Our objective is to create a pleasant and healthy atmosphere in underground car parks, which increases the safety of the users (both people and emergency services). RWA in parking garages involves the extraction of smoke gases and temperature. The ventilation of closed parking garages is a speciality. Because of its concept (several floors under the ground) and its specific application (parking of cars) the building deserves special attention.
In order to meet the specific requirements of car parks, our ventilation for closed parking garages is derived from and has grown out of our many years of experience.
The application of this ventilation is twofold:
- CO ventilation (daily ventilation linked to CO detection)
- RWA ventilation (controlled smoke and heat evacuation in case of fire linked to smoke detection) The ventilation system ventilates the closed garage in an optimal way, and because of its concept, is much more effective and efficient than a conventional ventilation (smoke evacuation based on smoke accumulation within smoke compartments).
The ventilation system is adapted to the actual occupancy rate of the car park and continuously monitors the air quality in all areas of the car park. When vehicles circulate in a closed space, the CO content in this space automatically increases. The proposed impulse ventilation system maintains an air movement in the car park so that optimum air quality is ensured in the entire car park, including all the corners.
Air is supplied and removed via structural shafts in which large axial fans are mounted. Impulse fans are fixed to the ceiling of each level to ensure a continuous uniform air movement. The system is connected to a CO detection centre. The system will automatically switch from its daily ventilation to a higher air regime when the CO concentration in the car park rises.
In case of a vehicle fire in the car park, the produced smoke and heat will be exhausted in a fully controlled way into predefined and calculated corridors (smoke zones). All evacuation routes that do not lead to these smoke zones will remain visible and accessible at all times. The best positioning of the air supply and exhaust air is very carefully chosen in function of the layout of the car park. The air volume and the ideal configuration of the impulse fans are precisely determined to ensure proper operation of the system.
The air is supplied and exhausted in the same way as for CO ventilation, but now entirely concentrated on the area of the burning vehicle. All steps are taken to send a maximum air flow over the fire at high speed. Only those fans that are strictly necessary for smoke extraction will be activated. In an aerodynamic way, we create a virtual compartment through which the smoke is led in a controlled way to the extraction shaft. We always create a smoke-free path up to 15m from the burning vehicles, so that intervention by the fire service is possible up to the burning vehicle. An addressable smoke detection installation is indispensable. The smoke evacuation must comply with the installation standard NBN S 21-208-2.
The system has many advantages in terms of design and management of the car park compared to conventional ventilation with smoke evacuation in case of fire based on smoke accumulation within smoke compartments.
Advantages of ventilation system :
Better mixing of the ventilation air with the contaminated air, resulting in lower concentrations of contaminants in the mixed air.
- A better ventilation in all parts and corners of the parking garage by the induction action of the impulse fans.
- No air duct system is required so that there is a considerable gain of space
Advantages for the users :
Safe evacuation of customers is assured.
Permanent accessibility of the entire car park (including the fire area) for the emergency services.
No major structural damage to the building above the fire, due to the huge cooling effect of the large flows.
In order to make a prediction of the situation in the parking garage during a car fire, a CFD simulation is carried out. In order to perform this simulation, a 3-dimensional model of the parking garage is set up. Subsequently, the technical installations, fire parameters and ventilation are processed in the model. When the model is equipped with the corresponding physical parameters, it is ready for the simulation. Using a finite volume method, the mass, impulse and energy balances are solved per time step.
The simulation results are analysed for different quantities per time step.