Shell-and-tube heat exchanger design statements: Pick the incorrect statement from the following commonly cited design facts.

Introduction / Context:
Shell-and-tube heat exchangers employ various mechanical features such as baffles, head types, and tube layouts to control heat transfer and pressure drop. Some statements about these features are accurate while others are misleading or outright false.

Given Data / Assumptions:

• Conventional shell-and-tube exchanger terminology is used.
• Focus is on typical industrial practice (segmental, orifice/rod, and no-tubes-in-window options).
• Evaporators may be configured horizontally or vertically with air venting provisions.

Concept / Approach:
Determine which statement contradicts accepted practice. Orifice (disc-and-doughnut) baffles are indeed used where low shell-side pressure drop and gentle crossflow are desired. Tube pitch affects shell-side flow area and thus pressure drop. Air blanketing in horizontal-tube evaporators is a known concern and is mitigated by proper venting, not inherently “avoided.” Floating head types such as split-ring (S-type) and pull-through (P-type) are standard.

Step-by-Step Solution:
Evaluate (a): Claiming orifice baffles are “never” used is false; they are used for specific duties.Evaluate (b): True—tube pitch influences crossflow area and pressure drop.Evaluate (c): Misleading as written; air blanketing is an issue, so it is not “avoided” by default.Evaluate (d): True—both listed floating head types are common.Therefore, the incorrect statement is (a).

Verification / Alternative check:
Design manuals include orifice baffles and rod-baffle systems as recognized variants for fouling-sensitive or low ΔP services.

Why Other Options Are Wrong:
(b) is correct: geometry (pitch/layout) alters shell-side hydraulics.

(c) as a blanket claim is not correct; however, the question requests a single incorrect statement, and (a) is definitively false.

(d) is correct, describing standard TEMA floating head choices.

Common Pitfalls:

• Treating “never” or “always” statements as true in engineering contexts.
• Confusing mitigation (venting) with inherent avoidance of air blanketing.

Final Answer:
Orifice baffles are never used in a shell-and-tube heat exchanger.