Application of air-conditioning ducts and insulation materials

In the ventilation project, the air duct production should be based on the project requirements of the selection of suitable materials for the air duct. Design and construction personnel, need to fully understand the different material properties of the duct and they can be used, application occasions, and in what circumstances need to duct insulation, so as to build a set of reasonable and durable ventilation duct network system.

The materials used for ventilation ducts are commonly used in the following ways:

A Sheet metal, sheet metal is the main material for making air ducts and components.

(1) Ordinary thin steel plate, with good processing performance and structural strength, is commonly used for general ventilation ducts and dust ducts. Its surface is prone to rust and should be painted to prevent corrosion.

(2) galvanized steel, galvanized from ordinary thin steel, its surface has a zinc layer to protect against rust. Because of its silver-white surface, also known as 'white iron'. White iron is generally thin, commonly used in air-conditioning systems without dust abrasion in the gas and not subject to the action of acid mist in the humid environment.

(3) Aluminum and aluminum alloy plate, good processing performance, corrosion resistance, friction is not easy to produce sparks, but the cost is higher, commonly used in the requirements of explosion-proof ventilation system.

(4) Stainless steel plate, with good corrosion resistance, its cost is higher, just in the higher requirements for corrosion resistance, such as chemical systems in the ventilation pipe.

B Non-metallic materials, there are more kinds of non-metallic materials used in ventilation ducts, but their applications are not as common as sheet metal.

(1) rigid polyvinyl chloride, acid, alkali and corrosion resistance, good mechanical processing performance, smooth surface, easy construction. Commonly used in corrosive gas ventilation system. But hard polyvinyl chloride is not resistant to high temperatures, the use of temperature is generally not more than 60 degrees, the coefficient of linear expansion is large, not easy to aging and fire prevention.

(2) glass fiber reinforced plastic, which is a glass fiber products as reinforcing materials, resin as a binder, after a certain molding process made of composite materials. Corrosion resistance is very good, commonly used in corrosive gases and water vapor containing exhaust systems

(3) Plastic composite steel plate, which is in the ordinary thin steel surface sprayed with a layer of 0.2-0.4mm thick plastic layer. This kind of steel plate is more expensive, 50% more expensive than ordinary carbon steel plate.

(4) Brick and concrete, which are the most common building materials, commonly used in the use of building space or laying underground air ducts.

Usually, the ducts made of the above materials have the following applications:

1) Thin steel plate: general ventilation and air conditioning system: 0.5~1.5mm; dust removal system: 1.5~3.0mm.

(2) Plastic plate: ventilation system containing corrosive gases.

(3) Inorganic fiberglass: occasions with high humidity.

(4) Various kinds of hoses: metal, plastic, some can be with insulation.

(5) Composite duct: double-layer aluminum foil with phenolic resin, single-layer aluminum foil with glass fiber, commonly used in air-conditioning systems with high dust-proof requirements and corrosion-resistant systems from -10℃ to 70℃.

(6) New flexible duct: superior air distribution uniformity, to avoid the feeling of blowing; light weight, easy and quick installation, low structural requirements; good flexibility, easy to change the system; easy to clean.

In the following cases, our construction workers should insulate the air duct:

(1) Due to the excessive cold and heat loss, it is economically unreasonable not to insulate;

(2) Due to cold, heat loss so that the medium temperature does not reach the temperature required by the design;

(3) Due to heat loss, the temperature of the gas being conveyed in the duct is reduced to the point where condensation or freezing is possible in the duct or in a subsequent dry dust collector;

(4) Condensation on the outside surface of the duct due to loss of cold;

(5) Due to the delivery of high temperature gases, the temperature of the outer surface of the duct is too high (e.g., greater than 50 ℃), which will cause scalding of the operation and maintenance personnel, or will cause gas, steam, dust explosion, fire occasions.

The specific requirements of insulation materials are:

(1) small thermal conductivity, generally no more than 0.23W/m-K;

(2) The material has high porosity and low density, and the density generally does not exceed 600kg/m3;

(3) Has a certain compressive strength, not easy to deform;

(4) Small hygroscopicity, no corrosive effect on the pipe wall;

(5) should not be used in organic and flammable materials, otherwise anti-corrosion and fire prevention treatment

(6) Used in high-temperature pipelines, it should be heat-resistant and have stable performance under high temperature;

(7) Easy construction and installation, low cost.

by Carol