Free power, steam and utilities calculators
14 boiler-house and utility calculations: boilers, steam, cooling towers, fuels, CO₂ and compressed air. Formula and practice for each.
Boilers and steam
Boiler efficiency (input-output method)
Dry saturated steam, blowdown neglected. State the basis: HHV (North America, natural gas ≈ 80 to 85 %) or LHV (≈ 88 to 93 %).
Steam flow for a heat duty
Dry saturated steam fully condensed, condensate leaving at saturation. Add 5 to 10 % for losses and start-up.
Flash steam from condensate
Saturated condensate at P₁. This low-pressure steam can be recovered (deaerator, heating) instead of being lost at the vent.
Boiler blowdown and cycles of concentration
Also works with TDS or chlorides (same unit on both sides). Typical blowdown: 1 to 8 % of feedwater; respect the manufacturer's TDS limit.
Condensate return and make-up water
Simplified balance (blowdown and deaerator steam neglected). Every point of return gained saves treated water, chemicals and fuel.
Cooling water and pumping
Cooling tower: range, approach, evaporation
E ≈ 0.00085 × gpm × °F, i.e. 0.00153 × Q × ΔT in m³/h and °C (about 85 % of the heat leaves by evaporation). Usual approach: 3 to 6 °C.
Cooling tower: cycles, blowdown and make-up
Measure conductivity (or chloride, silica) on the make-up and in the basin. Going from 3 to 6 cycles cuts make-up a lot; scaling sets the limit.
Pump power
Water at ρ = 1000 kg/m³ and g = 9.81 m/s². For another liquid multiply by its specific gravity. A pump far from its best efficiency point wastes energy.
Fuels, efficiency and CO₂
Fuel energy (LHV and HHV)
Typical values in MJ/kg (LHV / HHV): natural gas 47.1 / 52.2; propane 46.6 / 50.2; diesel 42.8 / 45.8; heavy fuel oil 39.5 / 42.2; coal 22.7 / 24.0; hydrogen 120.0 / 141.9. Use the supplier's analysis when known.
CO₂ from fuel burned
IPCC 2006 default values (Vol. 2, Tables 1.2 and 1.4), full oxidation. For official reporting use measured NCV and carbon content. Natural gas: about 0.7 to 0.8 kg/Sm³.
Heat rate and thermal efficiency
Benchmarks on LHV: engine or simple-cycle gas turbine 30 to 42 %; combined cycle 50 to 60 %. The lower the heat rate, the better. 1 kJ = 0.9478 Btu.
Compressed air
Compressed-air leak: flow and energy
Choked flow of an ideal gas (k = 1.4), air at 20 °C, valid above about 1 bar(g). Cd ≈ 0.61 for a sharp-edged hole, up to 0.97 for a rounded one. Free air referred to 20 °C and 1.013 bar.
Leak test by load / unload timing
Run the test with no air demand (plant stopped), over several cycles. Well-maintained system: under 10 %; 20 to 30 % is common. Unloaded power neglected.
Compressed-air receiver volume
Flows as free air. A receiver only covers a short peak: if the deficit lasts, you need more compressor capacity, not a bigger tank.
Learning and checking tools. The ranges shown are general guidance: always follow your plant's procedures, permits and set points. Nothing is sent anywhere: the calculations run in your browser.