Steam Properties Calculator

Why Steam Properties Matter Water and steam are used in boilers, turbines, heat exchangers, HVAC systems, and power plants worldwide. Steam properties depend on both temperature and pressure, and on the phase: liquid, saturated mixture, or superheated vapor. Engineers rely on steam tables (published since 1900s) or equations of state to look up these properties.

Phases of Water Subcooled liquid: water below saturation temperature at given pressure. Saturated mixture: water and steam coexist at saturation temperature/pressure. Superheated steam: steam above saturation temperature, dry, with no liquid droplets. The saturation curve defines the boundary between these phases.

Key Properties Saturation temperature T_sat: temperature at which water boils at a given pressure. At 1 atm (101.325 kPa): T_sat = 100°C. At 10 bar: T_sat ≈ 179.9°C. Enthalpy of vaporization (latent heat) hfg: energy to convert 1 kg of saturated liquid to saturated vapor. At 100°C: hfg ≈ 2257 kJ/kg. At 200°C: hfg ≈ 1940 kJ/kg. Specific enthalpy h: total heat content per kg (kJ/kg). Specific entropy s: irreversibility measure, used in turbine efficiency calculations.

Antoine Equation (saturation pressure) Approximate saturation pressure: log₁₀(P) = A − B/(C + T) For water (T in °C, P in mmHg): A = 8.07131, B = 1730.63, C = 233.426 (for 1–100°C range). Divide by 7.5 to get kPa. At 100°C this gives 760 mmHg = 101.3 kPa, one atmosphere. For higher temperatures, the IAPWS-IF97 formulation is the international standard.

Rankine Cycle (Steam Power Plants)

1. Feed water pump: liquid water pressurized (small work input)
2. Boiler: heat added at constant pressure → superheated steam
3. Turbine: steam expands, producing shaft work (turbine output)
4. Condenser: steam condenses back to liquid (heat rejection) Thermal efficiency: η = W_net / Q_in = 1 − Q_out/Q_in Modern coal plants: 35–45% efficient. Combined cycle gas plants: 55–60%.

Critical Point of Water The table behind this calculator is the classic saturated steam table, which puts the critical point at T_c = 374.14°C and P_c = 220.9 bar (22.09 MPa), with liquid and vapor sharing one specific volume of 0.003155 m³/kg, so ρ_c = 317 kg/m³. IAPWS-IF97, the current international formulation, revised those to 373.95°C, 220.64 bar and 322 kg/m³. The difference matters to a boiler designer and to nobody else: away from the critical point the two agree to within a fraction of a percent. Above the critical point there is no distinct liquid–vapor transition. Supercritical steam plants (P > 220 bar) run at higher efficiency but need special alloys in the boiler and headers.

HVAC and Process Engineering Steam at 5–15 psig (35–103 kPa gauge) is typical for building heating. High-pressure steam (150–600 psig) is used for industrial process heat. Flash steam: when high-pressure condensate is released to lower pressure, some re-vaporizes. Steam traps prevent live steam from bypassing heat exchangers.