|M.Sc Student||Mualem-Toledano Reut|
|Subject||Design of an air filteration system for a Cleanroom|
|Department||Department of Mechanical Engineering||Supervisor||Professor Emeritus Chaim Gutfinger|
|Full Thesis text|
This thesis was undertaken with the objective of furnishing the designer with computational tools from aerosol mechanics, in order to provide a scientific basis for the design of an air filtration system for a clean room. We have calculated the pressure drop and power consumption on the HEPA filter, which is part of the air filtration system in the clean room, and proposed a way to save energy by increasing the filtration area without increasing the replacement cost of the filters.
We have reviewed the various design systems of air handling for re-circulating air in a clean room and recommended the plenum design as the most efficient one. In addition, we have compared the power consumption operating costs with the replacement costs of HEPA filters and recommended a strategy for cost minimization.
All the calculations were performed on a class 10 clean room with coverage of 100% of the ceiling and a class 100 room with industry recommended 80% coverage, as well as 100% coverage of the ceiling. The pressure drop on the HEPA filter was calculated using the model developed by Davies (1952). This was used to obtain the power consumption for the original filtration area as well as for increased filter configurations.
The yearly cost of power consumption and filter replacement were calculated by taking into account the time for the filter to clog. While increasing filtration area decreases the yearly initial power consumption, the cost of the filter panels per year does not change. This is due to the fact that for the same air circulation rate in the clean room, a threefold increase in filter area will reduce to a third the airflow rate per filter panel and increase threefold the time for particle accumulation on the panel. Hence, the time for replacement of the filter panels will be three time longer, and the yearly cost of filter replacement will not change. At present, the dominant cost of yearly operation of a clean room is the price of the filter panels as compared to the yearly cost of power consumption.
An important outcome of this research has been determining that the yearly filter expense does not depend in the filter area; hence, it is recommend that filters should cover the maximum available area in the clean room.
In conclusion, we recommend designing an air filtration system for a clean room by using the maximum available ceiling coverage. This will lead to a lower pressure drop on the filters and lower initial power consumption. Moreover, the designer should consider increasing the filtration area over 100% by a pleated arrangement of the filter panels. Such an arrangement will further reduce the pressure drop and power consumption without increasing the yearly cost of the filter panels. On the other hand, this strategy will require raising the height of the ceiling, thus increasing the construction cost of the room. Hence, it should be taken into account while optimizing the design of the clean room.