With a constant fuel supply to the gas boiler, what effects do water inlet temperatures of 40 degrees and 60 degrees have on the boiler respectively?

Due to differences in feedwater temperature, the enthalpy difference between water and steam changes, resulting in slight variations in the boiler’s output； It will also affect the boiler’s flue gas temperature

Could you be more specific, please?

When the feedwater temperature decreases, the feedwater enthalpy also decreases; while, with the steam temperature and pressure at the boiler outlet remaining unchanged, the steam enthalpy stays the same. Steam enthalpy – feedwater enthalpy = heat required by the boiler. With constant fuel, meaning a constant amount of heat supplied to the boiler, the lower the feedwater temperature, the less heat is absorbed by the boiler water to turn into steam. The reduction in flue gas temperature is due to the fact that when the feedwater temperature decreases, the temperature difference between the economizer and the flue gas increases, resulting in more heat exchange in the economizer and thus a decrease in the flue gas temperature. The change from 60°C to 40°C is minimal, and its impact on the boiler’s evaporation rate and flue gas temperature is also limited. calculable

At a water supply temperature of 40 degrees, more fuel is required.

With a constant boiler efficiency and a constant gas supply, a lower feedwater temperature results in a relatively lower boiler output.