Qingdao Purification Project

QingdaoPurification ProjectIt refers to controlling the cleanliness, temperature, and humidity of the atmosphere that products (such as silicon chips) come into contact with, so that products can be produced and manufactured in a good environmental space. The design and construction process of this environmental space can be called purification engineering.

QingdaoPurification ProjectpartTurbulent flow cleanroom and unidirectional flow cleanroom

The main characteristic of a turbulent flow clean room is that the flow cross-section of the airflow from the inlet to the outlet (from the air supply outlet to the return outlet) varies. The clean room cross-section is much larger than the air supply outlet cross-section, so it cannot form a uniform airflow in the entire room cross-section or in the entire working area cross-section. So, the streamlines after the air supply outlet have a large or increasing angle with each other, and the curvature radius is very small. The airflow cannot flow in a single direction indoors and will collide with each other, resulting in backflow and vortex generation. This determines that the essence of the flow state in a turbulent clean room is: abrupt flow; Non uniform flow.

This is more accurate and comprehensive than using turbulence to describe turbulent flow cleanrooms. Turbulence is mainly determined by the Reynolds number, which is mainly influenced by the flow velocity. However, if a filter top air supply form is used, even if the flow velocity is extremely low, the above results will still occur because it is a sudden change flow and non-uniform flow. Therefore, in this situation, there is not only mixing between the flow layers due to turbulent flow, but also mixing caused by large backflow and vortices throughout the entire chamber.

Unidirectional flow cleanroom

There are generally two types of unidirectional flow cleanrooms, namely horizontal flow and vertical flow. In a horizontal flow system, airflow flows from one wall to another. In a vertical flow system, airflow flows from the ceiling to the ground. For situations where a lower concentration of suspended particles or microorganisms is required in the clean room, unidirectional airflow is used. Previously, this type of clean room was called a "laminar flow" clean room. The names of unidirectional flow and laminar flow both describe the condition of their airflow: the airflow flows in one direction (either vertical or horizontal) and flows through the entire space at an average velocity of generally 0.3 to 0.5 meters per second (60 to 100 feet per minute). Air is supplied into the room through filters installed on the ceiling of the cleanroom. The airflow is like an air piston, flowing downwards through the room, carrying away pollutants, and then being discharged from the ground. After mixing with some fresh air from the outside, it is recycled to the filter. The suspended pollution generated by personnel and processes can be immediately removed by this air, and the turbulent ventilation system adopts the principle of mixing and dilution. In an empty room without any obstacles, one-way flow can quickly remove pollutants with much lower wind speeds than mentioned earlier. But in an operating room, the machine and the people walking around it can create obstacles to the airflow. Obstacles can cause unidirectional flow to become turbulent, thereby forming air masses around the obstacle. The activities of personnel can also cause unidirectional flow to become turbulent. In these turbulent flows, due to the low wind speed, the degree of air dilution is small, resulting in a higher concentration of pollution. Therefore, the wind speed must be maintained within the range of 0.3 meters per second to 0.5 meters per second (60 feet per minute to 100 feet per minute) in order to quickly restore the interrupted unidirectional flow and fully dilute the pollution in the turbulent area around the obstacle. Wind speed can accurately represent unidirectional flow, as the higher the wind speed, the cleaner the indoor environment. The number of air changes per hour is related to the volume of the room, such as the height of the ceiling, so it is not suitable to represent one-way flow. The air supply volume in a unidirectional flow chamber is many times that of a turbulent flow chamber (10 to 100 times).