1. Lecture 16
Aeration

2. Aeration Natural air movement issues - moisture, temp
Management Issues
   keep center of bin within 10 degrees F of ambient temp
   .1 cfm / bushel for bins
   .2 cfm / bushel for flat storage
   not any lower than 32 degrees F
   not any higher than 60 degrees F
 Table 5.1

3. Positive vs. Negative Pressure
pushing adds 2 degrees F
   negative prevents condensation
   uses solar heat from top of bin
   bottom last to cool, difficult to determine when dry
   positive requires smaller duct diameters

4. Air Flow rates .1 cfm is adequate if larger fan, then less time
    — 32 .5
   caution - can overdry &/or add moisture

5. Caution w/Automatic controls
  humidistat not enough
   thermostat & humidistat required
   best if computer controlled
    saves energy
    less likely to damage grain
    record information (temp, etc.)

6. Duct types Used plastic, steel 6" - 36" round & ½ round
   6" - 36"
   round & ½ round
   plastic - perforations not as much
   plastic - cheaper

7. Sizing Assume level surface
   Depends on:   1. Cross sectional Area   2. Surface area exposed to grain
minimum cross sectional area     =    total volume (cfm)                                          Allowable duct velocity (fpm)  

8. Sizing Total air volume depends on: Exit velocity for escaping air fan
   bin
   grain type
Exit velocity for escaping air
Min. total surface area = 
Total air volume (cfm)
     Maximum velocity of duct exit air (fpm)