Exhaust Fan Selection

Exhaust fan selection

Selecting the right fan... By far the most important aspect of

designing a tunnel ventilated house:1) Determines the grower’s ability to cool his

birds: Wind-chill Temperature uniformity Trapped heat removal Reduces the effects of high humidity

2) Determines the grower’s electricity costs Electricity is quickly becoming a grower’s largest

expense.

1) Air moving capacity2) Energy efficiency energy efficiency ratio

3) Air moving capacity vs. static pressure air flow ratio

4) Drive type5) Quality of construction6) Price

Six factors to consider:

Air moving capacity of a 48 - 50” fan 15,000 to 30,000 cfm+

1) Air moving capacity

Bird cooling

Large differences in air moving capacitycan result in large differences in coolingif a poultry company only specifies thenumber of fans a house should have.

15,000 cfm Cfm = 135,000 cfm Temp diff. = 7.9 F Air vel. = 1.63 m/s Wind-chill = 2.7 C

23,000 cfm Cfm = 207,000 cfm Temp diff. = 2.8 C Air vel. = 2.5 m/s Wind-chill = 6.1 C

12m X 150m House with ninefans

Most poultry companies donot do this anymore...

But, you must be careful not to specifytunnel fans just by type ormanufacturer either.

Because there can be large differencesbetween fans of the same type, evenwithin the same manufacturer.

Example:

Choretime cone fans (0.05”) 38450-4822 17,900 cfm 38441-4822 20,400 cfm 43575-4822 22,800 cfm 38264-4821 24,000 cfm

Tunnel fan selection:

The first step in selection a fan for atunnel house is to understand thedifferent styles of fans available.

1) Traditional exterior shutter2) Slant wall3) Slant wall – Cone Most fan models are offered in all

three configurations

Three basic fansconfigurations

Exterior shutter Fan is often installed

in it woodenshipping box.

48” shutter mountedon the outside ofthe house.

Exterior shutter The relatively small

shutter, 48” shutteron 48” diameter fan,reduces air flow.

The exteriormounted shuttermakes it difficult topush air out of thehouse.

Air flow into a fan

Spinning fan blades

Air exiting a fan

Shutters restrict this flowpattern

Slant wall fan Larger shutter Air is pulled though

shutter instead ofbeing pushed.

Interior shutter

Larger shutter Air is pulled though

shutter Fan is tilted slightly

Match shutter angle Protects fan from

weather

Slant wall

Tilted fan

The combinationof the slant andthe interiorshutter increasesair flow 5 to 10%

Slant wall

Belt drive (Coolair NBF/CBL 48) exterior shutter (17,100 cfm) slant wall (19,200 cfm)

Fan configuration example

Larger shutter Air is pulled

though shutter Fan is tilted

slightly Easier to clean! Collects less dust

Slant wall

1) Traditional exterior shutter2) Slant wall

5 to 10 percent more air

3) Slant wall – Cone

Three basic fansconfigurations

Discharge cone fans Interior shutter

advantages Reduces “back”

pressure on fans

Tilted fan

Discharge cone

Discharge cone fans The discharge cone

can increase air flowan additional 5 to10%

Belt drive (Coolair NBF/CBL 48) exterior shutter (17,100 cfm) slant wall (19,200 cfm) slant wall with cone ( 21,000 cfm)

Fan configuration example

Though…

Slant wall tend to move more air thanfans with exterior shutters…

Cone fans tend to move more air thanslant wall fans…

There can still be significant differencebetween fans of the same configuration

Example

Choretime slant wall (0.05”) 38785-4822 16,500 cfm 42331-4822 18,000 cfm 45576-4822 20,500 cfm

Though… Slant wall tend to move more air than

fans with exterior shutters… Cone fans tend to move more air than

slant wall fans… There can still be significant difference

between fans of the same configuration This is why you must specify either fan

cfm or total cfm

Fan specifications:

Total cfm Or number of fans of that move a specific

amount of air I.e. nine fans that move between 22,000 and

24,000 cfm

Interior shutter Cone optional




Six factors to consider

Exhaust Fan Selection(energy efficiency)

Not specifying specific energy efficiencyratings for fans can result in... excessive energy bills for the producer poor bird management loss of income for the grower/company

The label “Energy Efficient” on a motormeans very little...

How much power will aparticular fan use?

Motor size does not tell the whole story. 1 h.p motor can use more power than a 1.5

h.p. motor

How much power will aparticular fan use?

Fan power(Two different 48” fans with discharge cones)

Bess #92093 1.5 h.p motor 24,600 cfm 1300 watts

Bess #98229 1.0 hp motor 21,500 cfm 1310 watts

Motor size does not tell the whole story. 1 h.p motor can use more power than a 1.5

h.p. motor

Plate amperage can be misleading. indicates full load amperage…not necessarily

working amperage.

How much power does a fanuse?

How much power will the fan use? motor size does not tell the whole story.

1 h.p motor can use more power than a 1.5h.p. motor

plate amperage can be misleading. indicates full load amperage…not necessarily

working amperage.

Just because a fan uses less powerdoes not mean it will save you money.

Energy efficiency

Fan power usage:(two different 48” fans)

Bess # 96321 918 watts

16,800 cfm

Fan power usage:(two different 48” fans)

Bess # 96321 918 watts

16,800 cfm

Bess #96132 1116 watts (18 % +)

24,000 cfm (30 % +)

A fan’s energy efficiency must beexpressed in terms of how much air itwill move per watt of power used:

Energy efficiency

Cfm/watt


Energy efficiency

1 Cfm/watt

For every 1 cfm moved…the fan will use 1 watt of power


Energy efficiency

The higher the number the better

Energy efficiency ratings typically rangebetween 15 and 25 cfm/watt

Can be obtained from independent fantest lab booklets.

Energy efficiency ratings

Fan A = 17 cfm/watt Fan B = 22 cfm/watt

Fan comparison(20,000 cfm, power cost $0.09 per kw*hr)

Power usage

Watts = cfm / cfm per watt

Fan A = 17 cfm/watt

Watts = 20,000 / 17 = 1,176

Fan B = 22 cfm/watt

Watts = 20,000 / 22 = 909


Power usage

1 Kw = 1,000 watts

Fan A = 17 cfm/watt

Watts = 20,000 / 17 = 1,176

Kw = 1.18

Fan B = 22 cfm/watt

Watts = 20,000 / 22 = 909

Kw = 0.91


Power usage

Cost = Power rate X Kw

Power rate is the charge of using 1 kw ofpower for an hour

Fan A = 17 cfm/watt 1.18 Kw 10.6 cents per hour

Fan B = 22 cfm/watt 0.91 Kw 8.2 cents per hour


Fan A = 17 cfm/watt 1.18 Kw 10.6 cents per hour Eight fans

$ 142 per week $ 2,544 per year

Fan B = 22 cfm/watt 0.91 Kw 8.2 cents per hour Eight fans

$110 per week $1,968 per year


A 2 cfm/watt difference will result inapproximately a 10 percent differencein electricity usage… Minimum acceptable rating is 19.1 Ideal rating is 20.1 or better

Energy efficiency ratings

Fan specifications:

Total cfm Or number of fans of that move a specific

amount of air


Minimum Cfm/watt = 19.1 Ideal 20.1 or better

Fan Output vs Static Pressure

02000400060008000

10000120001400016000

180002000022000

0 0.05 0.1 0.15 0.2 0.25

Static Pressure

Cfm

Fans react differently toincreases in static pressure...


02000400060008000

10000120001400016000

180002000022000

0 0.05 0.1 0.15 0.2 0.25

Static Pressure

Cfm

Most houses day one will operate at apressure around 0.10”

Over time it will increase Dirty shutters Evaporative cooling pads

Clogged evaporative cooling pads

You want a fan that holds upwell under pressure…

One way to quantify this iscomparing fans air flow ratio’s

Air Flow Ratio = air flow (0.20)/air flow (0.05)


02000400060008000

10000120001400016000180002000022000

0 0.05 0.1 0.15 0.2 0.25

Static Pressure

Cfm

AR = 1 AR=0.82 AR=.68 AR=0.55

Fan specifications: Total cfm

Or number of fans of that move a specific amountof air


Minimum Cfm/watt = 19.1 Ideal rating = 20.1+

Minimum air flow ratio = 0.67 Ideal rating = 0.72 +

Output at different static pressure Energy efficiency Air flow ratio

Independent fan performanceinformation

BESS Labs (Univ. of Ill) or AMCA


Tests conducted with shutters andguards in place.

Manufacturers can challenge oneanother

Poultry companies can send fans in fortesting


Obtaining information

Test booklets Web site

www.bess.uiuc.edu

Fan manufacturers

Direct drive advantages: No belts to tighten No belts to replace

Direct drive vs. Belt drive

Direct drive disadvantages Tend to move less air Tend to be less energy efficient


ACME AGD direct drive with cone 19,700 cfm (19 cfm/watt)

ACME BDR 48” slant wall with cone 21,400 cfm (21.4 cfm/watt)


ACME AGD direct drive with cone 19,700 cfm (19 cfm/watt)

ACME BDR 48” slant wall with cone 21,400 cfm (21.4 cfm/watt)

10 percent less air 10 percent less energy efficient


Direct Drive Tend to move less air Tend to be less energy efficient Often do not hold up as well under higher

static pressures


Direct Drive Tend to move less air Tend to be less energy efficient Often do not hold up as well under higher

static pressures expensive motors

But, if they meet the previously listedspecs, they can be used.


Quality of construction

Difficult to determine Thickness of metal/fiberglass on

housing and fan blades Length of warrantee Reputation

Price

Better fans tend to cost more...

Aerotech, Inc.

American Coolair

Canarm

Chore-Time

Cumberland

Ellison & Ellison Co., Inc.

General Shelters of Texas,S.B., Ltd.

Glacier Cor

Hired Hand, Inc.

Munters

TekSupply

Exhaust Fan Selection

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