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The working principle of chimney and the relationship between smoke outlet and smoke exhaust position

The principle of chimney smoke exhaust is that in buildings and structures (such as water towers) with unobstructed circulation space from bottom to top, air (including smoke) quickly diffuses or exhausts the building along the channel due to the effect of density difference, which is called stack effect.

In other words, the flue gas must be discharged from the bottom up, especially the hot flue gas itself has the property of floating up, and it is certainly not good for you to discharge downward at the chimney exit now. With the help of stack effect, indoor organized natural ventilation and smoke exhaust can be realized.

The combined effect of hot pressing caused by indoor and outdoor temperature difference and outdoor wind pressure is usually the former, and the hot pressing value is directly proportional to the air density difference caused by indoor and outdoor temperature difference and the height difference of air inlet and outlet. This shows that the higher the indoor temperature is than the outdoor temperature, the higher the building is, and the more obvious the stack effect is. At the same time, it also shows that the stack effect of civil buildings generally only occurs in winter.

Extended data:

When it is used as fuel with wood, they will form creosote deposits on the walls of buildings. The deposits of this substance will interfere with the airflow, and more importantly, they are flammable. If the sediment in the chimney is ignited, it will cause a dangerous chimney fire.

The heater burning natural gas greatly reduces the concentration of miscellaneous phenol produced by natural gas combustion, which is cleaner and more effective than traditional solid fuel. Although in most cases, it is not necessary to clean the chimney every year, this does not mean that other parts of the chimney will not be in disrepair for a long time.

For a class of public buildings with a building height of more than 50m and residential buildings with a building height of more than 100m, according to the requirements of the "High Code", it is appropriate to set up a mechanical pressurized air supply system, and some projects adopt natural smoke exhaust at the same time in the above parts, resulting in that when the mechanical pressurized air supply system and the natural smoke exhaust window are opened at the same time in a fire, it is difficult to form a positive pressure in the smoke prevention stairwell, and the smoke prevention effect is invalid.

Baidu encyclopedia-chimney

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