Waste Heat Recovery — online
How much heat a hot gas or flue gas can give back — as steam or to heat another stream — with fuel saved, CO₂ avoided and payback.
Yellow cells are inputs; orange cells are choices; blue cells choose the unit. Select or hover over an input to see its help in the box below the toolbar. The sheet is the same as the Excel tool (USD 49) — the Guide, method and references are in the Excel file.
What this waste heat recovery calculator does
Put a number on the heat going up your stack. How much heat a hot gas or flue gas can give back — as steam or to heat another stream — with fuel saved, CO₂ avoided and payback.
- Steam generation. Heat recovery steam generator with pinch and approach, blowdown, optional superheat and a stack temperature limit.
- Or heat a stream. Heat a liquid or gas with minimum temperature differences at both ends; receiver flow calculated or given.
- Any hot stream. Flue gas, process gas or liquid from the fluid library, or a gas mixture.
- Money and emissions. Fuel saved, cost saved per year, CO₂ avoided and simple payback.
- Zone duties. Economiser, evaporator and superheater duties and a temperature–heat diagram.
- Print-ready report. Inputs, results, findings and the chart on A4.
What you enter
- Fluid
- Flow given as
- Mass flow
- Standard volume flow
- Inlet temperature
- Pressure (absolute or gauge – pick the unit)
- Lowest allowed outlet (stack) temperature
- Heat loss of the recovery unit
- Use the heat for
- Steam pressure
- Feedwater temperature (economiser inlet)
- Superheated steam temperature (blank = saturated steam)
- Pinch (gas − saturation T at the evaporator exit)
- Economiser approach (saturation − water leaving the economiser)
What you get
- Waste stream mass flow
- Heat available down to the lowest outlet temperature
- Heat recovered
- Waste stream outlet (stack) temperature
- Steam generated
- Superheater duty
- Evaporator duty
- Economiser duty
- Gas temperature at the evaporator exit (pinch point)
- Water leaving the economiser
- Receiver outlet temperature reached
- Fuel saved
- Fuel cost saved per year
- Simple payback
How it was checked
Flue-gas steam generation and hot-water cases within 0.1 % of an independent reference calculation.
Related
- Free quick calculator — a simpler free version for a fast estimate.
- Calculation guide — the equations behind this tool, with a worked example.
- Waste Heat Recovery Excel tool — USD 49, keep the workbook and its Guide.
- All 40 online tools
Questions
Is the waste heat recovery calculator free?
You can enter and check all your data free. The full results, findings and printable sheet are unlocked with a 3-run pack (USD 9), a monthly subscription to all 40 online tools (USD 15) or a yearly one (USD 99).
Are the results the same as the Excel tool?
Yes. The online tool runs the formulas of the Waste Heat Recovery Excel workbook, checked cell by cell against the Excel file.
Which units can I use?
SI, US customary and British units — choose the unit next to each input.