Saudi Cultural Missions Theses & Dissertations
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Item Restricted Enhancing Indoor Air Quality and Minimizing Airborne Virus Dispersion Under Various Ventilation Strategies While Maintaining Thermal Comfort(CARDIFF UNIVERSITY, 2025) ALQARNI, ZAHI ALI SAEED; Yacine, RezguiIndoor air quality (IAQ) and thermal comfort are critical factors that influence occupant health, productivity, and general well-being in office environments. The COVID-19 pandemic has further highlighted the importance of effective ventilation strategies in mitigating the transmission of airborne viruses. This research investigates the performance of three ventilation strategies: indoor recirculation systems (4-way ceiling cassette air conditioners), natural ventilation, and mixed mode ventilation (AC + natural ventilation) in maintaining optimal IAQ, thermal comfort, and infection control in an open-plan office setting. Using a combination of computational fluid dynamics (CFD) simulations and real-world environmental monitoring, this study evaluates airflow patterns, pollutant dispersion, and thermal regulation under different ventilation conditions. This thesis explicitly demonstrates that IAQ, thermal comfort, and airborne virus transmission are deeply interconnected. Poor air quality not only impairs comfort and productivity but also prolongs aerosol suspension time, elevating infection risk. As such, ventilation strategies must be designed to address these three aspects holistically. The findings reveal that the air conditioning (AC) system, while providing controlled air distribution, often leads to stagnation zones that reduce air mixing efficiency and increase pollutant accumulation. Natural ventilation, though beneficial under favourable conditions, exhibits inconsistent performance due to external weather variations, leading to excessive humidity fluctuations and temperature instability. In contrast, mixed mode ventilation emerges as the most effective strategy, offering improved airflow uniformity, improved pollutant dilution, and greater adaptability to seasonal changes. The results demonstrate that a well-optimised hybrid system, which strategically combines an AC system and natural ventilation, can mitigate the limitations of standalone approaches by balancing fresh air intake, controlled temperature regulation, and efficient humidity management. This research contributes to a novel integrated methodological framework that bridges CFD simulations with IoT-based environmental monitoring, ensuring robust validation of ventilation performance under real-world conditions. The findings have significant implications for the optimisation of heating, ventilation and air conditioning (HVAC) and public health policies, particularly in the post-pandemic era, where IAQ is a major concern. By addressing critical knowledge gaps in ventilation performance, this thesis provides practical recommendations for facility managers, architects, and policy makers to develop more resilient and health-conscious indoor environments.11 0Item Restricted Mathematical Models Connected to the Respiratory System(University of Exeter, 2024-09-13) Alhammad, Muslim; Bicktashev, VadimThe respiratory system is intricately connected to various other systems in the human body. When abnormalities arise, whether their cause is known or unknown, mathematical models are crucial for identifying underlying issues that may not be detectable with current medical tools. This work focuses on mathematical models of normal and pathological respiratory conditions, including Cheyne-Stokes Respiration (CSR), a form of Central Sleep Apnea (CSA). These models, often described by delayed differential equations (DDEs), account for feedback control loops and time delays, as seen in the work of Mackey and Glass and Landa and Rosenblum. Our primary contribution is the modification of the Landa and Rosenblum model. We introduce a refined model with two delayed differential equations and perform numerical simulations analysis, conducted using MATLAB, aiming to pinpoint a new bifurcation parameter and keep the qualitative behavior of the original model that accounts for the cumulative description of CSR even at a longer time. Additionally, we address ambiguities in the parameterization presented by Dong and Langford (2008) and apply Hopf Bifurcation analysis to explore alternative causes of CSR beyond time delay.25 0Item Restricted The Efficacy of 10 Air Changes Per Hour Ventilation in Controlling Air Contamination in Dentistry(Saudi Digital Library, 2023-09-15) Alakkam, Khaled; Seoudi, Noha Professor; Mein, Chaz; Shahdad, ShakeelBackground: Acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 2019 (COVID-19) pandemic has heightened the need to protect healthcare workers, including dental. The use of mechanical ventilation, particularly high-efficiency particulate air (HEPA) ventilation, was recommended by UK Health Security Agency with a parameter of 6 air changes per hour (ACH) initially. The recommendation was changed to 10ACH for aerosol-generating procedures (AGPs). There have yet to be any previous studies investigating the effect of these two parameters on air contamination in dental hospitals outside the dirty zone. Therefore, this study aimed to fill this knowledge gap. Methodology: MD8 airscan was used (Sartorius, Epsom, UK) with sterile gelatine filters (80 mm diameter and 3 μm pores; Sartorius) to enable RNA extraction for SARS- CoV-2 Polymerase Chain Reaction (PCR) and with polystyrol culture media plate measuring 116 x 24 mm (BACTair culture media, Sartorius, Germany) for bacterial and fungal colony forming unit (CFU) quantification. Sampling air was performed from outside the dirty zone in open clinical areas with ventilation of 6ACH and 10 ACH when AGPs and non-AGPs were performed in two different dental settings; Barts Health NHS Dental Hospital (RLH) and Sir Ludwig Guttmann (SLG) Dental Centre. Results: The air contamination at 10ACH was significantly lower than 6ACH at baseline (13.83±5.4 vs 68.67±74.73; p=0.019), AGP (177.3±19.04 vs 288.5±108.6; p=0.023), and non-AGPs (114.7±23.69 vs 245.3±37.97; p=0.007) in RLH. In SLG, 10ACH maintained air contamination at 30.33±26.73 and 18.33±11.85 for non-AGP and AGP, respectively, compared to 192±34.64 for non-AGP in 6ACH (p=0.0003). XI Conclusion: This study proves that 10ACH is an efficient intervention to improve the air quality in open bay dental clinics during all types of dental procedures (AGPs and non-AGPs) in different dental settings, large dental hospital and outreach dental clinics, which has close similarity to community dental clinic environment.7 0Item Restricted Investigation Of The Ventilation And Thermal Performance Of Mashrabiya For Residential Buildings In The Hot-Humid Climate Of Saudi Arabia(Saudi Digital Library, 2022-06) Bagasi, Abdullah Abdulhameed; Calautit, JohnThe residential sector in Saudi Arabia is the most energy-consuming building sector, accounting for about 50% of the total energy generated. A large proportion of this energy is used to maintain the indoor air temperature at the required comfort level. While the lack of optimal use of natural resources in buildings, such as natural ventilation also contributes to the rising consumption. Traditionally, Saudi buildings were characterised by different architectural solutions and elements such as the mashrabiya, which was closely related to the local environment and responded to many factors, such as climatic conditions and occupants needs. Mashrabiya is an opening covered with a wooden lattice for ventilation, daylight, privacy, and an aesthetic appeal for houses. Although there are many studies and research on the mashrabiya, most studies addressed either the ventilation or daylight aspect and few included evaporative cooling without conducting field tests or validated modelling to investigate its actual performance and the extent of its impact on the internal thermal environment. Therefore, this research aims to investigate the effect of the mashrabiya on the indoor thermal environment and develop a mashrabiya design to enhance indoor thermal comfort in the residential buildings in hot climates with reference to Jeddah, Saudi Arabiya. The research, besides the literature review, includes field experiments and simulation works. The field experiment results indicated that opening the mashrabiya allowed more airflow into the room and reduced the indoor temperature by up to 2.4 °C compared to the closed mashrabiya. Furthermore, by integrating evaporative cooling strategies (pots, water sprays, and wet cloth) with the open mashrabiya, it was found that the most effective approach to improving the room air temperature was hanging a wet cloth and the average room temperature reduced by up to 6.8°C. Along with that, the thermal mass played a significant role in reducing indoor air temperatures' thermal swings. In order to expand its scope in the study and examination of the mashrabiya, a computational fluid dynamic simulation tool was used. The results of the base case of the mashrabiya in the simulation generally indicated that the slats' inclination plays a vital role in the direction of the airflow into the room, and this is evident with tilting the slats angle to +30 or -30, as the airflow becomes more directed and sharper to the ceiling or the floor. Also, compared to the benchmark case, the mashrabiya contributed to37 0