How many types of boilers there?

There are several types of boilers, primarily categorized into two main types: fire-tube and water-tube boilers. Fire-tube boilers have hot gases flowing through tubes submerged in water, while water-tube boilers have water circulating through tubes heated by external combustion gases. Additionally, there are variations such as electric boilers, steam boilers, and condensing boilers, each designed for specific applications and efficiency levels. Overall, the choice of boiler depends on factors like the intended use, capacity, and fuel type.