Ventilation (Air Changes-Hour0
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Transcript of Ventilation (Air Changes-Hour0
The rates of outdoor make up air in the table below can be used as a guideline in design of ventilation systems.
Type of Building and Room
Air Shiftsper hour
(1/h)
Airflow(l/s per m2
floor area)
OutdoorAirflow
(l/s)
Animals
Sheep 3 per animal
Horses 40 per animal
Hens 3 per animal
Cows100 per animal
Chickens 2 per animal
Pigs, sow 60 per animal
Piglet 15 per animal
Apartments15 - 20 per
person
Assembly halls 5 - 10 14 per person
Auditoriums10 - 15 per
person
BakeriesProduction 8
Pastry room 6
BanksService 2 - 3Archive 1
Staff 2 - 3Baths 5 - 8 15
Barber Shops15 - 25 per
person
Bars15 - 25 per
person
Beauty Shops15 - 25 per
person
Bowling Alleys15 - 20 per
person
Cafeterias 410 - 15 per
person
Cinemas/Theatres
5 - 107 - 15 per
person
Chemist's shops
Sterile room 15Laboratory 15
Packing room 4Store 1
Churches 210 - 15 per
person
Clubhouses15 - 25 per
person
Cocktail Lounges15 - 25 per
person
Computer Rooms15 - 20 per
person
Court Houses10 - 15 per
person
Dance halls15 - 30 per
personDental Clinics,
Offices15 - 20 per
personDepartment
Stores (cfm/Sq.Ft)0.3
Dining Halls10 - 15 per
person
Drug Shop10 - 15 per
personEngine rooms 4Exhibition halls 10 - 20
Fire Stations15 - 20 per
personGarages 5 - 6 > 1
Hospitals
General 25 per personTherapy 9
Operating theatre
14
Autopsy 9
HotelsReception
15 - 20 per person
Room 3Industries
Factory20 - 30 per
personCarpenter work shop
2 - 5
Car repair shop
4
Car repair shop, exhaust
60 - 80 per car
outletMechanical work shop
3 - 4
Welding 12 - 15Assembly 4 - 5
Jails10 - 15 per
person
Jewelry Shop10 - 15 per
person
Libraries10 - 15 per
personLunch Rooms, Luncheonettes
10 - 15 per person
Municipal Buildings
10 - 15 per person
Museums10 - 15 per
personSmithies 6 - 7
Kitchens
Small 20 - 40Large 10 - 20< 7 m2 15> 7 m2 20
Industrial in general
25 - 30
Gas ovens550/m2
outside wall
Electric ovens300/m2
outside wall
Grill table400/m2
outside wallFrying pan 300Boiling pan
100 l100
Boiling pan 200 l
200
Coffee machine
60
Refrigerated cabinet
7 - 10
Cooling and freezer room
0.3 - 0.5
Store 2 - 4Laundries 10 - 15Lavatories 5 - 10 10
Night Clubs15 - 25 per
personMalls 10 - 15 per
person
Motels15 - 20 per
person
Offices
Module 3 - 815 - 20 per
personLandscape 20 per personConference
room15 - 30 per
person
Lecture room10 - 15 per
person
Dining hall15 - 20 per
personStaff,
changing clothes
8 - 12
Dining room 8 - 10Resting room 15 per person
Police Stations15 - 20 per
person
Post Offices15 - 20 per
personPrecision
Manufacturing15 - 20 per
person
Restaurants 5 - 10 1015 - 20 per
personRetail Stores (cfm/Sq.Ft)
0.3
Schools Classroom 4 - 510 - 15 per
personShops 20 per person
Shopping Centers10 - 15 per
personSports halls 3 - 4
Supermarkets10 - 15 per
personSwimming pools 5 - 10
Taverns15 - 25 per
person
Town Halls15 - 20 per
person
1 dm3(litre)/s = 10-3 m3/s = 3.6 m3/h = 0.03532 ft3/s = 2.1189 ft3/min (cfm) = 13.200 Imp.gal (UK)/min = 15.852 gal (US)/min
Dust Concentration
Common dust concentrations exposed to filters in ventilation and air-condition systems
Rural and suburban districts - 0.45 to 1.0 mg/m3 air Metropolitan districts - 1.0 to 1.8 mg/m3 air Industrial districts - 1.8 to 3.5 mg/m3 air
Types of Filters
Washers
Large Air velocity through washer 2.5 m/s Water pressure required for spray nozzles 140 - 170 kN/m2
Water pressure required for flooding nozzles 30 - 70 kN/m2
Dry Filters
Felt, cloth, cellulose, glass, silk etc. without adhesive liquid
Flat Panel type - disposable Filters
Air velocity 0.1 - 1.0 m/s Resistance 25 - 250 N/m2
Efficiency 20-35%
Continuous roll - self cleaning Filters
Air velocity 2.5 m/s Resistance 30 - 175 N/m2
Efficiency 25%
Bag Filters
Efficiency 40-90%
HEPA (High Efficiency Particulate Air) Filters
Efficiency 99.97% for 0.3 micron particles and larger
ULPA (Ultra Low Penetrating Air) Filters
Efficiency 99.9997 for 0.12 micron particles or larger
Viscous Filters
Panel type - cloth with viscous fluid coating - washable or disposable
Plates about 500 mm x 500 mm Air velocity 1.5 - 2.5 m/s Resistance 20 - 150 N/m2
Continuous roll - continuously moving, self cleaning
Air velocity 2.5 m/s Resistance 30 - 175 N/m2
Electrostatic Precipitators
Cleaned automatically Air velocity 1.5 - 2.5 m/s Resistance negligible Efficiency 30-40%
Absolute
Dry panel with special coating - disposable or self cleaning Air velocity 2.5 m/s Resistance 250 - 625 N/m2
Standard European Filter Classification
Filter General propertiesClas
sEffect Applications
Basis filters
In general:- produced in synthetic
fibers- efficient for particles
> 4-5 mm- air speed < 2.5 m/s- start pressure drop approximately 50 Pa- final pressure drop
approximately 150 Pa
EU1
Protects against insects and fibers.
Limited effect against larger pollen (<70%)
Ineffective against smoke and blacking
particles
Window unitsHeat exchangers
Air heatersFiber filters in textile industry
EU2
Effective against larger pollen
(>85%) and larger atmospheric dust.
Limited effect against dust and blacking particles
Heating and cooling units in
electrical transformers
garagesindustrial halls
offices in industry
EU3
Effective against larger pollen
(>85%) and larger atmospheric dust.
Limited effect against dust and blacking particles
Heating and cooling units in
electrical transformers
garagesindustrial halls
offices in industry
EU4Limited effect
against dust and blacking particles
In addition to EU3 kitchens and spray paint work shops
Fine filters
In general:- produced in glass
fibers- efficient for particles
> 0.1 mm- air speed < 2- 3 m/s
EU5 Effective against pollen and finer
atmospheric dustConsiderable effect
against smoke.No effect against
Churches, sport halls, department stores, schools,
hotelsFood stores
- start pressure drop approximately 50-100
Pa- final pressure drop approximately 200 -
250 Pa
tobacco smoke
EU6 As EU5 As EU5
EU7Effective against
pollen and blacking dust
As EU6and food industry,
laboratories, theatres, hospital
rooms, data rooms
EU8
Very effective against particles
and blacking.Very effective
against microbes.Effective against tobacco smoke.
Operating theatres, production rooms for fine optics and
electronics.Hospital
examination rooms.
EU9 As EU8 As EU8
Micro filters
In general:- produced in glass
fibers in combination with separators of paper, plastic or
aluminum- efficient for particles
> 0.01 mm- air speed < 0.5 - 1.0
m/s- start pressure drop
approximately 250 Pa- final pressure drop according life span
and economy
EU10
EU11
EU12
EU13
EU14
Air flow, air velocity and required air-duct area is indicated below:
1 ft/min = 5.08x10-3 m/s 1 ft3/min = 1.7 m3/h = 0.47 l/s 1 ft2 = 0.0929 m2 = 144 in2
The diagram below indicates velocity and dynamic pressure in air ducts.
Pressure loss and air flow velocity for some common duct sizes and air flow volumes can be taken from the table below:
Pressure Loss (inches water gauge per 100 feet duct)
Air velocity (ft/min)
Air Volume (cfm)Duct Size (inches)
4 5 6 8 10 12 16
1000.65 0.21 0.09 0.02 0.01
1146 733 509 286 183
2000.8 0.32 0.08 0.02 0.01
1467 1019 573 367 255
4001.19 0.28 0.09 0.04 0.01
2037 1146 733 509 286
8000.34 0.14 0.03
1467 1019 573
16000.12
1146
The air velocity should not exceed certain limits to avoid unacceptable noise generation
Friction loss in standard air ducts are indicated in the diagram below.
1 m/s = 196.85 ft/min 1 m3/s = 3600 m3/h = 1000 dm3(liter)/s = 35.32 ft3/s = 2118.9 ft3/min =
13200 Imp.gal (UK)/min = 15852 gal (US)/min 1 mm H2O = 9.81 Pa = 9.807x10-6 N/mm2 = 0.0987 10-3 bar = 1 kp/m2 =
0.09678 10-3 atm = 1.422 10-3 psi (lbf/in2)
Example - Air Duct and Friction Loss
The friction loss in a 500 mm main duct in comfort system with air flow 1 m3/s can be estimated as indicated below to 0.05 mm H2O/m (~ 0.5 Pa/m).
The air velocity in the duct is 5 m/s.