1. 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, life  Energy  Perceive Value  Cost

2.  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 ΔP o – filter pressure drop  Potential issues:  Different ΔP o units  Results at different flow rate

3.  Example 1: E1 = 80% and ΔP o = 0.40” H 2 O α1 = - ln (1 – 0.8)/ 0.40 = 1.609/0.40 = 4.02  Example 2: E1 = 80% and ΔP o = 0.30” H 2 O α2 = - ln (1 – 0.8)/ 0.30 = 1.609/0.30 = 5.36  Example 3: E1 = 85% and ΔP o = 0.40” H 2 O α2 = - ln (1 – 0.85)/ 0.40 = 1.897/0.40 = 4.74

4.  Single Aggregate Objective Function (AOF)  Weighting method, linear AOF: MAX o E – filter efficiency; ΔP o – filter pressure drop o C – filter cost; DHC – filter dust holding capacity o λ – weighting factors; ∑ λ i = λ 1 + λ 2 + λ 3 + λ 4 =1 o λ – weighting factors are assigned based on priority - subjective

5.  Combination of objectives:  Other objectives: Cost, Energy

6.  MERV – is MERV a rating system?  Residential filters – Home Depot  FPR (Filter Performance Rating) = 1 – 10 scale Weighted Average = λ 1 (Efficiency Large Particles) + λ 2 (Efficiency Small Particles) + λ 3 DHC λ 1 + λ 2 + λ 3 = 0.6 + 0.3 + 0.1 =1  FPR = 10 for Weighted Average > 25  Residential filters – 3M  MPR – Microparticle Performance Rating ability to capture particles 0.3 – 10 µm (E1)