Ventilation duct is one of the very important facilities of modern buildings. Ventilation duct can keep indoor air circulation and discharge harmful gases. In the process of ventilation duct processing and design, the calculations involved mainly include air flow resistance in ventilation duct, pressure distribution in ventilation duct, hydraulic calculation of ventilation duct, calculation of uniform air supply duct, etc. Today, let's talk about some problems that should be paid attention to in the processing and design of air duct. Let's have a look.

1、通風系統的劃分：

1. Division of ventilation system:

不同地區的工業通風系統對送風和排風有不同的要求。當面積較大時，對應的供排氣點較多，可分為若干個供排氣子系統，一個系統由一個風機及其連接的管道組成，便于管理。系統劃分的主要依據是：如果生產過程和運行時間相同，建議將其劃分為一個系統;如果運行參數和空氣處理要求相同，建議將其分成一個系統;不建議將風扇附近排氣量較大的排氣點分成一個系統，這將增加排氣系統的阻力。此外，如果兩種或兩種以上的有害物質混合在一起，會增加毒性和腐蝕性，并容易引起火災和爆炸，它們不能被分成一個系統。建議單獨設置排氣系統。

Industrial ventilation systems in different regions have different requirements for air supply and exhaust. When the area is large, there are many corresponding air supply and exhaust points, which can be divided into several air supply and exhaust subsystems. One system is composed of a fan and its connected pipes, which is convenient for management. The main basis for system division is: if the production process and running time are the same, it is recommended to divide it into one system; If the operating parameters and air handling requirements are the same, it is recommended to divide them into one system; It is not recommended to divide the exhaust points with large exhaust volume near the fan into one system, which will increase the resistance of the exhaust system. In addition, if two or more hazardous substances are mixed together, they will increase toxicity and corrosivity, and easily cause fire and explosion. They cannot be divided into one system. It is recommended to set the exhaust system separately.

2.通風管道材料的選擇：

2. Selection of ventilation duct materials:

風管加工主要由鋼板、金屬軟管、塑料和橡膠軟管、纖維板、膠合板、石膏板、聚氯乙烯塑料板、磚和混凝土等制成。鋼板是通風管道常用的材料，具有耐腐蝕、耐高溫的特點，便于制造和安裝。一些通風管道在技術上需要經常移動，這需要柔性材料，如金屬軟管、塑料軟管和橡膠軟管。硬質聚氯乙烯塑料板表面光滑，加工方便，但不耐高溫，適用于腐蝕性工業通風和排氣系統。磚和混凝土制成的通風管主要適用于與建筑物連接，阻力小，經久耐用。總之，通風管道的材料應根據應用條件綜合選擇。

Air duct processing is mainly made of steel plate, metal hose, plastic and rubber hose, fiberboard, plywood, gypsum board, PVC plastic board, brick and concrete. Steel plate is a common material for ventilation pipe, which has the characteristics of corrosion resistance and high temperature resistance, and is convenient for manufacturing and installation. Some ventilation ducts technically need to be moved frequently, which requires flexible materials, such as metal hose, plastic hose and rubber hose. Rigid PVC plastic plate has smooth surface and convenient processing, but it is not resistant to high temperature. It is suitable for corrosive industrial ventilation and exhaust system. The ventilation pipe made of brick and concrete is mainly suitable for connection with buildings, with low resistance and durability. In short, the material of ventilation duct shall be comprehensively selected according to the application conditions.

3.通風管道截面形狀的選擇：

3. Selection of section shape of ventilation pipe:

風管加工時的截面形狀一般分為矩形和圓形。在相同橫截面積的情況下，圓形通風管道不僅阻力小，而且強度高，節省了管道。對于圓形通風管道，直徑越小，制造越容易，保溫越方便。但是，矩形通風管道的管件比圓形通風管道的管件容易制作，布局也比圓形通風管道簡單。在正常情況下，當通風管的橫截面較小，管內流速較高時，宜采用圓形通風管;通風管道截面較大時，應采用矩形通風管道，并能充分利用建筑空間。對于矩形通風管道，寬高比越接近1越好，這樣不僅可以節省運行功率，還可以節省投資。

The section shape of air duct processing is generally divided into rectangular and circular. In the case of the same cross-sectional area, the circular ventilation pipe has not only low resistance, but also high strength, saving the pipe. For circular ventilation pipes, the smaller the diameter, the easier it is to manufacture and the more convenient it is to keep heat. However, the pipe fittings of rectangular ventilation duct are easier to manufacture than those of circular ventilation duct, and the layout is simpler than that of circular ventilation duct. Under normal circumstances, when the cross section of the ventilation pipe is small and the flow rate in the pipe is high, the circular ventilation pipe should be used; When the cross section of ventilation duct is large, rectangular ventilation duct shall be adopted and the building space shall be fully utilized. For rectangular ventilation duct, the closer the aspect ratio is to 1, the better, which can not only save operating power, but also save investment.