Application of water in natural ventilation design of buildings _ Application of natural ventilation in buildings

Abstract: Natural ventilation is one of the most basic methods to improve indoor air quality and one of the main measures to save energy consumption of air conditioning. It is more important than ever to reintroduce this traditional architectural technology into modern architecture. This paper introduces the principle of natural ventilation, several different realization methods of natural ventilation and their advantages and disadvantages, and illustrates the application of natural ventilation with examples.

Keywords: natural ventilation; Save energy; App application

1 Principle, advantages and disadvantages of natural ventilation

1. 1 wind pressure natural ventilation

Wind pressure is the main means to realize natural ventilation in places with good external wind environment. In many hot and humid areas of China, buildings have open windows, light walls and far-reaching overhangs, and buildings are usually overhead to collect more cold air. Behind this form, it is only a means to promote indoor air circulation and improve indoor air quality by using wind pressure. When the wind blows to the building from the left side, it will generate energy conversion on the windward side of the building, and the dynamic pressure will become static pressure, so a positive pressure will be formed on the windward side, which will push the air into the building from this side, while the side and back of the building will form negative pressure due to the influence of air bypass, attracting the air in the building to flow out from the corresponding position, forming a continuous airflow, which becomes the wind pressure natural ventilation with comprehensive ventilation. The wind pressure around the building is related to the form of the building, the geometric shape of the building, the orientation of the building relative to the wind direction, the wind speed and the natural environment around the building. Generally speaking, when air blows vertically to the facade of a building, the positive pressure in the center of the facade is the greatest, while the negative pressure in the corners and roofs is the greatest. As shown in figure 1.

1.2 hot-pressing natural ventilation

Thermal pressure difference is another means to form natural ventilation of buildings, which is caused by the temperature difference between indoor and outdoor air, commonly known as "stack effect". When there is a heat source in the room, the air will be heated, the density will be reduced and it will float upwards. By setting the air outlet at the upper part of the building, dirty hot air can be discharged indoors, while fresh outdoor cold air will continuously flow in from the lower part of the building to fill the space left by the air flowing out from the upper part. The effect of hot pressing is related to the height difference between air inlet and air outlet and the temperature difference between indoor and outdoor. In the usual architectural design, most of the vertical cavities running through multiple floors in the building can be used to meet the height difference requirements of the air inlet and the air outlet, such as setting chimneys, ventilation towers, patios, atriums and so on. Different from wind pressure natural ventilation, natural ventilation under hot pressing is more suitable for long-term changes and unfavorable external wind environment.

1.3 Wind pressure and hot pressing work together to realize natural ventilation.

In the practical application process, they are usually complementary and inseparable, but their respective functions are strong and weak. Because wind pressure will be affected by weather, outdoor wind direction, building shape and natural environment around the building, the effect of wind pressure and hot pressing cannot be a simple linear superposition. Generally speaking, the parts with small building depth are directly ventilated by wind pressure, and the parts with large building depth are naturally ventilated by hot pressing.

1.4 Mechanical-assisted natural ventilation

Some large buildings make the ventilation path longer and the flow resistance is large. At this time, under the action of wind pressure and hot pressing, relying solely on natural ventilation is often ineffective. In addition, in some areas with serious air pollution, if only natural ventilation is used, it is likely to bring dirty outdoor air into the room, so mechanical auxiliary natural ventilation can be considered. That is, a complete air circulation channel is set up, air treatment means are added, and natural ventilation is carried out with the help of certain mechanical power.

1.5 Advantages and disadvantages of natural ventilation

Advantages: 1) Energy saving. Both natural ventilation and air conditioning can play the role of cooling and ventilation, but air conditioning needs a lot of energy and a lot of processing equipment. This alone, natural ventilation can reduce energy consumption by more than 45%.

2) Indoor air quality of buildings. In buildings using air conditioning, air conditioning controls indoor air temperature more than air quality. Most central air conditioners often lack fresh air and need to be supplemented. Natural ventilation can replenish fresh outdoor air indoors and exhaust dirty indoor air outdoors.

Disadvantages: 1) In the case that the outdoor environment itself is sultry, although fresh air can be exchanged by convection after opening the window, the indoor temperature cannot be reduced quickly, and the room temperature cannot be adjusted by ventilation at this time.

2) The outdoor air quality is poor and there are many pollutants. If natural ventilation is considered, many pollutants will be introduced into the room.

3) Some buildings have strict requirements on indoor cleanliness and wind speed. If the window is ventilated, it may not meet the requirements. There are also large modern buildings. Due to the large depth, some rooms cannot be opened. At this time, natural ventilation will be limited.

2 the realization of natural ventilation

There are many ways to realize natural ventilation in traditional buildings that are worth learning. In modern architectural design, natural ventilation is also actively considered and effectively combined with regional buildings to achieve the purpose of rational utilization and energy saving. Architectural design should be people-oriented, and its fundamental purpose is to create a healthy and comfortable working and living environment for people.

2. 1 building site selection, building modeling and building layout design: building site selection should be conducive to natural ventilation. The outdoor wind speed should be greater than 3m/s, and the main air inlet surface of the building should form an angle of 600 ~ 900 with the dominant wind direction in summer, and should not be less than 450. In architectural design, the problems of heat gain of single building and prevention of excessive solar radiation should be considered comprehensively, as well as the problems of building spacing and wind direction projection angle in the layout of building groups. Because of the influence of the former building on the ventilation of the latter building, the height, width, depth and even shape of the building should be controlled in the design. Don't blindly pursue large-scale, large-depth, high-density buildings, or the indoor clear height is too low, and the windows of buildings are not enough, or even push-pull half-windows or dead windows, which is too much.

Relying on central air conditioning and mechanical equipment, ignoring the requirements for indoor air quality.

2.2 Natural ventilation of the roof: an overhead insulation layer is set on the roof to take away heat through the air interlayer in the middle to reduce the roof temperature. Ventilation and heat insulation layer can also be set in the middle of structural layers, such as sloping roof structure.

2.3 organization that pays attention to natural ventilation: the building itself should take measures to realize or even strengthen natural ventilation. If natural ventilation is formed by hot pressing, wind shields are installed on both sides of the skylight, so that the skylight is always in the negative pressure area and cannot be discharged. Another example is to arrange the air inlet at the cornice reasonably, so that fresh air can still enter the room for natural ventilation when the doors and windows are closed. There is also a reasonable arrangement of the air inlet and air outlet of the building, so that the wind blows into the room from the windward side of the building and flows out from the air outlet on the leeward side.

3 Application of natural ventilation in Guangzhou Jiacheng International Apartment Project

Guangzhou Jiacheng International Apartment Project is located at the junction of Guangzhou Avenue and Tianhe Shuiyin Road. Due to land restrictions, the site selection cannot be changed, but the surrounding area is open and has good natural ventilation application conditions. In graphic design, we designed an open patio in the north and three open patios in the west, which are connected by open corridors and elevator halls. In the section design, we design the fifth floor as an overhead floor; Roof design overhead insulation layer; The practice of opening the patio makes the outdoor hot air cool and blow into the room, which takes away the indoor heat better. The whole building not only makes full use of natural ventilation, but also strengthens natural ventilation. As shown in figures 2 and 3. In the case of outdoor temperature of 28-30 degrees and outdoor breeze, people will feel hot and dry without turning on the air conditioner. However, in Jiacheng Apartment, when the door opens to the single apartment in the east, the indoor staff have good thermal comfort. This shows that natural ventilation is very successful in the design of this project.

4 conclusion

Generally speaking, natural ventilation technology, as an energy-saving means, is a sustainable energy-saving technology and a technology to reduce the operating cost of buildings. It involves a lot of contents, and we still need to do a lot of work to successfully apply natural ventilation to various buildings. In buildings with air conditioning and ventilation, natural ventilation should be fully considered as far as possible when circumstances permit. I believe that under the premise of modern science and technology, natural ventilation will provide us with a healthy and comfortable environment more effectively.

refer to

[1] Luo Hongan. Preliminary study on building energy-saving measures [J]. Sichuan Building Science Research, 2008

[2] Wang Peng, Tan Gang. Ventilation in Ecological Architecture [J]. World Architecture in 2000

[3] Guo Fei, Wang Shiyuan. Study on natural ventilation and energy-saving design of high-rise residential buildings in Shanghai [J]. Architectural Journal, 2008

[4] Zhong, Zeng Yijun. Analysis of natural ventilation design of buildings [J]. Journal of chongqing jianzhu university, 2004.