No description available.

Natural ventilation is a passive cooling method that has significant potential to reduce building energy consumption and to positively contribute to indoor environmental conditions. Because the window is an important element in naturally ventilated buildings, it can be used to adjust indoor air flow. However, lack of knowledge about occupants‘ window control behaviour and how this relates to different window typology would result in discrepancy between actual and proposed building performance. And also, limit the potential of natural ventilation in the building. This thesis explores the relationship between indoor air velocity, occupants‘ window control behaviour and window design. This study is based on field measurement and occupant comfort survey in four office buildings in a hot and humid climate in South-east China. The field study was carried in September and October of 2012. The indoor and outdoor thermal conditions, indoor air flow speed, window state and effective opening area were monitored. Occupant thermal comfort questionnaires were given to participants four times a day to record their comfort perceptions in the office. The field study gives new insights into the correlation between indoor air speed, occupants‘ window control behaviour and window design. For the research 14400 set of indoor and outdoor temperature and relative humidity data, 174560 indoor air velocity records and 1344 copies of questionnaires were collected. The results of this study defined comfort zone for this climate which is consistent with Givoni‘s comfort zone for a hot and humid climate. The indoor air flow path is identified by measuring the indoor air velocity across different parts of the office and related window opening combinations. Besides, the effective opening area is reduced with decreased indoor air temperature when the indoor air temperature is lower than 25°c. None of the windows is closed when the indoor air temperature is higher than 28°c. During the working hours, the changing of effective opening is related to the air velocity across the desk surface. And measured maximum indoor air velocity measured around the occupant is 1.8m/s which did not result in occupants‘ window changing behaviour to adjust for comfort. In conclusion, this study proved that occupants who live in hot and humid climate can accept higher humidity level. If the air velocity can be avoided across the occupant‘s working surface, then a higher indoor air velocity is still accepted by occupant as within their comfort threshold. So, there are great potentials for occupant to extend their comfort threshold and adapt to the local climate. Besides, window opening type and position has a significant impact on indoor air velocity and pattern. It would also influence convective cooling affect and occupant thermal comfort. This is evident from the indoor air velocity measurement results and the occupant comfort survey results. In addition, accessibility is important to window design. In the naturally ventilated office building, if occupants find it difficult to operate the window, this will have an influence on the natural ventilation potential in the building and cause the occupant discomfort. Thus, the findings of this study will help architects and engineers to design naturally ventilated office buildings in South-east China.

Having outlined the requirements of the heat pump, water and sodium hydroxide are selected as a suitable working fluid and absorbent. The advantages and disadvantages of this particular combination are outlined before dealing with the experimental work. The various components in the system are then discussed with particular attention to the absorber. From the results, suitable improvements to the design are suggested before describing possible alternative absorption systems. The technical details are all presented separately from the main text, in the Appendices.

<p>The demand for heat pumping technologies is expected to see tremendous growth over the next century. Traditional vapor compression cycles are approaching practical limits of efficiency and running out of possibilities for environmentally friendly and safe refrigerants. As a result, there is an increasing interest in pursuing non-vapor compression technologies that can achieve higher efficiencies with alternative working fluids. The chemical looping heat pump (CLHP) investigated here utilizes a chemical reaction to alternate a working fluid between more and less volatiles states. This allows the main compression to take place in the liquid phase and enables the utilization of a range of different working fluids that would not be appropriate for vapor compression technology. </p> <p> </p> <p>Thermodynamic models were developed to assess the potential performance of a chemical looping heat pump driven by electrochemical cells. A number of potential working fluids were identified and used to model the system. The thermodynamic models indicated that the chemical looping heat pump has the potential to provide 20% higher COPs than conventional vapor compression systems. </p> <p> </p> <p>An experimental test stand was developed to investigate the efficiency with which the electrochemical reactions could be performed. The working fluids selected were isopropanol and acetone for reasons of performance and availability. The test stand was designed to measure not only the power consumed to perform the conversion reaction but also the concentration of products formed after the reaction. The experimental tests showed that it was possible to perform the reactions at the voltages required for an efficient chemical looping heat pump. However, the tests also showed that the reactions proceed much slower than expected. To increase the rates of the reactions, an optimization effort on the membrane and catalyst selections was performed. </p> <p> </p> <p>Traditional catalyst materials used by solid polymer electrochemical cells, like those used in the testing, perform best in hydrated environments. The fluids isopropanol and acetone tend to displace water in the membranes, reducing the system conductivity. Multiple membrane types were explored for anhydrous operation. Reinforced sPEEK membranes were found to be the most suitable choice for compatibility with the CLHP working fluids. Multiple catalyst mixtures were also tested in the experimental setup. Density functional theory was used to develop a computational framework to develop activity maps which could predict the performance of catalyst materials based on calculated parameters. </p> <p> </p> <p>A detailed model of the CLHP electrochemical cell was developed. Built on open-source tools, the model was designed to determine the charge, mass, and heat transfers within the cell. The conversion of reactants along the channel of the cell as well as overall power consumption are predicted by the model. The model was validated against measurements and used to determine parameters for a CLHP cell that would have improved conversion performance and energy efficiency compared with the tested cell. </p> <p> </p> <p>The cell model was integrated into an overall system model which incorporates the effect of concentration changes throughout the entire cycle. Compared to the early-stage thermodynamic modeling, consideration of incomplete reactions provided more accurate predictions of the potential performance of CLHP systems. Different cell and system architectures were investigated to boost system performance. The model predictions demonstrated that the CLHP has the potential to provide high heat pumping efficiencies, but more work is still needed to improve the energy density of the system. </p>

A numerical investigation, based on mathematical modelling of some important phenomena relating to the chemical vapour deposition (CVD) process in a furnace, has been undertaken. This thesis is concerned with investigating the furnace design which results in the maximum possible recovery of the material in the form of flat deposition flux profiles. A finite difference technique is used to solve the Navier-Stokes and the diffusion equations which arise from the CVD process. In Chapter One, the main ideas of the problem are introduced. The investigation of the rectangular duct furnace is discussed in Chapter Two, and the importance of the axial diffusion term is studied. Chapter Three deals with the Plane Parallel wall furnace and the effect of varying certain parameters (i.e. Re, Pe and a) on the deposition flux profiles and the percentage recovery of the material. In Chapter Four, we investigate the impingement jet furnace, while in Chapter Five we study several furnace designs including the cylindrical furnace, the Plane Parallel wall furnace with various outlet configurations and the angled wall furnace. Also the effects of surface kinetics are discussed. Chapter Six describes the multigrid method as a fast method to solve the Navier-Stokes and the diffusion equations.

Vita. / Digitized by Kansas Correctional Industries

Energy consumption by human enhanced activities has led to distinctive environmental problems; in particular, climate change and global warming. In hot regions, the main reason for energy consumption comes from the cooling of many buildings. The intensity and duration of the sunshine in hot regions have a direct relation with the usage of cooling systems. The energy used for cooling purpose is continuously increasing and expected to increase in the following years. Evaporative cooling is one of the passive cooling method which has been used throughout history. As it is cheaper, environmentally-friendly and simpler compared to vapour compression systems, it is more widely used in residential, commercial and industrial buildings in hot and dry regions. Since this method is less efficient and limited under hot and humid climate, the desiccant based evaporative cooling system is preferred in such areas in order to dehumidify the air. The pad material used for evaporative cooling system is important as it helps to evaporate the water. Therefore, the material should be porous enough to absorb water which enhances the rate of evaporation. Moreover, the material should be available and cheap. This study shows the potential of using different materials for evaporative cooling systems. The aim of this study is to investigate the feasibility, suitability and potential of using local materials such as eucalyptus fibres, as cooling pads for evaporative cooling system in hot and dry regions. In addition to this, the liquid desiccant evaporative cooling systems by using potassium formate is also studied for hot and humid areas in Cyprus. Since Cyprus has multi-climate regions due to the topography and different weather condition, different cooling systems can be used for each region. The results are reported in terms of temperature difference, cooling output, COP, etc. The wind tunnel is used to test the eucalyptus fibres with an inlet air temperature of 35 °C to simulate the climate in Cyprus. It was found that the maximum reduction of air temperature was between 11.3 °C and 6.6 °C, while the maximum cooling efficiency was in the range of 71% and 49% at 0.1 and 0.6 m/s air velocity respectively. Corresponding cooling capacities were also calculated as 108 and 409 W indicating a directly proportional relation between air velocities and cooling performance. Following this, the conceptual design ideas of integrated eucalyptus fibres based evaporative cooling panel (EFECP) into building elements are considered to meet the demand for cooling and the architectural requirements of the building. These design ideas were developed for shutter, fenestration, toplighting elements, wind catcher-solar chimney and wall design of the building. The cooling performances of the hollow fibre integrated by using potassium formate desiccant based evaporative cooling system were experimentally investigated under the incoming air temperature in the range of 35 ˚C to 40 ˚C. The cooling capacity is increased as the air velocity is increased. At 3.5m/s, the cooling capacity is 1340 W, 1530 W and 1920 W respectively for incoming air relative humidity of 60%, 65% and 70%. Both evaporative cooling systems performances are discussed and clearly presented in this study. From the experimental testing in this thesis, it is concluded that local eucalyptus fibres can be used for hot-dry areas and liquid desiccant evaporative cooling systems can be used for hot-humid areas of Cyprus. Since using of eucalyptus fibres for evaporative cooling system is locally available, simple construction and easy to apply, the design ideas for integrating eucalyptus fibres with evaporative cooling system are developed within the scope of the thesis. The usage of local eucalyptus fibres and Polyvinylidene fluoride (PVDF) hollow fibres as evaporative cooling pad, the evaporative cooling process designed by using fibres and the conceptual building design ideas integrated local eucalyptus fibres combined with evaporative cooling system are all the novel ideas of this thesis.

No description available.

Due to the energy crisis in 1970, the energy saving is more important for the human civilization. The energy-saving policy is important for the economic growth and competition of Taiwan. The energy of daily life and business consumes 17% of the total energy, especially the air conditioning of architectures on the peak hours occupying a third in summer. So the building energy-saving policy is the most important in Taiwan. The main of theme building energy saving is not only to save energy but also to consider the comfortable and healthy of the living environment. So that, the optimal design of the building energy saving of commercial buildings in Taiwan has been established in this paper. In this study, theoretical analysis and a full scale experiment has been performed to validate this design. Results showed this design is suitable for the NPTC building in the weather condition of south Taiwan, which also complies with the energy code of Taiwan.

Thesis (Ph. D.)--School of Mechanical Engineering, Georgia Institute of Technology, 2004. Directed by Sheldon M. Jeter. / Vita. Includes bibliographical references (leaves 195-201).