published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

This study is set out to confirm the phenomenon commented on by Hassan Fathy (1986) that the temperature difference between courtyards has a role in the promotion of convective cooling through transitional spaces in a multiple-courtyards building in semi and regions. The transitional spaces situated between courtyards are identified with specific titles such as Takhtabüsh in the Egypt; and Tablinum in a Roman Domus. However, despite the historic significance of these spaces, most studies have mainly focused on the climatic performance of buildings with a single courtyard. Empirical and numerical study has not been conducted on the nature of this phenomenon. In order to confirm this conjecture, this thesis is set out to conduct fieldwork and theoretical investigation. This thesis is a single case study of the Casa de Pilatos in Seville, Spain. The case study is used to develop a methodology for analysis of multiple-courtyard phenomenon. Field measurement and mathematical models are used to determine the drivers for yard-to-yard airflows. The fieldwork uses data logging equipment to record dry bulb temperatures, relative humidity, and air velocity through the transitional spaces. The amount of cooling attributed to yard-to-yard flows and implication to cooling requirements in a contemporary environment are evaluated. Adaptive criteria of Nicol and Humphrey (2001)'and Brager and de Dear (2001) are used to predict the thermal comfort of subjects. The drivers are determined through analysis of buoyancy `stack' forces and local wind regime. The building mass introduces three hours delay with up to 2.5kW or 36W/m2 variation in heat balance in the transitional spaces by 15: 00h. The calculated volume flow rates through the transitional space are 5.3m3/s (equivalent to 5kW or 71 W/m2 in convective cooling) at 15: 00h. The DBT in the gardens are up to 11 k below the WBT. It is shown that multiple-courtyards phenomenon is a robust strategy accommodating a large variation in temperatures. The study confirms that temperature difference is the driver for convective flows through transitional spaces. This study presents an opportunity to investigate the applicability of this concept in the contemporary context. Findings of this study have direct application in the reduction of cooling energy in widely used courtyard concept in semi and regions.

Thesis (M.Sc.(Engineering))--University of the Witwatersrand, Faculty of Engineering, 1999

Introdução: Destaca-se a importância dos organismos do gênero Legionella como agentes causadores de doenças do aparelho respiratório como a legionelose ou doença do Legionário, e ainda de um controle na manutenção adequada de sistemas de ar condicionado, uma vez que estes foram identificados como ambientes favoráveis à proliferação desses microrganismos. Objetivo: Devido à importância de bactérias do gênero Legionella como agentes causadores de doenças, e um crescente número de casos de legionelose relacionados à permanência em ambientes fechados, este estudo teve como objetivo determinar a presença de Legionella em águas de bandejas de sistemas de ar condicionado. Métodos: Foram realizadas análises de amostras de água provenientes de bandejas de ar condicionado de dois hospitais, uma instituição de ensino superior e um centro comercial, totalizando 41 amostras. Volumes de 1L das amostras coletadas foram concentrados em membrana, seguida de tratamento ácido. Alíquotas das amostras tratadas e não tratadas com ácido, foram então inoculadas em meio Agar BCYE-, com e sem adição de antibióticos. As cepas isoladas foram submetidas a teste sorológico para identificação. Resultados: Das amostras analisadas, 4 (9,5%) apresentaram resultado positivo para Legionella sp.; uma no centro comercial e três em um dos hospitais estudados. Os isolados foram submetidos a teste sorológico, sendo um identificado como Legionella pneumophila sorogrupo 1 e três como seis prováveis espécies:L. longbeachae, L. bozemanni, L. dumoffi, L. gormanii, L. jordanis, L. micdadei, L. anisa . Conclusão: Os resultados deste estudo comprovam a presença de Legionella sp. nos sistemas de ar condicionado pesquisados, sendo observada maior freqüência dos isolados em amostras analisadas oriundas dos hospitais.Os resultados demonstraram a importância e a necessidade de planos de monitoramento em sistemas de 7 ar condicionado como medida preventiva à colonização por organismos patogênicos nesses sistemas e dessa forma proteger a saúde dos ocupantes e usuários de ambientes climatizados artificialmente. / Introduction: It highlights the importance of organisms genus Legionella as responsible for diseases of the respiratory system such as legionellosis or Legionnaires´disease, and a control on proper maintenance of air conditioning systems, as these were identified as favorable environment for the proliferation of these microorganisms. Objective: Due to the importance of Legionella as causative agents of disease and a growing number of cases of legionellosis related to stay indoors, this study aimed to determine the presence of Legionella in water samples from air-conditioning systems. Methods: We performed analysis of samples of water from trays of airconditioning systems in two hospitals, a university and a trade center, totalizing 41 samples. One liter volumes of water samples were concentrated on membrane, followed by acid treatment. Aliquots of the sample treated and not treated with acid, were inoculated on BCYE- agar medium, with and without added antibiotics. The strains were subjected to serological identification. Results: Out of the samples analyzed, 4 (9.5%) were positive for Legionella sp.; one in a trade center and three in one of the hospitals. Isolates were submitted to serological testing, one identified as Legionella pneumophila serogroup 1 and three as probable six species: L. longbeachae, L. bozemanni, L. dumoffi, L. gormanii, L. jordan, L. micdadei, L. anise. Conclusion: The results confirm the presence of Legionella sp. in air conditioning systems studied. It was observed a higher frequency in isolates from hospitals. The results demonstrated the importance and necessity of monitoring plans in air-conditioning systems as a preventive measure to colonization by pathogens in these systems and protect the health of occupants and users of these buildings.

Quando água quente é introduzida em um tanque de termoacumulação vertical, durante o ciclo de descarga, ocorre uma mistura parcial dessa água com a água fria armazenada. A intensidade dessa mistura depende de parâmetros geométricos do difusor de entrada e da dinâmica do escoamento no início do processo. Inúmeros estudos têm sido desenvolvidos no intuito de se projetar adequadamente o difusor de entrada, de forma a minimizar essa mistura, que corresponde a uma perda de capacidade do tanque. Porém, há uma outra forma de perda de capacidade do tanque, devida aos efeitos viscosos do escoamento. Quando um fluido escoa dentro de um tubo, há a formação de uma camada limite hidrodinâmica, devida à viscosidade do mesmo. Na região do comprimento hidrodinâmico de entrada, em cada seção transversal do tubo e dentro da camada limite, os efeitos viscosos geram um gradiente (radial) de velocidade. Fora dessa camada (no núcleo), esses efeitos são desprezíveis e o fluido escoa com velocidade uniforme. Porém, ao longo desse comprimento, o movimento do fluido no núcleo é acelerado. O escoamento em um tanque vertical de termoacumulação ocorre na região do comprimento hidrodinâmico de entrada. Considerando que não haja mistura das massas de água quando se inicia a introdução da água quente, irá se forma uma superfície de contato entre as mesmas. Essa superfície, por possuir velocidade no núcleo maior que a velocidade média de descarga, atingirá o difusor de saída mais rapidamente. Assim, para que seja garantida descarga de água na temperatura da água armazenada durante todo o ciclo de descarga, a altura do tanque deverá ser maior que a altura determinada utilizando-se a velocidade média do escoamento, sem considerar os efeitos viscosos (modelo ideal). A diferença entre essas alturas constitui, por si só, uma perda de capacidade do tanque. O estudo dos efeitos do escoamento viscoso no desempenho do tanque mostra que dois números adimensionais surgem naturalmente: o número de Reynolds relativo ao diâmetro, ReØ, necessário para se determinar o comprimento hidrodinâmico de entrada, e o número f, que relaciona a posição da superfície de contato das massas de água com o comprimento hidrodinâmico de entrada. Os resultados mostram que a perda devida aos efeitos do escoamento viscoso pode não ser desprezível e que a escolha do diâmetro do tanque é de fundamental importância para minimizar esses efeitos. Também, a análise qualitativa do escoamento sugere que as perdas de capacidade do tanque nos ciclos de descarga e carga não são iguais, pois a diferença de densidade das massas de água age de maneira diversa em cada caso. / When warm water is introduced into a vertical thermal storage tank, during the discharging cycle, a partial mixing between it and the cold water stored will occur. The extension of that mixing depends upon diffuser geometric parameters and the dynamics of the flow at the beginning of the process. So many works have been developed, trying to find the better diffuser design so that undesired mixing can be minimized. The mixing is accounted as a tank loss of capacity. But, there is another kind of tank loss of capacity due to viscous effects of the flow. When a fluid flows inside a tube, it forms a boundary layer due to fluid viscosity. At the hydrodynamic entry length region, in each cross section of the tube and inside the boundary layer, the viscous effects create a (radial) velocity gradient. Outside of the boundary layer (inside the core), the viscous effects are negligible and the fluid flows with a uniform velocity. However, along the entry length that velocity gets higher at each section. In a vertical thermal storage tank, water flows at the hydrodynamic entry length region. Considering that no mixing occurs at the beginning of the warm water introduction at the tank top, it will form a contact surface between the warm water and the cold one already in the tank. That contact surface has the velocity inside the core higher than the mean discharging flow velocity and it will reach the outlet diffuser at the tank bottom more quickly. Then, the tank height must be greater than that determined using the mean velocity flow alone without any viscous effect (ideal model), so that the discharging flow has the same stored water temperature during all the discharging cycle. The difference between those heights constitutes itself a tank loss of capacity. The study of the viscous effects on the tank performance shows that two non-dimensional parameters appear naturally: the Reynolds number related to the tank diameter, ReØ, used for determining the hydrodynamic entry length, and the f number that relates the position of the contact surface of the water masses to the hydrodynamic entry length. Results show that the loss due to viscous effects, may not be negligible and the choice of the tank diameter is essential to minimizes those effects. Also, there is a difference between tank losses of capacity during the charging and discharging cycles, since the effect of the density difference between the warm and cold water works in a different way in each one of those two situations.

Thesis. 1977. B.S.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / B.S.

1. A Diffusion-Absorption-Refrigeration (DAR) system for air conditioning (DAAC) is developed. It is directly driven by heat, uses a bubble pump to replace the mechanical pump, uses three-component working fluid, and operates under the same system pressure level. Hence, it is quiet, long lasting and environmental friendly. To investigate the practicality of using the DAAC system for air conditioning, the thermodynamic model is derived first, and then an experimental prototype is built for validation. From the experimental results under various operating conditions, it is found that the bubble pump is the key component that dominates the system performance, so it should be designed carefully with respect to the designed cooling capacity and operating condition. Meanwhile, the system also shows good performance under the ambient temperature disturbance. / 2. A novel absorption air conditioning system based on solar energy and energy storage is proposed. This system uses Lithium-Bromide water solution as refrigerant and is powered by solar energy. Moreover, a new energy storage technique is also proposed to transform and store the solar energy in the form of chemical potential difference of the working fluid. Thus, the system flexibility and energy usage efficiency are improved. To validate the system design, the thermodynamic models for the air conditioning system are developed. Then by computer simulation, the system characteristics and performance are achieved under the proposed operation strategy. It is found that the proposed air conditioning system is energy efficient with high energy storage density and shows great potential in the future. / 3. A complex absorption air conditioning system is proposed by using an advanced energy storage technology called Variable Mass Energy Transformation and Storage (VMETS). This system is based on both compression and absorption refrigeration, uses water-LiBr or ammonia-water as working fluid, and can shift the off-peak electric energy for effective air conditioning. The key of the technology is to regulate the chemical potential by controlling the refrigerant mass fraction in the working fluid with respect to time. By using a solution storage tank and a refrigerant storage tank, the energy transformation and storage can be carried out at the desirable time to provide the low cost air conditioning efficiently. Based on the derived system models, the system characteristics and performance under two system strategies, full-storage and partial-storage strategies, are investigated in details. By computer simulation, it is found that the VMETS technology has high energy conversion efficiency. / 4. A novel thermoelectric air conditioning system is developed. Different from the conventional air conditioning systems, this system is based on the thermoelectric effect and semiconductor technology. It consists of thermoelectric (TE) modules, a power supply, a water circulation system and a computer control system. The thermoelectric system has three functions: heating, cooling, and power generation. To improve the efficiency, it uses the so-called symbiotic generation to optimize the energy usage. In order to investigate the system performance, a theoretical model is developed. By computer simulation, it is found that the system can achieve acceptable performance for cooling and heating under a typical condition. A small experimental model is also built, and the testing result confirms the simulation results. / 5. An intelligent thermal comfort controller is developed to improve the comfort level for air conditioning system. This controller adopts Predicted Mean Vote (PMV) as the control objective rather than the conventional temperature control, and takes six variables into consideration. Meanwhile, a kind of direct neural network (NN) control algorithm is designed by combining a proposed energy saving strategy. By computer simulation, it is found that this controller can achieve high comfort level and energy saving for the conventional Heating, Ventilation and Air-Conditioning (HVAC) systems. Moreover, a compact thermal comfort controller is also developed for the DAAC system. / 6. A cost-effective Fault Detection and Diagnosis (FDD) method is proposed for HVAC system to maintain the energy saving and thermal comfort. It combines the model-based method and the neural network classifier, so it is called Model-Based Fault Detection and Diagnosis method (MBFDD). To validate the performance, the MBFDD is applied to a HVAC system by simulation. Based on the derived system models, the output variables sensitive to the faults can be selected. After pre-processing the acquired data under normal and faulty conditions, the MBFDD based on neural network classifier can be trained first, and then used for on-line monitoring and FDD. The simulation results show that this method is efficient for the HVAC system, and is able to enhance the comfort level and energy saving as well as the system health and safety. / Air conditioning system plays an important role in modern living. Every year millions of air conditioning systems are made and sold. Consequently, even small technological improvement may add up to significant energy saving. Currently, most of the air conditioning systems are based on the compression refrigeration technology, which uses electricity as power and chlorofluorocarbon (CFCs) as refrigerant. Facing the ever-increasing energy and environmental crisis in the world, developing energy-efficient and environmental-friendly air conditioning system is of great importance. / This thesis presents the research on developing air conditioning systems by employing several kinds of technologies: (1) absorption refrigeration technology; (2) bubble pump technology; (3) energy storage technology; (4) renewable energy technology; (5) thermoelectric refrigeration technology; (6) thermal comfort control technology; and (7) fault detection and diagnosis technology. Based on these technologies, this thesis addresses the following topics: / Liang Jian. / "June 2006." / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6700. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 175-194). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references. / The electric utilities in the United States are faced with continued rapid growth in electrical demand. The traditional response to growth in demand has been the expansion of generating capacity. However, economic, environmental, and scheduling constraints will combine to make adequate expansion difficult, if not impossible, in the 1980's. This thesis examines load management as an alternative to the proliferation of generating plants. This path is illustrated by the development of an air conditioning system designed to displace power consumption in commercial buildings from peak to off-peak periods. The urban domestic utilities face their peak loads during the summer air conditioning season. The displacement of daytime air conditioning will therefore reduce the utilities' annual peak load. The proposed air conditioning system uses off-peak power, and conventional mechanical equipment, to recharge a thermal energy storage system. The thermal storage medium is a sodium sulfate-based phase change material (PCM) enclosed in small thin bags. These bags are distributed throughout the ceiling plane of the building; supported by special ceiling tiles. At night, the PCM is charged by chilling the plenum space; during the day, the PCM, in direct contact with the occupied space, removes sensible heat gains by melting. System components are described by their programmatic requirements. The performance of the proposed off-peak cooling system was simulated under a variety of conditions involving interior zone commercial office spaces. It was found, using thermal comfort criteria, that the system performed well using a PCM set point temperature of 67°F. Under the operating parameters established, the simulations indicated that the energy flow rates were adequate for successful system performance. Finally, it was determined that the system can provide immediate savings through customer demand leveling and increased chiller efficiency. However, the major potential for savings will relate to anticipated utility incentives for off-peak electrical use. / Charles C. Benton / M.Arch.

Introdução: Destaca-se a importância dos organismos do gênero Legionella como agentes causadores de doenças do aparelho respiratório como a legionelose ou doença do Legionário, e ainda de um controle na manutenção adequada de sistemas de ar condicionado, uma vez que estes foram identificados como ambientes favoráveis à proliferação desses microrganismos. Objetivo: Devido à importância de bactérias do gênero Legionella como agentes causadores de doenças, e um crescente número de casos de legionelose relacionados à permanência em ambientes fechados, este estudo teve como objetivo determinar a presença de Legionella em águas de bandejas de sistemas de ar condicionado. Métodos: Foram realizadas análises de amostras de água provenientes de bandejas de ar condicionado de dois hospitais, uma instituição de ensino superior e um centro comercial, totalizando 41 amostras. Volumes de 1L das amostras coletadas foram concentrados em membrana, seguida de tratamento ácido. Alíquotas das amostras tratadas e não tratadas com ácido, foram então inoculadas em meio Agar BCYE-, com e sem adição de antibióticos. As cepas isoladas foram submetidas a teste sorológico para identificação. Resultados: Das amostras analisadas, 4 (9,5%) apresentaram resultado positivo para Legionella sp.; uma no centro comercial e três em um dos hospitais estudados. Os isolados foram submetidos a teste sorológico, sendo um identificado como Legionella pneumophila sorogrupo 1 e três como seis prováveis espécies:L. longbeachae, L. bozemanni, L. dumoffi, L. gormanii, L. jordanis, L. micdadei, L. anisa . Conclusão: Os resultados deste estudo comprovam a presença de Legionella sp. nos sistemas de ar condicionado pesquisados, sendo observada maior freqüência dos isolados em amostras analisadas oriundas dos hospitais.Os resultados demonstraram a importância e a necessidade de planos de monitoramento em sistemas de 7 ar condicionado como medida preventiva à colonização por organismos patogênicos nesses sistemas e dessa forma proteger a saúde dos ocupantes e usuários de ambientes climatizados artificialmente. / Introduction: It highlights the importance of organisms genus Legionella as responsible for diseases of the respiratory system such as legionellosis or Legionnaires´disease, and a control on proper maintenance of air conditioning systems, as these were identified as favorable environment for the proliferation of these microorganisms. Objective: Due to the importance of Legionella as causative agents of disease and a growing number of cases of legionellosis related to stay indoors, this study aimed to determine the presence of Legionella in water samples from air-conditioning systems. Methods: We performed analysis of samples of water from trays of airconditioning systems in two hospitals, a university and a trade center, totalizing 41 samples. One liter volumes of water samples were concentrated on membrane, followed by acid treatment. Aliquots of the sample treated and not treated with acid, were inoculated on BCYE- agar medium, with and without added antibiotics. The strains were subjected to serological identification. Results: Out of the samples analyzed, 4 (9.5%) were positive for Legionella sp.; one in a trade center and three in one of the hospitals. Isolates were submitted to serological testing, one identified as Legionella pneumophila serogroup 1 and three as probable six species: L. longbeachae, L. bozemanni, L. dumoffi, L. gormanii, L. jordan, L. micdadei, L. anise. Conclusion: The results confirm the presence of Legionella sp. in air conditioning systems studied. It was observed a higher frequency in isolates from hospitals. The results demonstrated the importance and necessity of monitoring plans in air-conditioning systems as a preventive measure to colonization by pathogens in these systems and protect the health of occupants and users of these buildings.

This thesis work is aiming to define and validate a simplified building model, which can be used to improve building energy efficiency. The building model is defined with two majors concerns : The building model is dynamic, called lumped model, i.e. built on a set of resistances and capacities, and solved by differential equations. The dynamic lumped model is associated to a building ventilation model,built on a set of resistances and generators. The building simplified dynamic model is validated by comparing its results to those provided by a detailed dynamic model, built on wall response factors. The building ventilation model is defined in order to deal with natural air movement as well as mechanical devices (fans and ducts). The model can yield infiltration and exfiltration. It is able to estimate the indoor air quality level, the thermal comfort when free-cooling is performed, and the building energy balance. The building lumped model is connected to equipments including heating and cooling terminal units as well as water pipes, air ducts, heating and cooling plants. The equipments models are simplified and built on parameters deduced from correlations drawn on more detailed equipment models. The connection between the building model and its system, through control laws, can provide an estimation of the system ability to maintain indoor comfort. Primary energy consumptions, carbon dioxide emissions and energy costs can also be evaluated. The complete model can be used to provide results regarding the influence of control strategies on comfort and energy consumption, and to estimate different equipments performances. All the models are developed through EES solver (Klein).