International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Energy and exergy analysis of deaerator from combined-cycle power plant is presented in this paper. The deaerator is analyzed in three operating regimes and in various ambient conditions. The lowest deaerator energy loss of 525.60 kW and the highest energy efficiency of 78.21 % are obtained for the lowest water temperature at the deaerator outlet – in the same operating regime is obtained the lowest deaerator exergy efficiency. Decrease in the ambient temperature resulted simultaneously with an increase in deaerator exergy destruction and with increase in exergy efficiency. Deaerator exergy efficiency in each operating regime and for each observed ambient temperature significantly varies (from 13.82 % to 45.94 %). From the efficiency aspect, deaerator energy and exergy analysis show diametrically opposed results in two observed operating regimes.

In this paper is presented energy (isentropic) analysis of high power, three-cylinder steam turbine with steam re-heating. A comparison of real (polytropic) and ideal (isentropic) steam expansion processes at nominal load show that observed turbine develops real power of 655.35 MW, while in ideal situation it can develop 716.18 MW. The highest energy loss and the lowest energy efficiency occur in the high pressure turbine cylinder (25.67 MW and 89.14%), while intermediate pressure cylinder has the highest energy efficiency and the lowest energy loss. The energy efficiency of the whole observed turbine is 91.51%, what is in the expected range for such high power steam turbines at nominal load. Further optimization of this steam turbine will be primarily based on the high pressure cylinder.

The paper present thermodynamic analysis of three-cylinder steam turbine, which operates in a combined cycle power plant. It is performed analysis of each turbine cylinder and of entire steam turbine. Comparison of steam turbine cylinders shows that intermediate pressure cylinder develops the highest real power and has the highest efficiencies while low pressure cylinder has the highest ideal (isentropic) power, the highest loses and the lowest efficiencies – therefore, improvement potential of the low pressure cylinder is the highest. Entire observed steam turbine has an energy efficiency equal to 86.58 % and exergy efficiency equal to 89.26 %, what is lower in
comparison to high power steam turbines from some conventional land-based steam power plants but also higher in comparison to low power marine steam turbines.

The paper presents an exergy analysis of steam condenser at three different loads and in the ambient temperature range between 5 °C and 20 °C. An increase in the condenser load and increase in the ambient temperature resulted with an increase in steam condenser exergy destruction (exergy power losses). At low load, condenser exergy destruction is for the order of magnitude lower if compared to middle and high condenser loads. Decrease of the condenser load and decrease of the ambient temperature resulted with an increase in condenser exergy efficiency. The highest steam condenser exergy efficiencies are obtained at the lowest observed ambient temperature of 5 °C and amounts 81.47 % at low condenser load, 76.10 % at middle condenser load and 74.54 % at high condenser load. From the exergy viewpoint, the optimal condenser operating regime is low load and the lowest possible ambient temperature.