# CFD Assessment of Car Park Ventilation System in Case of Fire Event
###### Abstract  
This scientific article presents the results of computational fluid dynamics (CFD) simulations conducted using OpenFOAM to evaluate the effectiveness of a jet fan ventilation system in managing the dispersion of smoke resulting from a car fire incident within an underground car park spanning a total area of 21,670 m\({}^{2}\), situated in Tabriz, Iran. The primary objective of the study is to determine the velocity fields and evaluate visibility conditions within a 10 m radius to gauge the efficiency and effectiveness of the system. The study employs a smoke concentration production rate of 5.49 \(\times\) 10\({}^{-4}\) kg/m\({}^{3}\)s for simulations involving fire scenarios. A total of 17 fire scenarios are examined, each extending 30 m in all directions from the initial location. The research findings demonstrate that the placement of jet fan components plays a significant role in the system's efficiency, with fans positioned near the ceiling leading to back-layering. To mitigate this issue, the recommended design solution involves the strategic installation of multiple jet fan arrays in specific zones with the addition of 10 extra jet fans, effectively curbing lateral smoke dispersion. Furthermore, the analysis of air flow rates shows that when jet fans direct an excessive airflow towards the exhaust shafts (which have a designated flow rate of 22.5 m\({}^{3}\)/s), recirculating flows occur, leading to the dispersion of smoke throughout the car park. Consequently, the utilization of low-velocity jet fans (11.2 m/s) proves to be more effective in clearing smoke compared to high-velocity jet fans (22.3 m/s). The study also emphasizes the importance of optimal positioning of supply and exhaust shafts to achieve effective smoke control, highlighting the need for placing them on opposite walls or minimizing airflow turns. Additionally, the research underscores the significance of fire resistance in jet fan units, as their failure during fire incidents can have severe consequences. induction fan; jet fan; indoor air quality; fire safety; computational fluid dynamics; smoke management; impulse ventilation +
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this approach is associated with high costs, necessitates extensive equipment, occupies significant space, and results in substantial head losses [3]. Recently, a novel mechanical ventilation system has emerged, utilizing jet fans (also termed as impulse fans or induction fans) mounted beneath the car park ceiling, known as positive pressure ventilation (PPV). This approach draws inspiration from the use of jet fans for longitudinal ventilation in tunnels [4]. While one-dimensional flow is commonly assumed in tunnel applications, the ventilation dynamics in underground car parks, where flow conditions are approximately isothermal, predominantly occur in two dimensions. Consequently, the design of such ventilation systems becomes more intricate [3]. The integration of jet fan ventilation systems into car park and tunnel ventilation holds substantial promise for advancing the concept of carbon neutrality. These systems have been shown through empirical evidence to exhibit a heightened level of energy efficiency when compared to traditional methods [5; 6]. This observation gains even greater significance within the current landscape, characterized by a discernible shift towards the replacement of conventional systems with environmentally conscious alternatives. This collective effort seeks to amplify the pursuit of carbon neutrality, particularly within the realm of building design and infrastructure development [7; 8; 9; 10; 11; 12]. In the context of this trend, the adoption of jet fan ventilation systems serves as a notable example of embracing innovative solutions to achieve heightened sustainability goals and mitigate global warming. The design complexity of jet fan ventilation systems necessitates the use of computational fluid dynamics (CFD) to model airflow within the car park and ensure optimal design effectiveness.