Shell-and-tube exchanger layout: What is the usual minimum recommended baffle spacing relative to shell diameter D?

Introduction / Context:
Baffles in shell-and-tube heat exchangers promote crossflow and increase heat transfer coefficients, but spacing that is too small can cause high pressure drop and vibration problems, while spacing that is too large reduces heat transfer effectiveness.

Given Data / Assumptions:

• Single-segmental baffles in a conventional shell-and-tube exchanger.
• Design rules of thumb guide preliminary layouts.

Concept / Approach:
A common guideline is to keep baffle spacing in the range of about 0.2 D to 1.0 D, with a typical minimum of approximately 0.2 D (and often not less than a practical lower bound, e.g., around 50 mm to 2 inches). This ensures sufficient flow redirection while avoiding excessive pressure drop and blockage.

Step-by-Step Solution:

Verification / Alternative check:
Thermal design software and correlations (e.g., Bell–Delaware method) confirm that very tight spacing produces high pressure drop with diminishing returns on heat transfer area effectiveness.

Why Other Options Are Wrong:

• 0.5 D, 0.66 D, 0.80 D may be acceptable spacings in some designs but are not the typical minimum recommendation.

Common Pitfalls:
Ignoring vibration risks or cleaning access; excessively close baffles complicate maintenance and can exacerbate fouling issues.

Final Answer:
0.2 D