What temperature must the air entering the bin be for drying to occur? Air entering a bin must be at least 10 degrees Celsius for drying to occur. Air molecules moving through a mass of grain that is less than 10 degrees Celsius do not have the ability to pick up moisture as they move through the mass.
How does Natural Air Drying work? For natural air drying to occur the ambient air temperature is required to be a minimum of 10 degrees Celsius and you must achieve at least 3/4 of a cfm per bushel. Cereal grains require 3/4 to 1 cfm/bu while oil seeds require up to 2 cfm/bu.
What is the rule of thumb for sizing fans on a Hopper Bottom bin? General rule of thumb for sizing fans on Hopper Bottom Bins 14' to 24' in diameter (2000 bu to 10,000 bu) is 1hp per 1000 bushels to within 500 bushels of max. e.g. 4000 bu bin requires a 5hp fan, while a 4800 bushel bin requires a 7hp fan
What is the value of installing roof vents? Roof vents are an important part of any aeration or drying system. Air that has been removed from the grain needs an adequate space to exit the bin. The General Rule of Thumb is 1 square foot of opening for every 1000 cfm. This requires you to size roof vents based on airflow, not necessarily bin size. If adequate roof vents are not provided, moisture laden air will collide with roof sheets and run or drip back down onto the top of the grain pile. Overfilling a bin or filling beyond the eaves of a bin also negatively impacts ventilation, a bin requires adequate head space for air to expel properly.
How does the air flow within my grain bin? Airflow will always follow the path of least resistance. In a grain bin the center core is the most densly packed area of the bin and hardest portion to move air through. Therefore, air will only move up and along the sidewalls of a bin. However, by fitting your smoothwall or galvanized hopper bottom bin with a Rocket Aeration System you overcome this obstacle and are able to more uniformly dry your grain.
What is a "Drying Front"? Why do I need to leave my fan on when Natural Air Drying? A drying front is formed in an natural air drying bin when the fan is running. This front is a 12" band of moisture laden air, which travels upwards as you run your fans. As the drying front travels upwards through the bin dry grain is left below, while moist grain remains above, with an extremly moist pocket in the 12" drying front band. It is important to leave your fan running once a drying front has started to maintain the moisture movement until the front pushes through the top of the pile. Failing to allow the drying front to exit your pile can result in a hard crust being formed in your pile which will not allow air to penetrate.
Common Terms
Aeration: Conditioning of grain accomplished by fanning air through a grain pile, cooling it and thereby, preserving its quality
Airflow: The rate at which fanned air flows through a grain pile; this flow is measured in cubic feet per minute through a bushel of grain (cfm/bu)
Ambient Air Temperature: The surrounding (outside) air temperature of a grain bin or grain pile
BTU: British Thermal Units - a measure of heat output
Bulk Storage: Grain stored in a contained or uncontained pile inside or outside, usually on a temporary basis
Centrifugal: A force impelling air outward from the center of rotation
Drying Front: A horizontal layer of wet grain in a bin or pile, approximately one foot thick, which is formed during the drying process; this front moves in a vertical direction through the grain pile. Its moisture is eventually exhausted through wall vents or roof vents into the outside air.
Equilibrium: Condition of a system where all influences are balanced
Exhaust: Expelling, or expelled air originating within stored grain
Fines: Impurities in a grain pile such as dust, grain fragments, chaff, etc.
Fungus: Moulds, rusts, mildews, smuts, etc.
Impellor: Fan wheel assembly
Infestation: Spreading or swarming in or over in a sample causing contamination
Louvered: Pertaining to a device, which has slotted openings allowing air to flow out, but which prevents grains from entering
Microorganism: An organism (living thing) of microscopic size
Mites: Minute arachnids (spiders)
Pulse Crop: Peas, beans, lentils and other edible leguminous seeds
Quonset: A prefabricated shelter with a semicircular arching roof, set on a foundation
Relative Humidity: The amount of water vapour present in air expressed as a percentage of the amount needed for saturation at the same time
Static Pressure: The amount of airflow force needed to push fanned air through a grain pile, measured in inches of water column
Uniform: Not varying or variable, always having the same form or manner; even distribution
