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What are the characteristics of airflow organization in ISO 14644 clean room clean room?

Popularity:8 Release time:2022-08-01 09:36:01

The airflow organization of ISO 14644 clean room clean room is different from that of general air-conditioned room. Its primary purpose is to supply enough clean air to replace and dilute the pollutants generated in the room, so as to keep the indoor cleanliness below the allowable value.

Features of ISO 14644 Cleanroom Airflow:

The general requirements for ISO 14644 cleanroom air flow organization are as follows:

1. The incoming clean air can be evenly distributed or diffused to the entire clean area as soon as possible, so as to dilute the air pollution caused by the dust and bacteria emitted by the indoor pollution source, and maintain the cleanliness required by the production environment.

2. It can quickly discharge the dust and bacteria from the pollution source to the ISO 14644 clean room clean room, avoid or reduce eddy currents and dead corners, shorten the residence time of dust and bacteria in the room, and reduce the probability of contact with the product.

3. Take into account the requirements of air conditioning, such as indoor temperature and humidity uniformity, and the comfort requirements of staff.

Since the main task of the air-conditioned room is different from that of the general air-conditioned room, the plan of airflow organization must also be different. For comfortable air-conditioned rooms and production workshops with ordinary temperature and humidity accuracy, the basis for considering the air-conditioning airflow organization plan is to use the largest possible air supply temperature difference in order to reduce the air supply volume and make the system equipment and pipes smaller. Lower investment and operating costs. Therefore, the dew point air supply is usually used in summer. Because the temperature difference between the incoming air and the room temperature is large, in order to avoid the uneven temperature of the indoor living area and the working area or the uncomfortable feeling of blowing cold air and hot air, whether it is using a side air outlet or a top air diffuser, it is required to The outlet air has a strong turbulence coefficient and a certain ejection ability, so that the air that has absorbed the indoor heat and humidity load is entrained and mixed into the air supply air flow, so that the temperature and humidity of the air supply air flow can be approached as soon as possible. In interior design temperature and humidity. When the supply air flow enters the living area and the working area in a backflow state, its temperature and humidity have entered the control accuracy range from the perspective of process requirements; from the perspective of human experience, it is also soft and acceptable. As shown in Figure 1-1, the side-to-side return of the ordinary air-conditioned room, and the supply of air to form an attached jet is a typical airflow organization scheme for an air-conditioned room.

ISO 14644 clean room air conditioning room air distribution is characterized by a lot of eddy currents in addition to the generally existing upward airflow on the supply air entraining surface. This upward airflow is opposite to the downward movement of dust and bacteria under the action of gravity. Dust and bacteria will be lifted up with the airflow. Some dust particles with larger particles will obviously lag behind the airflow and will stay indoors for a longer time. Eddy currents also promote the swirl of dust and bacteria in the room, rather than quickly leaving the room with the airflow. This is due to the difference from the principle of clean air flow organization.

Air flow patterns in ISO 14644 cleanroom cleanrooms

The airflow organization or airflow pattern of ISO 14644 clean room clean room is mainly divided into two categories. One type is non-unidirectional flow, which used to be called conventional flow pattern or turbulent flow pattern; the other type is unidirectional flow, which used to be called laminar flow pattern.

Different areas in the ISO 14644 clean room often have different cleanliness requirements, so the first two types of flow patterns are often combined. One-way flow is used in parts with high requirements, and non-one-way flow is used in other parts of the room. This airflow organization is called a mixed flow pattern. For example, in a potting workshop with constant wind, a so-called clean hood is only installed above the potting part, and a unidirectional airflow is sent downward. However, most of the workshops still use the non-unidirectional flow return air method of upper and lower return.

In addition, there is a more special form of airflow organization, called vector flow or radiative flow, also known as oblique flow. It should belong to the non-unidirectional flow, but it has the effect closer to the horizontal unidirectional flow, and is far simpler in structure than the unidirectional flow. Especially in the United States, the use of pharmaceutical companies is more common.

Non-unidirectional flow is suitable for most ISO 14644 cleanroom cleanrooms in pharmaceutical factories. The air flow organization form of the supply and return air is the most typical form of top delivery and side lower return. Although the top-feed high-efficiency filter tuyere is equipped with an orifice diffuser, which helps to spread the clean air in the air supply workshop, it is just below the high-efficiency filter tuyere, in the center of the so-called main flow area, its cleanliness Generally significantly higher than the surrounding. The surrounding area is the part covered by the continuous intake of polluted air and the continuous expansion of the air flow section after the air supply enters the room. The cleanliness of the parts that are not covered by the air supply air between adjacent air vents or the four corners of the room will be even worse. some.

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