ENDOGENOUS AND EXOGENOUS EXERGY DESTRUCTION-A RATIONAL APPROACH TO EVALUATE THE THERMODYNAMIC PERFORMANCE OF A 285 MW GAS TURBINE POWER PLANT

Abstract

ABSTRACT

In this work, the total exergy destruction in a component of a system is split into endogenous and exogenous parts to assess the thermodynamic performance of a gas turbine unit, which is located in the SARIR power station, in Libya. The power station consists of three units, Siemens gas turbines, type SGT5-PAC 4000F, each unit with 285 MW rated capacity with the three ordinary components (air compressor, combustion chamber and turbine) is considered.

The total exergy destruction is not only due the deficiency of that component, but also occurs by the deficiencies of the remaining components. The endogenous exergy destruction takes place when the other components of the system work perfectly without any exergy destruction, and the considered component works with its normal condition. Splitting the total exergy destruction into endogenous and exogenous parts must be considered when decision is made to enhance the thermodynamic performance of a system. The exergy destruction can be split into an avoidable and unavoidable exergy destruction, each of them can be split into an endogenous and exogenous exergy destruction. Only part of the exergy destruction can be avoided, the remaining cannot be avoided due to economic issues and technological limit.

The results show that for the compressor, 82% of the exergy destruction is endogenous and 18% is exogenous exergy destruction, for the gas turbine, 96.6% of the exergy destruction is endogenous and 3.4% is exogenous exergy destruction and for the combustion chamber, 69.60% of the exergy destruction is endogenous and 30.40% is exogenous exergy destruction. That is, 75.82 MW of the exergy destruction in the combustion chamber is exogenous, hence the performance of the other two components (compressor and turbine) must be improved or replaced to elevate the thermodynamic performance of the combustion chamber. The later finding cannot be recognized without splitting the total exergy destruction into endogenous and exogenous exergy destruction.