Cross Flow Dryers
One of the more popular continuous flow dryers are called Cross Flow Dryers. In this type of dryer the air flow is generally perpendicular to the grain flow. The grain flows by gravity down a 10 to 16" column as the heated air blows across the grain column. The energy efficiency is a function of the plenum air temperature and the air flow rate with the highest efficiency occurring at high plenum temperatures and low air flow rates.
In practice high efficiency is not achieved due to grain quality issues. The lower the air flow rate the higher the grain moisture content difference between the grain kernels on the inside versus the outside of the column. Many manufacturers have developed methods to mix the grain as it flows down the column to lessen the moisture variation at the dryer discharge.
The Cross Flow Dryers combine the simple operation of a batch system with the increased efficiency of a semi-continuous design. In this type of dryer, the blower forces hot air through many small ducts, or channels. Each tray slot has its own channel and receives a direct flow of air. This reduces drying time, and allows processing of all the trays at once. To prevent overheating of the trays, a cross flow dryer uses sensors to control the blower output. While this approach makes the design very efficient, it also increases the complexity and cost of the dryer.