What role do waterwall tubes primarily serve in a steam generation system?

Waterwall tubes primarily serve to create steam in a steam generation system. These tubes are designed to absorb heat from the combustion process occurring within a boiler. As water flows through the waterwall tubes, it is heated by the hot gases produced during combustion, causing it to change into steam.

The waterwall tubes are typically arranged around the furnace area of a boiler, ensuring that they receive maximum exposure to the heat generated by burning fuel. This arrangement helps in efficiently converting water into steam, which can then be used to drive turbines for electricity generation or for other industrial processes.

While cooling exhaust gases, providing structural support, and circulating feedwater are important functions in various components of a steam generation system, the primary function of waterwall tubes remains the conversion of water into steam, making option B the most accurate representation of their role.