工业通风管道设计需考虑的主要因素
Main factors to be considered in the design of industrial ventilation duct
工业通风管道设计过程中，需考虑的主要因素有通风管道内空气流动的阻力和通风管道内的压力分布。通风管道内空气流动的阻力有两部分。一部分是由于空气本身的粘滞性及与管壁之间的摩擦产生的能量损失，即摩擦阻力。另一部分是空气流经通风管道中的管件和设备时，流速的方向和大小的不断变化与产生涡流造成相对比较集中的能量损失，即局部阻力 。
In the design process of industrial ventilation pipe, the main factors to be considered are the resistance of air flow in the ventilation pipe and the pressure distribution in the ventilation pipe. There are two parts of the resistance of air flow in the ventilation duct. Part of it is due to the viscosity of air itself and the energy loss caused by the friction between the air and the pipe wall, namely the friction resistance. The other part is that when the air flows through the pipe fittings and equipment in the ventilation pipe, the constant change of the direction and size of the flow velocity and the generation of eddy current cause relatively concentrated energy loss, that is, local resistance.
在工业通风系统中，通风管道的摩擦阻力与空气在通风管道内的流动状态以及管壁的粗糙程度有关。一般情况下，高速风管的流动状态处于过渡区；薄钢板的通风管道的空气流动状态多处在紊流光滑区和粗糙区之间的过渡区；只有混凝土和砖的通风管道，在流速很高时，空气流动状态才是粗糙区。在工业通风系统中，当空气流过断面变化、流向变化和流量变化的管件时，都会产生局部阻力。局部阻力在工业通风系统中占有较大的比例，设计时应该注意，尽量减少局部阻力的产生 。
In the industrial ventilation system, the friction resistance of the ventilation pipe is related to the flow state of air in the ventilation pipe and the roughness of the pipe wall. Generally, the flow state of high-speed air duct is in the transition zone; the air flow state of thin steel plate ventilation duct is mostly in the transition zone between the turbulent smooth zone and the rough zone; only the concrete and brick ventilation duct, when the flow rate is very high, the air flow state is the rough zone. In the industrial ventilation system, when the air flows through the pipe fittings with different cross-section, flow direction and flow rate, it will produce local resistance. Local resistance occupies a large proportion in the industrial ventilation system. Attention should be paid to reduce the local resistance as much as possible in the design.