# Exam Question #1 â€“ drying

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2nd Examination, GRSC 710
November 8, 2001

This is a take home exam. The points for each question are listed in parenthesis.
Please return this exam on November 20th. Rizana Mahroof will give you
handouts necessary for answering questions on aeration and drying on
(bhs@wheat.ksu.edu) or Carl Reed (crr@wheat.ksu.edu). For essay type of

1. What are the differences between field fungi and storage fungi? Name two examples
of each. (10)

2. Describe conditions that predispose stored grain to mold infection, and explain how
you would manage your grain to prevent molds and mycotoxins. (10)

3. What is the difference between turning and transferring grain? Explain effects of grain
transfer and turning on insects, molds, and grain condition (15).
4. How can one improve grain sanitation, and what are the benefits of sanitation when it
comes to grain storage and handling? (15)

5. Corn is received at 20.5 % m.c. and will be dried to 16 % m.c. The elevator accounts
for this shrink (loss of weight) by subtracting 4.5 % from the weight of each load of wet
corn. What will the actual shrink be, as a % of the original weight? (5)    ________ %
What is the difference in monetary value (\$/t) between the weight subtracted and the
calculated change in weight if today’s price is \$59/t? (1)         ________ \$/t
In favor of the elevator or the producer? (4)               ____ elevator ___ producer

7. The corn will be passed through a continuous-flow dryer with a heating and a cooling
section. In the morning the ambient air temperature was 15 ºC with 70 % relative
humidity. In the afternoon the air temperature was 23 ºC with 45 % r.h. What is the
difference, in g water/kg air, in the absolute moisture at these two conditions (before
heating)? (5)                                                  ________ g H2O/kg air

8. The heater of the dryer heats the air by 30 ºC at both air conditions. As the heated air
passes through the grain column, it cools to 32 ºC in both cases. How many g of water is
removed from the grain per kg of air in each case? (5)
At 15 ºC and 70 % r.h.          ________ g water removed/kg air
At 23 ºC and 45 % r.h.          ________ g water removed/kg air

9. The corn enters the cooling section of the dryer at 17 % m.c. and 30 ºC. If the ambient
air comes to equilibrium with the grain condition, how many g H2O will be removed per
kg air? (5)
At 15 ºC and 70 % r.h.         ________ g water removed/kg air
At 23 ºC and 45 % r.h.         ________ g water removed/kg air

10. If the grain remains in the cooling section of the dryer for 2 hrs, and if only one-half
of the value you just calculated is removed from the grain, what will the final grain
moisture be? The airflow rate in the cooling section is 10 m3/min/t and the air is 23 ºC
and 45 % r.h. (5)                                      _______________ % m.c.
11. After the dried corn was transferred to the silo, one of the bins heated to 25 ºC. The
m.c. of the corn in this silo was 16.5 %. The silo was 120 ft tall and contained 30,000 bu
of grain. It had an aeration fan with a 5-hp motor that pulled air downward through the
grain. (4)
What was the expected airflow rate? ___________ cfm/bu

12. The bin was aerated by turning the fan on each evening for 5 days. Each night the fan
ran for 12 hours. The average air conditions were 10 ºC and 70 % r.h. (8)
What is the expected grain temperature 1 m below the grain surface? _____ ºC
What is the expected grain temperature 1 m above the bin floor?     _____ ºC

13. Will the grain dry or wet at the cooling front? (4)
______ dry ____ wet

14. How many g water/kg of air will be exchanged at the cooling front? (4)
______ g H2O/kg air

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