This work was undertaken to investigate the perceived problem of Thermal Discomfort in Malawi. One observable effect of thermal discomfort was the amount of foreign exchange that was spent to import air conditioning devices. The purpose of the work was to find out, and quantify the problem of thermal discomfort and outline its effects to the people and country. In order to investigate the problem of thermal discomfort in depth in a place where the necessary data hardly existed a lot of work had to be done. The work has been outlined in four stages of research, analysis and documentation and these are as follows 1 Literature Review The subject of Thermal Comfort appears to be location specific, but the general principles are universal. In that context it was necessary to read widely on both historical and contemporary current work. The problem of thermal comfort in general was being discussed as early as 1758 and still remains a big area of research and discussion today. A considerable number of literature that specifically relate to the problem of thermal comfort in the tropics has been reviewed. The problem of scales for thermal comfort measurement has been discussed in detail. It is still not possible to quote a scale that is satisfactory. However, the recent approach of Adaptive Thermal Comfort Model seems to be closer to the answer than the others 2 Analysing Existing Relevant Information And Data In Malawi In the course of this work it was found out that quite a large amount of useful data existed in Malawi. However, this data was not standardised. Most of this data had to be cleaned and updated. Some of the old formulae are quoted in their original formats in order not to confuse the referencing. The data that exists in Malawi has been recorded on three types of instruments; namely the Gunn Bellum Spherical Pyranometer, the Camp Bell Stoke Sunshine Recorder and the Eppley Pyranometer. Most of the data was recorded using the Camp Bell Stokes Sunshine Recorder. The data recorded on the Gunn Bellum Spherical Pyranometer had to be related to that from the Camp Bell Stokes Sunshine Recorder. The former gave data that was more accurate as was found out when a comparison was made with data recorded on an Eppley Pyranometer. A paper on this subject was accepted for publication in the Renewable Energy Journal of WREN. Wind speeds, air temperatures, and humidity have been analysed to investigate the severity of thermal discomfort relative to locations in Malawi. This has resulted in the identification of three climatic zones. A tool for testing Thermal Discomfort severity of a location by calculating number Degree Days (D. d) if the altitude (AL) has been developed; as D. d = -575.994 In AL + 4226.6 3 Field Measurements In order to investigate some of the issues that came out of this work, it was felt simpler to conduct field measurements. For example it would have been possible to build typical experimental houses, and extract performance data on Thermal Comfort from these buildings. However, this approach would have been very expensive. On the other hand it was felt that it was possible to find in the field that were representative of typical buildings and could be prepared and tested to extract performance data for use in the work. The latter approach was adopted and has proved to be more realistic than the former. 4 Field Surveys There were certain areas where the only way to find information was not to conduct experiments but to conduct field conduct surveys. This was done once to find the Preferred Bath Water Temperature (PBWT) and deduce the Neutral Temperature Range for Malawi. This yielded very useful results. The first published paper on this work was in this area (copy of this publication is attached). The second area of field survey was to survey traditional buildings in seven selected districts stretching from latitude 9°S to 17°S; covering a terrestrial distance of over 1000 km; over altitudes from 52 to over 1600 metres above mean sea level (m. a. m. s. l). This again yielded very useful environmental data that explained why traditional buildings have certain structural elements as functions of the environment and the need to achieve Thermal Comfort. A number of useful equations have been developed. From that sub routine of this research of PBWT survey an equation was developed that related the bath temperature (h) to the air temperature (tab) as; tb =0.3772 tab + 36.4401. Part of this work was also published separately in 2001. From this equation the Thermal Comfort Temperature Range for Malawi was deduced as 22-27°C. From the survey of the traditional buildings, a number of structural elements were that are functions of Thermal Comfort were identified as derivatives of the desire to have Thermal Comfort in the buildings. A regression equation that can give values of irradiation of the locality in MJm 1 Day' was developed. Lastly the results have been extracted as recommendations directed at policy makers, and both Architects and Engineers to use this data and the results in their design work. It is also further recommended that the national buildings regulations could be updated and revised to incorporate some of the findings. It is strongly believed that some of the findings will be incorporated to update the two main Laws that regulate Public Health in Malawi. These are the Public Health Act; Cap. 34.01, and the Health and Safety at Work Act, 1977; of the Malawi Laws. All data that has been cleaned up or measured specifically for this work has been organised and tabulated into ready-to-use tables and are included.

Orientador: Jorge Isaias Llagostera Beltran / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-04T03:16:10Z (GMT). No. of bitstreams: 1 GarridoGallego_Antonio_D.pdf: 11320974 bytes, checksum: d1702116bf8e0ebf5054039fdb95c556 (MD5) Previous issue date: 2004 / Resumo: O setor de papel e celulose é um grande consumidor de energia, na forma de eletricidade e vapor de processo. Sistemas de cogeração têm sido utilizados em fábricas de produção de celulose, em particular o processo Kraft, sendo responsável por aproximadamente 50 por cento do total de eletricidade consumida em empresas de produção de celulose e em empresas integradas. O sistema geralmente usado é composto de caldeira de biomassa, queimando cavacos, cascas e resíduos de madeira, e caldeira de recuperação Tomlinson, queimando licor negro, que contém substâncias orgânicas (lignina) dissolvidas provenientes das fibras de celulose. Como a produção de ambos combustíveis depende da produção de celulose, o aumento da geração de potência é limitado com a tecnologia atual. Vários centros de pesquisa propõem novas tecnologias como: Sistema Integrado de Gaseificação de Biomassa e Ciclo Combinado (BIG/CC) e Gaseificação de Licor Negro e Ciclo Combinado (BLG/CC) estas são tecnologias em desenvolvimento em países como Estados Unidos, Finlândia e Suécia. Estudos realizados indicam que a tecnologia de BLGCC tem potencial de aumentar significativamente a quantidade de eletricidade produzida a partir do licor negro. O Sistema de Gaseificação de Licor Negro e Ciclo Combinado(BLGCC) possui potencial de dobrar a energia elétrica a ser fomecida à indústria de celulose Kraft, além de melhores perspectivas ambientais e de custo se comparado com a caldeira de recuperação (caldeira Tomlinson) com turbina a vapor. Neste trabalho, diferentes configurações de Gaseificação de Licor Negro e Ciclo Combinado (BLGCC) foram propostas: gaseificador a baixa temperatura operando a 700ºC e ar a baixa pressão (0,2 MPa), gaseificador a alta temperatura operando a 950ºC e ar pressurizado a 2,5 MPa, gaseificador a alta temperatura operando a l000ºC e oxigênio pressurizado a 2,5 MPa, e gaseificador a alta temperatura operando a 1400ºC e oxigênio pressurizado a 2,5 MPa. Essas quatro configurações são comparadas ao sistema com Caldeira Tomlinson e turbina a vapor. Para avaliar as características termodinâmicas das diferentes configurações de ciclos, um programa computacional foi desenvolvido para modelar os equipamentos do ciclo de potência como gaseificador, turbina a gás, caldeira de recuperação, e turbina a vapor. Os resultados permitiram avaliar a influência dos vários parâmetros de desempenho do ciclo a partir do uso da primeira lei e da segunda lei da Termodinâmica. O modelo desenvolvido possibilitou identificar as irreversibilidades nos sistemas e sub-sistemas, as vantagens e na discussão sobre perspectivas para implantação da Gaseificação de Licor Negro e Ciclo Combinado (BLGCC) no setor de papel e celulose / Abstract: The pulp and paper industry is a large energy consumer, mainly in the forms of electricity and process steam. Cogeneration systems have long been applied in pulp mills, particularly in Kraft process, where they are responsible for roughly 50 per cent of the total of the electricity consumed by an pulp plant and integrated planto The most generally used system is composed of a biomass boiler, bmning bark, branches and waste wood and recovery Tomlison boiler, bmning black liquor which contains most of the organic substances (lignin) that must be dissolved in order to release the celulose fibbers. Since the production of both fuels depend on the pulp production, the increase in power generation is limited with the present technology. Many research centers have been proposing new technologies: the Biomass Integrated Gasifeir/Combined Cycle (BIG/CC) and Black Liquor Gasifer/ Combined Cycle (BLG/CC) are technologies in development in countries like United States, Finland and Sweden. Studies have indicated that BLG/CC technology have the potential for a significant increase in the amount of electricity produced ftom the b1ack liquor. B1ack Liquor Gasification with an integrated Combined Cycle (BLGCC) has the potential to double the amount of net electricity in a Kraft Pulp mill, with prospective environmental and capital cost benefits compared to a Recovery Boiler (Tomlison Boiler) with a steam turbine. In this work, a thermodynamic analysis of different proposals of B1ack Liquor Gasifer/ Combined Cycle (BLGCC) is made: low temperature gasifier, which operates at 700ºC and the air is blown at low pressure (0,2 MPa), high temperature gasifier operating at 950ºC and pressurized ar is blown at 2,5 MPa, high temperature gasifier operating at 1000°C and pressurized oxygen at 2,5 MPa and high temperature gasifier operating at 1400ºC and pressurized oxygen at 2,5 MPa. These four proposals are compared to a Tomlison Boiler with a steam turbine. To assess the thermodynamic characteristics of the different cycle configurations, a computer program was developed to model a power cycle equipped with a gasifier, a gas turbine, a heat recovery steam generator and a steam turbine. The resu1ts pennit to evaluate the influence of several parameters on the cycle performance according to the First and Second Laws of Thermodynamics. The developed modeling allowed the evaluated to identify the Ü'reversibilities in the systems and sub-systems, their advantages and to discuss the perspectives for the implementation ofB1ack Liquor Gasifer/ Combined Cycle (BLGCC) in the pulp and paper sector / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

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A new Trapped Vortex Combustor (TVC) concept has been studied for applications such as those in Unmanned Aerial Vehicles (UAVs) as it offers potential for superior flame stability and low pressure loss. Flame stability is ensured by a strong vortex in a physical cavity attached to the combustor wall, and low pressure loss is due to the absence of swirl. Earlier studies on a compact combustor concept showed that there are issues with ensuring stable combustion over a range of operating conditions. The present work focuses on experimental studies and numerical simulations to study the stability issues and performance optimization in this compact single-cavity TVC configuration. For performing numerical simulations, an accurate and yet computationally affordable Modified Eddy Dissipation Concept combustion model is built upon the KIVA-3V platform to account for turbulence-chemistry interactions. Detailed validation with a turbulent non-premixed CH4/H2/N2 flame from literature showed that the model is sufficiently accurate and the effect of various simulation strategies is assessed. Transient flame simulation capabilities are assessed by comparison with experimental data from an acoustically excited oscillatory H2-air diffusion flame reported in literature. Subsequent to successful validation of the model, studies on basic TVC flow oscillations are performed. Frequencies of flow oscillations are found to be independent of flow velocities and cavity length, but dependent on the cavity depth. Cavity injection and combustion individually affect the magnitude of flow oscillations but do not significantly alter the resonant frequencies. Reacting flow experiments and flow visualization studies in an existing experimental TVC rig with optical access and variable cavity L/D ratio show that TVC flame stability depends strongly on the cavity air velocity. A detailed set of numerical simulations also confirms this and helps to identify three basic modes of TVC flame stabilization. A clockwise cavity vortex stabilized flame is formed at low cavity air velocities relative to the mainstream, while a strong anticlockwise cavity vortex is formed at high cavity air velocities and low L/Ds. At intermediate conditions, the cavity vortex structure is found to be in a transition state which leads to large scale flame instabilities and flame blow-out. For solving the flame instability problem, a novel strategy of incorporating a flow guide vane is proposed to establish the advantageous anticlockwise vortex without the use of cavity air. Experimental results with the modified configuration are quite encouraging for TVC flame stability at laboratory conditions, while numerical results show good stability even at extreme operating conditions. Further design optimization studies are performed in a multi-parameter space using detailed simulations. From the results, a strategy of using inclined struts in the main flow path along with the flow guide vane seems most promising. This configuration is tested experimentally and results pertaining to pressure drop, pattern factor and flame stability are found to be satisfactory.

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