filter bypass testing - nafa...• filter bypass leads to – fouling of hvac equipment –...
TRANSCRIPT
Filter Bypass Testing Douglas Kosar
University of Illinois at Chicago (UIC)
Acknowledgements
Researchers UIC -- David Chojnowski and Paul Nigro University of Texas -- Jeffrey Siegel Collaborators Filtration Group and R. B. Hayward Company Sponsors National Center for Energy Management and Building Technologies and Department of Energy
2
Presentation Outline • Filter bypass as priority research • Siegel 2005 modeling presentation • UIC ASHRAE 52.2 test loop • Design of experimental setup • Filter bypass testing matrix • Initial testing and modeling results • Further testing and modeling plans • Conclusions and summary
3
Concerns Lead to Research
• Filter bypass leads to – Fouling of HVAC equipment – Degrading of indoor air quality
• Limited research quantifying bypass – Informal case studies and simple models – Siegel modeling presentation here in 2005
• Industry expert panel 2006 priorities #1 Filter bypass #5 Filter seals
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Ward & Siegel Filter Bypass Model
1. Pressure Driven Airflows – Gap dimensions – Right angle bends – Flow regimes
• Laminar • Turbulent
Adapts two building envelope crack models • Experimentally validated for infiltration • Unproven experimentally for filter bypass
2. Deposited Particles – Gravitational settling – Impaction removal – Diffusion penetration
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Research Methodology • Particulate filter efficiency degradation
– Test a range of MERV filters – Relate gap size to removal efficiency losses – Breakdown losses by particle size range – Evaluate straight thru and U channel bypass
• Formal ASHRAE 52.2 loop experiments • Modified filter test section for bypass • Test matrix for key bypass variables • Comparisons of test and model results • Enhancements to bypass model
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Nominal Test Loop Operation • 24 x 24 inch filter • 2000 cfm airflow • 500 fpm face velocity • Prescribed ASHRAE
KCl particles (& dust) • Initial efficiency tests
(& select full 52.2 tests) • Particle counts in 12
discrete size ranges
RangeUpper Bound
Lower Bound
Geometric Mean
µm µm µm1 0.30 0.40 0.34642 0.40 0.55 0.46903 0.55 0.70 0.62054 0.70 1.00 0.83675 1.00 1.30 1.14026 1.30 1.60 1.44227 1.60 2.20 1.87628 2.20 3.00 2.56909 3.00 4.00 3.464110 4.00 5.50 4.690411 5.50 7.00 6.204812 7.00 10.00 8.3666
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Filter Test Section Setup • Sealed pocket in
test window panel • Filter extends up to
2 inches into pocket • Gap exposed on
opposite side of loop • Dimensional gauges
confirm gap size • External set screws
& plate secures filter
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Filter Bypass Test Procedure • Tape all 4 sides
including bypass • Airflow at 2000 cfm • Record pressure drop • Remove bypass tape • Increase airflow to
match pressure drop • Run initial efficiency
(or full 52.2) filter test
11
Initial Filter Bypass Tests A - H
0.25 1.25 1.75 0.25 0.75 1.25 1.75
2
7 A B G C
11
14 D E H F
Shaded lettered cells indicate additional taped 'NO BYPASS' tests.
GAP SIZE (inches):
MERV
BYPASS TYPE: STRAIGHT
0.75
Tests are performed in alphabetical order.
NOTES: Each cell w/letter indicates initial efficiency test.
U-SHAPED
12
MERV 7 Bypass Test Results
0%
10%
20%
30%
40%
50%
60%
0.1 1 10Particle Diameter (μm)
Rem
oval
Effi
cien
cy
Test G (no bypass)Test A (0.25 inch)Test B (0.75 inch)Test C (1.25 inch)
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MERV 7 Model Comparisons -- 0.25 Inch Bypass Gap
0%
10%
20%
30%
40%
50%
60%
0.1 1 10
Particle Diameter (µm)
Rem
oval
Effi
cien
cy
Measured w/o bypassPredicted w/ bypassMeasured w/bypass
14
MERV 7 Model Comparisons -- 0.75 Inch Bypass Gap
0%
10%
20%
30%
40%
50%
60%
0.1 1 10
Particle Diameter (µm)
Rem
oval
Effi
cien
cy
Measured w/o bypassPredicted w/ bypassMeasured w/bypass
15
MERV 7 Model Comparisons -- 1.25 Inch Bypass Gap
0%
10%
20%
30%
40%
50%
60%
0.1 1 10
Particle Diameter (µm)
Rem
oval
Effi
cien
cy
Measured w/o bypassPredicted w/ bypassMeasured w/bypass
16
MERV 14 Bypass Test Results
40%
50%
60%
70%
80%
90%
100%
0.1 1 10Particle Diameter (μm)
Rem
oval
Effi
cien
cy
Test H (no bypass)Test D (0.25 inch)Test E (0.75 inch)Test F (1.25 inch)
17
MERV 14 Model Comparisons -- 0.25 Inch Bypass Gap
40%
50%
60%
70%
80%
90%
100%
0.1 1 10
Particle Diameter (µm)
Rem
oval
Effi
cien
cy
Measured w/o bypassPredicted w/ bypassMeasured w/bypass
18
MERV 14 Model Comparisons -- 0.75 Inch Bypass Gap
40%
50%
60%
70%
80%
90%
100%
0.1 1 10
Particle Diameter (µm)
Rem
oval
Effi
cien
cy
Measured w/o bypassPredicted w/ bypassMeasured w/bypass
19
MERV 14 Model Comparisons -- 1.25 Inch Bypass Gap
40%
50%
60%
70%
80%
90%
100%
0.1 1 10
Particle Diameter (µm)
Rem
oval
Effi
cien
cy
Measured w/o bypassPredicted w/ bypassMeasured w/bypass
20
MERV Reductions with Bypass
Bypass (inches) MERV 0.00 14 0.25 12 0.75 8 1.25 8
• MERV 7: up to 1 point MERV reduction • MERV 14: up to 6 point MERV reduction
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Planned Filter Bypass Tests I - ?
0.25 1.25 1.75 0.25 0.75 1.25 1.75
2 L M Q R S
7 A B G C J T U V W
11 O P X Y Z
14 D E H F I AA BB CC DD
Tests are performed in alphabetical order.
GAP SIZE (inches):
MERV
BYPASS TYPE: STRAIGHT
0.75
K
N
Additional FULL filter tests TBD. Shaded lettered cells indicate additional taped 'NO BYPASS' tests.
NOTES: Each cell w/letter indicates initial efficiency test.
U-SHAPED
22
Conclusions • Straight thru bypass testing quantified
efficiency loss for particulate filters – Higher efficiency filters strongly effected – Larger particle removal most effected
• Testing and modeling agree, except – Modeling generally under-predicts losses
• Filter bypass airflow ? • Larger particle deposition ?
– Error ranges on testing results TBD – More complex U channel testing still to come
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Summary
• Per Siegel in 2005 “bypass is important” • Testing has now validated that original
position based on modeling alone • Seal technology and rack installation
practices must address bypass issue • Ongoing testing and modeling can
contribute findings to those areas and foster future developments/initiatives
