What type of boiler is characterized by hot combustion gases traveling through tubes surrounded by boiler water?

The statement describes a firetube boiler. In a firetube boiler, combustion gases produced by the burning of fuel pass through tubes that are surrounded by water. This design allows for efficient heat transfer from the hot gases to the water, leading to the generation of steam or hot water.

Firetube boilers are commonly used in various applications due to their relatively simple design, ease of maintenance, and effectiveness in heating larger volumes of water. They are particularly effective when there is a need to produce steam quickly and with consistent pressure.

In contrast, watertube boilers operate on a different principle where water flows through tubes that are heated by combustion gases outside the tubes. This allows for a more compact design and is often used in applications that require high pressure and steam capacity. The other choices, like tubular and coil type boilers, don’t specifically describe the mechanism where hot combustion gases travel through tubes surrounded by water in the manner defined by firetube boilers.