This document defines aeration of stored grain as forcing low rates of air through the grain to preserve it from deterioration. The objectives of aeration are to remove heat and moisture from the grain to maintain uniform temperature and moisture levels throughout and reduce odors. Proper aeration systems include ducts to distribute air flow evenly at recommended rates depending on grain type and storage size. Fans and controls are selected based on the required air flow rate and static pressure. The document provides details on aeration system components, design considerations, and references for further information.

2. DEFINITION OF AERATION
 forcing air through stored grain at low flow rates
 preserves grain from deterioration

3. OBJECTIVES
 To remove generated heat and water from grain
 To maintain a uniform conditions (temperature,
moisture etc. in the grain bulk)
 equalizing temperature throughout the grain bulk
 Removing or reducing odors from grain
 Removing dryer heat
 Reduce moisture accumulation
 Fumigant application

5. PERFORATED FLOOR SYSTEM

6. WHEN TO AERATE?
 after placing it into storage.
 whenever average outside air temperatures are at least
5°C cooler than the warmest grain in the bin
 aeration fans should be started as soon as the average
outside temperature is 5-7°C higher than the grain
temperature.

7. PRINCIPLE CONSIDERATION OF
AERATION SYSTEM
AIR FLOW RATE:
 This is the volume of air required to maintain uniform
conditions in the stored bulk by removing the
generated heat and water.
 The recommended rate depends on the purpose of
aeration, the type of grain being aerated, the size and
type of storage structure, and climatic conditions.
FOR SILOS- O.8 litres/sec/tonne
FOR SHEDS- 1.6 litres/sec/tonne

8. FAN SELECTION:
 The selection of fan is normally based on the airflow
rate used for a particular grain, the kind of grain
handled and the grain depth.
 Two types of fan are used for aeration: centrifugal and
the axial flow fan .
 Generally, the axial flow fan will deliver more air
than centrifugal fans at a static pressure up to about 4
inches of water (1,000 Pa). For higher static pressures,
the centrifugal fans are recommended.

9. FAN CONNECTED WITH
SINGLE BIN
FAN CONNECTED WITH
MULTIPLE BIN

10. AIR DISTRIBUTION:
 This includes the ducts, false floors, etc. which are
used to move the air to the desired points.
 The proper sizing of the ducts, the sizing and spacing
of the openings in the ducts to let the air move
between the duct and aerated grain, the layout of the
duct system are important to maintain the entering (or
exiting) air at an acceptable velocity and provide
uniform airflow through the grain.

11. FLOOR DUCTS FOR AERATION

12. AVAILABLE AERATION SYSTEMS
 A single perforated duct.
 A cross duct arrangement.
 A V shaped duct.
 A rectangular perforated area located in the middle of
the floor.
 A fully perforated floor

13. MODERN CIRULAR AERATION
SYSTEM
Westeel's circ-air round pit
system delivers aeration
performance approaching that of
full floor, but at a cost about the
same as a square pit system.
Circ-air systems equally
distribute load stress for a longer
lasting, more durable concrete
base.

14. COMPONENTS OF AERATION
SYSTEM
 Aeration ducts
 Air supply duct
 Fan (blower)
 Fan operation control equipment
 Controller
 Storage bin

15. 1. FAN 2. SOLID DUCT 3. PERFORATED SECTION

16. Aeration duct system
 Determine the amount of bin storage in m³.
 Choose a desired aeration airflow rate in L/s-m³.
 Determine total airflow (1) x (2) L/s.
 .ind Minimum Duct area (m³), Minimum Floor Area (m²) and Minimum Roof
Vent Area (m²).
 Design your system using components which meet or exceed the above
minimums.
Air Flow
(L/s)
Minimum
Cross
Sectional
Duct Area
(m²)
Minimum
Perforated
Floor Area
(m²)
Minimum
Roof Vent
Area (m²)
250 0.03 2.5 0.05
500 0.07 5.0 0.10

18. DESIGN OF AERATION BULK
STORAGE
 Step 1 : Select design moisture
 Step 2 : Calculate the generated heat
 Step 3 : Select a design day
 Step 4 : Calculate equilibrium humidity
 Step 5 : Determine hours of operation per day
 Step 6 : Calculate kilogram of air needed per day
 Step 7 : Determine air volume and pressure
 Step 8 : Select fan
 Step 9 : Design the air distribution system
 Step 10 : Design the power and controls

19. REFERENCE
 http://www.post-gazette.com/
 http://www.patentstrom.us/patents/6586036.htm
 UNIT OPERATIONS OF AGRICULTURE AND
PROCESSING BY K.M. SAHAY AND K.K. SINGH