Storage Engineering Questions and Answers

Answer: A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both statements are true and the reason explains the assertion. Fines, dust, weed seeds and broken kernels carry a disproportionate share of the moisture, mould spores and insect eggs entering a store, and being metabolically active and damaged they spoil first, seeding trouble in the sound grain around them.

They also pack into the spaces between whole kernels, raising the resistance to airflow and creating pockets that aeration cannot reach. Cleaning therefore removes both the source of spoilage and the obstacle to controlling it.

Answer: B

Correct answer: 1 and 2 only

Statement 1 is correct: aeration flows are around \( 0.1 \) cubic metres per minute per tonne. Statement 2 is correct: cooling and equalising the bulk is exactly what aeration is for.

Statement 3 is false, and follows from statement 1. That flow is one to two orders of magnitude below what a dryer needs, so aeration cannot dry grain and cannot rescue grain stored too wet. Drying to the safe moisture must be completed before the grain goes into store.

Answer: C

Correct answer: 1 and 2 only

Statement 1 is correct: safe moisture is derived from the equilibrium relative humidity at which storage moulds grow, about 70 per cent. Statement 2 is correct: moisture and temperature compound one another, each multiplying the effect of the other on storage life.

Statement 3 is false and reverses the relation. Oilseeds are stored at a much lower moisture content than cereals - around 7 per cent for groundnut against 13 to 14 for wheat - because oil holds no water, so the same equilibrium relative humidity is reached at a lower stated moisture.

Answer: D

Correct answer: 1 and 2 only

Statement 1 is correct: respiration heat continues for as long as the produce is alive and in store, so it is a continuous load rather than a transient. Statement 2 is correct: infiltration is warm moist air entering through door openings and leaks.

Statement 3 is false. Compressor motor heat is rejected at the condenser, outside the insulated envelope, so it never enters the cooled space and is not part of the room's load. Only a compressor or motor sited inside the room would contribute.

Answer: A

Correct answer: 1 and 2 only

Statement 1 is correct: in a sealed structure the respiration of grain, insects and moulds depletes the oxygen and raises the carbon dioxide. Statement 2 is correct: that atmosphere is lethal to storage insects at every life stage, since they depend on aerobic respiration.

Statement 3 is false and would destroy the method. Ventilation restores the oxygen and resets the process, so a hermetic structure must stay sealed - the seal is the entire technology, and a leak is the only common cause of failure.

Answer: B

Correct answer: A-2, B-1, C-4, D-3

Each measure is matched to what it controls. Aeration (A) controls temperature and, by removing the gradients that drive convection, moisture migration (2). Fumigation (B) controls insects by direct chemical action (1).

Hermetic sealing (C) controls the oxygen available within the bulk (4), letting respiration create a lethal atmosphere. Precooling (D) removes field heat from a harvested perishable (3) - the only item on the list concerning fruit and vegetables rather than grain, which is the pairing to identify first.

Answer: C

Correct answer: A-2, B-1, C-4, D-3

Each structure is matched to its defining characteristic. A bag store (A) offers easy stock identification but costly handling (2), since every sack is moved individually. A metal silo (B) is cheap and quick to erect but thermally responsive (1), following ambient swings closely.

A concrete silo (C) has the thermal mass to even those swings out (4), which is why it suffers less moisture migration. A hermetic structure (D) depends absolutely on an airtight seal (3), because its whole action rests on the atmosphere the contents create.

Answer: D

Correct answer: A-2, B-1, C-4, D-3

Each load is matched to its source. The product load (A) is the heat removed in cooling produce from its arrival temperature (2) - large but transient. The respiration load (B) is the metabolic heat living produce generates (1), continuous for the whole storage period.

The transmission load (C) is heat conducted through walls, floor and roof (4), set by the insulation and the temperature difference. The infiltration load (D) is warm moist air entering through doors and leaks (3), which is why door discipline and air curtains matter.

Answer: A

Correct answer: A-2, B-1, C-4, D-3

Each problem is matched to its usual cause. Crusting on the top surface (A) comes from moisture migration by convection (2), which deposits moisture on the cold surface layer. A resistant insect population (B) comes from repeated sublethal fumigation in a leaky structure (1), which selects for the least susceptible survivors.

Rapid mould growth (C) comes from an equilibrium relative humidity above about 70 per cent (4), the mould threshold. Blocked airflow (D) comes from fines and broken grain not cleaned out before storage (3), which pack into the spaces between kernels.

Answer: B

Correct answer: Drying the grain to a safe moisture content

Drying is not a purpose of aeration. At around \( 0.1 \) cubic metres per minute per tonne the air flow is one to two orders of magnitude below a dryer's, so it cannot remove significant moisture and cannot rescue grain put away too wet - the grain must already be at a safe moisture before storage.

The other three are genuine purposes. Equalising the temperature removes the gradients that drive moisture migration, thereby preventing it; and cooling the bulk below about 15 degrees suppresses insect development.