Natural Air Drying (NAD) in Bins

     With NAD systems a crop may be harvested tough and in some cases damp. At this point it is a must to use a good quality bin aeration system that will distribute airflow evenly in the bin. Also a mid to high volume fan is required to get the job done.

     Air is introduced into the bottom of the grain bin. This air will absorb moisture from grain at the bottom until equilibrium is reached for that Temp/RH. Once the grain has reached equilibrium with the air no more drying will occur in that area. The air will then move through the grain at the bottom of the bin and begin drying the grain above it. The bin dries from the bottom up and no drying will occur at the top of the bin until the grain at the bottom is at equilibrium. By using a temperature cable it is possible to follow this drying process in the bin:

1: After the fan is turned on the whole bin will go to the same temperature if the moisture content is the same

2: As the grain reaches equilibrium at the bottom of the bin the temperature will be slightly higher in this area. The reason for this is that evaporation of moisture (cooling effect) has ceased.

3: Above the dry layer in the bin will be a wetter layer of grain. This area is called the drying front. The temperature in this region will be cooler than any other spot in the bin. This is because the greatest amount of evaporation (cooling effect) takes place here.

4: Above the drying front will be the grain not yet dried. The temperature of this grain will be warmer than the drying front but cooler that the dry grain.

5: NOTE: It is recommended that you do NOT stop the aeration fan until the bin is dry. It is possible that the drying front could stall in the bin and spoilage could occur.


For more information on temperature cables for bins please CLICK HERE.


Below is a chart listing normal temperatures/relative humidities for Manitoba:

AUGUST
Time Normal Normal EMC EMC EMC EMC EMC EMC
of Day Temp Rel. Hum. Wheat Oats Barley Canola Sunflower Soybean
7:00 AM 58F/14C 84% 18.7 16.7 18.9 13.3 N/A N/A
1:00 PM 73F/23C 54% 12.6 10.8 12.4 6.9 N/A N/A
7:00 PM 70F/21C 62% 13.9 12.0 13.8 7.9 N/A N/A
1:00 AM 59F/15C 82% 18.2 16.1 18.3 12.5 N/A N/A
Approx. Hrs/Day of Drying 17 17 16 18 N/A N/A
SEPTEMBER
Time Normal Normal EMC EMC EMC EMC EMC EMC
of Day Temp Rel. Hum. Wheat Oats Barley Canola Sunflower Soybean
7:00 AM 50F/10C 84% 19.3 17.3 19.1 13.6 N/A N/A
1:00 PM 61F/16C 56% 13.5 11.7 13.1 7.4 N/A N/A
7:00 PM 57F/14C 67% 15.4 13.5 15.0 9.0 N/A N/A
1:00 AM 47F/8C 80% 18.6 16.6 18.1 12.2 N/A N/A
Approx. Hrs/Day of Drying 10 12 9 11 N/A N/A
OCTOBER
Time Normal Normal EMC EMC EMC EMC EMC EMC
of Day Temp Rel. Hum. Wheat Oats Barley Canola Sunflower Soybean
7:00 AM 37F/3C 82% 20.0 N/A N/A N/A 10.9 20.4
1:00 PM 50F/10C 59% 14.6 N/A N/A N/A 7.4 10.9
7:00 PM 45F/7C 69% 16.6 N/A N/A N/A 8.7 13.8
1:00 AM 40F/4C 78% 18.8 N/A N/A N/A 10.1 17.7
Approx. Hrs/Day of Drying 6 N/A N/A N/A 16 8


As shown in the charts above very good results can be achieved by using natural air drying in the month of August. However as temperatures fall in September and October the number of drying hours per day is reduced. At this time Avonlea recommends that a LOW TEMPERATURE HEATER be added to the system. CLICK HERE for information on Low Temperature Grain Drying.
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