🔍 Key Concepts

• Natural circulation in water-tube boilers (how hot and cold water/steam move by density difference) • Role and location of downcomers versus risers in a boiler • Effect of temperature on water density and circulation inside the boiler

💭 Think About

• Think about what you want the water inside the downcomers to be like: hotter or cooler than the water in the riser tubes? How would that affect circulation? • If you mount downcomers outside the hot furnace/casing, what happens to their temperature compared to tubes inside the furnace? • Which choice best supports a strong, continuous circulation loop between drums and tube banks?

✅ Before You Answer

• Identify the primary function of downcomers (what they carry, and between which parts of the boiler). • Decide whether downcomers should be hot like risers or relatively cooler to help natural circulation. • Eliminate options that focus mainly on maintenance or solids settling, and focus on those related to circulation and temperature differences.