The finite element method is used to predict numerically steady state, two-dimensional laminar and turbulent thermal buoyant and convective recirculating flows. The governing equations are solved by the finite element method using Galerkin Weighting functions, with velocity, pressure, and temperature as dependent variables. Turbulent separating, recirculating flow in the complex geometry of a room with variable inlets, outlets and convective chimney ducts is investigated. The room is ventilated/air-conditioned utilising the solar energy via a flat plate collector and solar absorption airconditioning system. For this purpose the Navier-Stokes, continuity and general energy equations are solved in a coupled form and in an uncoupled form and solutions are compared amongst themselves and with the experimental results of hot wire anemometers and thermocouples. The parts where turbulent flows occurred especially in the convective duct and the room, the flows are analysed using the Prandtl- Kolmöjorov model to depict the effective viscosity. The analogy between thermal and momentum diffusivity via Prandtl number is used to depict the turbulent conductivity from the turbulent viscosity. The length scale of turbulence is specified as an algebraic function of position from empirical data and experience of other researchers . The kinetic energy is expressed as a function of velocity at the nodes together with the turbulence intensity which varies from ~5% - ~20%. This turbulence model is used to predict the flow including its recirculations in the solar ventilated/air-conditioned room, and the fully turbulent convective channel. The analysis includes temperature and heat transfer predictions in this complex geometry of combined free and forced convection, together with buoyancy effects and turbulent transport and recirculations. Results obtained are compared with the experimental data which showed very good agreement.

Studies on design for control optimization of air-conditioning (a/c) system for better performance in Hong Kong are reported in this thesis. Typical plant configuration data was collected from an in-depth survey of a/c systems and control used in Hong Kong. Control performance has been used for the first time as an objective for optimizing a/c system designs. The study investigates and illustrates that optimization of a/c systems for application in the Hong Kong by simulation is promising and flexible. The accuracy of simulation is enhanced by using the survey data. The survey shows that some a/c control systems and their control strategies are not well considered in the design stage and their operation and set-up are not properly addressed. Hence, there exists optimization opportunities in the a/c system design and control strategies for a/c systems used in Hong Kong. Parameters affecting the control performance of a/c systems were investigated by carrying out experiments. Identified parameters are the objective function of optimization, controller settings, control valve and drive and, in case of direct digital control, sampling rate. The influence of these factors on the control performance is an essential consideration for the entire optimization process. Strategies in applying the findings in optimizing an a/c system for control performance by simulation were developed and suggested. This study provides platform for further simulation study of optimization in both methodologies and control strategies for a/c system design and operation.

The overheating problem experienced during Islamic pilgrimage in recent years has caused serious thermal discomfort and a number of mortalities among pilgrims coming from various parts of the world to perform the annual event at Makkah in Saudi Arabia. This research aims to investigate the real dimension of thermal discomfort experienced inside the pilgrimage tents. The back bone of this task was the data collected from the field investigations during the Hajj season of 1989, including climatic measurements taken inside the tents for the first time during the Hajj season. The investigations also included a subjective evaluation for internal thermal conditions by the pilgrims from Europe, the Middle East, and South East Asia. This research also attempts to identify passive and natural cooling guidelines that are applicable to the tent's design. The author tested sets of experiments aimed to measure the thermal effects of some of the natural cooling techniques on pilgrimage tents at Makkah. The research concludes with design guidelines to improve the thermal quality of the pilgrimage tent. The recommended guidelines were based on the experimental results and practical examples of cooling strategies applied to tents in similar hot climates.

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Στη διπλωματική αυτή εργασία εξετάζονται οι τρέχουσες τεχνικές εξοικονόμησης ενέργειας σε κτιριακές εγκαταστάσεις, το τρέχον νομικό πλαίσιο και γίνεται μια μελέτη εξοικονόμησης ενέργειας κατοικίας. / --

Discomfort glare is considered to be an annoyance or distraction caused by sources of non-uniform or high luminance within the field of view of an observer. There are still significant gaps in our understanding of the conditions that characterise the magnitude and occurrence of discomfort glare, this being especially evident in the presence of large sources of luminance such as windows. The large degree of scatter that is observed when subjective evaluations of glare sensation are compared against calculated glare indices suggests that discomfort glare may be dependent on other variables beyond the physical and photometric parameters that are commonly embedded in glare formulae (e.g., source luminance, source size, background luminance, and position index). There are strong reasons to believe that some of these variables might be linked to the time of day when the observer is exposed to the glare source. In response, this thesis investigated the research hypothesis that subjective glare sensation is associated with temporal variability. This hypothesis was tested in two stages. The first stage was conducted within a laboratory setting, and sought to examine temporal effects under controlled artificial lighting conditions. The collection of temporal variables and personal factors – thereby examining the scatter in glare responses across the independent variable (time of day) and isolating potential confounding variables – enabled to identify factors that could influence the subjective evaluation of glare sensation along the day. Having established the presence of a temporal effect on glare response, the influences detected were further explored within a test room with direct access to daylight, whereby temporal variables and personal factors were measured in conjunction to glare sensation for them to be statistically masked from the analysis. The results confirmed the hypothesis of an increased tolerance to glare as the day progresses. This supported the conclusion that physical and photometric parameters alone are not sufficient for a robust prediction of discomfort glare.

The initial stage of the work was a study of an 80 tonne industrial furnace, taking observations, panel water temperature data and samples of slag layers from the sidewalls. This resulted in a simple model of layer formation which explained the observed structures, and also the effect of slag layer thickness on heat losses was examined. However, the complexity and variety of structures found were such that a full series of direct thermal conductivity measurements was deemed impractical, and so a theoretical model to calculate the thermal conductivity of complex structures from the thermal conductivities of it s components was developed. Other aspects of heat transfer both within the furnace and from the furnace interior to the water cooling were also explored. In order to obtain a reliable value of thermal conductivity for the slag component of layer structures, a technique was developed to measure the thermal conductivity of the slag. This consisted of firstly determining a viable route for the production of homogenous samples, followed by the design, construction and refinement of an experimental measuring rig. After a large number of preliminary measurements, a series of thermal conductivity values at temperatures between 300 and 800 °C were measured using operating conditions calibrated against a heat storage brick sample of known thermal conductivity. These results were used to provide the data for the theoretical thermal conductivity model, which was then applied to real structures for which thermal data was available. Comparison of the results showed good correlation. Finally, in the appended case study, the heat loss calculation was applied for various furnace situations to identify the potential heat loss savings that could be achieved by controlling the slag layer thickness and structure, and the financial implications.

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