🔍 Key Concepts

• Heat transfer in water-tube boilers (clean vs dirty generating tube surfaces) • Relationship between firing rate, steam demand, and gas temperatures entering the superheater • How gas flow path (furnace → generating bank → superheater) affects metal temperatures

💭 Think About

• Think about what happens to heat transfer to the water/steam inside the generating tubes when their outside surfaces are dirty or fouled. • If less heat is absorbed in the generating bank, what happens to the gas temperature and heat available when the gases reach the superheater? • Which option best describes a cause-and-effect chain starting with dirty generating tube surfaces and ending with higher than normal superheater outlet temperatures?

✅ Before You Answer

• Identify which choices actually start with the direct effect of dirty generating tube surfaces (reduced heat transfer vs gas-flow pattern changes). • Check which option is consistent with the normal gas flow sequence: furnace → generating bank → (screen tubes) → superheater. • Eliminate any option that describes an effect that would more likely lower rather than raise gas temperature at the superheater inlet.