How to determine air duct size for positive pressure air supply, exhaust air and smoke, and fresh ai

First you need to know the total air volume (fan air volume) Q, landscape area S=Q/3600/V

S unit m2

3600 unit s/h

V unit m/s

V is the pipe speed required by the water supply positive pressure air, smoke exhaust and exhaust, and fresh air systems.

The metal air duct of the positive pressure air supply, smoke exhaust and supplementary air system must not be higher than 20 m/s and the duct of civil air must not exceed 15 m/s for exhaust and fresh air; The air system (additional smoke-free exhaust air) is 5-8 m/s.

The exhaust fan has a motor that blows air towards the fan blades. Both the air supply fan and the exhaust fan are. the same fans, but they are installed in different directions and have transpo directionsrt different. That is, the fan has a motor that blows air towards the fan blades. The wind blows on the other side of the blades.

Air blower:

A fan that provides the air necessary for the combustion of fuel in the boiler. Arranged before the boiler air preheater. Air drawn from the atmosphere is sent to the air preheater. After being heated to the design temperature, part of it is used as boiler secondary air and is directly sent to the boiler furnace by the burner; system for preparing pulverized coal as a desiccant, then either as primary air, carrying the pulverized coal into the furnace through the burner, or as tertiary air, directly into the furnace through the burner.

Large scale units often use a medium speed coal mill positive pressure direct blow system. At present, if the sThe spray system is equipped with a main fan that specifically draws air from the atmosphere, the fan. supplies only secondary air to the boiler. Therefore, the selection of the air supply fan should not only ensure the required amount of air for boiler fuel combustion, but also overcome the corresponding resistance of the air supply duct system and the heating system. combustion.

Exhaust fan:

The exhaust fan produces a ventilation effect by exhausting air from inside or outside. The working principle of the exhaust fan is that the input electrical power drives the fan impeller to rotate through the motor to produce a suction or exhaust effect on the gas. The fan is composed of an air inlet, a turbine housing, a motor and other parts. The engine converts the powerthis electrical into mechanical power to drive the rotation of the turbine. The air inlet is used as a guide. The gas enters the turbine smoothly to transfer rotational kinetic energy to the gas.

The general operating condition of the exhaust fan is low speed exhaust. However, in some projects, the working conditions are low and high speed manual exhaust. When the two speed fan is used as an exhaust fan, the thermal relay will act when the fan motor is overloaded. Cut off the power to the main circuit via the contactor. If overload protection is installed, the overload protection can act on the alarm signal.

Detailed information:

Precautions for using the fan:

2. Reverse rotation of the fan is prohibited.

3. It is prohibited to operate with excessive external current.

4. It is prohibited to maintain the fan during operation.

Baidu Encyclopedia—Air supply fan

Baidu Encyclopedia—Exhaust fan