With the acceleration of urbanization, the problem of air quality has become increasingly prominent, especially in big cities. Pollution sources such as haze, automobile exhaust and industrial emissions have also seriously affected indoor air quality. In order to improve indoor air quality, fresh air system came into being. Fresh air system is a kind of equipment that can filter and purify the outdoor fresh air into the room, and at the same time discharge the indoor dirty air. It can not only effectively improve indoor air quality, but also adjust indoor temperature and humidity to enhance living comfort. This paper will introduce the working principle of fresh air system and its importance in modern life in detail.

First, the basic composition of the fresh air system

The fresh air system mainly consists of the following parts:
1. ** Air intake and exhaust ** : The air intake is responsible for bringing outdoor air into the system, and the exhaust is responsible for discharging the indoor dirty air. The air intake is usually installed in a place where the outdoor air is relatively clean, while the exhaust is installed in an area where the indoor air is dirty, such as the kitchen and bathroom.
2. ** Filtration system ** : The filtration system is the core part of the fresh air system, responsible for filtering and purifying the air entering the room. Common filters include primary filters, medium filters, and high efficiency filters (HEPA filters). The primary filter is mainly used to filter large particles, such as dust, hair, etc. Medium effect filter can filter smaller particles, such as pollen, bacteria, etc. Hepa filters filter smaller particles, such as PM2.5 and viruses.
3. ** Heat exchanger ** : The heat exchanger is an energy-saving device in the fresh air system, which can exchange heat between the inlet air and the exhaust air. In winter, the heat exchanger can transfer the heat in the exhaust air to the inlet air, thereby reducing the loss of indoor heat; In the summer, the heat exchanger can transfer the heat from the incoming air to the exhaust air, thereby reducing the loss of indoor cooling. This not only keeps the indoor temperature stable, but also reduces the energy consumption of air conditioning and heating.
4. ** Fan ** : The fan is the power source of the fresh air system, which is responsible for inhaling the outdoor air into the system and sending it into the room, while discharging the indoor dirty air. The power and air volume of the fan determine the ventilation efficiency of the fresh air system.

5. ** Control system ** : The control system is the "brain" of the fresh air system, which is responsible for adjusting the running speed and switch of the fan. Modern fresh air systems are usually equipped with intelligent control systems, and users can remotely control the operation of the system through mobile phone apps or remote controls.

Second, the working principle of the fresh air system

The working principle of the fresh air system can be simply summarized as five steps: "air intake - filtration - heat exchange - air supply - air exhaust".
1. ** Air intake ** : Outdoor air enters the fresh air system through the air intake. Air intakes are usually installed on the exterior walls or roofs of buildings to ensure that the air inhaled is relatively clean.
2. ** Filtration ** : The air entering the system first passes through the primary effect filter to filter out large particles; It then passes through a medium-effect filter to remove smaller particles; Finally through the high efficiency filter, filter out smaller particles, such as PM2.5, bacteria, viruses and so on. After multi-layer filtration, the pollutants in the air are effectively removed, and the air sent into the room becomes fresh and clean.
3. ** Heat exchange ** : The filtered air enters the heat exchanger and exchanges heat with the exhaust air. In winter, the heat exchanger transfers the heat from the exhaust air to the inlet air, which increases the temperature of the air entering the room. In the summer, the heat exchanger transfers the heat from the incoming air to the exhaust air, reducing the temperature of the air entering the room. This not only keeps the indoor temperature stable, but also reduces the energy consumption of air conditioning and heating.

4. ** Air supply ** : The air after heat exchange is sent into the room through the fan. Air supply outlets are usually installed in areas with frequent personnel activities such as living rooms and bedrooms to ensure that fresh air can be evenly distributed to all corners.

5. ** Exhaust air ** : indoor dirty air is discharged from the outside through the exhaust outlet. Exhaust vents are usually installed in areas with dirty air such as kitchens and bathrooms to ensure that dirty air can be discharged in time.
Third, the importance of fresh air system
1. ** Improve indoor air quality ** : The fresh air system can filter and purify the outdoor fresh air into the room, while discharging the indoor dirty air, effectively improving indoor air quality. Especially in hazy weather or areas with poor air quality, fresh air systems can provide clean air indoors and protect the health of residents.
2. ** Balance indoor temperature and humidity ** : The heat exchanger in the fresh air system can exchange heat between the inlet air and the exhaust air to keep the indoor temperature stable.
3. ** Energy saving and environmental protection ** : The heat exchanger in the fresh air system can effectively recover the heat in the exhaust air, reduce the energy consumption of air conditioning and heating, so as to achieve the purpose of energy saving and environmental protection. According to statistics, after the installation of fresh air systems, the energy consumption of air conditioning and heating can be reduced by 20%-30%.

4. ** Reduce noise pollution ** : Modern fresh air systems usually adopt a low noise design, and the noise of the fan is low during operation, which will not cause disturbance to indoor residents. In addition, the fresh air system can also control indoor noise by adjusting the air supply volume to improve living comfort.

5. ** Prevention of indoor air pollution ** : indoor air pollution sources include decoration materials, furniture, cleaners, etc. Long-term exposure to these sources of pollution will cause harm to human health. The fresh air system can discharge the indoor dirty air in time, reduce the accumulation of indoor air pollutants, and prevent indoor air pollution.
Fourth, the application scenario of fresh air system
Fresh air system is widely used in all kinds of buildings, including residential buildings, office buildings, schools, hospitals and so on. In residential buildings, fresh air system can provide clean air for residents and improve living comfort. In the office building, the fresh air system can improve the staff's office environment and improve work efficiency; In the school, the fresh air system can provide students with a healthy learning environment and ensure their health; In hospitals, fresh air systems can provide clean air for patients and promote patients' recovery.
V. Conclusion
As a kind of equipment that can improve indoor air quality, regulate indoor temperature and humidity, energy saving and environmental protection, fresh air system plays an increasingly important role in modern life. With the improvement of indoor air quality requirements, the application range of fresh air systems will be more and more extensive. In the future, with the continuous progress of technology, the fresh air system will become more intelligent and efficient, providing people with a more healthy and comfortable living environment.