What is the primary purpose of a boiler?

The primary purpose of a boiler is to generate steam or hot water for various applications, which can include heating systems, power generation, and industrial processes. Boilers are designed to convert the energy stored in fuel into thermal energy, which can then be used to produce steam or hot water. This steam or hot water is essential for various applications, such as heating buildings, providing hot water for domestic use, or serving as a driving force in turbines for electricity generation.

Other options mention functions that are either related but not primary, such as heating air, which is typically handled by furnaces instead of boilers, or storing fuel for energy production, which is a separate aspect of energy systems that doesn't define the function of a boiler. The cooling of hot fluids typically pertains to processes in cooling towers or condensers rather than the primary function of boilers, thus reinforcing the focus on steam and hot water generation as the core purpose of boiler operation.