What type of heat transfer is primarily utilized in water-tube boilers?

In water-tube boilers, convection is the primary method of heat transfer. This is because these systems are designed to circulate water through tubes that are heated outside by hot gases. As the hot gases flow over the tubes, they transfer their heat to the water inside. This process relies heavily on the movement of fluids: the hot water rises, and cooler water moves in to replace it, creating a continual flow that enhances heat transfer efficiency.

Convection is particularly effective in water-tube boilers due to the increased surface area available for heat exchange and the forced circulation of water, which helps to maintain uniform temperature distribution. While conduction does occur at the interface between the tube material and the water, it is the convective currents within the water that most significantly facilitate the overall heating process. Thus, understanding the principles of convection is essential for anyone working with water-tube boiler systems.