Combustion Efficiency Calculator
This combustion efficiency(CE) calculator determines how effectively the energy from fuel is converted into useful energy.
Combustion Efficiency
Combustion efficiency is a measure of how effectively the heat content of a fuel is transferred into usable heat.The stack temperature and flue gas oxygen (or carbon dioxide) concentrations are primary indicators of combustion efficiency.Calculate the combustion efficiency using the following formula
CE =
Where,
CO2 is dry volume concentration of CO2 in ppmv (Volume parts per million)
CO is dry volume concentration of CO in ppmv (Volume parts per million)
Heat Losses
It is important to keep heat losses to a minimum so that efficiency is maximized and more energy is conserved.
The following 4 significant types of energy losses apply to natural gas and heating oil systems.
1. Dry flue gas loss (LDG)
Calculate the dry flue gas loss (LDG) using the following formula:
LDG = [24 × DG × (FGT - CAT)] ÷ HHV
Where,
DG (lb./lb. fuel) = (11CO2 + 8O2 + 7N2) × (C + 0.375S) ÷ 3CO2
FGT is flue gas temperature, °F
CAT is combustion air temperature, °F
HHV is higher heating value of fuel, Btu/lb.
CO2 and O2 is percent by volume in the flue gas
N2 is 100 - CO2 - O2
C and S is weight fraction in fuel analysis
2. Loss due to moisture from the combustion of hydrogen (LH)
Calculate the LH using the following formula:
LH (%) = [900 × H2 × (hg - hf)] ÷ HHV
Where
H2 is hydrogen weight fraction in fuel analysis
hg is 1055 + (0.467 × FGT), Btu/lb.
hf is CAT - 32, Btu/lb.
3. Loss due to radiation and convection (LR)
For any boiler at operating temperature, the loss is constant.
4. Losses that are unaccounted for (LUA)
Use an assumed loss value of 0.1% for natural-gas-fired boiler systems and 0.2% for oil-fired systems.
Heat Losses Formula
Calculate the efficiency percentage(incl. all types of losses) using the following formula
Efficiency (E) % = 100 - LDG% - LH% - LR% - LUA%
Where,
LDG% is Dry flue gas loss
LH% is Moisture from hydrogen loss
LR% is Radiation and convection loss
LUA% is Unaccounted for losses
Conversions Table
| From | To |
|---|---|
| 1 Boiler Horsepower | 34.5 pounds per hour evaporation @ 212°F (100°C) |
| 1 Horsepower-hour = 2545 Btu | 1.34 HP - 1 KW |
| 1 Kilowatt-hour = 3412 Btu | 1.34 HP - 1 KW |
| 1 Atmosphere | = 14.696 pounds per square inch = 760.0 mm mercury |
TIP: Boilers often operate at excess air levels higher than the optimum. Periodically monitor flue gas composition and tune your boilers to maintain excess air at optimum levels.
Consider online monitoring of flue gas oxygen level to quickly identify energy loss trends that can provide early warning of control failures and allow data to drive your decision making.
An often-stated rule of thumb is that boiler efficiency can be increased by 1% for each 15% reduction in excess air or 40°F reduction in stack gas temperature.
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