🔍 Key Concepts

• Difference between natural circulation and forced-circulation boilers • How water/steam moves through coils vs. large drums and downcomers • Typical appearance of a once-through or coil-type steam generator used on small tug-barge units

💭 Think About

• Which figure shows water confined mainly to small tubes or coils that would clearly need a pump to move fluid, rather than relying on natural density differences? • Which arrangement has no large lower and upper drums connected by downcomers and risers, but instead a tube bundle with a defined inlet and outlet? • On an articulated tug-barge unit, would you expect a bulky, large-drum boiler, or a more compact, rapid-steaming coil-type unit?

✅ Before You Answer

• Look for labels such as coil inlet/coil outlet or indications that flow direction is controlled mechanically. • Verify whether the figure has drums with large water space (more typical of natural circulation) versus mostly tubes with very little water volume. • Confirm which design would best match a compact, packaged steam generator suitable for limited machinery space.