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The Cloth Air Duct

Ⅰ. Introduction:

The cloth air duct is a kind of air supply duct woven from ordinary fiber cloth and passed through the holes on the surface of the cloth. The cloth air duct originated in the frozen and refrigerated food industry in the 1950s and 1960s. In order to meet the special requirements of large cooling capacity and low wind speed in the cooling area, HVAC engineers in various countries have all tried to make air outlets with ordinary cotton fiber fabrics. This type of air duct is shaped like a cloth bag and is commonly known as a cloth air duct in China. Since the fiber permeability is not important, it cannot match the fan, so the air delivery is not good. And it will cause problems such as air holding and fiber life, leading to the gradual disappearance of the duct in the 1970s and 1980s.

Ⅱ. Advantages:

1. Low wind speed at the end. The cloth air ducts can ensure the low wind speed at the end by penetrating or opening holes on the surface of cotton fabric.

2. Lightweight and easy installation. Cloth air ducts made of cotton fiber fabric are light in weight, easy to install, and have no load-bearing requirements on the roof.

Ⅲ. Disadvantages:

1. Poor air delivery. Since the cloth air duct is woven with ordinary cotton fabric, it does not require accurate fiber permeability, which will not be able to match with the fan, resulting in air holding and pressure relief.

2. Poor fire resistance. Since the cloth air duct is woven with ordinary cotton fabric, it does not have fire performance or low fire rating, so it cannot meet the requirements of fire engineering acceptance.

3. Short service life. Since the cloth air duct is woven with ordinary cotton fabric, it has a short service life.

Ⅳ. Development:

At the beginning of the invention of the cloth air duct, it met the requirements of low wind speed in refrigeration places to a certain extent and was locally used in the frozen and refrigerated food industry. However, the cloth bag duct is woven from ordinary cloth, and due to the poor permeability of the fiber material, the cloth duct cannot match the fan. Its air supply effect is also poor, and there will be problems such as wind holding and fiber life, so the cloth duct gradually disappeared in the 1970s and 1980s.

In the 1980s and 1990s, with the continuous innovation of fiber material technology and textile technology in the world, it was possible to weave fiber materials with the required physical properties such as accurate permeability and fire resistance. More and more new materials are used in industrial production. Engineers in the foreign HVAC field have also noticed this trend and tried to use new fiber materials to replace the original ordinary cotton fabrics. The textile air duct made of this new material is no longer a traditional air distribution duct, but a new system product that matches the air-conditioning system by calculating the permeability of the fiber material and accurately designing the openings. In order to meet the best matching requirements with the air-conditioning system in different projects, so as to ensure the final air-conditioning effect, this new type of air distribution duct must match at least 10 types of permeability materials with different standard specifications, and the error rate of the permeability index must be less than 5%. Such as: 0mm/s (impermeable); 1mm/s, 2mm/s, 5mm/s (micro-penetration); 10mm/s, 20mm/s, 30mm/s (medium penetration); 40 mm/s, 80 mm/s s, 100 mm/s (large penetration) and more than 10 permeability standard specifications.

This upgraded new type of cloth air duct product was introduced into China at the beginning of the 21st century and is called SOX air duct.