Shell-and-tube bundle layout choice: compared with square pitch, what is a key hydraulic/thermal consequence of triangular tube pitch?

Introduction / Context:
Tube layout impacts thermal performance, pressure drop, cleaning, and mechanical integrity. The two common patterns—square and triangular—offer different trade-offs. Understanding these helps during exchanger specification and when reconciling performance with fouling behavior.

Given Data / Assumptions:

• Single-phase crossflow on shell side; comparable baffle arrangements.
• Same shell diameter and tube outside diameter across layouts.
• No exotic anti-fouling or low-fin tubes.

Concept / Approach:
Triangular pitch packs more tubes into a given shell diameter, increasing heat-transfer area per length and promoting mixing/turbulence due to narrower cross-flow lanes. The trade-off is higher shell-side pressure drop and more difficult mechanical rodding compared with square pitch. Square pitch is preferred for dirty shell-side service because straight cleaning lanes are available.

Step-by-Step Solution:
Compare layouts at fixed shell diameter: triangular places more tubes → tighter flow passages → higher velocity and turbulence.Higher turbulence typically raises shell-side h but also increases ΔP.Therefore, (a) is the best statement of consequence.

Verification / Alternative check:
Thermal rating software and TEMA guidance consistently show higher shell-side ΔP and h for triangular vs. square layouts, all else equal.

Why Other Options Are Wrong:
(b) is opposite of reality; (c) square—not triangular—eases cleaning; (d) turbulence is higher, not lower; (e) layout does not “eliminate” vibration concerns.

Common Pitfalls:
Optimizing only for area density without accounting for pump power; choosing triangular layout for very dirty shell-side services.

Final Answer:
Triangular pitch results in higher shell-side pressure drop (for the same shell diameter).