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

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.

The paper presents analysis of heat exchange and fuel consumption in the entire Marine Steam Generator (MSG) with steam reheating and in all of its components. Analysis is performed by using operating parameters from the steam generator exploitation. The highest heat amount transferred from combustion gases is used in the evaporator (48.17 % of the cumulative heat amount transferred in MSG). Proportionally, evaporator uses the highest fuel mass flow of 0.5172 kg/s when compared to other MSG components. In the high-pressure pipeline heat losses amounts 82.64 kW. Cumulative heat transferred from combustion gases to water/steam in all MSG components amounts 42048.47 kW. Cumulative water/steam specific entropy and temperature increase in the entire MSG is 4.5677 kJ/kg·K and 454.18 K, while the fuel mass flow in the entire MSG is equal to 1.0736 kg/s.

The paper presents an exergy analysis of pressure reduction valve mounted in the steam propulsion system on conventional LNG carrier. From exploitation are obtained that the valve pressure and temperature decrease become as higher as steam system load increases. Valve exergy power input and output decreases during the increase in steam system load, mostly because of the steam mass flow decrease. Steam system load increase in exploitation also causes a decrease in valve exergy destruction with a simultaneous decrease in valve exergy efficiency (from 68.42 % to 68.09 %). The ambient temperature variation showed that the valve exergy destruction is the lowest for the lowest observed ambient temperature, in any steam system load. The exergy efficiency of the pressure reduction valve is reverse proportional to valve exergy destruction. An increase in the ambient temperature for 10 °C causes a decrease in analyzed valve exergy efficiency for between 2.5 % and 3 %.

The paper presents a thermodynamic analysis of gas turbine with real open cycle. Gas turbine operates in combined heat and power (CHP) system. Analysis is provided by using measured operating parameters of operating mediums (air and combustion gases) in all required operating points. Cumulative real turbine developed power amounts 78611.63 kW. In the whole gas turbine process, the highest losses occur in combustion chambers during the heat supply process and amounts 13689.24 kW. Turbine power losses are equal to 7976.22 kW, while the turbo-compressor power losses amounts 4774.24 kW. While taking into account all analyzed gas turbine components, the highest efficiency of 90.79% has turbine, followed by combustion chambers which efficiency is equal to 89.01%. Turbo-compressor efficiency amounts 88.59% and the whole gas turbine cycle has efficiency equal to 33.15%.

The paper presents a thermodynamic analysis of gas turbine with real open cycle. Gas turbine operates in combined heat and power (CHP) system. Analysis is provided by using measured operating parameters of operating mediums (air and combustion gases) in all required operating points. Cumulative real turbine developed power amounts 78611.63 kW. In the whole gas turbine process, the highest losses occur in combustion chambers during the heat supply process and amounts 13689.24 kW. Turbine power losses are equal to 7976.22 kW, while the turbo-compressor power losses amounts 4774.24 kW. While taking into account all analyzed gas turbine components, the highest efficiency of 90.79% has turbine, followed by combustion chambers which efficiency is equal to 89.01%. Turbo-compressor efficiency amounts 88.59% and the whole gas turbine cycle has efficiency equal to 33.15%.

Developed power variation of turbo-generator (TG) steam turbine allows insight into the change of turbine energy efficiency and energy power losses. Measurements were performed in five different TG steam turbine operating points and analysis is presented in three randomly selected operating points. Turbine developed power was varied from 500 kW until the maximum power of 3850 kW in steps of 100 kW. Turbine energy efficiency increases from 500 kW to 2700 kW and maximum energy efficiency was obtained at 70.13 % of maximum turbine power (at 2700 kW) in each operating point. From 2700 kW until the maximum of 3850 kW, TG turbine energy efficiency decreases. Change in TG turbine energy efficiency is caused by an uneven intensity of increase in turbine power and steam mass flow. For all observed operating points, energy efficiency during turbine exploitation is approximately 10 % or more lower than the maximum obtained one. A continuous increase in turbine energy power losses during the developed turbine power increase are the most influenced by the continuous increase in steam mass flow through the turbine.

The paper presented a comparison of fuel costs between COGES and Diesel-electric propulsion systems for large conventional cruise ship. COGES propulsion system installed on the analyzed cruise ship saves ship’s space in comparison with Diesel-electric propulsion system. Diesel-electric propulsion system uses much more fuel for additional steam production and therefore, the additional fuel costs of this propulsion system are much higher in comparison with COGES system. Net profit of 50 additional cabins cannot compensate the difference in COGES system total annual fuel costs throughout the observed time period when compared to Diesel-electric propulsion system. The COGES propulsion system has much lower exhaust gas emissions in comparison with equivalent Diesel-electric system and therefore, in presented comparison, COGES could become profitable in the future if the emission regulations become more rigorous.