🔍 Key Concepts

• Function of downcomer tubes in a water-tube boiler circulation system • General location of cooler vs hotter water/steam in a water-tube boiler • Relationship between furnace/gas passages and water/steam spaces

💭 Think About

• Think about where the relatively cooler, denser water in the boiler would naturally be found compared with the hotter steam/water mixture. • Ask yourself: do downcomers normally carry water toward or away from the furnace area? Why would that matter for their location? • Visualize a modern water-tube boiler: where are the heated generating tubes that face the furnace, and where would the return path for water logically be placed?

✅ Before You Answer

• Verify what downcomer tubes actually carry: mostly water, mostly steam, or a mixture? • Check whether downcomers should be exposed to direct furnace flame and highest gas temperatures, or located in a relatively cooler area for structural reasons. • Confirm which of the listed locations would best support a natural or forced circulation loop: water down in one region, steam/water up in another.