Browsing by Author "Sousa, Nelson"
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- Caracterização energética e ambiental de recuperadores de calor para lareirasPublication . Nunes, Manuel; Sousa, Nelson; Santos, Carlos Miguel Andrade; Lamarão, António Hugo; Major, VirgílioO presente projecto nasceu da colaboração entre a Área Departamental de Engenharia Mecânica (ADEM) da Escola Superior de Tecnologia/Universidade do Algarve (EST/UAlg) e a empresa Vale Montanha, Serviços de Engenharia Lda, com o objectivo de caracterizar recuperadores de calor para lareiras e respectivos combustíveis.
- Caracterização energética e ambiental de recuperadores de calor para lareiras: manual de operações, resultadosPublication . Nunes, Manuel; Sousa, Nelson; Lamarão, António Hugo; Santos, Carlos Miguel Andrade; Broad, David; Stadler, Rudolf
- Crystal structures of the free and sterol-bound forms of beta-cinnamominPublication . Rodrigues, Maria Luisa; Archer, Margarida; Martel, Paulo; Miranda, Sandra; Thomaz, Mónica; Enguita, Francisco J.; Baptista, Ricardo P.; Melo, Eduardo P.; Sousa, Nelson; Cravador, A.; Carrondo, Maria A.The crystal structure of the elicitin h-cinnamomin (h-CIN) was determined in complex with ergosterol at 1.1 A° resolution. h-CIN/ergosterol complex crystallized in the monoclinic space group P21, with unit cell parameters of a =31.0, b =62.8, c =50.0 A° and b =93.4- and two molecules in the asymmetric unit. Ligand extraction with chloroform followed by crystallographic analysis yielded a 1.35 A° structure of h-CIN (P43212 space group) where the characteristic elicitin fold was kept. After incubation with cholesterol, a new complex structure was obtained, showing that the protein retains, after the extraction procedure, its ability to complex sterols. The necrotic effect of h-CIN on tobacco was also shown to remain unchanged. Theoretical docking studies of the triterpene lupeol to h-CIN provided an explanation for the apparent inability of h-CIN to bind this ligand, as observed experimentally. D 2005 Elsevier B.V. All rights reserved.
- Hydrodynamic model for a biomass grate fired systemPublication . Sousa, Nelson; Azevedo, João L.T.The present paper describes a hydrodynamic model for the solids motion in a grate fired combustion system. The overfed bed material is considered in a Lagrangian referential until the particles stop in a position over the bed or exit the domain. The solid material in the grate is then considered as an incompressible continuous media. The momentum balances are applied in an Eulerian referential to particle elements to calculate their velocity in the grate direction. For the conditions considered the calculated velocity of the elements increase always from the start of the grate towards the exit, so the motion in the vertical direction is always downward. This motion is calculated from continuity and the two components enable the definition of the solids flow within the bed. The application of the model for solids motion is shown to be representative of different situations that are analysed for a vibrating grate working with wood pellets. The distribution of solids in the bed is visually and computationally characterised for three situations: i) feeding particles above the bed over an inclined still grate, ii) vibrating an initial bed promoting the motion of particles and iii) vibrating the bed and feeding above the grate in order to achieve a continuous evolution. The comparison of the results show that the model provides a good representation of reality although it can be improved by adjusting model parameters. The model allows for the generation of solids flow patterns in the bed and is a base for the development of a model for grate fired combustion systems.
- Improvement on fuel characteristics of biomass and refused derived fuel with torrefactionPublication . Azpilicueta, Ander; Paudel, Pramod; Sousa, NelsonThe search for sustainable energy alternatives has been increasingly important, not only because the depletion of fossil fuels, but also due to the necessary reduction in the emission of greenhouse gases. The use of renewable energy has contributed to the mitigation of this problem, but this doesn’t always adapt to the requirements of energy demand. The energy of biomass, in particular by the combustion of vegetal biomass, is a form already in use and with broad application, from domestic heating equipment to thermoelectric power plants. An alternative energy source is the refuse derived fuels, RDF, which offer a double benefit, given they provide an energy resource and avoid the occupation of landfill space. However, the use of biomass or RDF has limitations, due to the fuel quality. As received, it presents low heating value, low adiabatic flame temperature and low density. The improvement of the properties of these fuels may be obtained by torrefaction. This is a low-temperature pyrolysis process, where the heating gradient, top temperature and process duration must be controlled. In this study, an experimental prototype was developed for torrefaction trials. During the torrefaction experiments the heating rate and maximum temperature were controlled, and were measured sample temperatures, mass decay and also the composition of the gases released. Later, the higher heating value, density and hydrophilicity of biomass and RDF samples, as received and with various stages of torrefaction, were measured, confirming the advantage of applying this thermal process in the improvement of the biomass and RDF fuel properties.
- In vitro and in vivo quantification of elicitin expression in Phytophthora cinnamomiPublication . Horta, Marília; Sousa, Nelson; Coelho, A. C.; Neves, D.; Cravador, A.The differential expression of four Phytophthora cinnamomi elicitin genes was analysed by Real Time RT-PCR. In in vitro cultures, the a-cinnamomin gene showed the highest level of expression, the b-cinnamomin gene (b-cin) was the most inducible, and the HAE transcripts were in low abundance. Transcription of all the elicitins was active during the active growth of the pathogen when infecting cork oak (Quercus suber) roots, and as host colonization progressed, the level of b-cin expression fell, while that of a-cin rose. In an antisense transgenic strain, the silencing of b-cin also negatively affected the expression of other elicitin genes in the cluster. The reduced in planta growth of the b-cin knock-out is related to the altered pattern of elicitin gene expression, supporting the idea that one of the functions of elicitins is related, directly or indirectly, with pathogenesis.
- Model simplifications on biomass particle combustionPublication . Sousa, Nelson; Azevedo, João L. T.Particle combustion modeling has been widely studied, although some considerations on the conversion processes are yet to be clarified. Thermal decomposition and final yield are addressed differentially in the literature, giving attention to the heating rate or to the peak temperature. It is assumed that the volatized gases are expelled immediately from the particle, neglecting homogeneous reactions, and in more simplified models that the particle is thermal and chemically uniform.This study presents an analysis of the modeling specifications required in the simulation of the conversion of a single biomass particle. This comprehensive approach shows the model requirements for more exact outcomes regarding the biomass particle size. The thermal model is discretized in concentric layers and may be used in cylindrical or parallelepiped geometry. Biomass decomposition is described by a competitive reaction model, justified by the analysis of the published experimental data. Temperature distribution is studied inside the particle as well as the gas flow, following a Darcy equation. Gas flow considers the diffusivity of oxygen to the interior of the particle and its reaction with the combustible gases and char.The validation of the numerical code is accomplished by the conversion of a 50 mm diameter wood trunk in a hot gas stream, measuring the mass loss and the temperature along the combustion process.Parametric tests were carried out to investigate the conversion of tars and oxidation of gases within the particle in typical combustion conditions. For biomass particles with a diameter more than 50 mm, the oxidation of combustible gases is considerable inside the particle, and therefore it is important to modulate the gas flow. Regarding the tar decomposition, the reactions involved are significant for particle diameters larger than 20 mm. In typical combustion conditions, small particles such as wood pellets, all properties can be considered uniform. The number of layers in the model can also be encountered considering the pyrolysis number.This study concludes that some process modulations are irrelevant for small particles. This is important when an expeditious method is required for the implementation in a multiparticle numerical code. (C) 2016 Elsevier Ltd. All rights reserved.
- Modeling biomass particle drying, devolatilization and combustion in a grate fired combustorPublication . Sousa, Nelson; Azevedo, João L.T.The paper presents the application of a numerical model to describe the evolution of a particle in a grate fired combustion system. Due to the particle dimensions, important temperature gradients exist inside the particles and reactions occur within the particles. A model using layers is used to describe the processes inside the particles. The biomass composition is expressed as fractions of moisture, unreacted biomass, char and ash. Biomass conversion is described by a competitive reaction model leading to the formation of light volatiles, tars and char. Tar is subject of secondary reactions inside the particles forming either light gases or char. Transport equations are solved for the gases within the particle including oxygen from the environment that reacts with gases or char. The model is applied to different heating rates leading to different amounts of tars and char in accordance with data from the literature. The model is also applied to simulate the combustion of a single trunk standing in a heated gas stream and comparisons are done for the temperature and mass loss.
- Modelo de escoamento e combustão de biomassa em grelhaPublication . Sousa, Nelson; Azevedo, João L. T.Este trabalho apresenta a formulação de um modelo de simulação de combustão de biomassa em grelha. O modelo inclui várias aproximações para cada um dos processos considerados, nomeadamente, o movimento dos sólidos já apresentado noutro artigo e o escoamento de gases através de meio granular, considerando a equação de Forchheimer. Para descrever a evolução das propriedades nos sólidos utiliza-se um modelo unidimensional para aproximar as partículas de combustível que é comparado com um modelo detalhado. Apresenta-se ainda o algoritmo em desenvolvimento para acoplar os diversos submodelos e a inclusão de balanços de energia e de massa com recção química.
- Paragens de autocarro inteligentes e inclusivasPublication . Rodrigues, Joao; Pires Rosa, Manuela; Viegas, Micael; Turner, Daniel; Veiga, Ricardo; Sousa, NelsonApresentam-se diferentes conceitos que determinam uma paragem inteligente e inclusiva, criando-se assim uma paragem de autocarros inovadora desde à geração da sua própria energia, tornando-a autossuficiente e sustentável, à integração na rede de autocarros para comunicação da quantidade de utilizadores à espera, até à criação de um ecrã interativo que se adapta às necessidades de qualquer utilizador através de uma inovadora framework desenvolvida no âmbito do projeto ACCES4ALL.