🔍 Key Concepts

• Fire-tube vs. water-tube boiler design – what is inside the tubes and what surrounds them • The path of hot gases from the furnace to the stack in a fire-tube boiler • Where combustion actually takes place in relation to the tubes

💭 Think About

• Ask yourself: in a fire-tube boiler, is it the water or the hot gases that are confined inside the tubes? • Think about where the burner flame is located: is it usually inside a large furnace space or inside many small tubes? • Visualize the heat-transfer surface: do the tubes carry the fluid being heated, or do they carry the heating medium (hot gases)?

✅ Before You Answer

• Be clear on the basic definition of a fire-tube boiler and how it differs from a water-tube boiler. • Verify where combustion physically occurs (in a furnace or in the tubes themselves?). • Confirm which substance – water or combustion gases – is intended to pass through the tubes in a fire-tube design.