Question

Identify the evaporator 

• A. Batch-type pan evaporator
• B. Falling-film evaporator
• C. Natural-circulation evaporator
• D. Rising-film evaporator

Hint:

In evaporators with vertical tubes, check the feed direction. Feed at the bottom that travels up with the vapor is a \textbf{rising-film}. Feed at the top that flows down the walls is a \textbf{falling-film}.

Answer 1

The Correct Option is D

Step 1: Examine the supplied diagram. 'Feed' enters the base of vertical tubes within a steam chest ('Steam in'), initiating boiling upon heating.

Step 2: Track the flow. Vapor generation causes the liquid to ascend along the tube walls as a thin film, driven by vapor bubbles. A 'Product' and 'Vapours' mixture then exits at the top.

Step 3: Relate the process to the options. The upward co-current flow of liquid and vapor within the heated tubes characterizes a Rising-film evaporator. Conversely, a falling-film evaporator introduces feed at the top for downward flow along the tube walls.