No description available.

In warm and humid climates, a primary source of building energy consumption is dehumidification of conditioned air supplied to the building spaces. The proposed system utilizes a selective membrane to remove water vapor from ambient air as opposed to a vapor compression cycle or a desiccant. This work provides an analysis of the membrane dehumidification system with a focus on the energy performance of the system. A system performance goal was set at the beginning for a given inlet and outlet ambient air condition and a total cooling load of one ton. The target COP of the combined sensible and latent cooling is 3.58 with a target value for only the latent system of 3.34. Two different simulations were developed including an initial simulation which uses a basic mass transfer model and a simpler condenser model. The initial model was used to develop the system, analyze operating parameters and provide initial performance results. The initial simulations indicate that the system requires two optimizations to meet the target performance: condenser pressure optimization and the use of multiple membrane segments operating at different pressures. The latent only COP including the optimizations was a maximum of 4.23. A second model was then developed which uses a more detailed mass transfer model and a more detailed condenser model based on the operating conditions. This simulation yielded a maximum latent only COP of 4.37 including the optimizations. The work also analyzes two different combined systems capable of providing both sensible and latent cooling. The first utilizes a conventional vapor compression cycle for sensible cooling and has a maximum COP of 3.93. The second uses multiple evaporative coolers in between multiple membrane dehumidification steps and was found to have a maximum COP of 3.73. Second law analysis of the systems was also conducted and found that the greatest reduction in latent system exergy loss can be obtained by improving the selectivity of the membrane. Apart from improving the membrane selectivity, the results show the greatest improvement can be found in improving the operation of the gas compression devices.

No description available.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 89-93). / viii, 93 leaves, bound ill. 29 cm

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references (leaves 87-94). Also available in electronic version.

Thesis (Ph. D.)--Oregon State University, 1998. / Typescript (photocopy). Includes bibliographical references (leaves 191-202). Also available on the World Wide Web.

Thesis (Ph. D.). UM #66-10,960. / Housner Earthquake Engineering Collection. Includes bibliographical references.

Thesis (MScEng)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

Orientadores: Teresa Massako Kakuta Ravagnani, Leila Peres / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-18T23:18:07Z (GMT). No. of bitstreams: 1 Araujo_PauloJardelPereira_D.pdf: 15740528 bytes, checksum: bd5969744efcacfde55b69c10f951f33 (MD5) Previous issue date: 2011 / Resumo: O biodiesel além de ser biodegradável e obtido de fontes renováveis, apresenta propriedades físico-químicas muito semelhantes ao diesel de petróleo, não necessitando de um novo motor para utilização do mesmo. A rota química mais comumente usada para obtenção do biodiesel é a transesterificação. Nesta, pela reação de um álcool com os triacilgliceróis (TAG) presentes principalmente em óleos vegetais e gordura animal, são produzidos o biodiesel e, como produto secundário, o glicerol em grandes quantidades. A presença deste glicerol é indesejada, pois além de diminuir a produtividade do biodiesel pelo equilíbrio termodinâmico estabelecido no processo, também aumenta seu custo pelo alto tempo de decantação e/ou uso de centrífugas para remover o glicerol do biodiesel. Devido a este inconveniente, o presente trabalho propõe rota alternativa para separação do glicerol, utilizando membrana de microfiltração (TiO2/Al2O3). Vários sistemas foram analisados, focando a separação do glicerol, o aumento do fluxo permeado e da conversão de TAG na catálise heterogênea. Inicialmente estudou-se a permeabilidade e seletividade dos reagentes e produtos obtidos na síntese do biodiesel com a membrana, através de experimentos binários. A partir destes resultados, estabeleceu-se uma nova configuração do sistema para então analisar estes fatores em misturas compostas pelos quatro constituintes do processo através de um planejamento fatorial. Os resultados apresentados geraram modelos que descrevem com 95% de confiabilidade o coeficiente de rejeição ao glicerol e o fluxo permeado frente aos fatores analisados (nível de emulsificação, razão molar óleo/etanol e conversão de TAG). Selecionou-se então, uma melhor faixa destes fatores que resultem em um máximo de rejeição ao glicerol com máximo fluxo permeado, obtendo um resultado bastante representativo do processo que apresentou um bom fluxo permeado (90,11kg/h.m2) com alta rejeição de glicerol (98,69%). Posteriormente propôs-se um estudo do processo simultâneo de reação e separação (leito fixo catalítico envolto em membrana), sendo selecionado para a reação de síntese um catalisador heterogêneo (SrO suportado em alumina), visando facilitar o processo de separação e reduzir significativamente o número de etapas de purificação dos produtos. Os resultados de conversão do TAG foram baixos, impossibilitando uma análise completa do sistema com esta configuração do ponto de vista de reação e separação concomitante / Abstract: In addition to being biodegradable and renewable, Biodiesel presents physicochemical properties very similar to those of petroleum-based diesel, so a new engine is not required for its use. The most commonly used chemical process for obtaining biodiesel is transesterification. In this process, through the reaction of an alcohol with triacylglycerols (TAG) present mainly in vegetable oils and animal fat, biodiesel is formed with large quantities of glycerol as a byproduct. The presence of glycerol is unwanted because besides reducing the productivity of biodiesel through the thermodynamic equilibrium established in the process, it also increases the cost due to the long time for settling and/or use of centrifuges for removing the glycerol from biodiesel. Taking into account this inconvenience, this paper proposes an alternative process for the separation of glycerol, using TiO2/Al2O3 membranes. Various systems were analyzed, focusing on the separation of glycerol, the increase of the permeate flux, and the increase in the TAG productivity in heterogeneous catalysis. At first we studied the permeability and selectivity of reagents and products obtained in the biodiesel synthesis with a membrane through binary experiments. From these results a new configuration of the system was established, with subsequent analysis of the new interaction in mixtures of the four components of the process (oil, Ethanol, Biodiesel, glycerol) using a factorial design as tool. Results presented in the factorial design generated models that describe with 95% reliability the glycerol rejection coefficient and the permeate flux compared to the analyzed factors (level of emulsification, molar ratio of oil/ethanol and TAG conversion). A best range of factors that result in a maximum glycerol rejection with maximum permeate flux was selected, obtaining a fairly representative result of the process showing a good permeate flux (90.11 kg/h.m2) with high glycerol rejection rate (98.69%). Subsequently, the study of the reaction and separation simultaneous process was proposed (fixed catalytic bed involved in a membrane) selecting an heterogeneous catalyst (SrO on alumina) to facilitate the separation process and significantly reduce the number of purification steps of products. Results of biodiesel conversion were low, preventing a full assessment of the system with this configuration considering simultaneous reaction and separation / Doutorado / Sistema de Processos Quimicos e Informatica / Doutor em Engenharia Química

The Centrifugal Membrane and Density Separation (CMDS) process is a novel type of membrane process that exploits the action of a centrifuge to generate process pressure for reverse osmosis and nanofiltration. The centrifuge could potentially enhance flux and alleviate fouling of the membrane as a result of the hydrodynamic environment of the centrifuge. All experimental work has been conducted on a prototype model of the CMDS process. The apparatus allows a membrane module to be fixed in space at a specified orientation, with respect to the rotation. This orientation in space is denoted by the terms “pitch, roll and yaw” (p,r,y). Experiments have been done using brine feed solutions at various concentrations to determine if the CMDS process minimizes the effects of concentration polarization. An example of this was illustrated with a 54% flux enhancement relative to a conventional membrane process using a 35000 ppm NaCl feed solution. Colloidal feed solutions were also used to examine how the CMDS process enhances flux in a fouling environment. These feed solutions include 21 g/L silica and 300 mg/L humic acid, with typical relative flux enhancement factors (κ) found to be 0.59 and 0.14, respectively. The final group of experiments examined the use of 50 g/L whey feed solutions with nanofiltration membranes. Results obtained here indicate that the centrifugal action enhanced the flux with an absolute flux enhancement factor (κ′) of 17.5 L/m² hr. These experiments have shown that a given orientation (90,270,0) best enhances the flux of a membrane with respect to colloidal fouling, while showing that another orientation (90,180,0) best reduces the effects of concentration polarization. Scanning electron microscopy (SEM) and an energy dispersive x-ray (EDX) detector have helped to examine the nature of the fouling layers and determine how well the layers adhere to the surface of the membrane. It was determined that in some cases, the fouling layer adhered better to the surface of a membrane used in the CMDS process. However, as the fluxes were typically higher in the dynamic process, it leads to the conclusion that the fouling layer on the CMDS membranes is more permeable. From the experimental work it has been concluded that the forces at work in the CMDS process create sufficient secondary flow instabilities to reduce the effects of fouling and concentration polarization on the membrane surface. The significance of this process with respect to industrial applications is considered, and the process is deemed feasible for such applications. / Graduate