Tube layout choice – triangular vs. square pitch in shell-and-tube exchangers Compared with a square pitch, a triangular pitch tube layout in a given shell diameter:

Introduction / Context:
Tube layout (triangular, rotated triangular, or square pitch) affects heat transfer area, shell-side pressure drop, and cleanability. Designers must balance compactness against maintenance and fouling considerations.

Given Data / Assumptions:

• Same shell diameter and tube outer diameter.
• Comparison of packing density, not thermal performance.
• No special cleaning lanes added unless specified.

Concept / Approach:
Triangular pitch offers the highest tube density, maximizing the number of tubes that can fit in a given shell diameter, hence greater heat transfer area. Square pitch, by contrast, allows straight cleaning lanes between tubes and is chosen for services requiring mechanical cleaning of the shell side. Therefore, triangular pitch does not facilitate easier external cleaning; it reduces clearances.

Step-by-Step Solution:

Verification / Alternative check:
TEMA and standard design references show triangular layouts providing up to ~15% more tubes than square pitch for the same shell size and tube OD.

Why Other Options Are Wrong:

• (a) Opposite of true packing behavior.
• (b) Incorrect; triangular layout is harder to clean externally.
• (d) Contains (b), which is incorrect.

Common Pitfalls:
Focusing only on area; in fouling services, square pitch may be preferable despite lower area due to cleanability.

Final Answer:
permits the use of more tubes in a given shell diameter.