What component is installed between the inner and outer casings of the boiler to facilitate water flow?

The correct component that is installed between the inner and outer casings of the boiler to facilitate water flow is the downcomers. Downcomers are vertical pipes that direct the flow of water from the steam drum down to the water wall sections of the boiler. This flow of water is essential for maintaining the circulation within the boiler, ensuring that the water is heated efficiently and that the steam generation process can take place effectively.

By enabling water to flow downward, downcomers play a key role in the overall functionality of the boiler, as they help to maintain an adequate water level in the steam drum and support the natural circulation of the water and steam mixture. This circulation is critical for the thermal efficiency of the boiler and for preventing issues such as water carryover.

The other options, while relevant to boiler operation, do not serve the specific function of facilitating water flow between the inner and outer casings. For instance, feedwater pumps are responsible for delivering water into the boiler system, but they are not installed between the casings. Heat exchangers are used to transfer heat between two fluids but do not operate in the same manner as downcomers within the boiler assembly. The steam drum is a vital component that collects steam and allows for separation of steam