Flash steam and condensate recovery
How much condensate flashes to steam when its pressure drops, how much is left, and what recovering both is worth a year.
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How this calculator works
When saturated condensate drops in pressure through a steam trap, the heat it can no longer hold boils off part of it as flash steam: flash fraction = (hf at P1 − hf at P2) / hfg at P2. Enthalpies come from IAPWS-IF97 steam tables (checked against an independent implementation to better than 0.01 %). The calculator also values the flash steam, and the fuel and water saved by returning the remaining condensate instead of draining it.
Example: 1,000 kg/h of condensate at 10 bar g (184.1 °C) flashing to atmospheric pressure (0 bar g, 100.0 °C): 16.1 % flashes — 161 kg/h of steam, occupying 269 m³/h — and 839 kg/h of condensate remains. At USD 30/t, the flash steam is worth about USD 38,500 a year over 8,000 h; returning the condensate saves a further 2,480 GJ of fuel (USD 19,900 at USD 8/GJ and 85 % boiler efficiency) and USD 7,000 of water.
Limits: the condensate is assumed saturated at P1; subcooled condensate flashes less. Heat losses from pipes and vessels are not included. References: IAPWS R7-97(2012); Perry's Chemical Engineers' Handbook §2 (steam tables); US DOE, Improving Steam System Performance: A Sourcebook for Industry.