In a deep bed grain dryer where hot dry air enters through a perforated floor at the bottom and moves upward, which distinct moisture zones develop chronologically?
Options:
(A) Dried zone at the bottom adjacent to the plenum chamber
(B) Drying front (drying zone) where active moisture transfer occurs
(C) Un-dried zone at the top remaining near initial moisture content and temperature
(D) Superheated steam zone at the topmost surface
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
Deep bed drying develops three characteristic zones progressing upward:
1. Dried zone at inlet (bottom)
2. Active drying zone (drying front)
3. Undried/wet zone ahead of the front.
Superheated steam does not occur in atmospheric convective grain drying (D is false).