What type of boiler uses water tubes to transfer heat?

The correct choice indicates that a water-tube boiler uses water tubes to transfer heat. In this type of boiler, water circulates through a series of tubes, which are heated by the combustion gases surrounding them. This design allows for high-pressure operations and is highly efficient at transferring heat. The configuration of water tubes allows for a larger surface area for heat exchange compared to other boiler types, which leads to superior thermal efficiency and the ability to handle higher pressures and temperatures.

This design also contributes to a lower risk of overheating, as the water inside the tubes helps regulate the temperature. Water-tube boilers are commonly used in power plants and large industrial applications where steam generation is critical. Understanding this configuration is crucial in stationary engineering, where efficiency and safety are paramount.