What kinds of air ducts are there and how to choose them?

Air duct mainly refers to the ventilation duct of central air conditioning system, which is often overlooked, but it is an important part of air conditioning system. At present, there are four kinds of common air ducts.

1) galvanized steel duct; 2) Inorganic FRP air duct; 3) Composite glass fiber board air duct; 4) Fiber fabric air duct

Galvanized steel plate air duct: one of the earliest air ducts, made of galvanized steel plate, is suitable for conveying general gas with small water content, and has the characteristics of easy rusting, no heat preservation and noise elimination function, long manufacturing and installation cycle, etc.

Inorganic glass fiber reinforced plastic air duct: a relatively new type of air duct, made of glass fiber reinforced inorganic materials, is incombustible in fire, corrosion-resistant, heavy, hard and brittle, easy to deform and crack under the influence of self-weight, without thermal insulation and noise reduction performance, and has a long manufacturing and installation cycle.

Composite glass fiber board air duct: In recent years, centrifugal glass fiber board is used as the base material, with glass fiber cloth inside and moisture-proof aluminum foil cloth outside (the imported board is coated with heat-sensitive black acrylic polymer, and the outer layer is sparse cloth/aluminum foil/kraft paper), which is then dried by flame retardant adhesive, cut, slotted and bonded and reinforced. Take appropriate reinforcement measures according to the section size and wind pressure of the air duct.

Fiber fabric air duct: also often called bag air duct, cloth air duct, fiber fabric air duct and fiber fabric air distributor. It is the latest type of air duct, a flexible air distribution system made of special fibers, and an air supply terminal system that replaces traditional air supply pipes, air valves, diffusers and thermal insulation materials. It is an air outlet terminal system which mainly provides uniform air supply through the unique air outlet mode of fiber infiltration and nozzle injection. With surface air outlet, large air volume and no blowing feeling; The overall air supply is evenly distributed; Anti-condensation; Easy to clean and maintain, healthy and environmentally friendly; Beautiful, upscale, colorful and personalized; Light weight, the roof load can be ignored; The system runs quietly, improving environmental quality; Simple installation, shortening the engineering cycle; Flexible installation, reusable; It completely saves the system cost and has high cost performance.

Performance comparison of four kinds of air ducts

Noise elimination performance;

Galvanized steel duct: it has no sound attenuation performance, and its own vibration will produce sound, so a muffler must be installed.

Inorganic glass fiber reinforced plastic air duct: it has no sound attenuation performance, and its sound insulation performance is better than galvanized steel air duct. A muffler must be installed.

Composite glass fiber board air duct: its wall is porous sound-absorbing material, which can save special muffler.

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

heat-proof quality

Galvanized steel duct: high thermal conductivity (60.4 W/m? K) When there is no thermal insulation performance, the temperature and protective layer must be added.

Inorganic FRP duct: high thermal conductivity (0.5W/m? K), no heat preservation performance.

Composite glass fiber board air duct: low thermal conductivity (less than 1 W/m at average temperature of 24℃? K), which has certain thermal insulation performance and does not need thermal insulation.

Fiber fabric air duct: the purpose of air duct insulation is to prevent energy loss and condensation on the surface of air duct. The fiber fabric air duct does the opposite, sacrificing a small amount of cold energy (less than 10%) to prevent condensation on the surface of the air duct (cold energy still enters the actual air supply area), and using the air permeability of the fiber 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 it will not condense, and a large number of thermal insulation materials are used in ordinary air ducts to achieve the same effect.

fire protecting performance

Galvanized steel duct: nonflammable, but whether its insulation layer burns depends on the material.

Inorganic FRP duct: same as galvanized steel duct.

Composite glass fiber board air duct: based on non-combustible glass fiber cotton board, it has certain fire resistance, but whether the finished product is flame retardant depends on the adhesive used in the air duct. (Most adhesives have poor fire protection effect. )

Fiber fabric duct: Fire resistance depends on fiber material. Fiber fabric air ducts generally adopt new flame retardant fibers, which meet the fire protection standard of GB8624-2006 B. If there is a high requirement for fire prevention, Sotheby's brand in China can meet the fire prevention standard of GB8624-2006 A by using special glass fiber cloth as air duct.

humidity resistance

Galvanized steel duct: It is easy to be corroded and rusted by moisture, especially when conveying air with high water content.

Inorganic FRP duct: Limited by the proportion of raw materials, the moisture-proof performance is unstable.

Composite glass fiber board air duct: there are no perishable materials and components, but because it is a porous material, it is necessary to prevent the inside of the pipeline, the pipe end and the incision from being soaked by water for a long time.

Fiber fabric air duct: Because there is a cold air layer on the surface, condensation will not occur, and the materials are all highly hydrophobic and not easy to get wet. Even if the air duct surface is stained with water, it will dry quickly because of the infiltration of the air duct surface.

intensity

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

Inorganic glass fiber reinforced plastic air duct: high strength, but fragile, because it is heavy, not easy to carry, easy to crack and damage after collision.

Composite glass fiber board air duct: it can meet the pressure requirements of general ventilation and air conditioning, and can bear the maximum wind pressure 1500Pa.

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

weight

Galvanized steel duct: unit weight 7870kg/m3, unit area weight 10kg/m2 ~ 16kg/m2.

Inorganic FRP duct: unit weight 2 100kg/m3, unit area weight 1 1kg/m2 ~ 23kg/m2.

Composite glass fiber board air duct: unit weight is 64kg/m3, and unit area weight is 2.8 kg/m2.

Fiber fabric duct: Needless to say, everyone knows. (Weight per unit area is less than 0.25 kg/m2)

friction drag

The inner wall of the composite glass fiber board air 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 plate. When the wind speed in the air duct is less than 15m/s, the resistance along the air duct is not more than 7% (including the resistance increased by the reinforcing struts in the air duct). In general air conditioning system, the resistance along the air duct only accounts for about 10% of the local resistance (which is basically the same as that of galvanized steel duct), so the ventilation resistance of glass fiber duct is smaller than that of galvanized steel duct by 1%, and the influence on the whole air duct system is not obvious, which can be basically ignored. The friction resistance of inorganic FRP duct is greater than that of galvanized steel duct and close to that of composite FRP duct. Fiber fabric air duct: about 1/3 of iron air duct.

Fiber shedding

The composite glass fiber cloth on the inner wall of the air duct has the ability to shield fiber diffusion. When the wind speed in the pipe is 15m/s, the fibers on the inner wall of the air duct will not fall off, which completely meets the national hygiene standards and ensures the indoor air quality and environment. Fiber fabric air duct: the material is textiles, not attached fibers. When the wind speed is 25m/s, the fiber shedding rate is less than 0.65438 0%.

Cleaning and maintenance

Galvanized steel duct: It needs advanced duct cleaning technology, even the cleaning robot popular this year, which is costly and time-consuming.

Inorganic FRP air duct: same as iron sheet air duct.

Composite glass fiber board air duct: Because of its loose and porous surface structure, bacteria and mold are easy to breed, but it is not suitable for cleaning.

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

Construction and installation

Galvanized steel duct: The duct is bulky, and the manufacturing and installation cycle is long, so it is time-consuming and laborious to change the size and direction of the duct. After the installation of the air duct, the insulation layer is installed on site, and the process is cumbersome.

Inorganic FRP duct: The duct is bulky, difficult to carry and high in strength, but fragile and easy to crack and be damaged by collision. The manufacturing and installation cycle is long, and the change of pipeline size and direction is labor-consuming and time-consuming. Noise elimination and heat preservation are the same as galvanized steel plate.

Composite glass fiber board air duct: Compared with iron sheet and glass fiber reinforced plastic air duct, it is lighter and easier to move, but it needs auxiliary support and has certain requirements for building structure.

Fiber fabric air duct: the mass is only 1/300 of that of composite air duct, and the installation is extremely simple. General projects can even be installed independently by one person, because they are suspended by steel ropes, and the requirements for building structure are not high. For example, the temporary tent of the Beijing Olympic Games temporary restaurant used this kind of air duct.

Galvanized steel duct: a traditional product, it has a wide range of uses and places of use, and its advantages and disadvantages have long been recognized by the majority of users. However, due to the particularity of its strength and structure, it cannot be completely replaced.

Inorganic FRP duct: it is a new product. Because of its advantages of fire prevention, anticorrosion and sound insulation, it once occupied half of the air duct market. However, in recent years, with the passage of time, people have gradually realized some shortcomings of inorganic FRP duct, which makes the market share of inorganic FRP duct gradually decrease.

Composite glass fiber board air duct: a popular air duct product, which is still used in a large area.

Fiber fabric air duct: The air duct that emerged in recent years has been quickly accepted by Chinese people because of its advantages of convenient installation, uniform air supply and easy cleaning, and is widely used in Carrefour, Olympic venues and other large space air supply places.

Different places and different requirements, all kinds of air ducts have their unique advantages. Because of the cleaning and installation characteristics of fiber fabric air duct, it has been widely valued and developed rapidly after the outbreak of SARS. We also expect it to learn from each other with the progress of science and technology and better adapt to the requirements of the times.