What type of boiler includes horizontal return tube and Scotch marine designs?

Firetube boilers are distinguished by their design, which involves hot gases from the combustion process flowing through tubes that are surrounded by water. This design allows for efficient heat transfer as the hot gases heat the water, producing steam. The horizontal return tube and Scotch marine designs are specific configurations of firetube boilers.

In the horizontal return tube design, the tubes run horizontally through the boiler, allowing for a compact design suitable for smaller spaces. The Scotch marine design features a larger combustion chamber and utilizes both the firetube principle and a second set of tubes that extend back into the boiler, enhancing efficiency and steam production.

Understanding these concepts is essential, especially when differentiating between various boiler designs and their applications in high-pressure situations.