What is true about bent tube watertube boilers?

Bent tube watertube boilers are designed with a specific configuration that allows water to circulate through tubes that are bent in various shapes, maximizing their efficiency and performance. When it comes to the furnace design, lining it with watertubes directly increases the surface area available to absorb radiant heat from the combustion process. This design enhances heat transfer, leading to improved efficiency, as more heat is captured and utilized to convert water into steam.

The inclusion of watertubes in the furnace section is particularly beneficial because it directly connects the heating surfaces with the area where high temperatures are generated, allowing for better absorption of that energy. This is a key feature of bent tube watertube boilers, distinguishing them from other boiler designs where alternative heat transfer methods are employed.

In contrast, the other options do not align with the characteristics of bent tube watertube boilers. For instance, many bent tube designs permit the furnace to be water-lined, providing an effective method to manage high temperatures and prevent overheating. Furthermore, bent tube watertube boilers can be internally or externally fired, and they can also be equipped with heat recovery systems to enhance system efficiency. Thus, the ability of these boilers to utilize watertubes for increased heat absorption is a significant feature that supports their effectiveness