Heat exchanger geometry: in a shell-and-tube exchanger, the “TUBE PITCH” is defined as the _____ between adjacent tubes on the same pattern.

Introduction / Context:
Proper geometric definitions are vital when laying out tube bundles to meet thermal duty and mechanical constraints. Tube pitch determines the number of tubes, shell-side flow area, and cleanability. This question clarifies the standard definition of tube pitch used in design drawings and vendor datasheets.

Given Data / Assumptions:

• Standard square or triangular tube layouts.
• Drilled tube sheet with regular pattern.
• No fouling or special spacers considered.

Concept / Approach:

Tube pitch is the center-to-center spacing between neighboring tubes, measured along the layout pattern (square or triangular). The ligament (metal between holes) equals pitch minus tube outside diameter. Using center-to-center spacing ensures consistent mechanical and thermal calculations across bundle patterns and sizes.

Step-by-Step Solution:

Verification / Alternative check:

Design standards and manufacturer drawings always label P (pitch) on tube centers, not on edges or hole boundaries.

Why Other Options Are Wrong:

Option (a) confuses pitch with tube diameter. Option (b) describes ligament, not pitch. Options (d) and (e) are unrelated dimensions (clearance and baffle geometry).

Common Pitfalls:

Confusing pitch with ligament; forgetting that minimum pitch is commonly specified as a multiple of tube OD to allow rolling/welding and cleaning.

Final Answer:

shortest centre-to-centre distance between adjacent tubes