🔍 Key Concepts

• conduction, convection, and radiation as methods of heat transfer in boilers • the difference between gas-side (fireside) and water-side layers at a metal surface • how still films vs. turbulent eddies affect heat transfer rates

💭 Think About

• Think about whether a still layer (film) or a moving, mixing layer (eddies) will slow down heat transfer more at a surface. • Decide whether conditions on the gas side or the water side of the tube usually provide the biggest overall resistance to heat flow. • Consider which medium (gas or water) naturally transfers heat more efficiently for the same temperature difference.

✅ Before You Answer

• Identify which has lower thermal conductivity: combustion gases or boiler water. • Decide whether a thin, turbulent boundary layer or a thicker, stagnant boundary layer offers more resistance to heat transfer. • Confirm that you are focusing on the fireside (gas side) boundary layer, not the metal or waterside resistance.