geaps amarillo 1_18_07

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Carol Jones, PhD.Stored Product EngineeringBiosystems and Ag. Engr. Dept.

Grain Aeration,“Just the Basics, Ma’am”

Tri-State GEAPS WorkshopAmarillo, TX

Jan. 18, 2007

http://ipm.okstate.edu/ipm/sprec/index.htm

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Carol Jones, PhD.Stored Product EngineeringBiosystems and Ag. Engr. Dept.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

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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!!

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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

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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%

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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)

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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)

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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

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Calculating Cycle Time

AT = aeration time, hours/cycle

AR = airflow rate, cfm/bu

TW = test weight, lb/bu

15

60

TWAT x

AR=

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Cycle Time, Flow Rate, and Test Weight

050

100150200250300350400450500

32 48 56 60

Test Weight (lb/bu)

Aer

atio

n C

ycle

(h) 0.025

0.050.10.20.250.50.751

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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)

Pres

sure

Dro

p (in

ch/ft

)

Wheat

Sorghum

Corn

Soybeans

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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

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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

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Fans

•Centrifugal and axial

•Use FANS program from Univ. of

Minnesota or Purdue

•Factors: power, efficiency, multiple fans in series or parallel

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FansAxial

– 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 manufacturerinfo. Sheets, AMCA certification is best info.

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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 speedcentrifugal

high speedcentrifugal

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Fans – selection in a nutshell

•Optimum performance

•Efficiency based on cfm/hp

•Noise, cost, reliability, mounting dimensions, space

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Air Distribution Systems

Consist of…–Transitions, manifolds, supply ducts

–Perforated ducts, pads or false floors

–Roof vents or exhaust fan systems

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TransitionsTransition smaller than air duct tunnel is BEST!

Transition

Air Tunnel

Foundation

Fan

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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

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Perforated Distribution Duct Velocities…

•Upright storages: 2000 fpm

•Flat storages: 1500 fpm

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Airflow Path Ratio

A + B <= 1.5 C

C: duct to grain peak

A + B … longest pathA

C

C

B

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Round Bin Floor Layouts

Square “Y” ..

Pad.

Double “T”

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More Floor Layouts – Large Bins

Double “H” Quad “F”

Double Pad

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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

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Perforated Floors

Cereal Grains: 3/32” diameter perf.

Smaller Seeds: 3/64 to 1/16”

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Coring to Improve Aeration

Can reduce cooling time and costs up to 30%

Day 1 Fil l

Day 2 Fil l

Day 3 Fil l

Day 4 Fil l

Day 5 Fil l

Day 6 Fil l

Core

1 / 4 to 1/ 3

of bin diameter

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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!!!

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What about Hopper Bins?Half-round Duct for Hopper Bin

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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

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Vent Types

•Gooseneck Vents

•Mushroom Vents

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Roof Exhausters Types

•Power Vents–200 – 250% of aeration rate–Run when aeration is on plus 15-20 minutes

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Controllable Roof Vents

•Normally closed

•Designed to open under pressure or vacuum

•Interlocked electrically with fans

•Reduces insect infiltration

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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

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RH and Temp Controllers

Partial list of vendors–OPI–The Boone Group–AgriDry Rimik Pty–GSI–Caldwell/Chief-Agri

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Cost Estimates

•Aeration System: 6.0 – 12.0 ¢/bu•Controller:0.3 – 1.0 ¢/bu•Temperature Cables:0.3 – 1.0 ¢/bu

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Monitoring Systems

•Manual Readout and log book

•Data Logger with manual plug in to thermocouples

•Computer interfaced automatic monitoring

Least expensive

Most expensive

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OPIGIMAC Temperature and Insect Monitoring, Aeration Fan Control System

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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

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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

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Info-Sites

http://www.biosystems.okstate.edu/home/jcarol/

http://www.biosystems.okstate.edu/sare/

Acknowledgements:USDA and Cooperative State Research Education and Extension ServiceDr. Ron Noyes, Grain Storage Engineering, LLC, Stillwater, OK (OSU Professor Emeritus)

http://ipm.okstate.edu/ipm/sprec/index.htm

geaps amarillo 1_18_07

Documents

carol jones

grain aeration

condition grain

pressure switchtop grain

storageuniform cooling

aeration time

negative pressure systems

hours of nighttime cooling