Steam Table, Enthalpy and Steam Energy Calculator

What is a steam table for?

The energy carried by steam is measured by enthalpy, not temperature. Water and steam at the same temperature differ hugely in energy: turning one kilogram of water at about 100 °C and 1 bar into steam takes roughly 2257 kJ. A steam table lists these values for every pressure and temperature. This calculator works them out from the IAPWS-IF97 equations instead of a printed table, so you never have to interpolate by hand.

Saturated, wet and superheated steam

• Saturated liquid is water at its boiling point, with enthalpy h_f.
• Saturated vapour is fully evaporated water at the same temperature, with enthalpy h_g. The difference is the enthalpy of vaporisation: h_fg = h_g − h_f.
• Wet steam carries droplets. With dryness fraction x its enthalpy is h_x = h_f + x × h_fg.
• Superheated steam has been heated above the saturation temperature. Its properties need both pressure and temperature.

How do you find boiler duty?

The heat rate to the steam is the steam flow times the enthalpy rise: Q = ṁ × (h_steam − h_feedwater). Example: making 1000 kg/h of dry saturated steam at 10 bar absolute from feedwater at 80 °C raises the enthalpy from 335.8 to 2777.1 kJ/kg. The rise is 2441.3 kJ/kg and the duty is 1000 / 3600 × 2441.3 = 678 kW. At 90 percent boiler efficiency the fuel input is 753 kW.

What is flash steam?

When hot condensate at high pressure is released to a lower pressure, its surplus heat evaporates part of it. The fraction is x = (h_f1 − h_f2) / h_fg2. Condensate at 10 bar dropping to 1 bar flashes about 15 percent of its mass. Used in a low pressure main, that steam stops being a loss.

Absolute or gauge pressure?

Steam tables use absolute pressure while a site gauge shows gauge pressure. If the gauge reads 9 bar the absolute pressure is about 10 bar. Remember to pick the pressure type: the wrong choice shifts the saturation temperature by several degrees.

Limits

The tool covers saturated steam below 350 °C and superheated steam below 800 °C. The region near the critical point (saturation above about 165 bar, around 374 °C and 221 bar) is not calculated. Results are for pure water: real boiler water with dissolved gases, salts and oil differs slightly.