Shell-and-tube heat exchangers – Purpose of shell-side baffles What is the principal effect of installing baffles on the shell side of a shell-and-tube heat exchanger?

Introduction / Context:
Baffles are common internals in shell-and-tube exchangers. Their geometry and spacing critically impact shell-side hydrodynamics, pressure drop, and heat transfer. Understanding their role guides trade-offs between performance and pumping cost.

Given Data / Assumptions:

• Single-phase shell-side flow; no phase change considered.
• Reasonable baffle cut and spacing practices.
• Goal: enhance heat transfer without excessive vibration or bypassing.

Concept / Approach:
Baffles direct shell-side flow across the tube bundle, creating crossflow and local turbulence, interrupting boundary layers, and reducing bypass streams. This increases the shell-side heat transfer coefficient h_s. It does not increase cross-sectional flow area; rather, it constrains flow path and raises velocity, typically increasing pressure drop as a trade-off.

Step-by-Step Solution:

Verification / Alternative check:
Bell–Delaware methods quantify h_s and pressure drop improvements due to baffles and associated correction factors for leakage and bypass streams.

Why Other Options Are Wrong:

• Increase cross-section: Opposite; effective flow area is restricted.
• Force parallel flow: Incorrect; baffles create crossflow.
• Decrease h_s: Contradicts the purpose of baffles.

Common Pitfalls:
Over-tight spacing causing high pressure drop and tube vibration; optimal design balances heat transfer gains and mechanical limits.

Final Answer:
increase the shell side heat transfer co-efficient.