I. Sources of Air Flow Resistance



The air flow resistance in ventilation pipes mainly includes two types: frictional resistance and local resistance:



1. Frictional resistance: Resistance generated by air flowing inside the pipe due to friction with the pipe wall, which is closely related to factors such as pipe length, pipe diameter, and air velocity.



2. Local resistance: Energy loss caused by the change of flow direction or cross-section when air flows through elbows, tees, reducers, valves, and other components.



II. Main Measures for Controlling Air Flow Resistance



# 1. Reasonable Selection of Pipe Materials and Inner Wall Roughness



The smoothness of the inner wall of pipes made of different materials varies, which also has a significant impact on air flow friction resistance. For example, galvanized steel pipe has high strength but a relatively rough inner wall, which is prone to generate greater friction resistance; while pipes made of PVC or glass fiber have smoother surfaces, which helps to reduce resistance. In actual engineering, appropriate materials should be selected according to system requirements.



# 2. Designing a Reasonable Pipe Layout



A good pipe layout can effectively reduce air flow disturbance and backflow. Specific measures include:



- Try to use straight layouts to reduce unnecessary elbows;



- Elbows should adopt large curvature radii to avoid sharp turns;



- Avoid sudden changes in pipe cross-section, use gradual transition sections;

　　- Reasonably arrange the connection angle between branch pipes and main pipes to reduce air flow disturbance.



# 3. Controlling Air Velocity

　　Excessive air speed will increase the resistance along the path and also exacerbate local resistance loss. Therefore, when designing ventilation systems, appropriate pipe diameter should be selected according to the air volume demand to control the air velocity within a reasonable range (usually the main air duct is controlled at 8~12 m/s, and the branch air duct is controlled at 4~6 m/s).



# 4. Regular Maintenance and Cleaning

　　During the long-term operation of ventilation pipes, it is easy to accumulate dust and impurities, which not only affects air quality but also increases the roughness of the inner wall, leading to increased air flow resistance. Therefore, regular cleaning and maintenance of the pipes is an important means to maintain the efficient operation of the system.

　　III. Intelligent Control and Optimal Design



With the development of intelligent building technology, an increasing number of ventilation systems are beginning to adopt CFD (Computational Fluid Dynamics) simulation and intelligent control systems to optimize air flow distribution. Through simulation analysis, air flow resistance distribution can be predicted in the design phase, and layout can be optimized; while the intelligent control system can dynamically adjust the fan speed and the opening of the air valve according to the actual operating status to achieve demand-driven air supply, further reducing energy consumption and improving efficiency.



Conclusion



In summary, controlling the air flow resistance in ventilation pipes is a systematic project involving aspects such as material selection, structural design, and operational management. Through scientific design and reasonable operation and maintenance, it can not only effectively reduce energy consumption but also extend the service life of equipment, improve the overall operation efficiency of the system, and enhance air quality. In the context of the trend of green buildings and energy saving and emission reduction, strengthening research and optimization of air flow resistance in ventilation systems has important practical significance and social value.