What does thermal efficiency of a boiler indicate?

The thermal efficiency of a boiler is an important measure that indicates how effectively the boiler converts the energy contained in fuel into useful output, which is typically in the form of steam or hot water. When we speak of thermal efficiency, we are referring specifically to the percentage of energy from the fuel that is transformed into usable energy, rather than being lost in the conversion process.

In this context, the correct understanding of thermal efficiency is that it represents the ratio of the useful energy output to the energy input from the fuel. This means that if a boiler has a high thermal efficiency rating, it successfully converts a large proportion of the energy from the fuel into useful work or energy, while minimizing waste heat and losses. Conversely, a low thermal efficiency means that a significant amount of fuel energy is wasted, often as heat that escapes through exhaust gases or other mechanisms.

This understanding helps power engineers assess and improve the efficiency of boiler operations, contributing to better fuel management and cost savings.