🔍 Key Concepts

• Boiler furnace refractory – what it is made of and why it’s used • Heat transfer in a furnace: radiation, conduction, convection • What protects tubes and casing in a water-tube boiler

💭 Think About

• Think about which part of the boiler the refractory actually touches and shields, and which choice best matches that location • Consider whether the refractory’s main role is structural support, heat retention, or protection of a specific component • Ask yourself: if the refractory were removed, what negative effect on furnace temperature and efficiency would you expect?

✅ Before You Answer

• Verify what refractory materials are designed to do at very high temperatures (insulate vs. support vs. shield specific parts) • Check which components (tubes, casing, superheater) are directly exposed to the combustion space and how they are normally protected • Confirm whether the primary function of furnace refractory is related to heat retention in the furnace or mechanical support of outer structures