Long-tube vertical (LTV) evaporator design checks: which statement is incorrect for typical LTV geometry and operation?

Introduction / Context:
Long-tube vertical evaporators are workhorses for concentrating relatively clean liquids at moderate temperature differences. Understanding their geometry and normal operating levels is essential for sizing, pressure-drop estimation, and boiling behavior (nucleate vs. film). This question tests recognition of standard LTV features and typical ranges found in practice and handbooks.

Given Data / Assumptions:

• Conventional LTV with a steam-heated shell and liquor boiling inside vertical tubes.
• Standard industrial scales matching common design references.
• Moderate fouling and non-extreme viscosities.

Concept / Approach:
LTVs generally use relatively small-diameter tubes (centimeters) and lengths of a few meters to encourage vigorous two-phase flow and high heat-transfer coefficients. Steam on the shell and liquor inside tubes is the canonical arrangement. Maintaining liquor level around one-third to one-half of tube height ensures proper boiling zone development while preventing dryout at the tube top and avoiding excessive static head.

Step-by-Step Solution:

Verification / Alternative check:
Textbook schematics and vendor literature show similar dimensions and level recommendations to foster stable boiling and good heat transfer with manageable pressure drop.

Why Other Options Are Wrong (as “wrong” choices):

• Options (a), (b), and (c) are each correct statements for typical LTV designs.

Common Pitfalls:
Confusing LTV with short-tube or falling-film evaporators; reversing the placement of steam/liquor; misinterpreting the level guidance as an exact value rather than a practical range.

Final Answer:
None of these.