Question

Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R).

Assertion (A): LSU dryer is considered as a continuous flow-mixing type of grain dryer.

Reason (R): In LSU dryer, inverted V-shaped air channels are arranged in such a way that air is forced through the descending grain while moving from feed end to discharge end.

In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Ask what specific design feature of the LSU dryer's ducts actually causes grain mixing, and check if the reason statement mentions that feature.

Answer 1

The Correct Option is B

Step 1: The LSU (Louisiana State University) dryer is indeed classified as a continuous flow, mixing type dryer, so Assertion (A) is true.

Step 2: The mixing behaviour comes from a specific construction detail: the dryer has alternating layers of inverted V-shaped ducts, one layer open to the air inlet and sealed at the far wall, the next layer sealed at the inlet wall and open to the exhaust. Crucially, the duct rows in successive layers are offset from each other, not stacked directly one below the other.

Step 3: As grain falls past this offset arrangement, a stream of grain that was close to a duct in one layer is forced sideways around the duct below it, and ends up farther from a duct in the next layer, and vice versa. This constant side-to-side shuffling as grain descends is what mixes the grain and is the actual reason LSU dryers dry more uniformly than a simple, non-offset crossflow column.

Step 4: Now look at Reason (R). It only says that air is forced through the descending grain from the feed end to the discharge end via the inverted V-ducts. That is also a true statement, air does pass through the grain at every level as the grain travels from top to bottom of the dryer.

Step 5: But this statement describes the basic crossflow air path common to any inverted-V duct dryer, mixing or not. It says nothing about the offset arrangement of duct rows, which is the actual feature responsible for mixing. So while (R) is a true fact about the LSU dryer, it does not correctly explain why the dryer is classified as a mixing type.

Both statements are true, but (R) is not the correct explanation of (A), so the answer is option 2.