Selecting the right fan...
Is by far the most important aspect of designing a
tunnel-ventilated house because a house’s fans
determines:
A grower’s ability to keep their birds cool during
hot weather
As well as year round electricity bills

1)
2)
Tunnel Fan Selection
Michael Czarick
The University of Georgia
Six factors to consider when selecting a
tunnel fan
1)
Air moving capacity
You can’t tell by simply looking at a fan how
much air it will move…
Air moving capacity

Air moving capacity of a tunnel fan varies from 15,000 to
over 50,000 cfm
How much air a fan will move is determined
by a variety of factors…

Such as:

Fan diameter




Lower rpm = deeper pitch
Fan speed


More blades = lower rpm
Blade pitch


Larger = more air
Number of blades
Higher speed = fewer blades, shallow pitch
Orifice design

deeper orifice/smaller tip clearance = better performance
1
Couple of the most significant factors that affect
fan capacity are shutter design and discharge
cones
Three basic fan configurations:



Fans with exterior shutters
Fans with exterior
shutters
Fans with interior shutters
Fans with discharge cones
Fans with exterior shutters

An exterior shutter
adversely affects the air
moving capacity of the
fan for a couple of
reasons:


Air exiting a fan rotates
Generally the shutter is
about the same size as
the fan
Exterior shutters
interferes with the air
flow pattern exiting a fan
Rotating fan blades cause exiting air to
rotate…
2
Exterior shutters disturbs the air flow
pattern of the air exiting a fan
The spinning pattern can be seen in
fans with dual panel shutters
Some exterior shutters are less restrictive to
air flow than traditional exterior shutters
Butterfly shutters offer little restriction to
the flow of air out of a fan

For example butterfly shutters
Split butterfly shutters are even less
restrictive
Butterfly shutters

Dust collection is much less of a problem because the
additional weight doesn’t cause the shutters to close
3
Butterfly shutters tend to increase overall
fan performance but…

Can have closing issues at time

Butterfly shutters tend to increase overall
fan performance but…

Can occasionally scare birds when they close
With an interior fan shutter
condensation only forms on shutter
Cold
Butterfly shutters tend to increase overall
fan performance but…
Allow more light into the house
Butterfly shutters tend to increase overall
fan performance but…

Are prone to condensation problems
Butterfly shutter fan condensation will tend
to form on all fan surfaces
Warm and moist
4
Most do not have slant wall housing so
moisture collects in the bottom of the fan
So condensation runs down interior walls
Moisture collecting on fan surfaces can also
end up damaging the fan
Another type of exterior shutter is the “Blow
away” shutter
Ammonia + Water

Typically a retrofit shutter for fan with exterior shutter



Fans with interior shutters
Better than a traditional exterior shutter
Can be affected by the wind
Difficult to predict fan performance.
Commonly referred to as “slant wall” fans
5
Fans with interior shutters


Slant wall housing

Interior shutter fans
Shutter opening is typically
larger than fan diameter
(+4” to 6”)
Air is pulled though
shutter instead of being
pushed through the
shutter.
Fan is tilted slightly

Slant wall housing

Match open shutter angle
Fan is tilted slightly


Slant wall housing with interior shutters

The combination of the
slant, interior shutter, and
exterior mounting
increases air flow 5 to
10%
Protects fan from weather
Condensation runs outside
Interior shutters


Relatively easy to clean
Fan can be easily
winterized
6
Winterizing fan
Without plastic
100.0°F
100
90
80
70
60.0°F
With plastic
Interior “butterfly” shutters
100.0°F
100


90


80
Fan performance is
maximized.
Maintenance is minimized
Heat loss is minimized
Condensation problems
are minimized
70
60.0°F
Interior “Roll seal” shutters




Fans with discharge cones
Is to get rid of the
shutter entirely:
Maximum air flow
Dust collection problems
virtually eliminated
But can have problems if
not maintained
7
Discharge cones

Fan without discharge cone
A discharge cone reduces “exit” pressure on fans
Fan with discharge cone
Discharge cones

Bess Labs all fans tested @0.10”
The discharge cone can increase air flow from a fan 5 to
10%.
Winterizing butterfly shutter fans
30,000
25,000
CFM
20,000
15,000
no cone
cone
10,000
5,000
0
36
48
50
52
Fan Size (inches)
53
8
Though…




Slant wall tend to move more air than fans with exterior
shutters…
Fans with cones tend to move more air than fans without
cones
There can still be significant difference in the amount of
air moved by fans of the same configuration
This is why you must specify total cfm…at the expected
operating static pressure.
Tunnel fan specifications
Total cfm at expected maximum pressure:
1)

400 ft/min = 0.09” - 0.11”
500 ft/min = 0.10” - 0.12”
600 ft/min = 0.13” - 0.15”
700 ft/min = 0.16” - 0.18”
800 ft/min = 0.18” - 0.20”

If exterior should be “butterfly” type shutter.




Interior shutter
2)
Discharge cone
3)
Six factors to consider
Energy efficiency
1) Air moving capacity
2) Energy efficiency

 energy efficiency ratio
Not specifying specific
energy efficiency ratings
for fans can result in...



How much power will a fan use?

First, an “Energy Efficient/Saver” label on a motor means
very little...
excessive energy bills for
the producer
poor bird management
loss of income for the
grower/company
How much power will a fan use?


Motor size is not necessarily a good measure either.
For instance, a fan with a 1 h.p motor can actually use
more power than a 1.5 h.p. motor
It all depends on how the motor is loaded…
9
Two different 48” fans with discharge cones




Bess #92093
1.5 h.p motor
24,600 cfm
1,300 watts




Bess #98229
1.0 hp motor
21,500 cfm
1,310 watts
Two different 48” fans


Bess # 96321
918 watts
Energy efficiency

Two different 48” fans
Bess #96132
1,116 watts

18% more power



Furthermore, just because a fan uses less power does not
necessarily mean it will save you money!

Bess # 96321
918 watts
16,800 cfm



Bess #96132
1,116 watts
24,000 cfm
Yes it uses 18% more power but
it moves 30% more air
To accurately compare two fans…

a fan’s energy efficiency must be expressed in terms of
how much air it will move per watt of power used:
Energy efficiency ratings

Typically range between 15 and 30 cfm/watt
Cfm/watt

1 cfm/watt….for every 1 cfm moved…the fan will use 1
watt of power
10
Example…two fans that move 20,000 cfm
(power cost $0.12 per kw*hr)

Fan A
= 17 cfm/watt

Fan B
= 22 cfm/watt
To calculate power usage (watts)…

Fan A
= 17 cfm/watt

Fan B
= 22 cfm/watt

Watts
= 20,000 / 17
= 1,176

Watts
= 20,000 / 22
= 909


To calculate power usage (watts)…

Fan A
= 17 cfm/watt

Fan B
= 22 cfm/watt

Watts
= 20,000 / 17
= 1,176
= 1.18

Watts
= 20,000 / 22
= 909
= 0.91
To calculate power usage (watts)…

Watts

Kw


Kw
cfm / cfm per watt
Power usage is typically measured in
Kilowatts

1 Kw
=
1,000 watts
To calculate operating cost…

Cost per hour = Power rate X Kw


=
Where “power rate” is the cost of using 1 kw of power for an
hour
11
To calculate operating cost…




Fan A = 17 cfm/watt
1.18 Kw X $0.12
14.2 cents per hour
Ten fans


$ 34.08 per day
$ 238.53 per week




Fan B = 22 cfm/watt
0.91 Kw X $0.12
11.3 cents per hour
Ten fans


$26.25 per day
$183.75 per week
Tunnel fan specifications
Total cfm at expected maximum pressure
1)




500 ft/min = 0.10” - 0.12”
600 ft/min= 0.13” - 0.15”
700 ft/min= 0.16” - 0.18”
800 ft/min = 0.18” - 0.20”
Interior shutter/Butterfly exterior
Discharge cone
Minimum Cfm/watt = 19 @0.10”
2)
3)
$55.78 difference
4)
Good = 20.8
Ideal = 22+



Larger fans are generally a
better investment than
smaller fans:



Lower initial cost
Lower operating cost
Lower maintenance cost
Larger fans also tend to be more energy
efficient
Initial fan cost

24” fan = $350 (5,800 cfm)




$0.06 per cfm
36” fan = $550 (9,900 cfm)
$0.055 per cfm
48” fan = $750 (19,700 cfm)

$0.038 per cfm
Bess Labs all fans tested @0.10”
Energy efficiency rating
How does fan size affect performance and
economics?
22
21
20
19
18
17
16
15
14
13
12
no cone
cone
36
48
50
52
Fan size (inches)
53
12
How large is too large?

Tunnel-ventilated dairy barn
Depends to some extent on house size

The larger the house…the larger the fan it can handle…
Tunnel-ventilated broiler house
70’ X 900’ Turkey house
70’ X 900’ Turkey house
Most 72” fans move around 50,000 cfm
13
They could be installed in a 66’ X 600’
The typical 66’ X 600’ broiler house…

would require approximately 360,000 cfm of tunnel fan
capacity.
5 – 72” fans = 240,000 cfm
Plus
5 – 48” fans = 120,000 cfm



Six factors to consider
Fan Output vs. Static Pressure
1) Air moving capacity
2) Energy efficiency
 energy efficiency ratio
Cfm
3) Air moving capacity vs. static pressure
 air flow ratio
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
Every fan reacts differently to increases in static pressure
0
0.05
0.1
0.15
0.2
0.25
0.3
Static Pressure
We want a fan that holds up well under
pressure…
Fan capacity vs. static pressure
Cfm
(Six 48” fans, between 21,000 and 22,000 cfm @ 0.10”)

26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0

Most houses will operate at a pressure greater than 0.10”
And over time it will increase


Dirty shutters
Evaporative cooling pads
But react differently as pressure increases
0
Fan A
0.05
Fan B
0.1
0.15
0.2
Static Pressure
Fan C
Fan D
Fan E
0.25
0.3
Fan F
14
One way to quantify this is comparing fan
air flow ratio’s

Tunnel fan specifications:
Total cfm at expected maximum pressure:
1)
Air Flow Ratio = air flow (0.20”)/air flow (0.05”)



Air flow ratio’s typically range between 0.65 and 0.85
The closer to 1.0 the better the fan will hold up to high
static pressures



2)
3)
4)
500 ft/min = 0.10” - 0.12”
600 ft/min = 0.13” - 0.15”
700 ft/min = 0.16” - 0.18”
800 ft/min = 0.18” - 0.20”
Interior shutter/exterior butterfly
Discharge cone
Minimum cfm/watt = 19.0 @0.10”


5)
Good rating = 20.8
Ideal rating = 22
Minimum air flow ratio = 0.70


Good rating = 0.76
Ideal rating = 0.79+
Fan output vs. Static pressure
(Six 48” fans, between 21,000 and 22,000 cfm @ 0.10”)
(Four 48” fans, between 21,000 and 22,000 cfm @ 0.10”)

0.3
0.28
0.26
0.24
0.2
0.22
0.18
0.16
0.14
0.1
0.12
0.08
0.04
0
0.02
0.3
Static Pressure
19
14.6
0.3
0.28
0.28
0.26
0.06
18.3
0.26
Good rating = 0.76
Ideal rating = 0.79+
0.24
Minimum air flow ratio = 0.70

0.22
5)
Good rating = 20.8
Ideal rating = 22
0.2

0.18

0.16
4)
Interior shutter/exterior butterfly
Discharge cone
Minimum cfm/watt = 19.0 @0.10”
0.14
3)
0.12

0.76
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
0.1

500 ft/min = 0.10” - 0.12”
600 ft/min = 0.13” - 0.15”
700 ft/min = 0.16” - 0.18”
800 ft/min = 0.18” - 0.20”
0.08

0.86
(Four 48” fans, between 21,000 and 22,000 cfm @ 0.10”)
Cfm

Static Pressure
0.84
Fan Output vs. Static Pressure
Total cfm at expected maximum pressure:
1)
2)
0.84
0.06
Tunnel fan specifications
0.67
0.04
0.76
0
0.74
0.24
0.2
Static Pressure
0.86
0.22
0.18
0.16
0.14
0.1
0.12
0.08
0.06
0.84
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
0.02
0.84
0.04
0
Cfm
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
0.02
Cfm
Fan output vs. Static pressure
18.2
15
Fan Output vs. Static Pressure
Six factors to consider
1) Air moving capacity
2) Energy efficiency
26,000
24,000
22,000
20,000
18,000
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
 energy efficiency ratio
3) Air moving capacity vs. static pressure
 air flow ratio
0.3
0.28
0.26
0.24
0.2
Static Pressure
0.22
0.18
0.16
0.14
0.1
0.12
0.08
0.06
0.04
0
4) Drive type
0.02
Cfm
(One 48” fan, between 21,000 and 22,000 cfm @ 0.10”)
19 cfm/watt and AFR = 0.84
Direct drive vs. Belt drive

Direct drive advantages:



No belts to tighten
No belts to replace
Direct drive disadvantages




Tend to move less air
Tend to be less energy efficient
Motors cost more
Tend to be louder
Direct drive vs. Belt drive

Direct drive vs. Belt drive

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
 10
percent less air
percent less energy efficient
Next generation of direct drive fans
Traditionally they have not been a good choice…But, if
they meet the previously listed specs, they can/should be
used.
16
Belt driven tunnel fans

Belt tensioners:





Keep the belt tight which
reduces wear…
Increases belt life
Should be a requirement
for new fans
Can hide a belt wear
problem
May require maintenance
Fiberglass, “plastic”, stainless steel

Are a good option for costal area’s


Within 20 miles of salt water
Are also a good choice for fans with butterfly shutters
Six factors to consider
1) Air moving capacity
2) Energy efficiency
 energy efficiency ratio
3) Air moving capacity vs. static pressure
 air flow ratio
4) Drive type
5) Construction material
Six factors to consider
1) Air moving capacity
2) Energy efficiency
 energy efficiency ratio
3) Air moving capacity vs. static pressure
 air flow ratio
4) Drive type
5) Construction material
6) Price
Price


Least important factor of all…
Lets assume a tunnel fan runs 2,000 hours a year







22,000 cfm
18 cfm/watt
$0.12 per kw*rh
Where do you find reliable fan performance
information?

Such as:



Air moving capacity at various static pressures
Energy efficiency ratings
Air flow ratio
Yearly operating cost is $293
15 year cost is $4,400
40 fans on a farm…$176,000
A fan that uses 25% less power could end up saving a
farm owner $44,000 dollars
17
BESS Labs at The University of Illinois
BESS Labs at The University of Illinois

Testing fans for over 20 years...
www.bess.uiuc.edu
BESS Labs at The University of Illinois

Fan description:
BESS Labs at The University of Illinois

Test results are published on the BESS Labs website
where you can obtain fan performance information for
well over 600 types of tunnel fans!
BESS Labs at The University of Illinois

Test results:
With so many fans to choose from it can be
a challenge to find the right fan.

To narrow the field down each year we take all the tunnel
fans (48” or larger) that have been tested and graph their
air flow ratio vs. their energy efficiency rating.
18
Then we selected those that meet the “good”
criteria:
All fans 48” diameter or larger
1

0.9

0.8

0.7

0.6
Air flow ratio
Minimum cfm/watt = 19 @0.10”
Minimum air flow ratio = 0.70

0.5

0.4
Good rating = 20.8
Ideal rating = 22+
Good rating = 0.76
Ideal rating = 0.79+
0.3
0.2
0.1
0
0
5
10
15
Cfm/watt
20
25
30
These are the top performers…any of which
would be a good choice
All fans 48” diameter or larger
1
0.94
0.9
0.92
0.8
0.9
0.7
0.88
Air flow ratio
Air flow ratio
0.6
0.5
0.4
0.3
0.2
0.86
0.84
0.82
0.8
0.78
0.1
0
0
5
10
15
Cfm/watt
20
25
30
0.76
20.8
22.8
24.8
Cfm/watt
26.8
28.8
2012 Top performing tunnel fan list
19
Fan performance laws
Fan performance laws

Cfm is proportional to fan speed

Air flow vs. Pressure
Air moving capacity (cfm)
For example…ACME DDPS50
Increase fan speed 10%...fan output is increased 10%
29,000
27,000
25,000
23,000
21,000
19,000
17,000
15,000
13,000
11,000
9,000
7,000
5,000
468 rpm
2.5” motor pulley
0
Air moving capacity (cfm)
Install a larger motor pulley to speed up the
fan blades and fan capacity increases
515 rpm

2.8”
0.25
Increase fan speed 10%...fan output is increased 10%
Power usage is exponentially related to fan speed

2.5”
0.2
Cfm is proportional to fan speed

468 rpm
0.1
0.15
Static pressure
Fan performance laws

29,000
27,000
25,000
23,000
21,000
19,000
17,000
15,000
13,000
11,000
9,000
7,000
5,000
0.05
Increase fan speed 10%...power usage is increased 30%
But, what would happen to power usage?
0
0.05
0.1
0.15
Static pressure
0.2
0.25
20
Air flow vs. Pressure
1,500
1,400
1,300
1,200
1,100
1,000
900
800
700
600
500
400
300
200
100
0
30,000
515 rpm
Air moving capacity (cfm)
Power (watts)
Power usage vs. Fan speed
0
50 100 150 200 250 300 350 400 450 500
RPM
Fan performance laws

1,090 watts
15,000
10,000
0.05
0.1
0.15
Static pressure
0.2
0.25
Air flow ratio
30,000
Decrease fan speed 10%...fan output is decrease 10%
Power usage is exponentially related to fan speed

1,450 watts
20,000
0
Cfm is proportional to fan speed

468 rpm
5,000
Decrease fan speed 10%...power usage is decreased 30%
515 rpm
Air moving capacity (cfm)

25,000
25,000
20,000
468 rpm
1,450 watts
397 rpm
1,090 watts
15,000
700 watts
10,000
5,000
0
Sometimes it is better to install more fans
spinning slower than fewer fans spinning faster
Fan
Cfm
@.10”
Energy
Efficiency
(cfm/watt)
Number of
Fans
Air Speed
(ft/min)
Yearly $
$0.10 kw*hr
Standard
23,300
19.4
12
590
$3,600
High flow 26,300
17.1
11
610
$4,650
0.05
0.1
0.15
Static pressure
0.2
0.25
What about other fans…
21
30 cfm/watt
Vs
22 cfm/watt
22