What is a clean room? Classification of clean rooms

Clean room definition

A clean room is a space where the cleanliness of the air reaches a specified level. Its function is to control the pollution of particles.

In order to achieve the specified level of cleanliness, effectively control the pollution of particles, and enable people to engage in sophisticated production and scientific experiments, the clean room is not limited to "clean", but must be a pair of heat, noise, illumination, Electrostatic and micro-vibration have a multi-functional complex that is quite required. It is a product of various professional technologies such as architectural decoration, air conditioning purification, pure water pure gas, and electrical control.

Classification of clean rooms

First, by purpose

According to the use, it can be divided into two categories:

(1) Industrial clean room - use inanimate particles as the control object. It mainly controls the pollution of the working object by the inanimate particles, and the inside generally maintains a positive pressure. It is suitable for the precision industry, electronics industry, aerospace industry, atomic energy industry, printing industry, photography industry and other departments.

(2) Biological clean room--with living particles as the control object, it can be divided into:

1 general biological clean room. It mainly controls the pollution of living objects by living particles. At the same time, the internal materials are subject to various sterilizing agents, and the interior generally maintains a positive pressure. Can be used in the pharmaceutical industry, food industry, medical facilities, experimental facilities, etc.

2 biosafety clean room. It mainly controls the pollution of the living particles of the working object to the outside world and people, and the internal pressure needs to be maintained. Used in laboratory facilities, bioengineering, medical facilities, etc.

Second, according to airflow classification

According to airflow, it can be divided into four categories:

(1) One-way flow clean room

(2) Non-unidirectional flow clean room (turbulent flow clean room)

(3) Yaw flow clean room

(4) Mixed flow clean room (partial one-way flow clean room)

Third, the principle and characteristics of the one-way flow clean room

(1) Definition

A unidirectional flow clean room is a clean room in which the airflow passes through the entire chamber section in a single direction along a parallel flow line at a uniform cross-sectional velocity.

(2) Principle

The one-way flow clean room is quickly squeezed by the “piston”-like squeeze of the air supply airflow.

To ensure the realization of the piston function, it is important that the high-efficiency filter must be full. Of course, the filter has a bezel, and the ceiling also has a bezel, and it is impossible to fill the filter 100%. Full ratio to measure the fullness of the filter:

Under normal circumstances, the ratio is 80%. The vertical unidirectional flow full cloth ratio should not be less than 60%, and the horizontal unidirectional flow should be less than 40%, otherwise it is a partial one-way flow.

(3) Characteristic indicators

1 streamline parallelism (streamline parallelism)

The parallel action of the streamline is to ensure that the dust particles emitted by the dust source do not propagate perpendicular to the flow direction. It is required that the flow lines should be parallel (the angle between the lines should not be less than 15° within a distance of 0.5 m), and the flow line should be as perpendicular as possible to the air supply surface (the inclination angle is not less than 65°).

2 turbulence (speed unevenness)

The effect of uniform speed is to ensure that the lateral exchange of the mass points between the streamlines is small. The turbulence is defined to illustrate the concentration or dispersion of the velocity field.

3 lower limit wind speed

This is to ensure that the clean room can control the following four kinds of pollution:

a. When the polluted airflow is spread in multiple directions, the airflow must be able to effectively control the scope of pollution;

b. When the polluted airflow is in the same direction as the airflow, the airflow must be able to effectively control the diffusion range of the polluted airflow to the downstream;

c. When the polluted airflow is opposite to the supply airflow, the supply airflow can suppress the polluted airflow within the necessary distance;

d. In the case of contamination of the entire room, it is sufficient to quickly make the indoor air clean at the right time.

Fourth, the principle and characteristics of the turbulent clean room

(1) Definition

A turbulent clean room is a clean room in which airflow flows non-parallel at uneven speeds, accompanied by backflow or eddy currents.

(2) Principle

The turbulent clean room continuously dilutes the indoor air by the supply air flow, and gradually discharges the indoor pollution to reach equilibrium. In order to ensure that the dilution is very good, the important point of Zui is that the indoor airflow spreads as quickly as possible.

(3) Characteristic indicators

1 number of air changes

The effect of the number of air changes is to ensure that there is sufficient clean air flow for dilution.

The number of air changes should be determined based on calculations and experience.

2 airflow organization

The function of the airflow organization is to ensure uniform air supply and return air, and to fully exert the dilution effect of the clean airflow. Therefore, it is required that the single tuyere has sufficient diffusion effect, the whole room return air is arranged evenly, and the quantity is better, and the eddy current and the airflow convolution should be minimized.

3 self-cleaning time

The self-cleaning time is a manifestation of the ability of the clean room to return from a contaminated state to a steady state, as short as possible. It can also be specified as the time from a certain pollution state to a clean state.

The self-cleaning time of the turbulent clean room is generally not more than 30 minutes.