Principle of Cleanroom
Cleanroom is the most important and most representative measure to create the clean microenvironment with air cleaning technology. The principle of cleanroom is the theoretical base for the design, operation, and maintenance of the cleanroom well.
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Principle of Cleanroom
Cleanroom is the most important and most representative measure to create the clean microenvironment with air cleaning technology. The principle of cleanroom is the theoretical base for the design, operation, and maintenance of the cleanroom well.
8.1
Approach to Control Contaminants
In terms of the controlled objects, cleanroom can be divided into two kinds: industrial cleanroom and biological cleanroom. The main task of industrial cleanroom is to control the pollution of nonbiological particles, while that of biological cleanroom is to control the biological particles. However, no matter it is nonbiological or biological particles, non-vital or vital particles, they are considered to be particles in the air cleaning technology field, which has the feature of particles. Therefore, no matter what kind of cleanroom it is, the approach to control particular pollution is the same. These methods have the following features: 1. Prevent the outdoor pollution from entering indoors (or effectively prevent indoor pollution from emission outdoors). This is the main approach to control the pollution in the cleanroom, which mainly includes the method of air cleaning and indoor pressurization, etc. 2. Exhaust the pollution that occurs indoors effectively, which mainly includes the indoor air distribution. This represents the key function of cleanroom. 3. Control the pollution source and reduce the generation of pollution, which mainly includes the method to place and manage the equipment which generates pollution, as well as the cleaning of people and objects entering into the cleanroom. The former belongs to the process problem, which will not be discussed. The latter will be introduced later. The above three items will be illustrated in this chapter and later. Z. Xu, Fundamentals of Air Cleaning Technology and Its Application in Cleanrooms, DOI 10.1007/978-3-642-39374-7_8, © Springer-Verlag Berlin Heidelberg 2014
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8.2
8 Principle of Cleanroom
Flow State
8.2.1
Several Fundamental Fluid States
In order to illustrate the principle of cleaning function by cleanroom from the airflow aspects, the following concepts of fluid dynamics are emphasized.
8.2.1.1
Steady-State Flow and Unsteady-State Flow
Various parameters of fluid particles (such as velocity, acceleration speed, density, and stress including the pressure, tension, shear force, and viscous force) differ with position of fluid particles, but remain the same with the time t. This kind of fluid is called steady-state flow. If various airflow parameters are function of both position (x, y, z) and time (t), it is called unsteady-state flow.
8.2.1.2
Gradually Varied Flow and Mutation Flow
When the flow has the following characteristics, it is called gradually varied flow, which is shown in Fig. 8.1. 1. The angle β between flow lines is very small, which means the distance between flow lines is almost equidistant. 2. The radius of curvature R is very large, which means the flow line is close to be straight (combined with the above
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