Occupants and office workers in high-rise buildings often worry about insufficient fresh air volume, while designers often feel aggrieved. On paper, the specified fresh air volume standards are not low, but we often overlook a key issue: how to ensure actual performance through design. The application of constant air volume valves in fresh air systems is an effective measure. Investigations show that in China, the HVAC configuration of fan coil units combined with fresh air systems remains widespread, particularly in hotel guest rooms; most office buildings adopt this approach.

It is common practice to install fresh air handling units on each floor, lay fresh air main ducts in the corridors, and connect dozens of branch ducts from the main duct to individual rooms. Taking hotel guest rooms as an example, the fresh air volume per room is generally 100m3/h. How can consistent airflow be achieved across all branch ducts?

Generally, designers tend to install an air volume control damper on each fresh air branch duct, expecting to complete air distribution through post-installation commissioning. According to the author's understanding from Refrigeration News, since fresh air systems typically have long main ducts and short branch ducts, and because dampers are neither intuitive to adjust nor ideal in terms of adjustment precision, plus the fresh air volume per guest room is only 100m3/h, which is very small, such commissioning is virtually impossible to complete.