1. Classification by use
They can be divided into two categories according to their uses:
(1) Industrial clean room - the control object is inanimate particles. It mainly controls the pollution of inanimate particles to the working objects, and generally maintains positive internal pressure. It is suitable for precision industry, electronics industry, aerospace industry, atomic energy industry, printing industry, photography industry and other sectors.
(2) Biological clean room - with living particles as the control object, can be divided into:
1) General biological clean room. It mainly controls the contamination of working objects by living particles. At the same time, the internal material should be eroded by various sterilizers, and the internal pressure is generally positive. It can be used in pharmaceutical industry, food industry, medical facilities, laboratory facilities, etc.
2) Biosafety clean room. The main control object is the contamination of living particles to the outside world and people, and the internal pressure should be kept negative. It is used in laboratory facilities, biological engineering, medical facilities and so on.
Classification by airflow
2.According to airflow, it can be divided into four categories:
(1) One-way flow clean room
(2) Non-unidirectional flow clean room (turbulent clean room)
(3) Sagittal angular flow cleaning room
(4) Mixed flow clean room (local one-way flow clean room)
3. Principle and characteristics of one-way flow clean room
One-way flow clean room is a clean room in which air flow passes through the whole room section in a single direction along a parallel streamline at a uniform cross-section velocity.
The one-way flow clean room relies on the piston-like extrusion of the air supply to expel the indoor pollution rapidly. In order to ensure the realization of piston function, the most important point is that the high-efficiency filter must be fully covered. Of course, filters have borders, and roofs have borders, so it's impossible to be 100% full of filters. Full coverage ratio is used to measure the full coverage of filters.
Under normal conditions, the full coverage ratio reaches 80%. Vertical unidirectional flow should not be less than 60%, horizontal unidirectional flow should be less than 40%, otherwise, local unidirectional flow.
(3) Characteristic indicators
1) Streamline parallelism
The function of streamline parallelism is to ensure that dust particles emitted from dust sources do not propagate perpendicularly to the flow direction. It requires that the streamlines be parallel (the angle between the inner lines should not be less than 15 degrees within 0.5 m distance), and that the streamlines should be as vertical as possible to the air supply surface (the minimum inclination should not be less than 65 degrees).
2) Turbulence (velocity inhomogeneity)
The function of velocity uniformity is to ensure the minimum transverse exchange of particles between streamlines. The turbulence degree is defined to indicate the concentration or dispersion of the velocity field.
3) Lower limit wind speed
This is to ensure that the clean room can control the minimum wind speed of the following four kinds of pollution:
A. When the polluted air is dispersed in many directions, the air supply should effectively control the range of pollution.
B. When the polluted air flow is in the same direction as the supply air flow, the supply air flow should effectively control the diffusion range of the polluted air flow to the downstream.
C. When the polluted air flow is in reverse with the supply air flow, the supply air flow can restrain the polluted air flow within the necessary distance.
D. In the case of contamination of the whole room, it is sufficient to quickly clean the indoor air at an appropriate time.
4. Principles and characteristics of turbulent clean rooms
The turbulent clean room is a clean room where the air flow is not parallel at an uneven speed, accompanied by backflow or eddy current.
The turbulent clean room continuously dilutes the indoor air by the air supply, and gradually discharges the indoor pollution to achieve balance. In order to ensure that the dilution effect is well realized, the most important thing is that the indoor air flow diffuses as quickly as possible, the more uniform the better.
(3) Characteristic indicators
1) Frequency of ventilation
The function of ventilation frequency is to ensure that there is enough clean air to dilute. The number of ventilation should be determined by calculation and experience.
2) Air distribution
The function of air distribution is to ensure uniform air supply and return, and to give full play to the dilution of clean air flow. Therefore, a single air outlet is required to have sufficient diffusion effect, the return air of the whole room is evenly arranged, and the number is more and better, and the eddy current and airflow cycles should be reduced as far as possible.
3) Self-purification time
Self-cleaning time is the reflection of the ability of clean room to return from polluted state to stable state, the shorter the better. It can also be designated as the time from a polluted state to a clean state. The self-cleaning time of turbulent clean room generally does not exceed 30 minutes.
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