The process of DC crossflow fan to realize the circulation and exhaust of air in the ventilation system is as follows:

1. Introducing fresh air: DC crossflow fan generates airflow through its rotating blades or blade assemblies. When the fan is working, it draws in outdoor air and pushes it into the ventilation system.

2. Air flow transmission: DC crossflow fan pushes airflow into the ventilation duct or ventilation channel through the rotation of its fan blades. The airflow generated by the rotation of the fan blades will form a certain pressure difference in the ventilation system, thereby promoting air flow.

3. Air distribution: The airflow coming out of the ventilation duct or ventilation channel will spread in the indoor space. The proper position and direction of the DC crossflow fan can ensure that the airflow is evenly distributed throughout the space, avoiding dead corners or local poor ventilation.

4. Dirty air exhaust: DC crossflow fans can also be used to exhaust dirty air in the room. In the ventilation system, they can push the dirty air in the room to the ventilation duct or vent by reversing or adjusting the direction of rotation to achieve effective exhaust.

Through the above process, DC crossflow fans can achieve air circulation and exhaust. They create airflow and push air, allowing fresh air to enter the room while exhausting dirty air outside, thereby keeping the air circulated and fresh. This helps provide good indoor air quality and ensure a comfortable and healthy environment.