Saturated Steam

Definition - What does Saturated Steam mean?

Saturated steam occurs at temperatures and pressures where both steam and water can coexist, which is when the rate of water vaporization is equal to the rate of condensation.

Saturated steam has superior heat transferring ability compared to unsaturated steam. Thus, saturated steam is preferred for heating applications.

Corrosionpedia explains Saturated Steam

Saturated steam is produced when water is heated to the boiling point and then vaporized with additional heat. If this steam is then further heated above the saturation point it becomes super-heated steam. Saturated steam occurs when steam and water are in equilibrium. Dry steam is saturated steam that has been very slightly superheated.

Saturated steam is used for heating, cooking and drying.

Saturated steam is an excellent heat source, particularly at temperatures of 100°C (212°F) and higher, and has following advantages:

  • The temperature can be quickly and precisely established
  • Requires a smaller heat transfer surface area, enabling a lower initial equipment outlay
  • Rapid, even heating through latent heat transfer
  • Safe, clean and low-cost

When the temperature of saturated steam is reduced (assuming the pressure is maintained) it will condense to produce water droplets, even if it is still considerably above the boiling point of 100°C (212°F) at standard pressure. These condensation droplets can damage steam turbine blades, so turbines rely on a supply of dry, super-heated steam.

Saturated steam has three main disadvantages in a steam engine:

  • It places a heavy demand on the boiler because a large amount of water must be evaporated per unit volume of steam
  • It contains small droplets of water that must be periodically drained from the cylinders
  • It inevitably condenses in the steam pipes and cylinders outside the boiler, causing a loss of steam volume as it does so
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