🔍 Key Concepts

• heat transfer surfaces in water-tube boilers (water inside the tubes, hot gases outside) • effects of surface area and cleanliness on conduction and convection • difference between combustion efficiency changes and heat transfer rate at the tube surface

💭 Think About

• Which options actually change the effective heat transfer surface area between hot gas and water in a water-tube boiler? • Which options mostly affect water chemistry or combustion air without directly increasing the tube’s ability to pick up heat? • Would lowering the water level expose more tube metal to gas, or reduce the area in contact with water that can absorb heat safely?

✅ Before You Answer

• Identify which choice directly increases fireside heat transfer surface area on the tubes themselves. • Eliminate any answer that mainly addresses water treatment or corrosion/oxygen control rather than heat transfer. • Consider which choice, if done excessively, would actually reduce boiler efficiency by carrying more heat up the stack instead of into the water.