Ductless Ventilation System Design

Designing a ductless ventilation system for car parking areas can be a challenging task. This guide will walk you through the process, focusing on the use of axial and centrifugal fans, their specifications, and placement. Additionally, we will discuss how to calculate the required number of fans and their positioning based on the area to be covered.

Understanding Axial and Centrifugal Fans

Axial Fans

Axial fans are commonly used in ductless ventilation systems due to their ability to move large volumes of air. These fans are typically installed in the ceiling or walls of the parking area. There are two main types of axial fans used:

1. 315mm Diameter Axial Fan: This fan has a thrust of 32 Newton and can cover an area of 400 square meters. It is suitable for smaller sections of the parking area, with dimensions of approximately 20 meters by 20 meters.
2. 400mm Diameter Axial Fan: This fan has a thrust of 50 Newton and can cover an area of 500 square meters. It is suitable for larger sections, with dimensions of approximately 25 meters by 20 meters.

Centrifugal Fans

Centrifugal fans work by sucking air from below and discharging it perpendicularly. These fans come in two capacities:

1. 50 Newton Thrust Centrifugal Fan: This fan can cover an area of 500 square meters, with dimensions of approximately 25 meters by 20 meters.
2. 100 Newton Thrust Centrifugal Fan: This fan can cover an area of 1000 square meters, with dimensions of approximately 50 meters by 20 meters.

Calculating the Required Number of Fans

To determine the number of fans needed for your parking area, follow these steps:

1. Determine the Area: Measure the total area of the parking space. For example, if the length is 100 meters and the width is 40 meters, the total area is 4000 square meters.

2. Divide the Area into Sections: Depending on the type of fan you are using, divide the area into smaller sections. For example, if you are using 315mm diameter axial fans, each fan can cover 400 square meters. Therefore, you would divide the total area by 400 to get the number of fans required.

3. Position the Fans: Place the fans in a grid-like pattern to ensure even coverage. For example, if your parking area is 100 meters by 40 meters, you could place fans every 20 meters along the length and width of the area.

Fan Control Mechanisms

The speed and operation of the fans can be controlled based on CO and CO2 levels in the parking area. Here is a basic control mechanism:

1. Low CO Levels (Below 50 ppm): Operate axial smoke extraction fans and axial fresh air fans at 50% speed. Impulse fans remain off.
2. Moderate CO Levels (50-100 ppm): Operate axial smoke extraction fans and axial fresh air fans at 50% speed. Impulse fans operate at low speed.
3. High CO Levels (Above 100 ppm): Operate axial smoke extraction fans and axial fresh air fans at 100% speed. Impulse fans operate at low speed.
4. Fire Mode: Operate axial smoke extraction fans at 100% speed. Fresh air fans are turned off to prevent the spread of fire. Impulse fans operate at high speed.

Conclusion

Designing a ductless ventilation system for car parking areas involves careful planning and calculation. By understanding the specifications and placement of axial and centrifugal fans, and implementing appropriate control mechanisms, you can ensure effective ventilation and safety in the parking area.

For more information on related topics, check out our pages on Introduction to HVAC Systems for Car Parking and Fan Control Mechanisms.