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1. HEPA Filter / Spot Cooler David Elting
2. Project Objective To design a HEPA filter / spot cooler system that maintains the 14’x8’x8’ class 100 clean room at a temperature of 72°F and filters 99.97% of all particles <0.3µm in diameter.
Main Question: How many cfm to filter, and cooling load in tons for the spot cooler?
3. Design Parameters Maintain Room Temperature ~ 72°F (Spot Cooler)
99.97% efficiency (Filter)
Filter Particles <0.3µm in diameter
ASHRAE notes that 85% - 95% of the ceiling should be covered with filters
4. Volumetric Flow Rate Currently, flow rate is at a maximum of 7920 cfm at manufacturer’s maximum velocity of 90 fpm. ASHRAE suggests a flow rate of 50 fpm multiplied by the surface area of the ceiling for a class 100 clean room.
In our case:
14ft*8ft*50 fpm = 5600 cfm
5. Cleanroom Air Velocity and Air Changes For a given cleanroom, the supply air volume Q (cfm) is:
6. Wall Heat Gain
7. Ventilation Flow Rate There are 7 air return ducts in the clean room, only one of which goes to the spot cooler.
8. Fresh Air Cooling Load Energy Balance:
9. Fresh Air Cooling Load
10. Lighting Heat Gain
11. Occupancy Heat Gain Heat gain from a single occupant performing light work can be estimated as:
12. Total Cooling Load
13. References ASHRAE Technical Committees and Task Groups. 2001 ASHRAE HANDBOOK, FUNDAMENTALS, Inch-Pound Edition. Atlanta: American Society of Heating and Air-Conditioning Engineers, Inc. 2001.
Cengel, Young A., and Michael A. Boles. Thermodynamics an Engineering Approach. 5th. Boston: McGraw Hill, 2006.