Clean workshop decoration air outlet layout
Clean pharmaceutical cleanroom decoration air outlet layout
The air supply outlet of the clean workshop is the key element of the airflow organization. The quantity and arrangement of the air supply outlet have an important influence on the airflow organization.
1. Properly arrange the air outlet to avoid short circuit of clean air
The location and uniformity of the air outlet will affect whether the airflow can be quickly mixed, diluted,...
Text label: clean workshop decoration, clean workshop air outlet layout
Air supply outlet layout for clean workshop decoration
The air supply outlet of the clean workshop is the key element of the airflow organization. The quantity and arrangement of the air supply outlet have an important influence on the airflow organization.
1. Properly arrange the air outlet to avoid short circuit of clean air
The location and uniformity of the air outlet will affect whether the airflow can be quickly mixed and diluted, and the result will affect the indoor cleanliness. Figure 6-17 shows a foreign experimental example: DOP smoke is released into the room, and then the indoor concentration attenuation is measured. Although the effective area of u200bu200bthe air outlet layout B is twice that of the layout C, the effect of the layout C is better than that of the layout B, mainly because the self-cleaning time is shorter, the layout C is about 260s, and the layout B is about 310s.
2. There should be enough air outlets
Due to the limitation of site conditions or due to the excessive pressure of investment in the design of clean workshops, the number of return air outlets is often inappropriately reduced. As a result, under the same number of air changes, the air outlet speed is increased and the speed is increased. The inhomogeneity of the field increases or expands the eddy current area, which is often manifested as an isolated maximum value in the actual measurement, or the standard deviation of the indoor concentration field is very large, so that the average statistical value of the chamber exceeds the standard, especially the average concentration of particles ≥ 5 μm. 37% of those who exceeded the statistical value were judged to be unqualified, and the reason was that the characteristics of large particles following the airflow were not as good as those of small particles.
Appropriately increasing the number of air supply ports is equivalent to increasing the air supply area under the same air volume conditions, and can obtain a smaller pollution degree in the mainstream area. For example, for an 8m2 clean room, when the ventilation is less than 15 times/h, it is better to expand the tuyere to two, and when the ventilation is more than 25 times/h, it can be expanded to four, and the enlarged area can make the air supply speed not low. At 0.13m/s as the limit, the pollution degree of the mainstream area is small at this time. That is to say, it is advisable to double the area of u200bu200bthe air outlet (concentrated arrangement) compared with the conventional arrangement. At this time, although the air volume does not change, the general trend of the concentration in the mainstream area decreases instead. Of course, similar results should be obtained when the area of u200bu200bthe distributed air outlet is increased. Zhongjing Global Purification can provide supporting services such as consultation, planning, design, construction, installation and transformation of GMP workshops and clean workshops.
3. The arrangement of the air supply pipe should be conducive to the balance of airflow
When there are multiple air outlets, try to ensure that the length of the air supply pipes of each air outlet is not too different, so as to affect the airflow balance. In the arrangement of air supply ducts, if the air ducts between the first row of air outlets and the last row of air outlets are too different, and the resistance is too different, it is an inappropriate arrangement; if the same number of air outlets below are the same as those above. The air volume between the number of tuyeres varies greatly, which is still not conducive to balance.
The ideal arrangement is that the distance between the air supply pipes is equal between each tuyere. The disadvantage is that there are many air ducts, the installation is troublesome, and there are many local resistance nodes, so the practicability is poor.
Air supply speed of local unidirectional flow
For the one-way flow of the whole room (that is, the whole room is grade 5), the wind speed at the outlet of the air supply surface is not much different from the wind speed on the working surface (0.8m above the ground), because the wind speed on the air outlet surface is not much different at this time. The blind spot that is blocked is very small, generally around 20%.
For the local unidirectional flow (that is, the local level 5) airflow organization, the difference between the wind speed at the outlet of the air supply surface and the wind speed on the working surface is relatively large, because the four sides of the unidirectional flow are not constrained by solid walls, and the airflow must be directed to the surrounding area. There is some diffusion (although the diffusion angle is small) and mixing, so that the velocity attenuation is larger.
Whether it is the specification of the clean room or the GMP, there is a requirement for the wind speed on the working surface. Studies have shown that the ratio of the wind speed ν at the working face to the wind speed ν0 on the supply face has the following relationship:
ν/ν0u003d1-0.09x/r
Where x-----the distance from the center of the air outlet to the wall;
r-----equivalent radius of air outlet (ru003d[length X width]/[length ten width).
Considering the reason that the size of the actual local level 5 and the attenuation rate should not be too low, for a clean room with a general floor height of about 2.5m, the application range of x/r can be 1~4, that is, the attenuation rate is 20%~ 40% is more reasonable, that is, a larger decay rate can reach:
1-ν/ν0u003d1-(1-0.09×4)u003d1-0.64u003d0.36
Conversely, it requires ν/ν0u003d1/(1-0.36)u003d1.56
That is, the wind speed at the outlet of the air supply surface should be 1.56 times larger than the wind speed required by the working surface, and the average is 1.37 times (take x/ru003d3).
For the local level 5 where the ratio of the air outlet to the room area is too small and the attenuation rate may exceed 40%, it is recommended to add a retaining wall to the local level 5 to reduce the velocity attenuation rate.
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