Steam, Boiler, and Blowdown Pressure are the same. Combustion Efficiency is the% of fuel energy that is directly added to the feedwater and not otherwise lost or used. Blowdown Rate is the% of incoming feedwater mass flow rate that leaves the boiler as a saturated liquid at boiler pressure. Download (Professional Calculators) Surveying Calculator fx-FD10 Pro. Preloaded basic formula programs Version 1.00 - Mar. Sample program to import Version 1.00.