According to the formula:
Wind pipe size = air volume / wind velocity, air volume = room area * room air changes.
Air volumeis 40,000
Wind velocityis 9m/s
The size of the wind pipe =40000/9/3600=1.23 m2
ReferencedUnified specification form for rectangular ventilation ducts, the size of the wind pipe type is 1600*800.
Above can be seen that the influence factors of wind pipe type are as follows:
1. Air volume;
The fact of air volume is total air volume per hour, in order to consistent with wind velocity, it need to be divided by 60*60. Although 3600 is a fixed value, Air volume is still affected by room volume and room air circulation ratio.
2. Room volume;
Generally speaking, it is provided by design. If not, we can confirm the volume by measuring.
3. ACH(Air changes);
It is significant for wind pipe design. And it is determined by GMP partitions.
4. Wind velocity;
There are two main factors affects the wind velocity. One of them is noise that is indoor environmental control factors. According the specification, within the allowable range of noise, different noise levels determine different wind velocity ranges.Another one is resistance .the more wind velocity, the more resistance is.
In summary, only control these four factors, we can get the sectional area of the wind pipe. Then compare to the Unified specification form for rectangular ventilation ducts. Considering the other factors such as origin design, site fact and so on, we can get the most close to the size of the wind pipe type.