Flue gas losses (definition)

Flue gas losses — these are heat losses that occur during the combustion of fuel in boiler, when some of the heat leaves with the flue gases through the chimney without being transferred to the coolant. These losses are one of the main reasons for the decrease in the efficiency of the boiler.

Flue Gas Losses: Key Aspects

• Loss mechanism:
  • Heat is lost with gases: When fuel burns, flue gases are formed, which, being hot, contain a significant amount of thermal energy. If this energy does not have time to be transferred to the coolant (water, air, etc.), it is lost along with the gases exiting through the chimney.
  • Flue gas temperature: The higher the temperature of the outgoing flue gases, the more heat is lost and, accordingly, the higher the level of losses.
• Impact on efficiency:
  • Decrease in efficiency: High heat losses with flue gases reduce the efficiency of the boiler, which is reflected in a decrease in its efficiency. This means that more fuel will be consumed to maintain a given level of heat.
  • Depends on boiler settings: Incorrect boiler settings (e.g. flue gas temperature too high) can increase losses and reduce efficiency.
• Factors Affecting Flue Gas Losses:
  • Temperature and velocity of flue gases: Rapid removal of hot gases through the chimney reduces the time of their contact with the heat exchanger, reducing heat transfer.
  • Fuel quality: Incompletely burned fuel increases the volume and temperature of flue gases, increasing heat losses.
  • Heat exchanger efficiency: If the heat exchanger does not transfer heat from the flue gases to the coolant efficiently enough, this also increases heat loss.
• Methods of reducing losses:
  • Condensing boilers: They use the heat of condensation of water vapor contained in the flue gases, which allows some of the heat to be returned back to the system and increases efficiency.
  • Traction adjustment: Optimization of chimney draft to reduce the rate of gas emission and increase their heat transfer.
  • Using economizers: These devices are installed at the outlet of the boiler and allow the utilization of the remaining heat of the flue gases, directing it back into the system.

Flue gas losses are an important factor influencing heat loss and overall boiler efficiency. Minimizing these losses through proper boiler adjustment, the use of highly efficient heat exchangers and modern technologies such as condensing boilers helps to significantly increase the efficiency of heating systems.