1. Positive pressure air supply is to supply air to the elevator front room and stairwell. When a fire breaks out in a building, the evacuation stairs are the only way for people to evacuate inside the building, and the front room and shared front room are used by firefighters. It is the starting point for fire fighting, so smoke prevention design must be carried out in these parts. In high-rise buildings, a large amount of hot smoke will be generated during a fire, which will quickly spread upward through vertical channels. This is the so-called chimney draft effect. . I am giving an example. When there is a fire, people are evacuating in the stairwell. At this time, smoke entering the stairwell will cause casualties. However, if there is pressurized air supply in the stairwell, it will cause the air in the stairwell to evacuate. If the pressure is greater than the air pressure in the external fire area, the smoke will be pushed outside and unable to enter, thus protecting personnel.
2. The fire supplementary air system is a pressure difference generated in the protective area due to smoke exhaust in the smoke exhaust system, and the air volume needs to be supplemented. The air supply volume shall not be less than 50% of the smoke exhaust volume.
3.
It should be determined according to its size and wind pressure. There is no need to distinguish the need for fire supplementary air. Please follow the "Construction Quality Acceptance Code for Ventilation and Air-Conditioning Projects" (GB 50243---2002): 4.2.1 The material variety, specifications, performance and thickness of metal air ducts should comply with the design and current national product standards. When there is no provision in the design, this specification should be followed. The thickness of the steel plate or galvanized steel plate shall not be less than the provisions of Table 4.2.1-1; the thickness of the stainless steel plate shall not be less than the provisions of Table 4.2.1-2; the thickness of the aluminum plate shall not be less than the provisions of Table 4.2.1-3. The specifications can be downloaded from "Baidu Library".
The effects that must be taken in high school geography are as follows:
1. Foehn effect.
The warm and moist air flowing over the hillside forms orographic rain on the windward slope. The water vapor in the atmosphere condenses and falls almost at the same time; on the leeward slope, as the airflow sinks, the altitude becomes lower, the temperature rises, and the air becomes both hot and dry. This phenomenon is called the "Foehn effect".
2. Oasis effect.
In desert areas, as long as there is a water source, the mixing of water and air can lower the air temperature and increase the relative humidity. The result of this mixing of water and air is cooling and humidification, which is very similar to the formation of oasis in the desert. Similar, so it is called the "oasis effect".
3. Basin effect.
On the surface inside the basin, in hot summers, the terrain is often low and the air density is high. The dense atmosphere blocks the radiation cooling of ground heat to high altitudes. In addition, the surrounding high and middle low terrain is not easy to dissipate heat, so that The temperature rises. For example, Oymyakon in Siberia, Russia, has become the cold pole of the northern hemisphere and has reached a low temperature of -71°C. It is located in a closed basin. The above phenomenon is called the "basin effect".
4. Plateau effect.
On a large plateau, the air density above it is low, the sunshine hours are long during the day, the solar radiation is strong, and the thermal insulation effect of the atmosphere is weak at night, resulting in a climate characterized by a large temperature difference between day and night. terrainThe higher the value, the more obvious this characteristic is, which is called the "plateau effect".
5. Narrow tube effect.
When the air flows from the open area into the canyon formed by the terrain, because the air quality cannot accumulate in large quantities, it accelerates through the canyon and the wind speed increases. As it exits the canyon, the air flow slows down again. The impact of this topographic canyon on airflow is called the "narrow tube effect."
6. Greenhouse effect.
Due to human social and economic activities in modern times, fossil fuels such as coal, oil, and natural gas have been burned in large quantities, and a large amount of greenhouse gases such as carbon dioxide have been emitted into the atmosphere. Greenhouse gases absorb a large amount of ground long-wave radiation, causing ground heat to be trapped in greenhouse gases. At the same time, the temperature of the atmosphere itself is also rising, and atmospheric radiation is emitted to the ground. Therefore, it has a thermal insulation effect on the ground similar to that of greenhouse glass, so it is called the "greenhouse effect".