Application of ventilation engineering smoke control and extraction engineering in building basement?

With the continuous improvement of people's living standards, the private ownership of small and medium-sized cars in cities has increased rapidly. In order to ensure a beautiful living environment in the residential area, the limited floor area in the residential area is mostly used for environmental greening. In order to solve the problem of parking difficulty, especially in winter in the north, and without occupying limited ground area, underground garages are generally set up in residential areas, which are mostly used as garages in peacetime and as shelters in wartime. For the basement, the most important thing is ventilation and smoke control.

As an underground garage, solving the problems of ventilation and smoke control is one of the main contents in daily use. The so-called ventilation means that dirty indoor air or waste gas discharged in the production process is discharged directly or after purification, and outdoor fresh air or treated clean air is sent indoors to replace the discharged air, so as to keep the indoor air fresh or maintain the required air conditions, so as to meet the sanitary standards of indoor air environment and production technology and ensure people's health and product quality; The ventilation of the garage is to remove automobile exhaust and gasoline vapor and send in fresh air, so that the content of harmful substances (mainly CO here) can be diluted to the requirements of national health standards. Smoke prevention and smoke extraction is to meet the requirements of fire smoke extraction, to ensure the rapid removal of trapped smoke, to limit the spread of smoke, to ensure the safe evacuation of personnel and vehicles from the scene and to reduce casualties.

Below, the influence of ventilation and smoke control works on the basement garage is briefly explained.

Ventilation overview

Comparison between traditional mechanical ventilation and new ventilation methods

The installation power of ventilation system can be divided into natural ventilation and mechanical ventilation; Natural ventilation is a kind of ventilation mode that makes indoor air and outdoor air exchange due to the air weight difference between indoor and outdoor air temperatures or the action of wind. Mechanical ventilation is a ventilation system that uses the power generated by a ventilator to distribute air to various locations indoors along a certain ventilation pipe network, or to exhaust dirty air from indoors to outdoors. However, due to its structural reasons, the basement can only adopt mechanical ventilation.

The ventilation mode of conventional basement is full ventilation mode, that is, according to several fire zones, there are several air supply and exhaust systems, which are also used as smoke exhaust systems in case of fire, which is called "integration into one". Because of the large air volume, these systems are composed of huge air ducts. This complex and huge ventilation duct not only occupies a high space, reduces the utilization rate of the garage, but also greatly increases the excavation cost, civil engineering investment and equipment investment of the building foundation. Moreover, the system is complex, the installation workload is heavy, the investment is high and the transformation is difficult. It is inevitable that the air duct will cross other electrical pipelines, spray pipelines and water supply and drainage pipelines, which is especially prominent in the garage with a garage area of more than 10000 square meters. To solve this problem, induced ventilation system came into being. After years of theoretical research and engineering practice, the system has been widely used in underground garages in developed countries such as Europe and America, and the application rate in Japan is as high as 80%. From 65438 to 0995, the system began to be popularized in China and gradually accepted by the majority of owners and design units.

Working principle of induced draft fan

The induced draft fan transfers air by induction, and its own air volume is very small. By stirring, the local air dead angle is eliminated and the local air is improved; The fan has high-speed jet and no air duct, which can form a complete ventilation and smoke exhaust system with the air supply fan and the exhaust fan. Its working principle is to guide outdoor fresh air or treated air to the needed area without air duct, so as to achieve the best indoor airflow organization and achieve efficient and economical ventilation effect.

Characteristics of induced draft fan

1.3. 1, with simple and flexible design.

The system has simple planning, flexible design, easy modification and small error probability;

1.3.2, saving space and reducing civil engineering investment.

The traditional mechanical ventilation pipe is laid under the beam, which reduces the spatial elevation. In order to obtain a satisfactory elevation, the basement needs to be dug deep, which increases the cost of engineering excavation and concrete pouring. The induced draft fan solves this problem. Generally, the induced draft fan box is only 250mm high, which is arranged between beams and directly hung under the floor. Compared with pipe ventilation, the design height of underground garage can be increased by 400mm, which makes the indoor space open and the layout simple and beautiful.

1.3.3, easy to install.

There is no need for a huge air duct, and the induced draft fan has the advantages of small volume, light weight, simple structure and convenient and flexible installation; The installation location is targeted, and the installation forms are various, including vertical hanging, horizontal hanging, wall hanging, etc. Easy to use, single-phase 220V power supply, simple wiring;

1.3.4, high efficiency and energy saving, convenient maintenance and low operating cost.

① The induction fan is equipped with an access door and a filter screen, which is convenient to clean and easy to repair and maintain; (2) Because there is no pipeline resistance loss in the induced draft fan, the required air pressure of the fan is low, which greatly reduces the power of the fan motor; (3) the air volume is induced by physical characteristics, which saves electricity, has low operating cost and small equipment volume, and reduces installation cost; (4) The induction fan adopts a high-efficiency low-noise fan, a silencing box and a high-speed nozzle which conform to the aerodynamic characteristic curve, and the used high-quality oil-free bearing motor does not need to add lubricating oil regularly, so the maintenance amount is very small;

1.3.5, with high ventilation quality.

(1) When harmful substances are stranded, the flexible nozzle can be adjusted universally, and the spraying direction can be adjusted at will to meet different building structural forms; (2) Inducing gas to circulate completely without dead angle, reducing waste gas concentration, avoiding pollution accumulation and improving air quality.

Overview of smoke control and extraction engineering

2. 1 basement fire and smoke partition

2. 1. 1, fire zone

Once a fire breaks out in a building, in order to prevent the fire from spreading and expanding, it is necessary to control the fire within a certain range and minimize the losses caused by the fire. In architectural design, the plane and space of the building are divided into several areas, that is, fire zones, by using various fire separation facilities. According to the Code for Fire Protection Design of High-rise Civil Buildings, the maximum allowable building area of each fire protection zone for Class I buildings, Class II buildings and basements is 1.500 square meters, 1.000 square meters and 500 square meters respectively. Without automatic fire extinguishing system, the area can be doubled.

2.2.2, smoke partition

In order to control the smoke in a certain range, a fire partition is divided into several communities by smoke partition, which is called smoke partition. Smoke partition is a subdivision of fire partition. The maximum construction area of each smoke-proof partition in the basement parking lot should not exceed 2000 square meters, and the smoke-proof partition should not cross the fire-proof partition. The function of smoke prevention zone is to effectively control the smoke flow of fire, but it can't prevent the fire from spreading. The smoke-proof partition in the basement can be separated by ceiling, partition wall or beam protruding from the ceiling with a height of not less than 0.5m.. Smoke-proof hanging wall is a fixed or mobile smoke-proof facility made of incombustible materials and hung at a distance of not less than 500 mm from the ceiling. In case of fire, the mobile smoke-proof hanging wall can automatically sag due to the effect of temperature sensing, smoke sensing or other control equipment. Generally, each smoke prevention zone adopts an independent smoke exhaust system or vertical smoke exhaust pipeline for smoke exhaust. If the smoke partition area is too small, the number of smoke exhaust systems or vertical smoke exhaust will increase, and the system cost will increase; If the smoke prevention area is too large, the diffusion area of high-temperature smoke will increase, and the affected area will increase, which is not conducive to safe evacuation and fighting.

2.2, the combination of smoke exhaust system and ventilation system

Because of the similarity between mechanical ventilation and mechanical smoke exhaust, the two systems can be superimposed into a composite system with two functions. * * * A fan is used to exhaust air and smoke. The fan can be a two-speed fire-fighting high-temperature smoke exhaust fan. At ordinary times, the smoke exhaust fire damper is opened, and the smoke exhaust drives the surrounding air by inducing the fan to eject airflow at high speed, so that a large amount of fresh air is mixed and diluted with indoor air, and then moves to the exhaust port in the preset direction, and is exhausted outside by the exhaust fan. When there is a fire in the smoke partition, the induced draft fan is turned off and the fan runs at high speed to smoke. When the flue gas temperature exceeds 280℃, the smoke exhaust fire damper automatically closes and the fan stops running. The allowable wind speed of common air duct and tuyere at ordinary times will be considered as exhaust. There is a mechanical air supply system in the smoke-proof partition wall, and the smoke-proof partition wall has an evacuation outlet directly leading to the outside. The air supply fan is turned off at ordinary times and operated in case of fire. When the supply air temperature exceeds 70℃, the fire damper at the inlet of the fan automatically closes and the fan stops running.

To sum up, high-rise buildings are the inevitable product of social and urban development, and it is the general trend to build underground garages in high-rise buildings, and the ventilation, smoke control and smoke extraction system of underground garages is very important. Therefore, every HVAC worker should correctly use the standard, adopt a reasonable and optimized design scheme, and strictly follow the drawings in the construction, so as to ensure that the ventilation, smoke control and smoke extraction system of each building project is fully equipped and the project is perfect, and truly play its role in fire prevention and disaster reduction.

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