Geaps amarillo 1_18_07

1
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.
Grain Aeration,
“Just the Basics, Ma’am”
Tri-State GEAPS Workshop
Amarillo, TX
Jan. 18, 2007

2
Carol Jones, PhD.
Stillwater, OK
Why Do We Aerate?
•Condition grain by cooling to
safe level for storage
•Uniform cooling prevents
moisture migration
•Very powerful IPM tool
•With more air, used for grain
drying

3
Carol Jones, PhD.
Stillwater, OK
Aeration as IPM Tool
•Control insects by cooling to
< 60° F
•15°F drop (ex: 90° to 75 °)
reduces activity 50 – 75%
•Very powerful IPM tool
•Aeration = Crop Insurance!!

4
Carol Jones, PhD.
Stillwater, OK
Suggested Plan for Southern
States
•At binning, cool to mid 70’s using
nighttime air
•Mid September, aerate second
time
to low 60’s
•Can prevent the need to fumigate
•Eliminates insect population
buildup
and damage

5
Carol Jones, PhD.
Stillwater, OK
Suggested Plan for South
•General suggested rates:
–Steel bins and flat storage: 0.1 cfm/bu (1/10th
cfm/bu)
–Concrete upright bins: 0.05 cfm/bu (1/20th
cfm/bu)
•For southern states:
–0.2 cfm/bu at least, 0.25 to 0.3 is best if
affordable
•At 0.3 cfm/bu: takes 30-35 hours of
nighttime
cooling to drop 15° in summer
•Expect wheat shrinkage of about 0.8%

6
Carol Jones, PhD.
Stillwater, OK
General Design Factors…
What to consider
•Grain Type (coarse vs. small)
•Location/harvest date
•Storage structure
•Available energy
•Cooling speed vs. energy cost
(cool as fast as you can afford)

7
Carol Jones, PhD.
Stillwater, OK
Specifics…
What to consider
•Airflow rate (fast is better
…insurance)
•Grain airflow resistance
–Wheat static pressure = 2x corn or
soybeans
•Propeller vs. centrifugal fan type
•Airflow direction (suction or
pressure)
•Distribution (ducts or perforated
floor)
•Control (manual or automatic)

8
Carol Jones, PhD.
Stillwater, OK
Components
•Fans
•Ducts…transition and supply
•Floor distribution system
•Roof vents, exhaust fans
•Controls for fan regulation
•Pressure switch on fans for negative
pressure systems

9
Carol Jones, PhD.
Stillwater, OK
Calculating Cycle Time
AT = aeration time, hours/cycle
AR = airflow rate, cfm/bu
TW = test weight, lb/bu
15
60
TW
AT x
AR
=

10
Carol Jones, PhD.
Stillwater, OK
Cycle Time, Flow Rate, and
Test Weight
0
50
100
150
200
250
300
350
400
450
500
32 48 56 60
Test Weight (lb/bu)
AerationCycle(h)
0.025
0.05
0.1
0.2
0.25
0.5
0.75
1

11
Carol Jones, PhD.
Stillwater, OK
Airflow vs. Pressure Drop
0
0.5
1
1.5
2
2.5
3
1 2 3 4 5 6 7 8 9 10 20 30 40 50 60 70 80
Airflow (cfm/ft^2)
PressureDrop(inch/ft)
Wheat
Sorghum
Corn
Soybeans

12
Carol Jones, PhD.
Stillwater, OK
Positive or Negative
Airflow
•Negative Airflow:
–Pros…
•Reduced condensation under steel
roofs
•Cooling zone movement estimated by
fan exhaust air temperatures
•Can hold covers on outdoor grain piles
–Cons…
•Needs larger transition/duct cross-
section areas (especially in flat storage)
•Roof damage if vents freeze (use neg.
pressure switch)
•Top grain heat moves through all grain

13
Carol Jones, PhD.
Stillwater, OK
Positive or Negative
Airflow
•Positive Airflow:
–Pros…
•Distribution in flat storage is more
uniform
•Add warm grain w/o heating cool grain
•Aeration zone finished when surface
grain cools
•Less plugging of perf. floors or ducts
–Cons…
•Condensation under steel roofs
•Heat of compression raises air temp.
3-10° F

14
Carol Jones, PhD.
Stillwater, OK
Fans
•Centrifugal and axial
•Use FANS program from Univ. of
Minnesota or Purdue
•Factors: power, efficiency, multiple
fans in series or parallel

15
Carol Jones, PhD.
Stillwater, OK
Fans
Axial
– Van-axial
– Tube-axial (small - 2Hp or less)
– Low cost, noisy
– 3 – 5 inches static pressure
Centrifugal
– 1460 to 3500 rpm
– Higher cost
– Quieter
– More airflow per HP above
5” static pressure
Fan Performance…consult manufacturer
info. Sheets, AMCA certification is best info.

16
Carol Jones, PhD.
Stillwater, OK
Fans
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
0 2 4 6 8 10 12 14
Static Pressure (in of H20)
CFM
vane axial
low speed
centrifugal
high speed
centrifugal

17
Carol Jones, PhD.
Stillwater, OK
Fans – selection in a nutshell
•Optimum performance
•Efficiency based on cfm/hp
•Noise, cost, reliability, mounting
dimensions, space

18
Carol Jones, PhD.
Stillwater, OK
Air Distribution Systems
Consist of…
–Transitions, manifolds, supply
ducts
–Perforated ducts, pads or false
floors
–Roof vents or exhaust fan systems

19
Carol Jones, PhD.
Stillwater, OK
Transitions
Transition smaller than air duct
tunnel is BEST!
Transition
Air
Tunnel
Foundation
Fan

20
Carol Jones, PhD.
Stillwater, OK
Transition/Supply Duct
Air Velocities
•Maximum design air velocity…
–positive pressure: 2500 fpm
–negative pressure: 2000 fpm
•Preferred design air velocity…
–positive pressure: 1500-2000 fpm
–negative pressure: 1000-1500 fpm

21
Carol Jones, PhD.
Stillwater, OK
Perforated Distribution Duct
Velocities…
•Upright storages: 2000 fpm
•Flat storages: 1500 fpm

22
Carol Jones, PhD.
Stillwater, OK
Airflow Path Ratio
A + B <= 1.5 C
C: duct to grain peak
A + B … longest path
A
C
C
B

23
Carol Jones, PhD.
Stillwater, OK
Round Bin Floor Layouts
Square “Y” ..
Pad.
Double “T”

24
Carol Jones, PhD.
Stillwater, OK
More Floor Layouts – Large Bins
Double “H” Quad “F”
Double Pad

25
Carol Jones, PhD.
Stillwater, OK
Vertical Aerator …
Big Bins with Dia:Sidewall > 2.5:1
50'
46'
69'
50'
81'
20'
50'
70'
35'1/4 Dia. =
89'
73'
65'
45'
61'
Radius

26
Carol Jones, PhD.
Stillwater, OK
Perforated Floors
Cereal Grains: 3/32” diameter perf.
Smaller Seeds: 3/64 to 1/16”

27
Carol Jones, PhD.
Stillwater, OK
Coring to Improve Aeration
Can reduce cooling
time and costs up
to 30%
Day 1 Fill
Day 2 Fill
Day 3 Fill
Day 4 Fill
Day 5 Fill
Day 6 Fill
Core
1 / 4 to 1/ 3
of bin diameter

28
Carol Jones, PhD.
Stillwater, OK
Flat Storage Duct Layout
Up to 100 ft
70 to 90 ft
50 to 70 ft
Up to 150 ft
c
c
90 - 150 ft
Repeat Pattern -- No Limit
•Less airflow under valleys
•More airflow under peaks
•Requires non-uniform
distribution to get uniform
delivery!!!

29
Carol Jones, PhD.
Stillwater, OK
What about Hopper Bins?
Half-round Duct
for Hopper Bin

30
Carol Jones, PhD.
Stillwater, OK
Roof Venting
•Pressure System needs exhaust vents
–1 ft2
cross-section area per 1000-1500 cfm
•Suction System needs inlet vents
–1 ft2
cross-section area per 800-1000 cfm
•Keep static pressure in bin head space
to 1/8” or less

31
Carol Jones, PhD.
Stillwater, OK
Vent Types
•Gooseneck Vents
•Mushroom Vents

32
Carol Jones, PhD.
Stillwater, OK
Roof Exhausters Types
•Power Vents
–200 – 250% of
aeration rate
–Run when
aeration is on
plus 15-20
minutes

33
Carol Jones, PhD.
Stillwater, OK
Controllable Roof Vents
•Normally closed
•Designed to open under pressure or
vacuum
•Interlocked electrically with fans
•Reduces insect infiltration

34
Carol Jones, PhD.
Stillwater, OK
Fan Controllers
•Temperature limit thermostats
•Humidity control
•NEMA 4R housing
•Hour meter, selector switch
•Time delay relays (TDR) for multiple
fans
•Off-the-shelf components

35
Carol Jones, PhD.
Stillwater, OK
RH and Temp Controllers
Partial list of vendors
–OPI
–The Boone Group
–AgriDry Rimik Pty
–GSI
–Caldwell/Chief-Agri

36
Carol Jones, PhD.
Stillwater, OK
Cost Estimates
•Aeration System:
6.0 – 12.0 ¢/bu
•Controller:
0.3 – 1.0 ¢/bu
•Temperature Cables:
0.3 – 1.0 ¢/bu

37
Carol Jones, PhD.
Stillwater, OK
Monitoring Systems
•Manual Readout and log
book
•Data Logger with manual
plug in to thermocouples
•Computer interfaced
automatic monitoring
Least expensive
Most expensive

38
Carol Jones, PhD.
Stillwater, OK
OPIGIMAC Temperature and Insect
Monitoring, Aeration Fan Control System

39
Carol Jones, PhD.
Stillwater, OK
More New Technology
•Closed Loop Aeration working
with CLF system in sealed storage
•Cross-Flow Aeration
–As much as 30% less power than
vertical airflow

40
Carol Jones, PhD.
Stillwater, OK
More New Technology
•USDA Electronic Insect Monitoring
System now commercialized by OPI as
“the Insector”
•Purdue Univ. working on a mold
sniffing system to detect development of
mold by CO2 detection

41
Carol Jones, PhD.
Stillwater, OK
Info-Sites
http://www.biosystems.okstate.edu/
home/jcarol/
http://www.biosystems.okstate.edu/
sare/
Acknowledgements:
USDA and Cooperative State Research Education and Extension
Service
Dr. Ron Noyes, Grain Storage Engineering, LLC, Stillwater, OK
(OSU Professor Emeritus)

Geaps amarillo 1_18_07

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