| Budget Amount *help |
¥5,700,000 (Direct Cost: ¥5,700,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥4,700,000 (Direct Cost: ¥4,700,000)
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| Research Abstract |
With increasing demand for highly-purified space in high-tech industry, ULPA (Ultra low Penetration Air) filters have been used in clean rooms in place of the conventional HEPA (High Efficiency Particulate Air) filters. Further, in semiconductor industry, membrane filters which have collection efficiency much higher than the ULPA and HEPA are currently used to eliminate particulate matter from pressurized process gases.
Under these present situations, the next requirement for these air filters is to reduce their pressure drop without sacrificing their high collection efficiency.
In the present work, an index for filter performance, defined as the ratio of logarithm of particle penetration to pressure drop was introduced to evaluate collection performance of various air filters by taking account of both the filter collection efficiency and the pressure drop. On the basis of the filter performance index, the influence of filter structure of fibrous and membrane filters on the collection pe
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rformance was investigated. Furthermore, the collection performance of electret filter which utilizes electrostatic Charge to collect particles was evaluated in order to examine whether it can be used as an economical high collection performance air filter.
As a result, it was found that the collection performance of fibrous air filter can be improved (1) by reducing the fiber diameter, (2) by increasing the fraction of fibers which lie parallel to airflow direction, and (3) by reducing the amount of binder. Concerning the membrane filters, we classified them into five groups according to their structure, and found that the membrane filters with fiber-like structure have a higher collection performance than those with pore-like structure. Further, the collection efficiency of membrane filters with a relatively high-packing density was predicted by a newly proposed model based on internal flow collection model. Concerning the collection performance of electret filters, we presented a theoretical model to calculate initial collection efficiency, and experimentally showed that the electret charge on the elect fiber is stable in humid air and that the collection efficiency for solid and atmospheric particles do not decrease with dust load. However, when the electret filter was used for organic mist particles, the charge was neutralized in a short time, leading to a significant decrease in the collection efficiency. Less
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