Properties of Steam

Boiler output which is required to generate turbine generator is steam. Engineer or designer of steam boiler must have good understand about properties of steam. The properties of steam should be known are specific volume, specific entropy and enthalpy.

Specific volume of steam is volume (expressed as m3) divided by unit mass (expressed as kg) of steam at certain pressure. Specific volume will different if steam is produced at different pressure. Specific entropy of steam is the amount of energy (expressed as Joule) which be divided by unit mass (expressed by kg) at certain temperature (expressed as C). Enthalpy is measure energy (expressed as Joule) which is divided unit mass (expressed by kg).

The properties of steam can be seen in the steam table of ASME International Steam Tables for Industrial Use and the calculation properties of steam can be performed based on code International Association for the Properties of Water and Steam (IAPWS). At saturation condition by means that steam and water are mixed, steam will has different properties based on temperature and pressure. If the mixture heated exceeds saturation temperature, the steam will be superheated, but on contrary if the mixture cooled under saturation temperature, the water will be sub cooled.