Air duct mainly refers to the ventilation duct of central air conditioning system, which is often ignored, but it is an important part of air conditioning system. There are four kinds of common air duct at present

1) The results show that: 1) galvanized steel sheet air duct; 2) inorganic glass fiber reinforced plastic air duct; 3) composite fiberglass board air duct; 4) fiber fabric air duct

Galvanized steel sheet air duct: one of the earliest used air ducts, which is made of galvanized steel sheet, is suitable for the transportation of general gas with small moisture content. It has the characteristics of easy rusting, no heat preservation and noise elimination, and long production and installation cycle.

Inorganic glass fiber reinforced plastic air duct: a relatively new type of air duct, made of glass fiber reinforced inorganic material, non combustible in case of fire, corrosion resistance, heavy weight, high hardness but relatively brittle, easy to deform and crack under the influence of self weight, no heat preservation and sound attenuation performance, long production and installation cycle.

Composite fiberglass board air duct: the type of air duct in recent years, with centrifugal fiberglass board as the base material, with glass fiber cloth inside and moisture-proof aluminum foil cloth on the outside (the imported plate is coated with heat-sensitive black acrylic polymer, and the outer layer is thin cloth / aluminum foil / kraft paper) It is made by cutting, slotting, bonding and strengthening after drying with fireproof adhesive. Appropriate reinforcement measures are adopted according to the cross-section size and wind pressure of the air duct.

Fabric air duct: also known as bag duct, fabric duct, fabric air distributor, is the latest type of duct. It is a kind of flexible air distribution system made of special fibers. It is a kind of air outlet end system which replaces the traditional air supply pipe, air valve, diffuser and thermal insulation material. It is a kind of air terminal system which can supply air evenly mainly by fiber infiltration and orifice jet. It has surface type air outlet, large air volume, no sense of blowing; the overall air supply is evenly distributed; anti condensation; easy to clean and maintain, healthy and environmental protection; beautiful and high-grade, color diversity, personalized prominent; light weight, the roof load can be ignored; the system runs quietly and improves the environmental quality; the installation is simple and the project cycle is shortened; the installation is flexible and can be reused; the system cost is comprehensively saved, High cost performance and other advantages.

Performance comparison of four kinds of air duct

Anechoic performance;

Galvanized steel sheet air duct: no sound attenuation performance, its vibration will produce sound, must be equipped with muffler.

Inorganic glass fiber reinforced plastic air duct: no sound attenuation performance, sound insulation performance is better than galvanized steel sheet air duct, must be equipped with muffler.

Composite fiberglass board air duct: its wall is a kind of porous sound-absorbing material, so special muffler can be omitted.

Fiber fabric air duct: its wall is flexible fiber fabric, which is the poor conductor and absorber of sound. It will not produce sound and can absorb equipment noise to a certain extent. With the extension of the pipeline, the effect is more obvious, and special muffler can be omitted.

Thermal insulation performance

Galvanized steel sheet air duct: the thermal conductivity is very large (60.4 w / m · K), without thermal insulation performance, so it is necessary to add thermal insulation layer and protective layer.

Inorganic glass fiber reinforced plastic air duct: high thermal conductivity (0.5 w / m · K), no thermal insulation performance.

Composite fiberglass board air duct: small thermal conductivity (less than 1 W / m · K at average temperature of 24 ℃), with certain thermal insulation performance, without thermal insulation.

Fiber fabric duct: the purpose of duct insulation is to prevent energy loss and condensation on the duct surface. Fiber fabric air duct works in the opposite way, sacrificing a small amount of cooling capacity (less than 10%) to prevent condensation on the surface of the air duct (the cooling capacity still enters the actual air supply area). By using the permeability of the fabric itself, a cold air layer is formed on the surface of the air duct, so that there is no temperature difference between the inside and outside of the pipe wall, so there is no condensation. The same effect can be achieved by using a large number of thermal insulation materials for ordinary air duct.

Fire performance

Galvanized steel sheet air duct: non combustible, but whether the insulation layer burns depends on the material.

Inorganic glass fiber reinforced plastic air duct: the same as galvanized steel sheet air duct.

Composite fiberglass board air duct: non combustible glass fiber cotton board as the base material, has a certain fire resistance, but whether the finished product is flame retardant depends on the adhesive used in the air duct. (most of the adhesives have poor fire prevention effect)

Fiber fabric air duct: the fire resistance characteristics depend on the fiber material. The general fiber fabric air duct adopts new flame retardant fiber, which meets the GB 8624-2006 B-class fire protection standard. If the fire prevention requirements are high, there is a Sox brand in China. The air duct made of special glass fiber cloth can meet the class a fire protection standard of GB8624-2006.

Moisture resistance

Galvanized steel sheet air duct: easy to be affected by moisture, corrosion and rust, especially when transporting air with large moisture content.

Inorganic glass fiber reinforced plastic air duct: restricted by the proportion of raw materials, the stability of its moisture-proof performance is poor.

Composite fiberglass board air duct: no perishable materials and components, but due to its porous material, it is necessary to prevent the pipe interior, pipe end and incision from being soaked in water for a long time.

Fiber fabric air duct: due to the surface of the air-conditioning layer, so it will not produce condensation, materials are strong hydrophobic materials, not susceptible to moisture. Even if the surface of the air duct is stained with water, it will dry rapidly due to the penetration of the air duct surface.

strength

Galvanized steel sheet air duct: high strength, strong static pressure resistance, when the section size is large, it must be reinforced according to regulations.

Inorganic glass fiber reinforced plastic air duct: high strength, but relatively fragile, because of its heavy, not easy to handle, easy to be collided, resulting in cracking and damage.

Composite fiberglass board air duct: it can meet the pressure bearing requirements of general ventilation and air conditioning, and can bear the maximum wind pressure of 1500pa.

Fabric duct: flexible material, but good toughness. The withstand voltage is greater than 2000Pa.

weight

Galvanized steel sheet air duct: volume weight is 7870kg / m3, unit area weight is 10kg / m2 ~ 16KG / m2.

Inorganic glass fiber reinforced plastic air duct: volume weight is 2100Kg / m3, unit area weight is 11kg / m2 ~ 23kg / m2.

Composite fiberglass board air duct: volume weight is 64kg / m3, unit area weight is 2.8kg/m2.

Fabric duct: Needless to say, everyone on earth knows it. (weight per unit area less than 0.25kg/m2)

Frictional resistance

The inner wall of the composite fiberglass duct is made of glass fiber cloth, and the surface roughness is 0.2mm, which is slightly larger than the measured value of galvanized steel sheet. When the wind speed in the air duct is less than 15m / s, the resistance along the way is less than 7% compared with that of the galvanized sheet steel duct (including the increased resistance of the reinforcement strut in the air duct) In general air conditioning system, the resistance along the way only accounts for about 10% of the local resistance (which is basically the same as that of galvanized sheet steel duct). Therefore, the increase of ventilation resistance of glass fiber duct is less than 1% compared with that of galvanized sheet steel duct, which has no obvious effect on the whole air duct system and can be ignored. The friction resistance of inorganic glass fiber reinforced plastic air duct is greater than that of galvanized steel sheet air duct, and is close to that of composite fiberglass board air duct. Fabric duct: about 1 / 3 of the sheet iron duct.

Fiber shedding

The inner wall of air duct is composed of glass fiber cloth, which has the ability of shielding fiber dispersion. Under the condition of 15m / s wind speed in the duct, the fiber on the inner wall of the air duct does not fall off, which fully conforms to the national health standards and ensures the indoor air quality and environment. Fiber fabric air duct: the material is textile, not attached fiber, and the fiber shedding rate is less than 0.1% at 25m / s wind speed.

Cleaning and maintenance

Galvanized steel sheet air duct: it needs to use advanced air duct cleaning technology, even the popular cleaning robot this year, which costs a lot and takes a long time.

Inorganic glass fiber reinforced plastic air duct: the same as iron sheet air duct

Composite fiberglass board air duct: due to its porous surface structure, bacteria and mold are easy to breed, but it is not suitable for cleaning.

Fiber fabric air duct: it can be directly put into the washing machine after disassembly, and the disassembly cycle is short.

Construction and installation

Galvanized steel sheet air duct: the pipe is heavy, the production and installation cycle is long, and the change of pipe size and direction is laborious and laborious. After the air duct is installed, the insulation layer is installed on site, and the process is complicated,.

Inorganic glass fiber reinforced plastic air duct: heavy, not easy to handle, high strength, but relatively fragile, vulnerable to impact, resulting in cracking and damage. The manufacturing and installation cycle is long, and the change of pipe size and direction is time-consuming. Noise reduction and heat preservation are the same as galvanized steel sheet.

Composite fiberglass board air duct: compared with iron sheet and glass fiber reinforced plastic air duct, the weight is lighter, and the material is easy to use, but auxiliary support is needed for throwing, which has certain requirements for the building structure.

Fiber fabric air duct: the quality is only 1 / 300 of the composite air duct, and the installation is extremely simple. In general projects, it can even be installed independently by a single person. Because the steel rope suspension is adopted, the structural requirements of the building are low. For example, this kind of air duct is used in the temporary tent of Beijing Olympic Temporary restaurant.

Galvanized steel sheet air duct: it is a traditional product, which has a wide range of uses and places of use. Its advantages and disadvantages have been recognized by the majority of users. However, due to its special strength and structure, it can not be completely replaced.

Inorganic glass fiber reinforced plastic air duct: it belongs to the second new product. Because of its advantages of fire prevention, corrosion prevention and noise isolation, it once occupied most of the air duct market. However, with the passage of time in recent years, people gradually understand some shortcomings of inorganic glass fiber reinforced plastic air duct, which makes the market share of inorganic glass fiber reinforced plastic wind pipe gradually shrink.

Composite fiberglass duct: the popular duct products are still used in large area.

Fiber fabric air duct: in recent years, due to its convenient installation, uniform air supply and easy cleaning characteristics, it makes up for the shortcomings of traditional air duct, and is quickly accepted by Chinese people. It is widely used in large space air supply places such as Carrefour and other large-scale supermarkets and Olympic venues.

Different places, different requirements, all kinds of air ducts have their own advantages. Due to the characteristics of cleaning and installation of fiber fabric duct, it has been widely valued after the outbreak of SARS, and its development is particularly rapid. We also expect that it can learn from each other with the progress of science and technology, and better comply with the requirements of the times.