Simplified dynamic heat exchanger models for heat recovery steam generators
DOI:
https://doi.org/10.24425/ather.2025.154197Abstract
Monitoring power plants necessitates sophisticated methods and reliable dynamic models, especially with the increasing flexibility demand. The primary challenge of this work is to develop a modelling strategy for heat recovery steam generators (HRSG) that enables simple yet accurate simulation of their dynamic behaviour, accounting for the delayed response of their heat exchangers to load variations caused by high thermal inertia. The proposed modelling methodology aims to build models suitable for monitoring power plants based on a set of sensor measurements, which can realistically be found in a power plant. This approach eliminates the need for extensive system design information, which may not always be accessible to the modeller. First, fully detailed, pseudo three dimensional Modelica model of the monophasic heat exchangers is developed. The model is then simplified progressively while the impact on accuracy is assessed. A more simplified model is later developed by assuming a lumped global heat transfer coefficient and a mass. The simplified model provides promising results, demonstrating a good compromise between simple calibration process and accuracy. A model of the evaporator is also presented and validated based on literature. Finally, a qualitative analysis of the full HRSG model is conducted. The dynamic behaviour as well as the time constants of the heat exchangers are analysed. The results demonstrate a good agreement with the expected physical behaviour.References
[1] IEA. (2024). Electricity 2024. https://www.iea.org/reports/electricity-2024 [accessed 30 Nov. 2024].
[2] Holttinen, H. (2012). Wind integration: experience, issues, and challenges. WIREs Energy and Environment, 1(3), 243–255. https://doi.org/10.1002/wene.18
[3] IRENA. (2019). Innovation landscape brief: Flexibility in conventional power plants. International Renewable Energy Agency. https://www.irena.org/-/media/Files/IRENA/Agency/Publication/2019/Sep/IRENA_Flexibility_in_CPPs_2019.pdf [accessed 25 Oct. 2024].
[4] Casella, F., & Pretolani, F. (2006). Fast start-up of a combined-cycle power plant: A simulation study. 5th Modelica Conference. https://modelica.org/events/modelica2006/Proceedings/sessions/Session1a1.pdf [accessed 15 Sept. 2024].
[5] Alobaid, F., Postler, R., Ströhle, J., Epple, B., & Kim, H.-G. (2008). Modeling and investigation of start-up procedures of a combined cycle power plant. Applied Energy, 85(12), 1173–1189. https://doi.org/10.1016/j.apenergy.2008.03.003
[6] Benato, A., Stoppato, A., & Bracco, S. (2014). Combined cycle power plants: Comparison of dynamic models. Energy Conversion and Management, 87, 1269–1280. https://doi.org/10.1016/j.enconman.2014.06.017
[7] Farahani, Y., Jafarian, A., & Mahdavi Keshavar, O. (2022). Dynamic simulation of a hybrid HRSG. Energy, 242, 122996. https://doi.org/10.1016/j.energy.2021.122996
[8] Jain, P., Poon, J., Singh, J.P., Spanos, C., Sanders, S.R., & Panda, S.K. (2020). Digital twin for fault diagnosis in PV systems. IEEE Transactions on Power Electronics, 35(1), 940–956. https://doi.org/10.1109/TPEL.2019.2911594
[9] Allard De Grandmaison, I., Muszynski, L., & Schwartz, A. (2019). AI diagnosis for maintenance teams. VGB PowerTech, 99(8), 67–72.
[10] Mertens, N., Alobaid, F., Starkloff, R., Epple, B., & Kim, H.-G. (2015). Drum-type vs once-through HRSG during start-up. Applied Energy, 144, 250–260. https://doi.org/10.1016/j.apenergy.2015.01.065
[11] Dittus, F.W., & Boelter, L.M.K. (1985). Heat transfer in automobile radiators. International Communications in Heat and Mass Transfer, 12(1), 3–22. https://doi.org/10.1016/0735-1933(85)90003-X
[12] Walter, H., & Hofmann, R. (2011). Heat transfer correlations for finned tubes in HRSG simulation. Applied Thermal Engineering, 31(4), 405–417. https://doi.org/10.1016/j.applthermaleng.2010.08.015
[13] Can Gülen, S., & Kim, K. (2014). Gas turbine combined cycle dynamic simulation. Journal of Engineering for Gas Turbines and Power, 136(1), 011601. https://doi.org/10.1115/1.4025318
[14] Dechamps, P.J. (1995). Modelling transient behaviour of HRSG. Proceedings of the IMechE Part A, 209(4), 265–273. https://doi.org/10.1243/PIME_PROC_1995_209_005_01
[15] Modelica Association. (2000). Modelica – A unified object-oriented language for physical systems modeling (Version 1.4 tutorial). https://modelica.org/documents/ModelicaTutorial14.pdf [accessed 11 Aug. 2023].
[16] Dassault Systèmes. (2023). Dymola. https://www.3ds.com/products-services/catia/products/dymola/ [accessed 18 July 2023].
[17] Metroscope. (2023). Metroscope modeling library. https://github.com/Metroscope-dev/metroscope-modeling-library [accessed 18 July 2023].
[18] Åström, K.J., & Bell, R.D. (2000). Drum-boiler dynamics. Automatica, 36(3), 363–378. https://doi.org/10.1016/S0005-1098(99)00171-5
