Shell-and-tube heat exchangers: which of the following tube lengths is normally NOT used in practice for standard bundles and maintenance access?

Introduction / Context:
Standard tube lengths in shell-and-tube heat exchangers balance thermal performance, pressure drop, and maintainability. Very short tubes complicate tube-to-tubesheet fabrication, reduce area per pass dramatically, and hinder economical layout. Understanding typical lengths helps in quick “sanity checks” during specification and vendor bid reviews.

Given Data / Assumptions:

• Conventional exchangers with removable or fixed bundles.
• Normal fabrication practices using standard tube stock lengths (often in ~2.4 m, 3 m, 4.5 m, 6 m ranges, etc.).
• Focus is on what is normally not used, not what is theoretically possible.

Concept / Approach:
Common practice favors tube lengths of a few meters (e.g., 2.5–6 m or more), which provide sufficient heat-transfer area without excessive shell length. Extremely short tubes (e.g., 0.5 m) cause disproportionate header space, poor economic utilization of shell hardware, and limited thermal effectiveness per unit cost.

Step-by-Step Solution:

Verification / Alternative check:
Vendor catalogs and TEMA-based datasheets show preferred standard lengths aligned with stocking and bundle assembly considerations.

Why Other Options Are Wrong:

• 2.5 m, 3 m, 6 m, 10 m are all common in various duties and sizes.

Common Pitfalls:
Confusing small lab/pilot units (which could use short tubes) with industrial practice; overlooking maintenance access space for pulling bundles.

Final Answer:
0.5 metre