Ventilation in enclosed spaces such as parking lots is essential to eliminate from the atmosphere all those pollutants harmful to people inside the enclosure, providing fresh air necessary for passers-by or drivers
Inside a parking lot, Jet Fans induce air movement to the last extraction point to ensure good ventilation in all areas. These fans have the function of distributing and controlling the air around the entire enclosure.
As we know, carbon monoxide (CO) is the most dangerous pollutant emitted by a car, for stays of less than an hour. The recommended concentration of CO can reach 125 ppm, however, for a stay equal to an eight-hour working day, the maximum permissible level is 50 ppm (57 mg / m3), therefore, there are three systems to adequately ventilate parking lots.
INJECTION VENTILATION. Its main advantage is that the input air comes from the outside, however, publications such as NBI – CPI 96, ANSI/ASHRAE standard 62, and NFPA standard 88 request the evacuation of smoke in case of fire, discarding this method.
VENTILATION BY EXTRACTION. It has the advantage of being able to control the discharge through ducts, to the appropriate place in accordance with current regulations. There are some very useful criteria in the design that are not mandatory, for example, having extraction grids at the rate of every 100 m2 and no more than 10 m of separation from each other. In order to avoid turbulence inside the ducts the speed should not exceed 10m/sec. As a consequence the sound level will also be at an acceptable level, 68 dB (A) measured at 1.5 m. from the fixed source.
MIXED SYSTEM (IMPULSION AND EXTRACTION). Through this, it is possible to obtain an optimal distribution of air inside the parking lot, reaching almost every corner. The drive system will transport fresh air from the outside and, therefore, a normal fan will be used, while the extraction system is capable of evacuating smoke in case of fire, withstanding temperatures of 400°C for 90 minutes.
Forced ventilation must meet the following conditions:
Be able to carry out six renovations per hour, being activated by automatic detectors. Have independent switches for each plant that allow the start-up of the fans. Guarantee the operation of all its components for 90 minutes, at a temperature of 400°C. Have direct power supply from the main panel. In both natural and forced ventilation, no point shall be more than 25 m away from a hollow or smoke extraction point. Outdoor air catchment mouths must be removed from the garden floor, separated from luminous signs, away from air discharges and never on the ground because it can be obstructed by objects or debris. Duct flows into a place of public access, the exit mouth must be at a height of at least 2.5 m from the ground, or exceeding one meter the maximum height of the adjacent buildings, always being more than 10 m from any opening.The principle used for ventilation within a parking lot is based on the amount of air that can be induced by jet fans, as well as its dimensions, since the amount of air, sound level and power consumed depend on this.
Figure 1. Shape of the airflow of a Jet FanFigure 2. Airflow induction
Jet Fans must be located inside the parking lot by the system designer. A very useful tool for this is the analysis and simulation using CDF (Computational Fluodynamics). This is a computer-specific tool for numerical simulation of the behavior of fluid flow systems, heat transfer, chemical reaction and other related physical phenomena. It is possible to solve the fluid flow equations in the region or domain of interest, with specific conditions in the contours of the domain, these equations are known as Navier-Stock.
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