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Open AccessEditor’s ChoiceArticle

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

1
Maritime Department, University of Zadar, Mihovila Pavlinovića 1, 23000 Zadar, Croatia
2
Faculty of Engineering, University of Rijeka, Vukovarska 58, 51000 Rijeka, Croatia
3
Faculty of Maritime Studies, University of Rijeka, Studentska 2, 51000 Rijeka, Croatia
*
Author to whom correspondence should be addressed.
Entropy 2020, 22(1), 115; https://doi.org/10.3390/e22010115
Received: 8 December 2019 / Revised: 11 January 2020 / Accepted: 14 January 2020 / Published: 17 January 2020
(This article belongs to the Special Issue Carnot Cycle and Heat Engine Fundamentals and Applications)
Data from a two-stage axial vapor cryogenic compressor on the dual-fuel diesel–electric (DFDE) liquefied natural gas (LNG) carrier were measured and analyzed to investigate compressor energy and exergy efficiency in real exploitation conditions. The running parameters of the two-stage compressor were collected while changing the main propeller shafts rpm. As the compressor supply of vaporized gas to the main engines increases, so does the load and rpm in propulsion electric motors, and vice versa. The results show that when the main engine load varied from 46 to 56 rpm at main propulsion shafts increased mass flow rate of vaporized LNG at a two-stage compressor has an influence on compressor performance. Compressor average energy efficiency is around 50%, while the exergy efficiency of the compressor is significantly lower in all measured ranges and on average is around 34%. The change in the ambient temperature from 0 to 50 °C also influences the compressor’s exergy efficiency. Higher exergy efficiency is achieved at lower ambient temperatures. As temperature increases, overall compressor exergy efficiency decreases by about 7% on average over the whole analyzed range. The proposed new concept of energy-saving and increasing the compressor efficiency based on pre-cooling of the compressor second stage is also analyzed. The temperature at the second stage was varied in the range from 0 to −50 °C, which results in power savings up to 26 kW for optimal running regimes. View Full-Text
Keywords: two-stage LNG compressor; energy losses; exergy destruction; energy efficiency; exergy efficiency two-stage LNG compressor; energy losses; exergy destruction; energy efficiency; exergy efficiency
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MDPI and ACS Style

Poljak, I.; Orović, J.; Mrzljak, V.; Bernečić, D. Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier. Entropy 2020, 22, 115. https://doi.org/10.3390/e22010115

AMA Style

Poljak I, Orović J, Mrzljak V, Bernečić D. Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier. Entropy. 2020; 22(1):115. https://doi.org/10.3390/e22010115

Chicago/Turabian Style

Poljak, Igor; Orović, Josip; Mrzljak, Vedran; Bernečić, Dean. 2020. "Energy and Exergy Evaluation of a Two-Stage Axial Vapour Compressor on the LNG Carrier" Entropy 22, no. 1: 115. https://doi.org/10.3390/e22010115

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