🔍 Key Concepts

• Soot and deposits on boiler tubes and how they affect heat transfer • Relationship between stack (exhaust) temperature and boiler efficiency • Effect of blowing tubes (cleaning) on combustion conditions and required excess air

💭 Think About

• Think about what happens to heat transfer from the flame to the water/steam when tubes are dirty vs when they are clean. • If the tubes are cleaned, does more or less heat go into the water? What happens to the temperature of the gases leaving up the stack? • Does tube cleaning directly change fuel temperature or the chemistry of combustion (like CO formation), or does it primarily affect how efficiently heat is absorbed?

✅ Before You Answer

• Identify which option is most directly related to improved heat transfer after cleaning tubes. • Ask: after better heat transfer, should the exhaust gases be hotter or cooler when they leave the boiler? • Check which choices describe something that would change immediately and predictably as a result of removing soot from tube surfaces.