Example Data Table
| Input |
Example Value |
Unit |
| Fuel flow rate | 125000 | kg/hr |
| Fuel heating value | 25000 | kJ/kg |
| Main steam flow | 400000 | kg/hr |
| Main steam enthalpy | 3400 | kJ/kg |
| Feedwater enthalpy | 900 | kJ/kg |
| Gross generator output | 110 | MW |
| Auxiliary power | 8 | MW |
| Condenser heat rejection | 185 | MW |
Formula Used
Fuel heat input: Fuel flow × heating value ÷ 3,600,000.
Boiler absorbed heat: Steam flow × (main steam enthalpy − feedwater enthalpy) ÷ 3,600,000.
Turbine steam work: Steam flow × (inlet enthalpy − exhaust enthalpy) ÷ 3,600,000.
Net output: Gross generator output − auxiliary power.
Net heat rate: Fuel heat input ÷ net output × 3,600.
Overall efficiency: Net output ÷ fuel heat input × 100.
Balance closure: Known heat exits ÷ fuel heat input × 100.
How to Use This Calculator
Enter the fuel flow rate and heating value first. Add steam flow and enthalpy values from the same plant condition. Enter gross generator output and auxiliary power. Add condenser heat and known plant losses. Press the calculate button. Review heat rate, efficiency, closure, and unaccounted heat.
Power Plant Heat Balance Guide
What the calculation shows
A power plant heat balance traces energy from fuel to electricity. It also shows where energy leaves the cycle. The main inputs are fuel rate, fuel heating value, steam flow, enthalpy change, generator output, auxiliary load, and known losses. These values help operators judge boiler duty, turbine work, condenser rejection, and total plant efficiency.
Why heat balance matters
Heat balance work is useful during acceptance tests, daily performance checks, and troubleshooting. A small change in feedwater temperature, condenser pressure, steam enthalpy, or auxiliary demand can change the final heat rate. The result can reveal fouled heaters, wet steam, poor combustion, excess blowdown, high cooling losses, or inaccurate instruments. It also gives managers a common number for comparing fuel cost against delivered net power.
Important input ideas
Fuel heat input comes from mass flow multiplied by heating value. Boiler absorbed heat comes from steam flow multiplied by the enthalpy rise across the boiler. Turbine steam work uses the enthalpy drop through the turbine. Net electrical output is gross generator output minus auxiliary load. When all major flows are entered, the remaining unaccounted heat shows the balance gap.
Reading the results
Net heat rate is one of the most important outputs. A lower value means the plant needs less fuel for each kilowatt hour. Overall efficiency is the opposite view. A higher value means more fuel heat becomes usable electricity. Boiler efficiency compares absorbed steam heat with fuel heat. Generator conversion compares electrical output with steam energy available at the turbine. The condenser share shows how much heat must be removed by cooling water or air.
Practical use
Use consistent units before entering data. Keep enthalpy values from the same steam table method. Use average readings over a steady operating period. Do not mix startup data with full load data. Compare today’s balance with a clean baseline, not only with design figures. If the balance gap is large, check meters, sampling time, fuel moisture, steam quality, and loss assumptions before changing equipment settings.
Limits of the method
This calculator gives engineering estimates. It does not replace a full design model. Use manufacturer curves and calibrated plant instruments for final guarantees and test contracts.
FAQs
What is a power plant heat balance?
It is an energy accounting method. It compares fuel heat input with electricity, condenser rejection, auxiliary use, and losses. The goal is to show where the heat goes.
What is heat rate?
Heat rate shows how much fuel energy is needed to produce one kilowatt hour. Lower heat rate usually means better plant performance.
Why is net output important?
Net output subtracts auxiliary power from gross generator output. It shows the useful power available outside the plant.
What causes a high balance gap?
A high gap may come from bad instruments, wrong enthalpy data, missing losses, fuel moisture, unstable load, or inconsistent operating readings.
Can this work for coal plants?
Yes. Enter coal flow and heating value. Use matching steam, generator, and loss readings for the same operating period.
Can this work for gas turbine plants?
Yes, but the inputs should match gas turbine data. Replace steam values with equivalent heat recovery or cycle data where needed.
Which efficiency should I compare?
Use net efficiency for plant economics. Use boiler efficiency for steam generator checks. Use balance closure for data quality checks.
Are these results final test values?
No. They are engineering estimates. Formal testing needs calibrated instruments, correction curves, stable conditions, and accepted test procedures.