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State-of-the-art solar-thermal flat-plate collectors suffer from a limited potential to decrease production costs for the necessary higher economic benefit of so-lar-thermal systems. Costly metallic materials and corresponding manufactur-ing processes prevent further cost reductions. For that issues, plastic materials can offer a promising approach. The main hurdle for the use of cost-effective plastics lies in the high thermal loads on the collector components — absorber and insulation — which were identified in a field-testing. The necessary overheating protection approaches to lower these thermal loads were investigated in a literature review. A large number of relevant concepts was evaluated related to achievable temperature reduction, influence on solar yield, additional costs and intrinsic safety. There-fore, a mathematical model was developed to determine the solar-thermal col-lector´s behaviour in a solar-thermal system for hot water and space heating. This way, the most promising overheating concepts were simulated and ana-lysed with regard to component temperatures and system performance. Omitting the selective absorber coating and reducing the backside insulation was found to be the most suitable solution for component materials with limited temperature resistance like polypropylene. In the second part of the research, collector design concepts were developed on the basis of the characteristics of plastic material processing. The identified unit costs showed savings of more than 50 % in comparison to stateof- the-art collectors. The analysis regarding temperature loads and annual solar yield by simulation proved the performance of the concepts. The collector costs and the simulation results were used to define the total costs of the solar-thermal sys-tems and to evaluate the economic benefits by means of the collector con-cepts. The benefits were similar to state-of-the-art set-ups. Thus, further adjustments at system level are necessary to lower the total costs. Therefore, the system set-up has to be harmonised with the collector requirements and investigated in detail.

My dissertation focuses on the articulation of the concepts of precarity —i.e., temporary, affective, creative, immaterial and insecure labor—and community in an overheating system. My site of inquiry is homelessness broadly, but more specifically the labor of panhandling and the identity of “the panhandler.” I recognize that primary theorizations of precarity have located it as a problem of labor and economy. Others have looked at it from the sociological domain. My work looks at precarity as diffuse across social, political, and communal systems, but primarily as an effect of the problem of overheating as it manifests at varying levels of scale. Narrowing the global vision of such instability and insecurity to a local landscape—to streets, corners, traffic, the people who occupy infrastructural liminal zones and whose lives are precariously bound to the forces of speed and heat—reveals the critical nature of elemental metaphors. That is to say, if we might accept the thesis that we are in an epoch in which speed and time subsumes space and place, and if speed is another way of talking about heat, about intensities, then communication in the over-sped, overheated system is in dire straights. Precarity, I argue, is not causally linked to the breakdown in economy or the breakdown in affiliative bonds or networks—it does not precede or presage these shutdowns. Rather it is the shutdown. Precarity may now be viewed as the management and organization of social, political, affective, and communal bonds around economic and affiliative insecurities. I use ethnographic data from institutional meetings, and conversations with the key stakeholders at varying levels of scale, as well as textual analyses of local policies, news coverage, and public responses to those texts in order to understand how precarious communicative conditions affect the structuration of community and politics.

The emphasis for UK dwelling refurbishment to date has centred on reducing heating energy use. However, there has been increasing evidence pointing to the need for a more holistic approach. Many existing dwellings already experience overheating during hot weather periods. Climate change projections predict increases in both the frequency and severity of extreme weather events including heat waves such as the one in August 2003, which is estimated to have claimed the lives of over 35,000 people throughout Europe, including 2,000 in the UK. Demand for housing exceeds the supply of new stock and it is estimated that over 70% of the dwellings that will be in use in 2050 have already been built. Therefore existing dwellings will require adaptation to provide more comfortable and safe environments, to reduce both summertime overheating and heating energy use. In this research, dynamic thermal simulation computer modelling was used to assess and rank the effectiveness of selected single and combined passive interventions (adaptations) on dwelling overheating during a heat wave period. Simulations were also carried out to assess the effect of those interventions on annual space heating energy use. Four distinct dwelling types were selected to represent the housing stock in London and South East England, producing seven modelling variants: 19th century end and mid-terraced houses; 1930s semi-detached house; 1960s ground, mid and top floor flats and a modern detached house. Simulations were carried out for two different occupancy profiles and four building orientations and the cost of interventions was also considered in the analysis. The first occupancy profile assumed a ‘typical’ family who left the dwellings unoccupied during the daytime, the second assumed residents who were at home all the time (e.g. elderly or infirm). Of the dwelling types studied the 1960s mid and top floor flats and the modern (2006) detached house (Tier 2) experienced more than twice as much overheating as the other dwelling types (Tier 1). Tier 2 dwellings were “harder to treat” and unlike Tier 1 dwellings their overheating exposure could not be eliminated using the selected passive interventions. It was possible to substantially reduce overheating and annual heating energy use of Tier 1 dwellings at moderate cost, whereas the costs for retrofitting Tier 2 dwellings were estimated to be many times higher. The results demonstrated that overheating exposure can be significantly greater for residents who have to stay at home during the daytime and they should not, where possible, be housed in the most vulnerable dwellings. External window shutters were found to be the single most effective intervention for overheating reduction in most of the dwelling types considered, typically resulting in a 50% reduction in overheating exposure. The exception was the 19th century terraced houses, where applying a solar reflective (high albedo) coating to the solid external walls was often more effective. In some cases the addition of insulation increased overheating and external wall insulation consistently outperformed internal wall insulation when considering the effect on overheating, though the latter could be effective as an element of combined interventions. Adaptation should therefore be considered together with mitigation, both in design practice and in regulations. If existing dwellings (for example the 19th century terraced houses) are retrofitted for energy efficiency, without considering summer use, overheating could increase dramatically. Subsequent corrective measures could be costly and energy efficiency may suffer as a result. This research builds on previous publications and research to generate systematic, quantitative and holistic guidance for retrofitting UK dwellings to reduce overheating risk during heat waves, whilst minimising annual space heating energy use and considering the cost of retrofit. An interactive retrofit advice toolkit has been developed (and made publicly available) as part of the research, which allows selection of the best performing interventions within a given budget. Recommendations for further development of the research are also suggested.

Approximately 30% of the UK s housing stock is comprised of older, solid wall buildings. Solid walls have no cavity and were built without insulation; therefore these buildings have high heat loss, can be uncomfortable for occupants throughout the winter and require an above-average amount of energy to heat. Solid wall buildings can be made more energy efficient by retrofitting internal wall insulation (IWI). However, there is little empirical evidence on how much energy can be saved by insulating solid wall buildings and there are concerns that internal wall insulation could lead to overheating in the summer. This thesis reports measured results obtained from a unique facility comprised of a matched pair of unoccupied, solid wall, semi-detached houses. In the winter of 2015 one house of the pair was fitted with internal wall insulation then both houses had their thermal performance measured to see how differently they behaved. Measuring the thermal performance was the process of measuring the wall U-values, the whole house heat transfer coefficient and the whole house airtightness of the original and insulated houses. Both houses were then monitored in the winter of 2015, monitoring was the process of measuring the houses energy demand while using synthetic occupancy to create normal occupancy conditions. In the summer of 2015 indoor temperatures were monitored in the houses to assess overheating. The monitoring was done firstly to see how differently an insulated and an uninsulated house perform under normal operating conditions: with the blinds open through the day and the windows closed. Secondly, a mitigation strategy was applied to reduce high indoor operative temperatures in the houses, which involved closing the blinds in the day to reduce solar gains and opening the windows at night to purge warm air from the houses. The original solid walls were measured to have U-values of 1.72 W/m2K, while with internal wall insulation the walls had U-values of 0.21 W/m2K, a reduction of 88%. The house without IWI had a heat transfer coefficient of 238 W/K; this was reduced by 39% to 144 W/K by installing IWI. The monitored data from winter was extrapolated into yearly energy demand; the internally insulated house used 52% less gas than before retrofit. The measured U-values, whole house heat loss and energy demand were all compared to those produced from RdSAP models. The house was found to be more energy efficient than expected in its original state and to continue to use less energy than modelled once insulated. This has important implications for potential carbon savings and calculating pay-back times for retrofit measures. In summer, operative temperatures in the living room and main bedroom were observed to be higher, by 2.2 oC and 1.5 oC respectively, in the internally insulated house in comparison to the uninsulated house. Both of these rooms overheated according to CIBSE TM52 criteria; however the tests were conducted during an exceptionally warm period of weather. With the simple mitigation strategy applied the indoor operative temperature in the internally insulated house was reduced to a similar level as observed in the uninsulated house. This demonstrates that any increased overheating risk due to the installation of internal wall insulation can be mitigated through the use of simple, low cost mitigation measures. This research contributes field-measured evidence gathered under realistic controlled conditions to show that internal wall insulation can significantly reduce the energy demand of a solid wall house; this in turn can reduce greenhouse gas emissions and could help alleviate fuel poverty. Further to this it has been demonstrated that in this archetype and location IWI would cause overheating only in unusually hot weather and that indoor temperatures can be reduced to those found in an uninsulated house through the use of a simple and low cost mitigation strategy. It is concluded that IWI can provide a comfortable indoor environment, and that overheating should not be considered a barrier to the uptake of IWI in the UK.

The British National Health Service (NHS) is one of the largest public services in the world and consequentially in 2004 it produced 25% of the total public sector carbon emissions for England. To meet national carbon targets the NHS must reduce its emissions; 26% by 2020, 64% by 2030, 80% by 2050 and is therefore interested in the development of strategies for reducing carbon dioxide emissions from buildings. The NHS building stock consists of a range of building archetypes constructed over the past 100 years. The energy used for heating and cooling hospital premises is the source of 22% of all NHS carbon emissions. The individual buildings are distributed across hospital sites that often have centralised energy plants, which make it difficult to monitor energy consumption on an individual building level. This thesis develops a method for monitoring the energy consumption of individual hospital buildings. The method was implemented on three case study buildings at Bradford Royal infirmary (BRI); a 1920s Nightingale, a nucleus and a modern modular building. Lessons were gathered from these studies to advance the knowledge on monitoring in UK hospitals. One of the key findings was that empirical models based on measured data are useful for estimating individual buildings annual heating energy consumption. The results show that the mechanically ventilated nucleus building had the highest energy consumption (808.7kWh/m2), followed by the naturally ventilated Nightingale building (420.7kWh/m2) and then the mixed-mode modular building (289.0kWh/m2). The internal environment was optimal in the nucleus building, but the Nightingale and modular buildings underperformed, with the modular overheating in summer and both buildings failing to meet air quality recommendations. Taking energy consumption and summer thermal resilience into consideration the Nightingale building had the best performance, demonstrating the longevity of the traditional design. The work identified a number of useful hospital design features; well-insulated heavyweight building fabric, well-controlled space heating, use of heat recovery ventilation and installation of localised monitoring equipment. Further useful research into this area could involve: using dynamic thermal simulation to test recommended building design features, investigating the monitoring method on a wider sample of sites and investigating air quality monitoring in hospitals.

Orientador: Rezende Gomes dos Santos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-06T09:53:26Z (GMT). No. of bitstreams: 1 Sousa_TonnyfranXavierdeAraujo_M.pdf: 6216112 bytes, checksum: 8c56f86b7dd957a9bef95dc947db6ed6 (MD5) Previous issue date: 2006 / Resumo: O objetivo do trabalho é o desenvolvimento de uma análise comparativa do processo de solidificação de uma liga de alumínio a partir de diferentes graus de superaquecimento. São determinados experimentalmente os principais parâmetros do processo de solidificação afetados pelo grau de superaquecimento e sua influência na formação da microestrutura. Foi escolhida a liga AA5052, contendo cerca de 3% de magnésio pelo seu interesse comercial. A liga foi vazada com três diferentes graus de superaquecimento, em um dispositivo que permite a solidificação unidirecional e o monitoramento, através de um sistema de aquisição de dados, das variações de temperatura em diferentes posições da peça. A partir dos resultados de temperatura são determinados outros parâmetros do processo. Os espaçamentos interdendriticos são determinados a partir das micrografias. Através da análise experimental é determinada a influência do grau de superaquecimento nos seguintes parâmetros relativos ao processo de solidificação: coeficiente de transferência de calor na interface metal/molde, velocidade de avanço da frente de solidificação, gradiente de temperatura em frente à isoterma liquidus, taxa de resfriamento, tempo local de solidificação e espaçamentos interdendriticos primário e secundário. Também é analisada a transição entre a estrutura colunar e equiaxial / Abstract: The objective of this work is the development of a comparative analysis of solidification process of the aluminum 5052 alloy with different overheating ranges. The main parameters of the solidification process, experimentally determined, are affected by the overheating range and its influence on the microstructure arrangement. lt was selected the 5052 alloy, containing about 3% of magnesium, used for commercial purposes. The al1oy was poured with three different overheating ranges in a device which allows the unidirectional solidification and its monitoring through an acquisition data system thru the temperature variation from different positions on the sample. From the temperature results, the process parameters are determined. The dendritic spacing is determined using the micrographs. Through experimental analysis is established the influence of the overheating range at the fol1owing parameters related to solidification process: heat transfer coefficient at the metal/mold interface, solidification rate, thermal gradient at the liquidus isotherm, cooling rate, local solidification time and secondary arm spacing. The change between the structure columnar and equiaxed is also studied. / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

The research conducted at the department of Electrical Engineering of the University of South Florida campus in Tampa only covers the electrical aspect of electric drives. However, the performance of electric machinery is significantly impacted by temperature variation. The literature review shows three main control techniques in use today in electric drives namely, Scalar control, Direct Torque control and Field Oriented control. This thesis presents a temperature rise of rotor bars, stator winding, stator core and stator frame in a running three phase field-oriented controlled induction machine. A literature search shows that none of research has been carried out to investigate a thermal response of a field-oriented controlled induction motor. With this motivation, we were able to implement a lumped parameters thermal model of a three-phase field-oriented IM in MATLAB Simulink, which allows us to determine that rotor bars have the highest temperatures rising to 84 degrees Celsius. This confirms that rotors bars are the hottest part of a running IM as stipulated in literature.

Typical deep level mines use up to 27 ML water per day for mining operations. Multistage centrifugal pumps up to 2500 MW are used in an upward cascading manor to dewater the shaft. The dewatering systems at some mines are automated to enable surface control. Automation of the pumps is typically based on the best practice procedure known when implemented. Best practice procedures are used to ensure safe pumping operations. It was found that pump failures could still occur even with the best practice implemented. Unexpected failures of pumps are of major concern because they can result in the flooding of a mine. Flooding increases the risk of environmental damage and injury to the mining personnel. An additional concern is the maintenance cost of multistage centrifugal pumps. Overhaul cost of a seized multistage centrifugal pump is almost R1-million. The aim of this study was to improve established best practice procedures for pump automation. This could be achieved by investigating the general root cause of failures of automated pumps. Additional instrumentation and protection devices to prevent similar incidents were examined. Revised system control parameters were developed to ensure that the pumps operated within the design specifications. The improved best practices proved to prevent failures as a result of overheating and cavitation. Increasing the pump reliability and availability enabled surface control. The control of the automated dewatering system realised an electricity cost saving of R6-million. The automated system also made it possible to calculate the real-time pump efficiency within 5%. Previous best practice procedure was found to be inadequate to prevent all possibilities of failure. Additional precaution measurements were added to prevent pump failure. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

Typical deep level mines use up to 27 ML water per day for mining operations. Multistage centrifugal pumps up to 2500 MW are used in an upward cascading manor to dewater the shaft. The dewatering systems at some mines are automated to enable surface control. Automation of the pumps is typically based on the best practice procedure known when implemented. Best practice procedures are used to ensure safe pumping operations. It was found that pump failures could still occur even with the best practice implemented. Unexpected failures of pumps are of major concern because they can result in the flooding of a mine. Flooding increases the risk of environmental damage and injury to the mining personnel. An additional concern is the maintenance cost of multistage centrifugal pumps. Overhaul cost of a seized multistage centrifugal pump is almost R1-million. The aim of this study was to improve established best practice procedures for pump automation. This could be achieved by investigating the general root cause of failures of automated pumps. Additional instrumentation and protection devices to prevent similar incidents were examined. Revised system control parameters were developed to ensure that the pumps operated within the design specifications. The improved best practices proved to prevent failures as a result of overheating and cavitation. Increasing the pump reliability and availability enabled surface control. The control of the automated dewatering system realised an electricity cost saving of R6-million. The automated system also made it possible to calculate the real-time pump efficiency within 5%. Previous best practice procedure was found to be inadequate to prevent all possibilities of failure. Additional precaution measurements were added to prevent pump failure. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015