Shell-side heat transfer: for the same tube size and shell-side flow conditions, how does the shell-side heat transfer coefficient for a SQUARE tube pitch compare with that for a TRIANGULAR pitch bundle?

Introduction / Context:
The layout of tubes in a shell-and-tube exchanger (triangular vs square pitch) influences crossflow, turbulence, and fouling resistance. Designers choose the pitch to balance heat transfer performance and cleanability. This question focuses on the relative shell-side heat transfer coefficient between square and triangular pitches for similar conditions.

Given Data / Assumptions:

• Identical tube outside diameter and shell-side mass flow rate.
• Comparable baffle configuration and clearances.
• Clean service (no fouling penalty differences considered).

Concept / Approach:

Triangular pitch packs tubes more tightly, increasing velocity through narrower crossflow lanes and promoting higher turbulence. This generally yields a higher shell-side heat transfer coefficient compared to square pitch. Square pitch, though offering easier mechanical cleaning with straight lanes, tends to have lower heat transfer and slightly lower pressure drop at the same flow rate.

Step-by-Step Solution:

Verification / Alternative check:

Empirical charts and design heuristics consistently rate triangular pitch as superior for heat transfer, while square pitch is chosen for mechanical cleaning or special services.

Why Other Options Are Wrong:

“More” contradicts standard practice; “same” is unrealistic; “twice” is an overstatement; cleanability considerations do not reverse the basic trend.

Common Pitfalls:

Ignoring the influence of baffle cut/spacing and leakage; assuming gains in heat transfer come without pressure drop penalties.

Final Answer:

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