As modern architecture places increasing demands on indoor environmental quality, traditional metal duct systems are gradually revealing limitations in noise control, airflow organization, installation convenience, and aesthetics. Against this backdrop, fabric ducts (also known as textile ducts, fiber ducts, or air distribution systems) have gained widespread application in commercial, industrial, medical, sports, and cleanroom settings as a novel form of air terminal. The design of fabric ducts involves not only airflow performance but also a multidimensional integration of thermal comfort, acoustic control, materials science, and architectural aesthetics.

1. Fundamental Principles and Structural Characteristics

Fabric ducts are woven from polymer fiber materials through specialized processes, with internal composite functional coatings such as microporous layers, anti-mold layers, and flame-retardant layers. Their core operating principle utilizes the inherent permeability of the fabric or supply outlets (such as slits, round holes, and nozzles) opened at specific locations to release conditioned air into the target area at low speed and uniformly. Compared to traditional metal ducts that rely on centralized air supply through outlets, fabric ducts achieve "surface" or "linear" air distribution, effectively avoiding issues such as uneven temperature and strong draft sensations.

Typically, fabric ducts are suspended below the ceiling in circular or semi-circular shapes. They are extremely lightweight (only 1/20 to 1/30 the weight of metal ducts), placing low load requirements on building structures, and are simple to install without the need for complex flange connections and insulation construction. Additionally, their surfaces can be customized with colors, patterns, and even light-transmitting effects, becoming part of interior decoration, especially suitable for venues with high visual requirements such as exhibition halls, hotel lobbies, and theaters.

2. Key Elements of Fabric Duct Design

Airflow Organization and Supply Mode Selection

At the beginning of the design, it is necessary to clarify the space usage, personnel density, heat source distribution, and temperature and humidity requirements. Based on these parameters, determine whether to adopt fully permeable air supply, partially permeable + local jet, or pure jet air supply modes. For example, in tall spaces (such as gymnasiums and workshops), bottom slits or directional nozzles are often used to achieve long-distance air supply; while in office areas or hospital wards, fully permeable or microporous uniform air supply is preferred to create a quiet and comfortable micro-environment.

Duct Size and Pressure Loss Calculation

The diameter of the fabric duct directly affects the internal air velocity and frictional resistance. During design, it is necessary to balance the air supply volume and static pressure requirements to ensure that there is still sufficient static pressure at the end to drive the air through the fabric or outlets. Typically, the inlet static pressure is controlled between 50–250 Pa. Too low will lead to uneven air supply, while too high may cause the fabric to bulge, deform, or increase noise. Professional design software can simulate pressure distribution under different operating conditions to optimize duct diameter and branch layout.

Material Selection and Functional Adaptation

Different application scenarios have varying requirements for material performance. Food factories and pharmaceutical workshops need to select hygienic-grade materials that are antibacterial, anti-mold, and easy to clean; swimming pools, cold storage, and other high-humidity environments emphasize anti-condensation and corrosion resistance; while places with strict fire codes must use fabrics that meet national B1-level or higher flame-retardant standards. In addition, additional functions such as light transmission, UV resistance, and anti-static properties also need to be considered in material selection.

Noise Control and Thermal Comfort

Fabric ducts themselves have good sound absorption performance, which can significantly reduce airflow noise. During design, local air velocity should be avoided from being too high (generally controlled below 2 m/s), and reasonable arrangement of air supply points should be made to reduce vortices and disturbances. At the same time, utilizing the characteristic that fabric surfaces are not prone to condensation when supplying cold air (due to large surface area and uniform temperature distribution), the supply air temperature can be increased, reducing energy consumption and realizing an energy-saving strategy of "high-temperature cooling and low-temperature heating".

3. Comparative Advantages over Traditional Systems

From a full life cycle perspective, fabric ducts outperform traditional metal ducts in multiple dimensions. First, their integrated air supply and insulation design eliminates the need for additional insulation construction, shortening the construction period by more than 30%; second, their light weight and high modularity make them easy to transport and assemble on-site, especially suitable for renovation projects or projects with tight schedules; third, the smooth fabric surface is not prone to dust accumulation, and with a detachable design, maintenance and cleaning are extremely convenient, helping to maintain indoor air quality; finally, their flexible appearance breaks the cold feeling of traditional mechanical and electrical equipment, achieving "invisible air supply" and enhancing spatial aesthetics.

4. Key Considerations in Design Practice

Despite their significant advantages, fabric duct design still needs to avoid several misunderstandings. For example, the design logic of metal ducts cannot be simply applied, ignoring the unique pressure-flow-permeability relationship of fabrics; in variable air volume systems, special attention needs to be paid to ensuring air supply uniformity under low air volume conditions; for places with extremely high cleanliness requirements (such as operating rooms), it should be verified whether the fabric material meets particle shedding and microbial control standards. In addition, collaborative design with architecture, structure, electrical, and other disciplines is crucial to ensure that suspension points, maintenance channels, and lighting layouts are coordinated.

Conclusion

Fabric ducts are not only terminal components of ventilation and air conditioning systems but also a bridge connecting technology and humanity. Their design process reflects a shift from "functional satisfaction" to "experience optimization". In the future, with the integration of smart materials, IoT sensing, and digital twin technologies, fabric ducts are expected to achieve intelligent functions such as dynamically adjusting air supply modes and real-time monitoring of air quality, further promoting the development of green buildings and healthy living environments. In the context of the "dual carbon" goals and high-quality development, the design philosophy and practice of fabric ducts undoubtedly provide a new paradigm for the HVAC industry that combines efficiency, comfort, and aesthetics.