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Background

Background. Prior study demonstrated practicality of controlling air flow by measuring particle counts Benchmarking quantified large savings during periods of airflow setback Increasing interest in reducing airflow during periods of inactivity

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Background

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  1. Background • Prior study demonstrated practicality of controlling air flow by measuring particle counts • Benchmarking quantified large savings during periods of airflow setback • Increasing interest in reducing airflow during periods of inactivity • Parallel research project in CA and implementation in NY • Two Industrial partners ready for demonstrations

  2. Demand controlled filtration Definition: A method of controlling cleanliness (particle counts) in a room by changing the recirculation flow rate based upon real-time measurements of particle concentrations.

  3. Air-change rates and air velocity Not an exact science… • The Institute of Environmental Sciences and Technology (IEST), ASHRAE Applications Handbook, and other sources provide recommended recirculation air-change rates • Many large companies set their own criteria • Many owners and design firms use rules of thumb • Studies have shown that more airflow is not necessarily better suggesting a “sweet spot” between too little and too much airflow

  4. Benchmarks of recirculation air-changes and velocities

  5. Recirculation set-back Good contamination control while achieving energy savings was demonstrated in case studies

  6. Pilot study • Air set-back when not occupied • Particle counter detected 0.10 – 1.0 micron particles and separated them into six size bins • Data was logged for 23 days (2004) • Some correlation between fan speed and particle counts • No attempt to optimize air change rates

  7. Changes in airflow and particle counts

  8. Changes over different time periods

  9. Pilot study conclusions • Higher fan speeds don’t necessarily result in lower particle counts. There may be an optimum airflow that is unique to each room • Large energy savings may be possible with no adverse impact on contamination control • Particle counter placement and particle sizes collected are key parameters • Demonstrations in operating industrial cleanrooms should be pursued – more study is needed

  10. University study • Public interest energy research co-funding • Installation of particle counters and control in 17,000 sf cleanroom • Simple payback expected - approximately three years

  11. University study details • 25 particle counters updating counts every second • Airflow increased if necessary for cooling • Two particle size ranges monitored • Calibration of single location counters by use of portable mobile counters • Data only being collected in first year – control provided after first year

  12. Case study - recirculation setback

  13. Conclusions • Energy efficiency can be achieved in cleanrooms without affecting contamination control • Different strategies can be used to control recirculation air flow • Demand controlled filtration offers promise • It may be possible to optimize cleanroom air flow for cleanliness and energy efficiency

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