How to use the condensate recovery and flash steam calculator
High pressure condensate leaving a steam trap flashes into steam as soon as it reaches the lower recovery pressure. Venting that flash steam to atmosphere throws away heat and treated water at the same time, and ignoring its volume leaves the return line badly undersized. This tool shows how much flash is produced, what your recovery rate is, and what the returned condensate is worth in fuel.
Flash fraction is (liquid enthalpy at trap inlet − liquid enthalpy at recovery pressure) ÷ latent heat at recovery pressure. Condensate at 100 psig flashing to atmosphere gives roughly 13 %. Enthalpies are interpolated from a saturated steam table covering 0.5 to 30 bar absolute.
Heat recovered is based on how much hotter the returned condensate is than makeup water, and the fuel saving divides that by boiler efficiency to get actual fuel input. Chemical treatment and water and sewer charges are not included, so the real payback is larger than shown. Size return piping separately, because the two-phase mixture created by flashing needs far more area than the liquid alone.
Frequently asked questions
Yes. A flash vessel separates it as low pressure steam that can feed preheating or the deaerator, and only the remaining liquid goes on to the condensate receiver.
Indirect heating plant that does not inject steam into the product usually returns 70 to 90 %. Anything under 50 % points to failed traps or a blocked return line, so investigate those first.