Question 385Steam Plants - Assistant Engineer

The correct answer is D) downcomer. In a boiler, the downcomer is a vertical pipe or tube that carries the cooler, denser water from the steam drum down to the bottom of the boiler. This water then circulates back up through the water wall tubes (indicated by "C") to the steam drum, completing the circulation loop. The downcomer is responsible for ensuring proper water flow and distribution within the boiler, which is crucial for efficient heat transfer and steam generation. The other options are incorrect because they do not accurately describe the component indicated by the arrow "E" in the given boiler illustration. Support tubes, recirculating tubes, and water wall tubes serve different functions within the boiler design.