The energy dissipation resulted from restrictive device in pipelines is commonly existing in the steam piping network of a thermal power plant. In order to accurately calculate the available energy dissipation resulted from the steam flowing through a restrictive device

a new view point for measuring energy in steam piping network system has been put forward

i.e. a model for computing the available energy dissipation has been obtained through entropy equation in occurrence process of the resistance

which is deduced from steam condition equation of IAPWS-IF 97. The result of checking analysis shows that the model can be used for calculating the energy dissipation while steam passing through a restrictive device. being more convenient and accurate than using traditional method.