nafa technical seminar april 19, 2012
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NAFA Technical Seminar April 19, 2012. ANSI/ASHRAE 52.2 Can we fix this Method of Test?. History of the Test procedure. 10+ years in development prior to 1999 release - PowerPoint PPT PresentationTRANSCRIPT
• NAFA Technical Seminar• April 19, 2012
ANSI/ASHRAE 52.2Can we fix this
Method of Test?
History of the Test procedure
• 10+ years in development prior to 1999 release • Task of 52.2 Committee "create a test method
based on particle size removal efficiency for end user evaluation of filter performance"
• Research projects led to greater understanding of the physical science in filtration
• MERV - scales were created with minimal data and educated guesses at value spread
Committee Efforts
• Std published in 1999 for the first usage• No revisions through 2007 (other than edits)• 2008 Arrestance and DHC were added from
52.1 predominantly for MERVs 1-4• 52.1 was removed from ASHRAE Standards• Addition of "Voluntary Conditioning Step"
MERV's Status?
• ASHRAE Rating system?
• No certification of personnel performing tests
• No policing entity to produce a rating system
ISO Standards
• Working groups creating standards for • Cleanroom and HEPA usage completed• UVC, Rotating Equipment, dust collection• Working group 3 - General HVAC filtration is
looking to use 52.2 MOT for developing PM efficiency values
Definition:•System of classification according to merit or amount
•Assessment of something in terms of quality, quantity or both
•What filter parameters should be included?Filter Performance – pressure drop, efficiency,
lifeEnergyPerceive ValueCost
Filter Rating
Is it possible to combine filter performance characteristics into one criterion?Greater value of the criterion equal to “better”
filter
Traditional quality factor (figure of merit):
o E – filter efficiency and ΔPo – filter pressure drop
Potential issues:
Different ΔPo units
Results at different flow rate
Filter Rating
oP
ELn
)1(
Example 1: E1 = 80% and ΔPo = 0.40” H2O
α1 = - ln (1 – 0.8)/ 0.40 = 1.609/0.40 = 4.02
Example 2: E1 = 80% and ΔPo = 0.30” H2O
α2 = - ln (1 – 0.8)/ 0.30 = 1.609/0.30 = 5.36
Example 3: E1 = 85% and ΔPo = 0.40” H2O
α2 = - ln (1 – 0.85)/ 0.40 = 1.897/0.40 = 4.74
Filter Rating
Single Aggregate Objective Function (AOF) Weighting method, linear AOF:
MAX
o E – filter efficiency; ΔPo – filter pressure drop
o C – filter cost; DHC – filter dust holding capacity
o λ – weighting factors; ∑ λi = λ1 + λ2 + λ3 + λ4 =1
o λ – weighting factors are assigned based on priority - subjective
Filter Rating
DHCCPEL 4321
Combination of objectives:
Other objectives: Cost,Energy
Filter Rating
DHCP
ELnDHCa
o
)1(
MERV – is MERV a rating system?
Residential filters – Home DepotFPR (Filter Performance Rating) = 1 – 10 scale
Weighted Average = λ1 (Efficiency Large Particles) +
λ2 (Efficiency Small Particles) + λ3 DHC
λ1 + λ2 + λ3 = 0.6 + 0.3 + 0.1 =1 FPR = 10 for Weighted Average > 25
Residential filters – 3MMPR – Microparticle Performance Rating
ability to capture particles 0.3 – 10 µm (E1)
Filter Rating - Examples
“Too Many MERV’s” ??According to ASHRAE and IEST – 20 Possible Assignable MERV’s
Three “Markets” E3 Arrestance MERV 1-4 General Equipment E2 Middle Efficiency MERV 5-12 Equipment and People E1 High Efficiency MERV 13-20 Marginalized Health People and Specialized End UsesReal Differences Between the Markets
Arrestance High Efficiency
Real Differences Within These Markets MERV 5 MERV12
DifficultiesVariety of End UsesVariety of Air Handling TypesVariety of Pollutants
Conditioning Step is Too Expensive
15
Conditioning Step Not Real World
16
Mechano-ElectretFilter
Mechanical OnlyFilter
52.2 Positive Attributesbefore Conditioning
17
Analogy—Gas Mileage Testing
http://www.caranddriver.com/reviews/2012-ford-focus-sel-test-review 18
ASHRAE 52.2-2007
Tom Justice
2010 Round Robin
2011 Round Robin
Issues under Review by Task Groups
• Current MERV boundaries• Humidity Range• OPC particle counter specifications• Air density calculation• Shedding• IPA vapor conditioning• Test variability
Reported Values
Channel E1 E2 E3 Reporting Value
Particle Size Range .3 to 1 1 to 3 3 to 10
Filter 1 37% 65% 84% MERV 8
Filter 2 36% 65% 85% MERV 11
Issues under Review by Task Groups
• Current MERV boundaries• Humidity Range• OPC particle counter specifications• Air density calculation• Shedding• IPA vapor conditioning• Test variability
Fig. 8 ASHRAE 1287 RPFig. 8 ASHRAE 1287 RP
KCL @ 0% to 85% RHKCL @ 0% to 85% RH
Other Potential Issues
• Test dust• Specifications for particle generator• Radioactive versus corona discharge in
neutralization of airstream• Initial resistance calibration