Which type of boiler has the combustion chamber surrounded by water?

The type of boiler that has the combustion chamber surrounded by water is known as an internally fired boiler. In these boilers, the fuel is burned inside a chamber that is located within the water space, allowing the heat from combustion to be absorbed directly by the water surrounding it. This design is beneficial as it enhances the efficiency of heat transfer and maximizes the steam generation process.

Internally fired boilers are typically designed to operate under higher pressures and can produce steam rapidly, making them suitable for a variety of applications in power engineering. Their configuration allows for better temperature control and stability compared to externally fired boilers, where the combustion takes place outside the water space, affecting the heat transfer efficiency and potentially leading to more complex designs in heat exchange.

In contrast, externally fired boilers have the combustion chamber located outside the water space, which can reduce the efficiency of heat transfer as the hot gases must travel to heat the water. Modular and packaged boilers refer to specific configurations or system setups but do not fundamentally define the placement of the combustion chamber relative to the water. Hence, the defining characteristic of internal firing in terms of combustion chamber placement makes it the correct choice in this context.