Discussion on ventilation and smoke control design of underground garage in residential quarters?

In recent years, with the development of economy and the improvement of people's living standards, the number of private cars has soared, while the available land resources in cities have been decreasing. Therefore, more and more real estate developers solve the parking problem by building underground garages. In order to prevent and reduce fire hazards and protect personal and automobile safety, it is particularly important to strengthen the ventilation and smoke control design of underground garages. This paper mainly discusses the ventilation and smoke control design of underground garage in residential quarters, and the underground garage under commercial buildings is not included in this discussion.

1, design basis

At present, the national standards and specifications concerning the ventilation and smoke control design of underground garages mainly include: GB50045-95 Code for Fire Protection Design of High-rise Civil Buildings (2005 edition), Code for Fire Protection Design of Garages, Garages and Parking Lots GB50067-97 and Code for Garages Design JJ100-98. When designing an underground garage, whether it is an underground garage of a high-rise building or an underground garage with civil air defense function, the Code for Fire Protection Design of Garage, Garage and Parking Lot should be strictly implemented. In addition, we are also affected by the national civil engineering design technical measures, HVAC? Power (2009 edition).

2, smoke partition and fire partition

According to Code for Fire Protection Design of Garage, Repair Garage and Parking Lot, the maximum allowable building area of underground garage fire protection zone is 2000m2 (excluding Class A and Class B cargo transport vehicles). When the garage is equipped with automatic fire extinguishing system, it can be doubled to 4000m2. It is also stipulated in the specification that the underground garage above 10 vehicle must be equipped with an automatic fire extinguishing system. In this way, the general garage is equipped with an automatic fire extinguishing system, and the maximum allowable building area of the fire zone is 4000m2. In addition, the underground garage with a specified area of more than 2000m2 should be equipped with a mechanical smoke exhaust system, and the construction area of each smoke-proof partition should not exceed 2000m2, and the smoke-proof partition cannot cross the fire-proof partition.

3. Design of smoke exhaust system

We will definitely discuss the underground garage in the community. Architecture majors generally divide a fire zone with an area less than 4000m2, so our HVAC major needs to set up two smoke-proof zones in a fire zone. Now, according to the Code for Fire Protection Design of Garage, Repair Garage and Parking Lot, the smoke exhaust volume of the smoke exhaust fan should be no less than 6 times per hour, and the floor height should be calculated according to the actual floor height. Exhaust air volume according to the national "technical measures for civil building engineering design: HVAC? Article 4.3.2 on electricity: For residential buildings with low frequency of car access, it is calculated as 4 times /h ventilation. When the storey height is higher than 3m, press 3m; If the height is less than 3m, it shall be calculated according to the actual height.

In the case that the basement height is ≥4.2m, the basement height is now 4.2m, and the net height at the bottom of the slab is 4m. The garage covers an area of 3500 square meters. The smoke exhaust quantity is calculated as: 3500x4x6=84000. Take two range hoods, the number of each fan is 84000 ÷ 2×1.1= 46200. The calculation of exhaust air volume is: 3500x3x4=42000. Take an exhaust fan for example, the volume of a single fan is 42,000 x1.1= 46,200. Generally, there are two ways to choose the exhaust machine.

3. 1 Select two smoke exhaust fans (with external motors). In case of fire, two fans will be turned on at the same time to smoke, and only one fan will be turned on for ventilation at ordinary times. Because the wind speed of the air duct should not exceed 20m/s when exhausting smoke and 10m/s when exhausting air, a set of exhaust air duct can be designed.

3.2 Choose two double-speed smoke exhaust fans, which can be turned on at high speed in case of fire and at low speed at ordinary times. At this time, the general designer calculates the exhaust air volume according to 6 times /h ventilation, which is 3500x3x6=63000. Take two exhaust fans, and the single exhaust air volume is 63000 ÷ 2x1.1= 34650. According to the sample of windward energy-saving low-noise fan, the exhaust air volume can only be 46,200m3/h. Low speed: air volume 34,965,438+100m3/h, wind pressure 482Pa, power 15kw). In fact, the wind pressure required to calculate the high-speed operation of the fan is only about 550Pa (the length of the air duct is generally over 60 meters).

I prefer the first choice of the two. On the premise of meeting the requirements of the code, the system is economical and simple, with simple control and small air duct size, which is very beneficial to the height of the basement.

When the height of the basement is less than 4.2m, it is assumed that the height of the basement is 3.7m and the net height of the slab bottom is 3.5m. The garage covers an area of 3,500 square meters. The smoke exhaust quantity is calculated as: 3500x3.5x6=73500. Two smoke exhaust fans are used, and the capacity of a single fan is 73500 ÷ 2×1.1= 40425. The calculation of exhaust air volume is: 4 times, 3500x3x4=42000, take 1 exhaust fan, and the capacity of a single fan is 42000×1= 46200; Press 6 times, 3500x3x6=63000, and take two exhaust fans, each with a capacity of 63000 \ The operation here is as follows: turn on two exhaust fans in case of fire, and turn on two exhaust fans in case of ventilation at ordinary times. There is no need to distinguish between two speeds of running. Some people here may ask, why not use one machine and two machines to distinguish between normal operation and hot work operation? The author thinks so. If we want to do this, we need to choose the fan according to the single wind capacity of 46200 and the wind pressure of 550. The selected fan is No.36, and the power is increased to 18.5kw, so the configuration is larger than the original one. According to the current usage of garage ventilation, property management is intermittent. Therefore, developers should pay more attention to the economy of initial investment.

According to the height of different underground garages, designers should consider them differently.

4. Design of air supply and air supply system

The calculation of air supply volume should be greater than 80% of exhaust air volume. Fire air supply should be greater than 50% of smoke exhaust. Both methods can calculate larger values. If there is no fire shutter in the entrance and exit lane, it can be used as a ventilation passage.

5, duct and tuyere layout

The smoke outlet is a common outlet, which is generally designed as a side outlet. The uniform arrangement of smoke outlets not only meets the ventilation requirements, but also meets the distance requirements of fire smoke outlets. The wind speed of the smoke outlet is designed to be not less than 3m/s, and the exhaust pipe should be arranged above the parking space as far as possible to avoid being arranged above the driveway. There is no uniform arrangement requirement for air supply outlets.

6. Conclusion

Ventilation and smoke exhaust design in basement is a relatively simple part of HVAC design. But it also needs to be carefully analyzed and treated. Especially now, the real estate market is very good, and there is a lot of room for the development of residential quarters around. Developers are very concerned about the height of the basement and the input of equipment. As a designer, we should pay attention to make the design not only meet the specification and use requirements, but also make the system simple, economical and reliable.

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