Thermodynamic assessment of potential for using liquefied natural gas in autonomous refrigerated car

Introduction. Diesel generators sets are commonly used to power the refrigeration units of autonomous refrigerated cars. In order to increase energy efficiency of autonomous refrigerated cars it is proposed to switch from diesel fuel to liquefied natural gas (LNG), with transition from diesel fuel to LNG and introduction of cold recovery units from LNG regasification for additional cooling of cargo area in conjunction with the main refrigeration unit. This transition necessitates a comprehensive assessment of the potential for utilising the physical exergy available during the regasification process. The aim of the study is to determine the thermodynamic limits and justify the selection of operating parameters for LNG cold energy recovery in the auxiliary cooling circuit of the cargo compartment.

Materials and methods. The study employed numerical thermodynamic processes simulation of an open regasification cycle for LNG fuel. Energy and exergy analyses, along with the heat balance method, were utilised. Key indicators, including specific cooling capacity and second-law exergetic efficiency relative to the Carnot cycle, were calculated.

Results. The authors examined LNG cold recovery scheme based on an open cycle with a cryogenic pump. The results of the numerical simulation of the thermophysical regasification processes are presented. The dependencies of specific cooling capacity and exergetic efficiency on operating pressure were evaluated, and parameters ensuring the prevention of LNG boiling outside the recovery circuit were determined. It was established that pressure increase in the regasification line significantly enhances the thermodynamic efficiency of the system with negligible reduction in enthalpy potential.

Discussion and conclusion. Exergetic efficiency criteria for autonomous systems were formulated, enabling a transition from an enthalpy-based to an exergy-based assessment of LNG recovery potential. A rational range of operating pressures was identified, achieving a thermodynamic optimum for cold recovery. This operating mode is essential for ensuring the hydraulic stability of the fuel supply system, simplifying the refrigerated car design and unifying the fuel supply scheme during the transition to LNG usage.

1. Kolin S.A., Kondratenko S.E., Bortnikov N.A. Evaluation of the economic costs of air pollution by urban transport (a case study of Saint Petersburg). Gas Industry. 2021;(6(817)):98–104. (In Russ.). EDN: https://elibrary.ru/psnndf.

2. Banaszkiewicz T., Chorowski M., Gizicki W., Jedrusyna A., Kielar J., et al. Liquefied natural gas in mobile applications — opportunities and challenges. Energies. 2020;13(21):5673. https://doi.org/10.3390/en13215673.

3. Voron O.A. The use of liquefied natural gas in the combined power unit of autonomous refrigerated car. Russian Railway Science Journal. 2019;78(3):188–192. (In Russ.). https://doi.org/10.21780/2223-9731-2019-78-3-188-192. EDN: https://elibrary.ru/rocdwh.

4. Brodyanskiy V.M., Fratsher V., Mikhalek K. Exergetic method and its applications. Moscow: Energoatomizdat; 1988. 288 p. (In Russ.).

5. Khor J.O., Walnum H.T., Ertesvåg I.S., RomagnoliA. Recovery of cold energy from LNG regasification. Energy Conversion and Management. 2018;174:539–555. https://doi.org/10.1016/j.enconman.2018.08.028.

6. Dorosz P., Wojcieszak P., Malecha Z. Exergetic analysis, optimization and comparison of LNG cold exergy recovery systems for transportation. Entropy. 2018;20(1):59. https://doi.org/10.3390/e20010059.

7. Noor Akashah M.H., Mohammad Rozali N.E., Mahadzir S., Liew P.Y. Utilization of cold energy from LNG regasification process: A review of current trends. Processes. 2023;11(2):517. https://doi.org/10.3390/pr11020517. EDN: https://elibrary.ru/jsuvbv.

8. Zonfrilli M., Facchino M., Serinelli R., Chesti M., De Falco M., Capocelli M. Thermodynamic analysis of cold energy recovery from LNG regasification. Journal of Cleaner Production. 2023;420(4):138443. https://doi.org/10.1016/j.jclepro.2023.138443. EDN: https://elibrary.ru/jjbxhu.

9. Wang Yu., Ren J. J., Bi M.Sh. Analysis on the heat transfer performance of supercritical liquified natural gas in horizontal tubes during regasification process. Energy. 2023;262:125444. https://doi.org/10.1016/j.energy.2022.125444. EDN: https://elibrary.ru/diisus.

10. Chen B., Zou T., Li H., He W. Simulative and experimental research on the heat exchanger for cold energy recovery of liquefied natural gas. Applied Thermal Engineering. 2024;237:121798. https://doi.org/10.1016/j.applthermaleng.2023.121798. EDN: https://elibrary.ru/djffyr.

11. Wei A., Yu L., Qiu L., Zhang X. Cavitation in cryogenic fluids: A critical research review. Physics of Fluids. 2022;34(10):101303. https:// doi.org/10.1063/5.0102876. EDN: https://elibrary.ru/ejevgt.

12. Kiselyov I.G., Komissarov S.B., Monastyrsky D.Ya. On the expediency of using liquefied natural gas in refrigerated containers with mounted diesel generators. Bulletin of scientific research results. 2021;(4):104–113. (In Russ.). https://doi.org/10.20295/2223-9987-2021-4-104-113. EDN: https://elibrary.ru/gqvuyv.