2007 ashrae annual meeting conserving natural resource use in buildings william tschudi –...
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2007 ASHRAE Annual Meeting
Conserving Natural Resource Use in Buildings
William Tschudi – [email protected] Xu – [email protected]
Lawrence Berkeley National Laboratoryhttp://hightech.lbl.gov
ASHRAE Annual MeetingLong Beach, California
Fan-Filter Testing - The Results Are In
Overview
Background leading to testing fan-filter units
Description of test configuration Illustrative results Use of the procedure Possible next steps
Background
Previous cleanroom benchmarking illustrated a large variation in air recirculation efficiency
Systems with fan-filter units typically were found to be less efficient
Chillers and Pumps21%
Recirc and Make-up Fans19%
Process Tools34%
Exhuast Fans7%
Nitrogen Plant7%
Support3%Process Water
Pumping4%
DI Water5%
Benchmarked Recirculation System Efficiencies
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 10
Press.Plen.
Fac. FClass 10
Press.Plen.
Fac. FClass 10
Press.Plen.
Fac. FClass 10k
CFM
/ kW
(hig
her i
s be
tter)
Averages (cfm / kW)FFU: 1664
Ducted: 1733Pressurized Plenum: 5152
Background, con’t
In 2000, a Taiwanese Research Institute evaluated fan-filter units – a wide range of performance was notedAverage Outlet Velocity, m/s
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Ele
ctr
ic E
ffic
ien
cy
, %
0
5
10
15
20
25
30
35
40 FFU AFFU BFFU CFFU DFFU EFFU FFFU GFFU HFFU I-1FFU I-2FFU JFFU KFFU LFFU MFFU NERL FFU (AC)ERL FFU (ACS)ERL FFU (DC)FFU P-1FFU P-2
4'X2' FFU
Background, con’t
We then began developing a standard test procedure for fan-filter units to help get “apples-to-apples” comparisons
The procedure is now available on our website. It was used in the evaluation of 17 2’x4’ fan-filter units to “test” the procedure and obtain performance information
Test Configuration
Layout in test lab
MD
4
F
Humidity
Booster
Fan
Damper
Temperature
Power meterRPM meter
PressureSensor
Fan-filter Unit
Airflow
Straightener
AirflowNozzle
Configuration was dictated by space available
Flow meter
An Accurate, Calibrated Flow Nozzle Determined Air Flow
Flow measurement:
Measurement Comparison of Airflow Rates
y = 0.9267x
R2 = 0.9996
0
100
200
300
400
500
600
700
800
0 100 200 300 400 500 600 700 800
Flowhood (cfm)
No
zzle
(cf
m)
Accuracy of a flow Accuracy of a flow meter (Nozzle) meter (Nozzle) compared to a flow compared to a flow hood was studiedhood was studied
Discrepancies were Discrepancies were observed across units observed across units between the two between the two methodsmethods
Flow meter gives Flow meter gives consistent, accurate consistent, accurate resultsresults
Pressure Tap (Pitot Tube)
Pressures were determined at various places throughout the system
Electric Power Monitoring Equip.
Available From Utility Tool Lending Library
Testing Considerations
Air flow rate measurements Pressure measurements Power Device calibration and uncertainties Integrity of the testing system, e.g. leakage Size of testing rig Additional parameters, e.g., space/material
cost Ambient conditions
Sample Operating conditions
Unit with AC motor tested within its operating range
0
100
200
300
400
500
600
700
800
900
1000
0 50 100 150 200 250Pressure (Pa)
Air
Flo
w (
scfm
)
Operating conditions, cont.
Unit with ECM motor tested within its operating range
0
100
200
300
400
500
600
700
800
900
1000
0 50 100 150 200 250Pressure (Pa)
Air
Flo
w (
scfm
)
Total electric power demand of the fan filter unit under selected operable conditions: 20 Pa ≤ Dp ≤ 150 Pa, Q ≥ 9.9 m3/min (or 0.08 iwc ≤ Dp ≤ 0.6 iwc, Q ≥ 350 scfm)
Total Electric Power Demand (W)
Pressure (Pa)
20 40 60 80 100 120 140
Airflow
Rate (scfm
)
400
500
600
700
800
160 170 180
Air
flow
cfm
Total Pressure Efficiency
For FFUs with a multi-speed-drive, the total electric power demand may be calculated as:
Dp is the pressure differential across the fan filter unit
Q is the airflow rate across the unit under standard atmospheric condition.
Ci,j (i, j = 0, 1, 2) is a coefficient developed from experimental data through polynomial regressions.
p
t 2 20 1 p 2 11 p 12 p 22
Q·D =
C + C ·D + C ·Q+C D + C ·D ·Q + C ·Q
FFU power efficiency
FFU power efficiency (Et) is defined as the airflow dynamic power divided by the total electric power input to the FFU unit. The FFU power efficiency includes electrical and mechanical efficiency of the FFU unit taking into account fan motors, fan design, housing, etc.
Et = Pt Q / W Pt = FFU pressure rise (Pa)Q = air flow rate (m3/s)W = electric power input to FFU (W)
0
2
4
6
8
10
12
14
16
18
20
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Airflow Speed at Exit (m/s)
Tota
l Pre
ssur
e E
ffici
ency
(%)
1,600 RPM (Max)
1,500 RPM
1,300 RPM
1,100 RPM
900 RPM
Power
PQ TotalOut,
FFU Total Pressure Efficiency
Total pressure efficiency of the fan filter unit under selected operable conditions: 20 Pa ≤ Dp ≤ 150 Pa, Q ≥ 9.9 m3/min (or 0.08 iwc ≤ Dp ≤ 0.6 iwc, Q ≥ 350 scfm)
Total Pressure Efficiency
Pressure (Pa)
20 40 60 80 100 120
Airflo
w R
ate (scfm)
350
400
450
500
550
600
0.05 0.10 0.15 0.20
Air
flow
cfm
Total pressure efficiency of the fan filter unit under selected operable conditions: 20 Pa ≤ Dp ≤ 150 Pa, Q ≥ 9.9 m3/min (or 0.08 iwc ≤ Dp ≤ 0.6 iwc, Q ≥ 350 scfm)
Total Pressure Efficiency
Pressure (Pa)
20 40 60 80 100 120 140
Airflo
w R
ate
(sc
fm)
400
500
600
700
800
0.00 0.05 0.10 0.15 0.20
Air
flow
cfm
Efficiency Comparisons
Variations in electric power and efficiency More than a factor of 10 difference for the
same unit across different operating conditions
Different units varied by 3 to 4 times for the same operating condition
Variation patterns not obvious
Efficiency in the Range of Interest
0
10
20
30
40
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
Airflow Speed at FFU Exit (m/s)
To
tal
Pre
ssu
re E
ffic
ien
cy (
%)
Airflow Range 60-90 fpm
0.3-0.45 m/s
Variation of FFU Efficiency
Total Pressure Efficiency
0%
5%
10%
15%
20%
25%
30%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Percentile Ranking: A higher percentile corresponds to higher total pressure efficiency
Xu, T. 2006 (9). Cleanrooms Magazine. Standard Development and Laboratory Testing of Fan Filter Units
Efficiency Comparisons
ECM motors tended to be more efficient however overall unit design influences efficiency
Simple metrics not sufficient – depends upon pressure and flow
How to Identify Efficient FFUs
Implement Standard Lab Testing Standard test protocols to fully characterize
performance Standard reporting
Determine expected range of operating conditions
Review test results in range of expected operation
Select unit considering energy performance along with other desired features
Incentive Criteria Development
Relative performance ranking system quantify the observed difference identify rebate-criteria.
Relative ranking scores examine the robustness of the
suggested initial rebate criteria. Once an incentive criteria is set, units that
exceed that threshold can be selected
Recommended Practice
IEST RP CC036.1 – Testing Fan Filter Units
Working draft of RP036.1 is being developed
Interested parties are encouraged to participate
Recommendations
Owners/designers - define requirements for Air recirculation
Air change rate Air flow rate
Cleanliness Uniform air flow System design Pressure conditions
Recommendations
Procurement of fan-filter units
Define range of operating conditions Require testing in accordance with
standard test procedure Evaluate performance in the range
of interest Select based upon efficiency or
perform life cycle cost analysis
Use of the standard test procedure
A major semiconductor manufacturer adopted standard, built a test rig, and required bidders to provide units for testing as part of the procurement process
An Asian company required FFU manufacturers to provide test results during the procurement process
A semiconductor manufacturer investigated replacing aged FFUs with more efficient units as determined by the test procedure
Reaction to the standard test procedure
Manufacturers are eager to know the performance of their units - product improvement is expected
Recommended Practice (RP) CC036.1 is planning on adopting the procedure
A major utility is considering adding fan-filter units to their incentive program
Possible next steps
Recommended practice issued for use
Optimize test rig (size)
Testing of 4’x4’ units
Utility incentive programs
Questions??