What is the difference between a fire-tube and a water-tube boiler?

The distinction between fire-tube and water-tube boilers lies primarily in their design and the flow of fluids in relation to the heat transfer process. In a fire-tube boiler, hot gases produced from combustion pass through tubes that are surrounded by water. The heat from these gases is transferred to the water, creating steam. This type of boiler typically has a lower pressure limit and is simpler in design, making it suitable for smaller applications or lower-capacity operations.

Conversely, in a water-tube boiler, water circulates through tubes that are surrounded by hot combustion gases. This design allows for a more efficient heat exchange and can handle higher pressures, making water-tube boilers ideal for larger industrial applications. Their construction enables them to achieve higher efficiency and quicker response to load changes.

The correct option highlights this fundamental operational difference, making it clear how the flow of hot gases and water is configured in each type of boiler, which is crucial for understanding their applications and efficiencies.