A Study Water Steam Enthalpy-Exergy Diagram And Its Application

The proposal of the concept of Exergy solved the problem of how to appraise the quality of energy, this concept is meaningful profoundly,theoretically and practically. Because the enthalpy- exergy diagram can directly show the change of enthalpy and exergy, it can conveniently get the value of enthalpy and exergy. Thus in analysis of the second law of thermodynamics, especially in the exergy analysis,it has the prospect of wide application.Thus, this paper has introduced the IAPWS-IF97 formula ,a new formulation for the thermodynamic properties of water and steam, by which we have developed a software to calculate thermodynamic properties of water and steam (including exergy).With help of this package, the enthalpy- exergy diagram of water and steam is drawn. The advantage in the second law of thermodynamics analysis is obviously illustrated with comparing enthalpy- exergy diagram to frequently utilized thermodynamic diagram. The enthalpy- exergy diagram is used to analyze the basical thermodynamic course in the second law of thermodynamics. The basical analysis method of the enthalpy- exergy diagram is introduced ,and on this foundation, some thermal systems of fossil - fired power plant are analyzed in this paper.