ASHRAE 52 Air Filters

transcript

Air Filters

SETP 2004Stephanie Shenefelt

Agenda• Filtration Principles

• Why Filter?

• Filter Ratings

• Filter Types (Availability in YW)

• Filter Applications

Filtration Principles• Impingement (Inertial Impaction)

• Straining

• Diffusion

• Electrostatic Attraction

Filtration Principles• Impingement (Inertial

Impaction)– Air flows around filter media– Particles in airstream resist

direction change– Inertia causes particles to

impact filter fibers– Affects larger particles more

than smaller particles– Minimum velocity– Filter fibers can be coated with

adhesive to help process

Filtration Principles• Straining

– Fiber openings smaller than particles

– Particles trapped and collected in filter media

Filtration Principles• Diffusion

– Sub-micron particles– Brownian motion

Brownian motion – indiscriminate motion occurring with particulate matter, due to extraneous surrounding molecular activity. Applies to particles not exceeding 0.2 micron. Effect is reduced as air velocity increases.

Filtration Principles• Electrostatic Attraction

– Dust particles pick up charge– Charged particles are attracted to charged filter fibers– Most filters require an induced electrical field to provide

the charge

Why Filter?• Remove airborne contaminants

• Avoid sick building syndrome

• Keep HVAC equipment clean– Lower energy consumption– Reduce maintenance costs

Why Filter?• Airborne contaminants:

– Dust (solid, granular particles)– Smoke (incomplete combustion products)– Fumes (small, solid particles)– Fog (small, liquid particles formed from condensed

vapors)– Mist (like fog, larger particles)– Living organisms

• viruses• bacteria• fungal spores• pollens

Filter Ratings• Arrestance (filter dust holding capacity)

• Efficiency (% of atmospheric contaminants removed)

• MERV

• Air flow resistance (airside pressure drop)

30% efficient, 98% arrestance

Filter Rating• Arrestance - %, by weight, of ASHRAE Synthetic test dust

that is held by a filter before the resistance rises to its final rated PD

• More applicable to low efficiency filters• Larger particles account for most of the weight • Affects filter service life

• service life - time between filter installation and replacement

2” Pleated Filter 4” Pleated Filter Efficiency 30% 30% Arrestance 90% 95% Service Life 4 mo 8 mo Airside Pressure Drop (clean)

0.3” 0.6”

Filter Rating• Efficiency - percent of atmospheric contaminants

removed (not size specific)• Measured by the discoloration of two white paper

targets (ASHRAE 52.1)• Always specified in bid documents

20% efficient 30% efficient 65% efficient 95% efficient

Filter Rating• MERV: Minimum Efficiency Rating Value • Introduced by ASHRAE Standard 52.2. • Based on Particle Size Efficiency - the filter’s ability to

remove airborne particles in specific size ranges from 0.3 to 10 microns

Source: Heating/Piping/AirConditioning • October 1999

Filter Rating

• Increased APD => Decreased air flow• Increased APD => Increased fan horsepower• Increased face area => Reduced APD• Increased efficiency => Increased APD

APD = Airside Pressure Drop

High APDLow APD

Resistance - measure the pressure drop across the filter due to the opposition of the filter (inches of water, gauge – “w.g.”)

Filter Manufacturer• American Air Filter - standard airside

product filter manufacturer

• Filter data can be found at www.aafintl.com

• Pre-filters– Pleated 30% eff (MERV 6)

• Perfect Pleat• Consistent, self-supporting DuraFlex media• No wire support

– Safer handling– Avoid Rust– Totally incinerable

– Cleanable (MERV 1)• Permanent Metal Air Filters• Aluminum (std) & with drain holes• High moisture applications • Easy to handle/clean

– Throwaway (MERV 4)• 5700• Fiberglass media• Extra heavy dust

Filter Types

Filter Types• Throwaway, panel

construction• Pleated (2”PerfectPleat or

4”AmAir 200E) • Cleanable

AF Segment in YorkWorks

Filter Types

Only 2”

FF Segment in YorkWorks

Filter Types

2” - three options

4” - pleated only

Higher efficiency filters:• 4” Mini-pleat – VariCel II

efficiency: 60-65% 80-85% 90-95% MERV: 11 13 14

• 12” Rigid - VariCelefficiency: 60-65% 80-85% 90-95% MERV: 11 13 14

• 21” Bag – DriPakefficiency: 60-65% 80-85% 90-95% MERV: 11 13 14

Filter Types

Ultra-fine glass fiber mediaCorrugated aluminum separatorsMetal sides, steel header

Ultra-fine glass fiber mediaNon-supported extended surface

Micro-glass paper with water repellant binder mediaFoil laminated fiber board frame

Filter Types• Bag• Rigid, cartridge • Mini-pleat

RF Segment in YorkWorks

Filter Types

4 options:2” pleated2” cleanable2” throwaway4” pleated

RF Segment in YorkWorksFilter Types

Filter Types

HEPA – High Efficiency Particulate Air Filter

• High capacity AstroCel HCX• 11.5” deep – 500 fpm @1.4” w.g.• Each filter tested at AAF• Extruded aluminum bevel-welded

frames from AAF (Solution)• Front-loading only• Minimum efficiency on 0.3 micron

particles: 99.97% (MERV 17) 99.99% (MERV 18)

Filter TypesHF Segment in YorkWorks

Filter Types• Roll• Electrostatic• Gaseous contaminant

Carbon Filters• Gaseous and odor control• Pre/carbon/post filter configuration• Three options

– Disposable • AAF AmAir/C 2” – directly interchangeable

– Rechargeable• FARR Riga-sorb 80R

– Incinerable• FARR Riga-sorb 80D – totally disposable

Filter Types

CF Segment in YorkWorks

Filter Types

Filter Applications

Cartridge Filter

Pleated Pre-Filter

Airflow

Filter Applications

Cartridge FilterUsed in varying airflow applications because pleats won’t collapse when airflow decreases

Bag FilterUsed only in constant airflow applications so that bags don’t collapse and rub

ASHRAE 52 Air Filters

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