Cleanrooms: Two promising research areas

William Tschudi – LBNLPeter Rumsey – Rumsey Engineers

November 4, 2004

Two promising research areas

Demand controlled filtration

Fan-filter unit energy performance

Demand controlled filtration

The goal: Match airflow to cleanliness. Through real-time monitoring of cleanliness in the cleanroom, allow lower airflow unless excessive numbers of particles are detected. If particle counters record increased particulates, airflow is automatically increased through variable speed drives on recirculation fans.

Demand controlled filtration – pilot study

Pilot study in LBNL cleanroom confirmed feasibility

Particle sizes of concern were studied

Fan speed controlled by particle counts

Optimum airflow is not too high or too low

Location and numbers of particle counters need additional study

Demand controlled filtration – demonstrations

LBNL is planning a demonstration to use the concept in an operating industrial cleanroom

Cornell University will be demonstrating the concept in its new Duffield Hall cleanroom

Demand controlled filtration – other options

Turndown of airflow can be achieved through simple controls:

Manual Timers Occupancy sensors Combinations of these

An informal survey of the ASHRAE TC 9.11 committee (cleanspaces) found a that number of cleanrooms are currently turning down airflow

Fan-filter units

The Need: A standard method of testing and reporting performance so that owners and designers can select units based upon performance – not hype. Performance can include: energy use, noise, vibration, filtration effectiveness, etc.

The players

Industrial Technology Research Institute (ITRI) Institute of Environmental Sciences and

Technology (IEST) Air Movement and Control Association

International (AMCA) SEMATECH International FFU manufacturers and end users CA Energy Commission and public utility

companies

FFU’s are popular

Fan-filter units are increasingly specified in cleanrooms in various industries

Fan-filter units are used in mini-environments

Many manufacturers produce fan-filter units for use in cleanrooms

Why the need for standardized reporting?

Benchmarking and testing in Taiwan has shown wide variations in performance

Fan-Filter manufacturers report performance in different ways

Cleanroom Owners and Designers need a standard comparison

Incentive programs need a baseline and standard comparison

Serious cost and energy efficiency implications

11

Recirculation systems

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

Fac. AClass 10 Press.Plen.

Fac. AClass 100

Press.Plen.

Fac. B.1Class 100

Ducted

Fac. B.1Class 100

FFU

Fac. B.2Class 100

Ducted

Fac. B.2Class 100

FFU

Fac. CClass 100

Press.Plen.

Fac. DClass 10Ducted

Fac. EClass 100

FFU

Fac. EClass 100

Press.Plen.

Fac. FClass 10Press.Plen.

Fac. FClass 10Press.Plen.

Fac. FClass 10Press.Plen.

Fac. FClass 10k

CFM / kW (higher is better)

Averages (cfm / kW)FFU: 1664

Ducted: 1733Pressurized Plenum: 5152

Recirculation Efficiencies

0

500

1000

1500

2000

2500

3000

3500

4000

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Facility

CFM/kW

Average 3440

Average 1953

LBNL Data

Sematech Data

Comparing fan-Filter units

If fan-filters are desired, how can their energy efficiency be determined?

Confusing claims and catalogue information:

Watts/fpm Noise (dBA @ distance)

for single unit vs. many External static Flow area

Fan Filter Units' CFM/kW at .8"w.g. system pressure

0

1000

2000

3000

4000

5000

6000

7000

Mgf. 1 Mfg. 2 Mfg.3 Mfg. 4 Mfg. 5

CFM/kW

FFU energy efficiency

Source: Rumsey Engineers

Taiwan test data

Test procedure development

LBNL has developed a draft test procedure addressing energy performance

Draft procedure available on LBNL website – comments welcome

Test procedure considerations Available total pressure

Air flow Quantity/Variable flow

Uniformity

Sensible cooling (if provided)

Total power consumption

Noise and vibration levels

Filter area

Size of FFU (2’ x 4’, 4’ x 4’, etc.)

Test arrangements

Similar to testing large fans

Discharge

Pressure Tube

Damper

FFU Being Tested

Booster FanSettling Screens Nozzles

Establishing a baseline

PG&E is sponsoring a test of the test procedure at their test facility

CA Energy Commission Public Interest Energy Research (PIER) is sponsoring testing to establish baseline

If you can loan units for testing let us know

Expected outcomes

An IEST recommended practice will be issued

CA public utilities will establish baseline and include in incentive programs

Owners and designers will have a standard way to compare performance

Owners can evaluate first cost vs operating cost

Improvement in performance will follow

Energy-efficient Fan-filter Units

Design Considerations Contour of inlet airflow path Baffles to direct flow and deaden sound Motor efficiency – AC or DC Fan efficiency Clearances Filter media Depth of box Filter area Controls

More efficient units have considered all of this

Questions?

Thank you!

http://hightech.lbl.gov