Superheated steam

Superheated steam is water vapor heated above its saturation temperature at a given pressure. It is a single vapor phase, with no liquid droplets in equilibrium.

Saturation temperature: The temperature at which a substance changes phase between liquid and vapor at a specified pressure. Steam becomes superheated only after its temperature rises above this pressure-dependent boundary.
Steam turbine: A rotary machine that extracts mechanical work from expanding steam. Superheated inlet steam can expand through turbine stages before condensation begins.
Wet steam: A mixture of saturated water vapor and suspended liquid water droplets. Unlike superheated steam, wet steam contains a liquid phase.
Phase diagram: A graph showing the stable phases of a substance under different conditions, such as pressure and temperature. The water phase diagram locates the liquid–vapor boundary that superheated steam lies beyond.
Saturated steam: Water vapor at the saturation temperature corresponding to its pressure, in equilibrium with liquid water. It marks the boundary between wet or saturated steam and superheated steam.
Rankine cycle: A thermodynamic cycle that converts heat into work using a working fluid, commonly water and steam. Superheating can increase cycle efficiency and reduce moisture during turbine expansion.
Dry saturated steam: Water vapor at saturation pressure and temperature with no liquid droplets present. It is droplet-free but not superheated; any additional heat at fixed pressure raises its temperature.
Critical point (thermodynamics): The pressure and temperature at which the distinction between a liquid and its vapor disappears. Above water’s critical point, heating does not create superheated steam through ordinary boiling.
Steam tables: Reference tables listing thermodynamic properties of water and steam at specified pressures and temperatures. They give superheated steam’s enthalpy, entropy, and specific volume for engineering calculations.
Steam locomotive: A railway locomotive that uses steam from a boiler to drive reciprocating pistons. Superheaters supplied hotter, drier steam to cylinders, improving locomotive performance.

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