1. System differentiation

The differentiation of ventilation and smoke exhaust systems should be considered in conjunction with building fire compartments, achieving both the benefits of the ventilation system serving as a smoke exhaust system and avoiding the phenomenon of smoke exhaust ducts crossing fire compartments. According to reference [1], when active sprinkler fire extinguishing facilities are installed in the basement, the fire compartment area is 1000m2, which can be divided into two smoke compartments. The smoke exhaust volume is calculated at 60m3/(h · m2), and the smoke exhaust volume of this fire compartment is 60000m3/h. The normal ventilation volume is calculated based on the air exchange rate of 8h-1, and the floor height (net height) is calculated as 3.9m, with a ventilation volume of 1000 × 3.9 × 8=31200m3/h. It can be seen that the difference between the normal ventilation volume and the smoke exhaust volume during a fire is about half, and the wind speed of the main duct of the normal ventilation pipe is generally planned at 8-10 m/s. The wind speed of the smoke exhaust duct during a fire is allowed to reach 20 m/s. Therefore, using a set of air systems can meet the ventilation and smoke exhaust requirements, but it should be noted that when sharing a set of air ducts, the air ducts should meet the wall thickness required by the smoke exhaust duct (thickness should not be less than 1mm). So each fire zone should be equipped with a ventilation and smoke exhaust system, as well as a mechanical air intake system, with an air intake volume of half of the smoke exhaust volume during a fire. This air intake system can not only ensure the activation of supplementary air in case of fire, but also enable supplementary air in normal times, especially for underground floors and deeper basements where it is no longer possible to rely on the lane for supplementary air.

2 Ventilation methods

Uniform exhaust is used for regular ventilation, that is, exhaust pipes and vents are uniformly installed in the basement for regular ventilation, and also serve as smoke exhaust pipes and vents in case of fire; The underground level is considered to have air intake through the lane, while the other levels will have air intake systems that also serve as regular air intake during a fire. The mechanical air intake system does not require connecting air ducts or connecting a small section of air ducts to collect and supply air. This ventilation method is better than uniform air supply and concentrated exhaust. Other than that, each fire compartment corresponds to an exhaust and smoke exhaust system as well as an intake system. An intake shaft and an exhaust shaft should be set up, and the intake should be located in a clean area on the ground, with some distance from the main building on the ground, so that it is less affected by fire smoke; The position of the exhaust outlet should be higher than the roof of the attached building to reduce the impact of exhaust on the above ground environment.

Setting of 3-exhaust smoke exhaust fan and inlet fan

Fan selection: Centrifugal fans or high-temperature axial flow fans can be selected as exhaust and smoke exhaust fans. Ordinary centrifugal fans can meet the requirements of exhaust and smoke removal, but high air volume centrifugal fans can only be installed on the ground, occupying a large area and requiring a large machine room. The high-temperature axial flow fan is a fire-fighting fan that can also meet the requirement of operating at a smoke temperature of 280 ℃ for 30 minutes. However, the high-temperature axial flow fan has a small volume and can generally be lifted. If the machine room area is also small, in practical engineering design, high-temperature axial flow fans are often used for smoke exhaust. Below, we will discuss the combination of high-temperature axial flow fans and ordinary axial flow fans in smoke exhaust and ventilation systems.

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