What is the 'heat loss method' for determining boiler efficiency, and what parameters does it consider?

The 'heat loss method' for determining boiler efficiency calculates the efficiency by subtracting the sum of all heat losses from 100%. It is an indirect method, as opposed to the direct method which measures the energy input and output. In essence, it determines how much of the energy from the fuel is *notconverted into useful steam and accounts for these losses. The key parameters considered in the heat loss method include: 1) Heat loss due to dry flue gas: This is the sensible heat carried away by the dry components of the flue gas (excluding water vapor). It depends on the flue gas temperature, the ambient temperature, and the specific heat capacity of the flue gas. 2) Heat loss due to moisture in fuel: Biomass fuels often contain significant moisture. The energy required to evaporate this moisture and superheat the resulting steam is a heat loss. It depends on the moisture content of the fuel and the flue gas temperature. 3) Heat loss due to moisture in air: The moisture present in the combustion air also absorbs heat as it is evaporated and superheated. This loss depends on the humidity of the air and the flue gas temperature. 4) Heat loss due to unburned carbon in ash: Incomplete combustion results in some carbon remaining in the ash. The heating value of this unburned carbon represents a heat loss. It depends on the amount of carbon in the ash and the heating value of carbon. 5) Heat loss due to radiation and convection from the boiler surface: Heat is lost from the boiler surface to the surroundings through radiation and convection. This loss depends on the surface temperature of the boiler, the ambient temperature, and the surface area of the boiler. 6) Heat loss due to unburned gases: If combustion is incomplete, some combustible gases (e.g., CO, H2, CH4) may be present in the flue gas. The heating value of these gases represents a heat loss. 7) Other minor losses: These may include heat loss due to blowdown, heat loss due to sensible heat in ash, etc. By quantifying all these heat losses and subtracting their sum from 100%, the boiler efficiency can be determined. This method provides insights into the areas where improvements can be made to enhance boiler performance.