Step 1: Understanding the Concept:
This question asks to identify a process from the given options that involves the simultaneous transfer of both heat and mass. We need to analyze the fundamental principles of each process.
Step 2: Detailed Explanation:
Let's analyze the processes:
(A) Milling: This is a mechanical process of breaking down solid materials into smaller pieces. It is a form of size reduction. While some heat is generated due to friction, the primary mechanism is mechanical force, and there is no inherent mass transfer operation.
(B) Drying: Drying is the process of removing moisture (usually water) from a solid, semi-solid, or liquid. This process inherently involves:
Heat Transfer: Heat energy (latent heat of vaporization) must be supplied to the material to evaporate the moisture. This heat is transferred from the drying medium (e.g., hot air) to the material.
Mass Transfer: The evaporated moisture (water vapor) must move from the interior of the material to its surface, and then from the surface into the surrounding drying medium. This movement of water mass is a mass transfer operation.
Since both heat and mass are transferred at the same time, this fits the description perfectly.
(C) Size reduction: This is a general term for processes like milling, grinding, or crushing. As explained for milling, it's primarily a mechanical operation.
(D) Decortication: This is the process of removing the outer layer, husk, or shell from seeds or grains (e.g., removing the hull from a groundnut). It is a mechanical operation.
Step 3: Final Answer:
Drying is the process that simultaneously involves both heat transfer (to provide energy for evaporation) and mass transfer (the movement of moisture). Therefore, option (B) is the correct answer.