What is the purpose of screen tubes in a superheater section?

The function of screen tubes in the superheater section is primarily to protect the inlet tubes from excessive radiant heat. Superheaters are designed to further heat steam above its saturation temperature to enhance its energy content before it enters the turbine for power generation. In achieving this, they operate in high-temperature environments where radiant heat from combustion gases can be significantly intense.

Screen tubes are strategically placed in this area to act as a barrier. They absorb some of the radiant heat and thereby lower the temperature that the inlet tubes experience. This thermal protection is crucial as it prevents damage to the inlet tubes that could otherwise occur due to prolonged exposure to high temperatures, ensuring safe and efficient operation of the boiler system.

The other options, while they might involve aspects of heat management or gas flow in a boiler system, do not accurately reflect the primary role of screen tubes as protective elements for inlet tubes against radiant heat.