What does "stack temperature" indicate in a boiler system?

Stack temperature refers to the temperature of the flue gases exiting the boiler through the stack (or chimney). This measurement plays a crucial role in assessing the efficiency of combustion within the boiler system. A lower stack temperature typically indicates that more heat is being transferred to the water or steam instead of being lost through the flue gases. Conversely, if the stack temperature is high, it suggests that a significant amount of heat is being wasted, which can negatively impact the overall efficiency of the boiler.

Monitoring stack temperature helps operators determine if the combustion process is operating optimally. By analyzing the stack temperature, adjustments can be made to the air-to-fuel ratio, ensuring that combustion is complete and efficient, reducing fuel consumption and emissions. This connection between stack temperature and combustion efficiency makes the correct answer particularly relevant in the context of evaluating boiler performance.