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

Energy and exergy analyses results of steam turbine and steam condenser, which operate in commercial combined cycle power plant are presented in this paper. Energy analysis shows that steam turbine has high energy (isentropic) loss equal to 71.71 MW, and very low energy (isentropic) efficiency of 58.79% only. Simultaneously, steam condenser is an almost perfect component from the energy viewpoint. At the base ambient state, steam turbine has high exergy destruction of 61.80 MW and low exergy efficiency of 62.34%, so both used analyses show that steam turbine operation can and should be notably improved. Steam condenser has an exergy destruction of 17.12 MW and exergy efficiency of 55.17% at the base ambient state, what are acceptable results. Observed steam condenser is much more sensitive to the ambient temperature change than steam turbine. Increase in the ambient temperature from 5 °C to 35 °C decreases steam condenser exergy efficiency for 35.90%, while the same increase in the ambient temperature decreases steam turbine exergy efficiency for 2.39% only.

This paper presents exergy analysis results of a complex three cylinder steam turbine with nominal power 210 MW. The analysis is performed for each cylinder, cylinder part and whole turbine as well as for each segment of each turbine cylinder. In the observed turbine, Low Pressure Cylinder (LPC) has the highest exergy destruction (8668.15 kW) and the lowest exergy efficiency (87.19%), while Intermediate Pressure Cylinder (IPC) has the highest exergy efficiency (92.15%) of all cylinders. Exergy efficiency is the highest for each segment at each cylinder entrance and continuously decreases for all segments during steam expansion through each cylinder. In each cylinder, a segment which is the lowest influenced by the ambient temperature change is inlet segment – as steam expands through each cylinder, further segments became more and more influenced by the ambient temperature change. Steam re-heating process has a very beneficial influence on the exergy efficiency of the first two IPC segments (Seg. 3 and Seg. 4) which have the highest exergy efficiency in comparison to all other segments.

This paper presents energy and exergy analysis results of whole gas turbine set and all its components. From the energy viewpoint, combustion chamber has the lowest energy loss (21.31 MW) and the highest energy efficiency (97.20%) of all gas turbine set components. Exergy analysis shows totally opposite trend in comparison to the energy analysis. From the exergy viewpoint, turbocompressor and turbine have low exergy destruction (both around 12 MW) and very high exergy efficiencies (92.43% for turbocompressor and 96.12% for turbine) at the base ambient state. Simultaneously, at the base ambient state combustion chamber has an exergy destruction of 159 MW and low exergy efficiency of 73.29% only. The combustion chamber is the most sensitive to the ambient temperature change of all components from the gas turbine set – the ambient temperature change of 10 °C will result with combustion chamber exergy efficiency change of approximately 0.67%. Whole gas turbine set (plant) has an energy efficiency of 34.40% and exergy efficiency of 33.08%.

Exergy analysis of three cylinder steam turbine segments is performed in this research. The highest mechanical power of 47389.66 kW is developed in the first segment (Seg. I, which actually represents the entire HPC – High Pressure Cylinder). Intermediate Pressure Cylinder (IPC) is the dominant mechanical power producer of all cylinders and it develops 48.95% of cumulative mechanical power produced in the whole turbine. The outlet Low Pressure Cylinder (LPC) segments (Seg. VII and IX) have the highest exergy destructions and the lowest exergy efficiency (equal to 61.27%) of all turbine segments. The best exergy performance shows IPC segments – Seg. V has the lowest exergy destruction (equal to 363.84 kW), while Seg. II has the highest exergy efficiency (equal to 94.04%) of all turbine segments. Outlet LPC segments (Seg. VII and IX) are the most sensitive to the ambient temperature change – their exergy efficiency decreases for 3.19% when the ambient temperature increases from 5 °C to 45 °C.

In this paper are presented results of the energy and exergy analyses related to the steam generator from nuclear power plant at four observed operating regimes. It is shown how the optimization processes and algorithms influence observed steam generator operation. The highest steam generator energy outlet is equal to 3012.17 MW and the lowest energy loss is 0.07 MW – both of them are obtained by using Genetic Algorithm (GA). Whale Optimization Algorithm (WOA) gives fluid operating parameters which will result with the lowest steam generator exergy destruction (107.05 MW) and the highest exergy efficiency (92.709%) in comparison to all other operating regimes. During the increase in ambient temperature from 5 °C up to 45 °C the lowest decrease in steam generator exergy efficiency (equal to 2.0136%) is obtained in the second operating regime which operating parameters are defined by using WOA. Final conclusion which can be derived from the observed research is that WOA has the most beneficial influence on the steam generator operation.

This paper presents exergy analysis of the main steam condenser, which operates in nuclear power plant. The analysis is performed in four main condenser operating regimes (loads) for a variety of the ambient temperatures. It is found that the main steam condenser has the lowest exergy destruction (equal to 72091.56 kW) and the highest exergy efficiency (equal to 66.66%) at the lowest observed ambient temperature (5 °C) and for the highest of four observed loads. Also, it is noted that an increase in the ambient temperature from 20 °C to 25 °C (two the highest observed ambient temperatures) significantly decreases main steam condenser exergy efficiency for about 21%, regardless of the observed load.

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.

The exergy analysis of deaerator at three different steam power plant loads is performed in this paper. Also, the influence of the ambient temperature change on deaerator exergy efficiency and losses is analyzed. From the exergy viewpoint, deaerator operation shows the best characteristics at middle and high power plant loads. The lowest deaerator exergy destruction of 363.94 kW and the highest exergy efficiency of 93.27 % will be obtained at middle power plant load and at the ambient temperature of 5 °C. The highest deaerator exergy destruction of 1349.99 kW and the lowest exergy efficiency of 81.83 % will be obtained at low power plant load and at the ambient temperature of 45 °C. Deaerator operation is preferable at the lowest possible ambient temperature, regardless of the current power plant load.