Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier

Poljak, Igor; Orović, Josip; Mrzljak, Vedran; Bernečić, Dean

doi:10.3390/e22010115

Cited by 7 publications

(5 citation statements)

References 43 publications

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“…is the total energy fl ow of any fl uid stream and is the total exergy fl ow of any fl uid stream. Both of these variables are defi ned according to [54,55]:…”

Section: Overall (General) Equations and Balances / Ukupne (Opće) Jed...mentioning

confidence: 99%

Thermodynamic Analysis and Comparison of Two Marine Steam Propulsion Turbines

Poljak¹,

Mrzljak²

2023

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This paper presents thermodynamic (energy and exergy) analysis and comparison of two different marine propulsion steam turbines based on their operating parameters from exploitation. The first turbine did not possess steam reheating and had only two cylinders (high-pressure and low-pressure cylinders), while the second turbine possesses steam reheating and has one additional cylinder (intermediate-pressure cylinder). In the literature at the moment, there cannot be found a direct and exact comparison of these two marine steam turbines and their cylinders based on real exploitation conditions. Along with energy and exergy analyses, the research it is investigated the sensitivity of exergy parameters to the ambient temperature change for both turbines and each cylinder. It is also presented the influence of the steam reheating process on the energy and exergy efficiency of the entire power plant. For both observed turbines and their cylinders it is valid that relative losses and efficiencies (both energy and exergy) are reverse proportional. The operation of an intermediate pressure cylinder from a steam turbine with reheating is the closest to optimal. Due to the different origins of losses considered in energy and exergy analyses, each analysis detects different turbine cylinders as the most problematic ones. The steam reheating process decreases losses and increases efficiencies (both energy of each turbine cylinder and the whole turbine. The whole turbine with reheating has an energy efficiency equal to 81.46% and an exergy efficiency equal to 86.48%, while the whole turbine without reheating has energy and exergy efficiencies equal to 76.47% and 80.94%, respectively. Exergy parameters of a steam turbine without reheating as well as its cylinders are much more influenced by the ambient temperature change in comparison to the steam turbine with reheating and its cylinders. The steam reheating process will increase the efficiency of the whole power plant in real exploitation conditions between 10% and 12%.

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“…is the total energy fl ow of any fl uid stream and is the total exergy fl ow of any fl uid stream. Both of these variables are defi ned according to [54,55]:…”

Section: Overall (General) Equations and Balances / Ukupne (Opće) Jed...mentioning

confidence: 99%

Thermodynamic Analysis and Comparison of Two Marine Steam Propulsion Turbines

Poljak¹,

Mrzljak²

2023

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“…Thermodynamic performance is best evaluated using exergy analysis because it provides more insights and is more useful in efficiency-improvement efforts than energy analysis alone [64,65]. For any observed control volume, exergy analysis shows performance in relation to the environment [66,67], while energy analysis did not have any relation with the environment in which control volume operates [68][69][70]. Therefore, in the scientific and professional literature can be found that many researchers selected exergy analysis instead of energy analysis for researching the operation of various control volumes or systems [71][72][73].…”

Section: Exergy Analysis Equationsmentioning

confidence: 99%

The influence of various optimization algorithms on nuclear power plant steam turbine exergy efficiency and destruction

et al. 2021

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This paper presents an exergy analysis of the whole turbine, turbine cylinders and cylinder parts in four different operating regimes. Analyzed turbine operates in nuclear power plant while three of four operating regimes are obtained by using optimization algorithms – SA (Simplex Algorithm), GA (Genetic Algorithm) and IGSA (Improved Genetic-Simplex Algorithm). IGSA operating regime gives the highest developed mechanical power of the whole turbine equal to 1022.48 MW, followed by GA (1020.06 MW) and SA (1017.16 MW), while in Original operating regime whole turbine develop mechanical power equal to 996.29 MW. In addition, IGSA causes the highest increase in developed mechanical power of almost all cylinders and cylinder parts in comparison to the Original operating regime. All observed optimization algorithms increases the exergy destruction of the whole turbine in comparison to Original operating regime - the lowest increase causes IGSA, followed by GA and finally SA. The highest exergy efficiency of the whole turbine, equal to 85.92% is obtained by IGSA, followed by GA (85.89%) and SA (85.82%), while the lowest exergy efficiency is obtained in Original operating regime (85.70%). Analyzed turbine, which operates by using wet steam is low influenced by the ambient temperature change. IGSA, which shows dominant performance in exergy analysis parameters of the analyzed turbine, in certain situations is overpowered by GA. Therefore, in optimization of steam turbine performance, IGSA and GA can be recommended.

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“…The specific exergy from Equation (8) at standard ambient state of 0.1 MPa and 25 • C is taken as per the recommendations in [36][37][38]:…”

Section: Thermodynamic Analysismentioning

confidence: 99%

Analysis and Optimization of Atmospheric Drain Tank of Lng Carrier Steam Power Plant

Poljak

Bielić

Mrzljak

et al. 2020

JMSE

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The atmospheric drain condensate system of a marine steam power plant is described and evaluated from the energetic and exergetic point of view at a conventional liquefied natural gas (LNG) carrier. Energy loss and exergy destruction rate were calculated for individual stream flows joined in an atmospheric drain tank with variations of the main turbine propulsion speed rate. The energy efficiency of joining streams was noted to be above 98% at all observed points as the atmospheric drain tank was the direct heater. The exergy efficiency of the stream flows into the drain tank was in the range of 80% to 90%. The exergy stream flow to the tank was modeled and optimized by the gradient reduced gradient (GRG) method. Optimization variables comprised contaminated and clean condensate temperature of the atmospheric drain tank and distillate water inlet to the atmospheric drain tank with respect to condensate outlet temperature. The optimal temperatures improves the exergy efficiency of the tank as direct heater, to about 5% in port and 3% to 4% when the LNG carrier was at sea, which is the aim of optimizing. Proposals for improvement and recommendations are given for proper plant supervision, which may be implemented in real applications.

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Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier

Cited by 7 publications

References 43 publications

Thermodynamic Analysis and Comparison of Two Marine Steam Propulsion Turbines

Thermodynamic Analysis and Comparison of Two Marine Steam Propulsion Turbines

The influence of various optimization algorithms on nuclear power plant steam turbine exergy efficiency and destruction

Analysis and Optimization of Atmospheric Drain Tank of Lng Carrier Steam Power Plant

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