1. Lecture 5 Grain Drying Fundamentals

2. The Drying Process  Moisture removed from one point to another at a rate dependant on the difference in water vapor between the two locations  Air passed through the bed of grain will either gain or lose moisture  Air passing through wet grain will gain moisture  Airflow rate  Too fast-not as much removed  Too slow- not as much removed

3. Drying Zones  Grain does not dry uniformly  Especially bin type dryer with low air flow  Three Zones  Dried Zone  Drying Zone-most potential for drying  Undried Zone-rewetting zone, condensation occurs here

4. Developing a Uniform drying front  Uniform air flow  Parallel air flow

5. Drying Calculations  Size of bin  Rating of fan  Moisture of grain currently & desired  Temp of drying air  RH of drying air

6. Size Groupings of Drying Systems  Low Capacity  Less than 10,000 bushel/yr & 500 bu/day  Medium Capacity  10,000-30,000 bu/yr & 500-1500 bu/day  High Capacity  More than 30,000 bu/yr & 1,500 bu/day

7. Natural Air Drying  Only energy required is that to run the fan  Occurs if RH allow a net moisture transfer  Equipment Needed  Perforate floor & fanspreader, sweep auger  Stirring devices are not needed  Portable auger-sized to handle harvest needs  At least 500 bu capacity/hr

8. Natural Air Drying  Advantages  Most energy efficient  Low Cost  Move grain only one time ( usually)  Disadvantages  Slowest method  Greatest potential for spoilage  Highest level of management  More time needed for inspection spoilage  Insect problems

9. Other factors of Natural Drying  Rate of drying directly related to the airflow delivered & the RH  Quantity of grain may effect air flow  Depth of grain  Dockage of grain  Settling of grain

10. Concerns with fans  Fans of same Hp are not always capable of same air flow  Doubling air flow increases energy requirements by 5 times  Systems have limited auxiliary drying capacity  May require you to partially dry in the fall & complete drying in the spring  Maximize efficiency by adding layers, & watching grain temp