Air Distribution System in Seed Drying
1. Main Duct and Laterals Air Distribution System:
This type of air distribution system is shown in .In this system, the main duct can be located in the centre of the bin, or it can be located at one side of the bin.
When the central duct is located outside the bin, under the floor, it can also serve to empty the bin. Side located main ducts can be built inside the bin, or built on to the wall outside the bin.
An interior side located main duct or outside located main ducts, have the advantage of not obstructing the floor as much as an interior central main duct.
2. Single Central Perforated Duct System:
This type of air distribution system is illustrated. It is fabricated for special seed storage structure. For this air distribution system there must be an equal thickness of seed, not exceeding 6 feet, around the duct, which is made of perforated metal. For drying, the air should be forced upward thorough the seed. The side walls of the bin must be either slatted or perforated, so that air can flow laterally thorough the seed. This air distribution system is more commonly used for drying ear corn than for seed of small grains.
3. Perforated False Floor Air Distribution System:
Generally speaking, this is most satisfactory and most commonly used air distribution system for heated air drying. In this air distribution system, air is introduced under the perforated false floor, passes up through perforations and thorough the seed.
The false floor can be made of hardware cloth and screen or perforated metal. The metal false floors are more durable and convenient to use. The metal sheets are lapped when installed. It is recommended that this flooring be supported on concrete blocks, laid so that open areas in blocks are horizontal. Typical farm loading conditions requires 90-120 cm spacing of the blocks. When these recommendations are followed the floor will support loads up to 500 pounds per square feet. Adequate clearance and arrangement of support chambers between the regular bin floor and the false floor must be provided, so that entering air moves freely and is uniformly distributed. The channels and the opening for the flow of air must be carefully designed to carry air stream satisfactorily. The air inlet opening must allow one square foot of cross-section for each 100 CFM of air.
When perforated metal flooring is used, the total area of all the openings in the steel sheet should not be less than 8 to 10 percent of the storage floor area. This requirement is especially important when the drying floor does not extend completely to the side walls.