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

This paper presents an energy analysis of middle-power steam turbine with two cylinders (High Pressure Cylinder – HPC and Low Pressure Cylinder – LPC) and steam re-heater after the HPC (and before the LPC). Based on a steam operating parameters from the literature, performed energy analysis show that LPC develops higher power and has higher energy efficiency (81.45%) in comparison to HPC (which energy efficiency equals 80.12%). Re-heater is a heat exchanger (flue gases are used for steam heating) which has low energy loss (824.19 kW) and high energy efficiency (97.76%), what is expected energy performance of such heat exchanger. The entire analyzed turbine develops a power of 127480.60 kW and has energy loss equal to 29848.21 kW with energy efficiency of 81.03%.

In this paper is performed energy evaluation of steam turbine from the solar-based combined cycle power plant which includes analysis of each cylinder and the whole turbine. Steam turbine has three cylinders – high, intermediate and low pressure cylinders (HPC, IPC and LPC). Observed turbine is interesting because it possesses steam cooling before its expansion through the last cylinder (LPC). Due to unknown steam mass flow rates through each cylinder, for the evaluation are used specific variables. The highest specific work is obtained in LPC, while the lowest specific work is obtained in IPC. The highest loss of a specific work is obtained in LPC (29.8 kJ/kg), followed by HPC (24.5 kJ/kg), while the lowest loss of a specific work is obtained for the IPC (19.5 kJ/kg). Regardless of higher loss in specific work, HPC has higher energy efficiency in comparison to IPC (95.08% in comparison to 95.02%), while the lowest energy efficiency of all cylinders has LPC (94.92%). For the whole observed steam turbine loss of a specific work is equal to 73.8 kJ/kg, while the energy efficiency of the whole turbine is 95.00%.

This paper presents thermodynamic (energy and exergy) analysis of backpressure (BPT) and condensing (CT) steam turbines from cogeneration system. Based on the measurement data from exploitation it is performed calculation of main operating parameters for both turbines and its comparison. Analysis shows that BPT develops significantly lower mechanical power (22821.90 kW) in comparison to CT (30893.10 kW), but also BPT has more than four times lower energy and exergy power losses when compared to CT. Due to much lower losses, BPT has significantly higher energy and exergy efficiencies (93.26% and 94.95%, respectively) in comparison to CT (82.63% and 83.87%, respectively). Energy and exergy power of a steam flow related to both observed turbines show that the BPT is the dominant heat supplier for all heat consumers inside the cogeneration system.

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.

In this paper is analyzed back-pressure steam turbine which operates in CHP (Combined Heat and Power) plant from the aspect of energy and exergy losses. Produced turbine power, used for electricity generator drive equals 62548.77 kW, while the turbine mechanical loss is 1934.50 kW. Exergy analysis of the turbine shows that cumulative exergy loss is composed of two losses – mechanical loss and steam exergy loss. Steam exergy loss is additional loss which takes into account the state of the ambient in which turbine operates (unlike energy analysis which is independent of the ambient state). Change in the ambient temperature resulted with a change in turbine exergy efficiency and exergy loss. Ambient temperature change for 10 °C resulted with change in turbine exergy efficiency for less than 0.5 % on average, while the change in the turbine exergy loss (for the same temperature change) equals 266.21 kW on average.

This paper presents an analysis and comparison of three steam turbines and its cylinders: from the conventional steam power plant, from nuclear power plant and from the marine propulsion plant. The best parameters for the comparison of whole turbines and its cylinders are: energy loss per unit of produced mechanical power, exergy destruction per unit of produced mechanical power, energy efficiency and exergy efficiency. Steam turbine from marine propulsion plant shows the worst performance, regardless if observing each cylinder or the whole turbine – it has the highest losses per unit of produced mechanical power and the lowest efficiencies (both energy and exergy). Such results can be explained by a fact that marine steam turbine must be much more dynamic in operation in comparison to other two turbines. Also, marine steam turbine analyzed in this paper did not possess steam reheating between the cylinders as the other two observed steam turbines, what has a dominant impact on the obtained results.

In this paper is performed energy analysis of the whole low power steam turbine as well as energy analysis of all the turbine segments. Analysis of the whole turbine resulted with energy loss of 14642.48 kW and energy efficiency of 75.01%, what is in range with similar comparable low power steam turbines. Energy analysis of the turbine segments presents a different conclusion than the energy analysis of the whole turbine. The fifth turbine segment (S5) has unacceptable high energy loss and unacceptable low energy efficiency (energy loss of 6785.93 kW and energy efficiency of 26.87%), so it should be repaired as soon as possible. This comparison sh ow that proper energy analysis of turbine parts (segments) can detect the precise location of the problems during the turbine operation. Such analysis can be very helpful for the engineers because it allows detection not only the problematic components in the power plant, but also allows detection of the problematic parts of a component.

Paper presents exergy efficiency and loss analysis of condensate extraction pump (CEP) and main boiler feed pump (BFP) from a conventional steam power plant. Based on the required measured operating parameters at four different loads, it was observed that an increase in driving power for both pumps follows an increase in power plant cumulative developed power. Both analyzed pumps do not have the highest exergy losses at the highest observed load, as can be usually expected. Main boiler feed pump has the highest exergy efficiency, which is equal to 87.00%, at power plant nominal load, while the highest exergy efficiency of condensate extraction pump (95.77%) was observed at 60% of power plant nominal load. The influence of the ambient temperature on both pumps exergy efficiencies and losses is almost negligible.

Exergy analysis of steam turbine governing valve from a super critical thermal power plant is presented in this paper. Governing valve was analyzed not only at the highest, but also on two partial steam system loads. The lowest valve exergy destruction is 3598 kW and is obtained at the highest steam system load, while at partial loads of 80% and 60% valve exergy destruction is 13550 kW and 21360 kW. Valve exergy efficiency increases with an increase in system load, from 95.58% at 60% of load to 97.87% at 80% of load. At the highest load, valve exergy efficiency is the highest and is 99.57%. Change in valve steam specific entropy increment (difference in steam specific entropy between valve outlet and inlet) can be used as a tool for quick assessment of valve losses change. The ambient temperature influence on governing valve exergy analysis is low, especially in the highest steam system load where the majority of valve operation can be expected.

The paper presents an exergy analysis of condensate low-pressure heating system of a cogeneration power plant, which consists of one heater, one condensate pump and one pressure reduction valve. The entire system is investigated at three different plant loads. Regardless of the plant load, the highest exergy destruction is noted for the condensate heater (between 416.41 kW and 771.46 kW), after which follows pressure reduction valve with exergy destruction between 57.43 kW and 120.61 kW. Exergy destruction of condensate pump is almost negligible at any plant load and therefore condensate pump has the highest exergy efficiency (between 75.86 % and 77.08 %). Exergy efficiency of condensate heater is between 56.13 % and 59.29 %, while pressure reduction valve has the lowest exergy efficiency of all three analyzed system components and is between 36.98 % and 48.42 %.

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.

This paper presents an exergy analysis of wet cooling tower at three different loads and in a range of the ambient temperatures. Increase in cooling tower load increases its exergy destruction and simultaneously decreases cooling tower exergy efficiency, while an increase in the ambient temperature causes a decrease in cooling tower exergy destruction and simultaneously decreases its exergy efficiency. The lowest cooling tower exergy destructions (between 1417.54 kW and 2925.65 kW) are obtained at low load. The highest cooling tower exergy efficiencies are calculated at the lowest observed ambient temperature of 5 °C – they amount 64.31 % at low load, 54.80 % at middle load and 53.94 % at high load. The change in ambient temperature for 5 °C resulted with a change in cooling tower exergy efficiency of 4 % or more on average.