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09 Steam and Condensate


Steam is water which has taken in heat and passed through to the complete vaporization stage.

At atmospheric pressure, boiling water and steam have the same temperature, ie 100°C.

As in practice, a differential pressure is required to cause steam to flow along a pipe, steam is normally supplied at a pressure, some way above atmospheric pressure. Above atmospheric pressure the steam temperature rises; this temperature gradient makes the steam more useful as a heating agent.

There are three quantities of heat in steam:

  1. Specific enthalpy of water (sensible heat) — this is the heat which is added to the water up to the point at which it is converted into steam.

  2. Specific enthalpy of evaporation (latent heat) — which must be added to the water at the vapour change state to convert all the water into steam at the same temperature.

  3. Specific enthalpy of steam — this is the sum of 1 and 2.

Compiled and published by: The Institute of Plumbing
  Last revision: 2002
  Edition: 1
  Number of pages: 12
  Format: PDF