This work is concerned with evaluating and studying the possibilities of enhancing natural ventilation performance and its use as a passive cooling strategy in walk-up public housing blocks within the Egyptian desert climatic region. This research attempts to maximize the benefits from the vast investments made in housing projects in Egypt through providing thermally comfortable housing prototypes that could use by contrast less energy for cooling purposes. This is considered essential in the light of the current concerns about energy all over the world. Egypt was devided to seven different climatic regions by the Egyptian organization for energy conservation and planning. The Egyptian desert climatic region, which was chosen as the research context, is the largest climatic region of Egypt. Most of the Egyptian new cities that accommodate the majority of the recent public housing projects are located within this desert climatic region that represents the typical hot arid climate characteristics. Nationally, the problem of the misuse of the housing prototyping was spotted. According to previous researchers, the same basic prototypical designs are being built all over the country without giving enough consideration to the actual effects of different climates and the diversity in the residents social needs. Regionally, within the Egyptian desert climatic region, the harsh climatic conditions rate the problem of achieving thermal comfort within these housing prototypes as the most urgent problem that needs to be examined in depth. A pilot study that used observation and monitoring methods was conducted in the New Al-Minya city (The representative city of the desert climatic design region) in order to closely investigate this problem and identify its dimensions. The results confirmed thermal discomfort conditions of the housing prototypes built there, especially during the hot summer period. The passive design strategies analysis of the climatic context indicated that night purge ventilation is the most effective passive strategy that could enhance thermal comfort. These results go along with the rule of natural ventilation in reducing the used energy for cooling and the actually massive national income spent on these housing prototypes encourage this work so to concentrate on natural ventilation. Different studies using multi-approaches research techniques were employed in order to achieve the main aim of the research. These techniques included; literature review, monitoring, questionnaire and computer simulation.A critical literature review was conducted including; the physical science of natural ventilation, its strategic design as well as the design measures that control natural ventilation and the airflow in; the macro, intermediate and micro design levels. The results of the investigations were discussed and interpreted in the light of this review. A representative case study was chosen for the study. The natural ventilation performance in the case study was quantitatively and qualitatively evaluated through conducting field objective and subjective assessment respectively. In evaluation study, the thermal performance of the case study under different ventilation scenarios was monitored, the airflow inside it was simulated using CFD (computational fluid dynamics) software “FloVent” and a sample of residents were questioned. This study identified many problems associated natural ventilation uses and indicated its poor performance within the case study. A number of design measures were formulated based on the literature review and considering the evaluation study results along with the research context nature. The proposed natural ventilation design measures were applied to the case studies and their effectiveness in terms of enhancing the natural ventilation performance was quantified using “FloVent”. Results reported that the proposed natural ventilation design measures could significantly enhance the natural ventilation performance inside the case study quantitatively and qualitatively. This in turn maximizes the potential of providing thermal comfort by using both natural ventilation strategies; comfort ventilation and night purge ventilation. However, all the applied measures could not achieve neither an acceptable airspeed at any of the case study spaces nor a good airflow circulation at some of its spaces. It can be concluded that the current design of the case study can not achieve quality airflow without the use of the mechanical assisted ventilation. In general, it seems very difficult to optimize the air velocity within all spaces in a very dense multi-space design like this case study. A new design that considers natural ventilation and its drivers has to be introduced.

Les conditions actuelles de réchauffement de la planète ont mené aux pays du monde à s'engager dans la durabilité et l’efficacité énergétique et la réduction des émissions de gaz à effet de serre. En tant que troisième consommateur d'énergie, le bâtiment représente un élément clé envers l'efficacité énergétique et de la stabilisation de la température globale. Plusieurs solutions existent pour la réalisation de ces objectifs, et les travaux présentés tout au long de cette thèse concernent un composant solaire particulier à la construction externe du bâtiment, appelé cheminée solaire. Cette thèse de doctorat porte sur l'analyse expérimentale et numérique des dispositifs de stockage d'énergie, sous forme de matériaux à changement de phase (PCM), afin d'optimiser les performances de cette technologie solaire. Le but de cette étude est de caractériser l’impact des panneaux Rubitherm RT44 PCM sur une cheminée solaire en laboratoire et in situ afin de permettre une comparaison avec la version classique. De plus, un modèle numérique a été développé et testé dans le but d'obtenir un outil numérique capable de représenter le comportement d'une cheminée solaire. Enfin, une optimisation à deux objectifs du modèle numérique de cheminée solaire intégrée PCM a été réalisée afin de déterminer certains des paramètres optimaux de ce type de technologie afin d’obtenir le flux d’air sortant le plus élevé possible, tout en maintenant une température suffisamment élevée dans la cheminée atteindre la gamme de fusion des PCM. / The current global warming conditions have led nations across the world to commit into energetic sustainability and greenhouse gas emission reduction. Being the third greatest energetic consumer, the building represents a major key towards energy efficiency and global temperature stabilization. Several solutions exist for the accomplishment of these goals, and the works presented throughout this dissertation concerns a particular external building solar-driven component known as solar chimney. This PhD thesis focuses on the experimental and numerical analysis of energy storage devices, in the form of Phase Changing Materials (PCMs), for the optimisation of the performance of this solar technology. The aim of this study is to characterize the impact of Rubitherm RT44 PCM panels on a solar chimney under laboratory and in-situ conditions to carry out a comparison against the classic version. Additionally, a numerical model was developed and tested in the interest of obtaining a numerical tool capable of representing the behaviour of a solar chimney. Finally a bi-objective optimization of the PCM integrated solar chimney numerical model was carried out in order to determine some of the optimal parameters of this type of technology to obtain the highest exiting air flow, all while maintaining a high enough temperature across the chimney to reach the fusion range of the PCMs.

Wards occupy significant proportions of hospital floor areas and due to their constant use, represent a worthwhile focus of study. Single-bed wards are specifically of interest owing to the isolation aspect they bring to infection control, including airborne pathogens, but threats posed by airborne pandemics and family-involvement in hospital care means cross-infection is still a potential problem. In its natural mode, ventilation driven by combined wind and buoyancy forces can lead to energy savings and achieve thermal comfort and high air change rates through secure openings. These are advantageous for controlling indoor airborne pathogens and external air and noise pollution. However, there is lack of detailed evidence and guidance is needed to gain optimum performance from available natural ventilation systems. This research is a proof of concept investigation into the feasibility and impact of natural ventilation systems targeting airflow rates, thermal comfort, heating energy and control of pathogenic bio-aerosols in hospital wards. In particular, it provides insights into the optimal areas of vent openings which could satisfy the complex three-pronged criteria of contaminant dilution, low heating energy and acceptable thermal comfort for occupants in a naturally ventilated single bed ward. The main aim of this thesis is the structured study of four systems categorised into three groups: Simple Natural Ventilation (SNV) in which single and dual-openings are used on the same external wall; Advanced Natural Ventilation (ANV) which is an emerging concept; and finally Natural Personalised Ventilation (NPV) which is an entirely new concept borne out of the limitations of previous systems and gaps in literature. The focus of this research is in the exploratory study of the weaknesses and potentials of the four systems, based on multi-criteria performances metrics within three architecturally distinct single-bed ward designs. In contributing to the body of existing knowledge, this thesis provides a better understanding of the performances of three existing systems while presenting the new NPV system. The analysis is based on dynamic thermal modelling and computational fluid dynamics and in the case of the NPV system, salt-bath experiments for validation and visualisation of transient flows. In all cases, wards were assumed to be free of mechanical ventilation systems that might influence the natural flow of air. The thesis meets three major objectives which have resulted in the following contributions to current knowledge: An understanding of the limitations and potentials of same-side openings, especially why and how dual-openings can be useful when retrofitted into existing wards. Detailed analysis of bulk airflow, thermal comfort, heating energy and room air distribution achievable from existing SNV and ANV systems, including insights to acceptable trickle ventilation rates, which will be particular useful in meeting minimum dilution and energy requirements in winter. This also includes qualitative predictions of the airflow pattern and direction obtainable from both systems. The innovation and study of a new natural ventilation system called Natural Personalised Ventilation (NPV) which provides fresh air directly over a patient s bed, creating a mixing regime in the space and evaluation of its comfort and energy performances. A low-energy solution for airborne infection control in clinical spaces is demonstrated by achieving buoyancy-driven mixing ventilation via the NPV system, and a derivative called ceiling-based natural ventilation (CBNV) is shown. A comparative analysis of four unique natural ventilation strategies including their performance rankings for airflow rates, thermal comfort, energy consumption and contaminant dilution or removal using an existing single-bed ward design as case study. Development of design and operational recommendations for future guidelines on utilising natural ventilation in single-bed wards either for refurbishment or for proposed designs. These contributions can be extended to other clinical and non-clinical spaces which are suitable to be naturally ventilated including treatment rooms, office spaces and waiting areas. The findings signify that natural ventilation is not only feasible for ward spaces but that there is opportunity for innovation in its application through further research. Future work could focus on related aspects like: impacts of fan-assisted ventilation for a hybrid flow regime; pre-heating of supply air; integration with passive heat recovery systems as well the use of full-scale experiments to fine-tune and validate findings.