In a watertube boiler, what passes through the tubes?

In a watertube boiler, water passes through the tubes. This design is essential for how watertube boilers operate. In these systems, water is contained inside tubes that are heated by combustion gases from the burner, which move around the outside of the tubes. As the combustion gases increase in temperature, they transfer heat to the water within the tubes, causing it to turn into steam or increase in temperature.

This contrasts with firetube boilers, where the combustion gases pass through the tubes, and water surrounds them. The watertube design is particularly advantageous for generating high-pressure steam and efficiently managing heat transfer due to the larger surface area of the tubes and the ability to withstand high pressures.

Understanding this fundamental operation helps clarify the design and efficiency benefits of watertube boilers, particularly in applications requiring rapid response to load changes and the ability to handle varying steam demands.