G2 Gas Fitter Practice Exam

How do boilers transfer heat to water?

1. Radiation

2. Convection

3. Conduction

4. Evaporation

The correct answer is: Conduction

Boilers transfer heat to water primarily through the process of conduction. In this context, conduction refers to the transfer of heat through direct contact between materials that are at different temperatures. The boiler's heat exchanger is designed for maximum surface area contact with the water that flows through it. When the heat exchanger is heated by the combustion process, the heat is conducted from the hot surfaces of the exchanger directly into the water. This principle is essential for the efficient functioning of boilers, as it allows for rapid heat transfer, ensuring that water is heated quickly and effectively. The design of the boiler and the materials used are optimized to facilitate this conductive heat transfer, making it a critical aspect of the boiler's operation. While radiation and convection are also mechanisms of heat transfer, their roles in the direct heating of water in a boiler are minimal compared to conduction. Radiation involves the transfer of heat through electromagnetic waves, and convection involves the movement of fluids (like the movement of heated water), but in a boiler, the direct contact between hot surfaces and water is what primarily drives the heating process. Evaporation is a phase change of water that is not directly related to the heat transfer mechanism in a boiler system but rather is an outcome when water reaches its boiling point.