Where is the convection section of a heater located?

• A. Below the radiant tubes
• B. Above the radiant tubes
• C. Adjacent to the feed
• D. Inside the combustion chamber

Answer: (B)

Heat is transferred in two stages inside a heater: first, radiant heat from the flame warms the tubes directly in the lower part of the furnace, and then hot combustion gases move through a convection section where the remaining heat is transferred to the water as the gases flow past more tubes. The convection section sits above the radiant tubes because the hot gases naturally rise after delivering radiant heat, allowing them to pass over the convection tubes and transfer heat efficiently by convection. Placing this section higher also keeps the hottest, most radiant zone separate from the convection area, making the overall heat transfer more efficient and the tubes less exposed to direct flame exposure. If the convection section were placed below the radiant tubes or inside the combustion chamber, heat transfer would be less efficient or would interfere with the combustion zone.