tratamiento de recesiones gingivales vestibulares utilizando una membrana no reabsorbible de n-PTFE de alta densidad por Adriana Mayela Herrera Rodríguez

Tesis (Maestría en Ciencias Odontológicas) U.A.N.L.

Validación de un método basado en filtración por membrana para la detección de patógenos bacterianos en melón, Cucumis melo (L,. 1753) y chile jalapeño, Capsicum annuum (L., 1753).

Tesis (Maestro en Ciencias con acentuación en Microbiología) UANL, 2014.

Cálculo de la permeabilidad de un modelo de membrana celular hacia dos agentes antifímicos.

Tesis (Maestría en Ciencias con orientación en Farmacia) UANL, 2014.

CFD Simulation of Multiphase Reactors

Regional Research Laboratory

Comparative effectiveness of solar disinfection using small-scale batch reactors with reflective, absorptive and transmissive rear surfaces

This study investigated the enhancement of solar disinfection using custom-made batch reactors with reflective (foil-backed) or absorptive (black-backed) rear surfaces, under a range of weather conditions in India. Plate counts of Escherichia coli ATCC11775 were made under aerobic conditions and under conditions where reactive oxygen species (ROS) were neutralised, i.e. in growth medium supplemented with 0.05% w/v sodium pyruvate plus incubation under anaerobic conditions. While the addition of either an absorptive or a reflective backing enhanced reactor performance under strong sunlight, the reflective reactor was the only system to show consistent enhancement under low sunlight, where the process was slowest. Counts performed under ROS-neutralised conditions were slightly higher than those in air, indicating that a fraction of the cells become sub-lethally injured during exposure to sunlight to the extent that they were unable to grow aerobically. However, the influence of this phenomenon on the dynamics of inactivation was relatively small