What is another name commonly used for a Scotch Marine Boiler?

The Scotch Marine Boiler is commonly referred to as a horizontal return tube boiler. This type of boiler features a design where the furnace, or combustion chamber, is located at one end and the flue gases travel through a series of horizontal tubes before returning to the smoke box, hence the name "horizontal return." This setup allows for effective heat transfer and efficient steam generation, as the water surrounds the tubes, absorbing heat from the flue gases.

In contrast, the other options do not accurately describe the characteristics of a Scotch Marine Boiler. A vertical return boiler would have a different design orientation, the single pass boiler typically refers to a design that allows the flue gas to pass through the boiler only once without reversing direction, and a circulating fluidized bed boiler utilizes a completely different combustion process. Thus, the terminology specific to the Scotch Marine Boiler is correctly represented by the name horizontal return tube boiler, highlighting its particular construction and functionality.