Why can the thermal efficiency of a steam generator exceed 100%?

When people hear about "efficiency exceeding 100%", many feel that this violates the law of conservation of energy in physics. After all, energy cannot be created or destroyed out of thin air, so how could any device output more energy than it inputs? However, in the industrial field, the thermal efficiency of steam generators often shows values ​​like "100.27%" or "101.21%". This is not false advertising by merchants, nor is it an exception to the laws of physics, but rather stems from a set of "heat calculation rules".Steam generators typically use natural gas as fuel, the main component of which is methane (CH4). When methane burns, the chemical equation for complete combustion is CH4 + 2O2 → CO2 + 2H2O, which is an exothermic reaction. If combustion is incomplete, substances such as carbon monoxide will be produced, along with the release of heat.From a thermal efficiency calculation perspective, the thermal efficiency of a conventional natural gas boiler is 100% − heat loss from incomplete fuel combustion − heat dissipation loss − flue gas heat loss + latent heat from flue gas condensate recovery. However, for a high-performance composite steam generator, the heat loss from incomplete fuel combustion can be considered 0% due to near-zero carbon monoxide emissions; heat dissipation loss accounts for only 0.5% due to furnace surface temperatures below 45 degrees Celsius; and flue gas heat loss accounts for only 2.23% due to flue gas temperatures below 60 degrees Celsius.The key lies in the latent heat of flue gas condensate recovery. Methane combustion produces a large amount of water, which is in a gaseous state in the high-temperature flue gas. When the flue gas is cooled to below 60 degrees Celsius by the condenser, a large amount of gaseous water condenses. This condensation of water vapor releases a significant amount of latent heat of vaporization, which is absorbed by the condenser. Since this heat does not originate from the fuel itself, this recovered latent heat (accounting for 4%) is added when calculating the thermal efficiency. The final thermal efficiency can reach 100%−0%−0.5%−2.23%+4%=101.27%, thus achieving a thermal efficiency exceeding 100%.Therefore, we can understand that the secret to the seemingly "breakthrough" 100% thermal efficiency of steam generators does not lie in violating the fundamental law of conservation of energy in physics, but rather in its unique heat calculation logic. Only in this way can we more comprehensively measure the effectiveness of energy utilization, truly understand the energy potential of each unit of fuel, and maximize its value, allowing its value to be fully realized and manifested.