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The arrival of cool fall weather means that Virginia grain producers should begin cooling their grain for winter storage.
Using aeration fans to cool grain bins reduces the activity of molds and insects and prevents moisture migration, reported William F. Wilcke, Extension specialist at Virginia Tech.
“Moisture migration occurs when the grain in the center of a bin is warmer than outdoor air,” explained Mr. Wilcke, an agricultural engineer. “The temperature difference sets up convection currents that move moisture to the top center of the bin where grain rewets and eventually spoils.”
In fall aeration, cool outdoor air is used to remove stored heat and lower the grain temperature. As a general rule, the grain will cool to the outdoor air’s average temperature for the hours the fan was on. For 24 hour per day operation, the average temperature approximately equals the daytime high plus the nighttime low divided by two.
Smaller storage bins with a capacity of under 1,500 bushels usually do not require aeration. “The short distance between the center and exterior surfaces of the bin allows the grain to cool by conduction,” Mr. Wilcke said.
If a grain bin is equipped with a relatively small aeration fan (one that delivers around 0.1 cubic feet of air per minute (cfm) per bushel) between 150-200 hours of fan operation
will be required to cool the grain. Operate the fan continuously for this period of time unless the weather becomes unusually warm or damp, the Extension specialist recommended.
Bins equipped with drying fans (fans that deliver 1 cfm/bushel or more and require at least one horsepower per 1,000 bushels) can usually
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