🔍 Key Concepts

• Thermal expansion and why long straight tubes in a fixed shell need special arrangements • Different types of tube support/termination: packed tube sheet, floating tube sheet, bayonet tubes, U-tubes • What is meant by a "tube-within-a-tube" construction in heat exchangers

💭 Think About

• For each option, picture (or quickly sketch) what the tube bundle actually looks like and how it is allowed to expand when heated. • Ask yourself: which of these arrangements literally uses one tube sliding or fitting inside another to handle expansion, rather than just bending or floating? • Think about which designs are commonly used on cargo heaters or fuel heaters where an inner tube carries the product and an outer tube carries the heating medium.

✅ Before You Answer

• Verify which design is explicitly described in textbooks as having concentric tubes (one inside another). • Check which options (packed tube sheet, floating tube sheet, bayonet, U-tube) rely on bending of the tube versus sliding of a tube inside another tube. • Confirm that the choice you pick is known for simple removal and replacement of the inner element because it sits inside an outer tube.