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Ventilation systems designed for indoor car parks are planned based on two basic needs. These systems are designed for daily operation, evacuation of harmful vehicle exhaust gases and in case of emergency fire, to help people escape and firefighters intervene in fire.
Ventilation systems installed in closed car parks with Jet Fans have been seen in Europe for the last 7–8 years. In our country, it has been widely demanded in the last 2-3 years. This new approach to parking ventilation brings many technical and financial advantages, as well as causing a number of conceptual confusion.
The purpose of this article is to make a brief introduction and comparison of jet fan systems and classical ducted systems at the beginning; While jet fan systems are designed in our country, it is to highlight the contradictions between the targeted objectives and the criteria taken into consideration during the design.
To clarify “Smoke Control” and “Smoke Evacuation”.
VENTILATION NEEDS AND MISCELLANEOUS SYSTEMS
When the ventilation systems of the closed areas inside the building are examined in general; It can be seen that the conditioned fresh air is conveyed from the ceiling level or relatively high level of the neighborhood by means of a duct system and fed into the environment through a large number of vents or diffusers. Fresh air supplied from these vents and diffusers triggers the air movement and mixture in the environment with its induction effect. Fresh air is mixed with the ambient air in the area, providing a homogeneous air distribution and comfort conditions in the environment. As a basic principle, since the amount of fresh air and supply points are kept under control, the exhausted air exhausted from the space becomes relatively insignificant.
In car parks, designs and applications have been carried out for the last 20 years on the principle of obtaining a certain amount of change in the car park volume through an exhaust-based duct system. Providing fresh air to the car parks is relatively less important than exhaust. For the amount of fresh air, an indirect fresh air control is created by keeping the amount of exhaust air under control. In general, it is essential to take fresh air naturally from ramps, openings, and kuranglez.
In extreme cases, if there is insufficient natural clearance in the parking lot, a limited number of fresh air fans and fresh air is supplied to the parking lot.
JET FAN SYSTEM
Jet Fan applications, on the other hand, are based on numerous, small-sized fans that can create high air speeds instead of the duct system in the car park. Jet Fans have been used in tunnel applications for a very long time. Principle; It was built upon the fans creating very high air velocities at the firing mouths and pushing the large air masses in front of them. The momentum in the high velocity air mass exiting the fan will affect the whole environment and with the induction effect it will activate a much more air mass than the air passing through the fan.
Jet Fans are strategically placed in the car park and transmit the above mentioned air mass movement towards the exhaust shafts. Jet Fans take on the task of creating air flow on the desired route in a controlled way in the parking lot. Compared to the ducted system, they replace the ducts and equipment such as grilles, diffusers and dampers.
The main exhaust fans in the shafts, on the other hand, should provide the amount of exhaust (the amount of ventilation) required by the car park. The difference to note here is that compared to a ducted system, the main exhaust fans located in the shafts will work against a much lower, in some cases almost negligible, resistance, since there will be no suction ducts on the car park side from the shaft. This difference allows Jet Fan systems to consume less energy in terms of operation, thus making their operation more economical.
Jet Fans are known for their thrust – Newton values. The propulsion force of a Jet Fan is proportional to the amount of air mass passing through it and the speed it gives to this mass.
(Thrust Force = Amount of air passing through the fan x Specific gravity of the air x Fan Firing Speed)
CLOSED CAR PARKS
As stated in the introduction paragraph, ventilation systems in indoor parking lots have two main objectives; In daily operation, in the event of evacuation of harmful vehicle exhaust gases and emergency fire, it should be designed to help people escape and firefighters’ response to fire.
According to the British Building Regulations, the ventilation system;
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• It should provide 6 Air Exchange of the total parking volume in Daily Work. (In our country, 4,5 or 5 air changes are taken as basis. Sometimes German Parking Regulation is also taken into consideration. Daily ventilation designs are made in Germany as 12-16 m3 / hour / m2.)
• For Air Evacuation, 10 Air Exchanges of single floor parking volume should be provided in an emergency.