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Article

Analysis on the Thermal Balance and Operational Parameters for the District Heating System with Peak Load Boilers in Heating Substations

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Institute of Building Environment and Facility Engineering, School of Civil Engineering, Dalian University of Technology, Dalian 116024, China
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Department of Mathematics and Systems Analysis, School of Science, Aalto University, P.O. BOX 11100, FI-00076 Aalto, Finland
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Planora Oy, PL 43, Voudintie 6, 90401 Oulu, Finland
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Department of Mechanical Engineering, School of Engineering, Aalto University, P.O. BOX 14100, FI-00076 Aalto, Finland
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Institute of Building Environment and Energy, China Academy of Building Research, Beijing 100013, China
*
Author to whom correspondence should be addressed.
Energies 2020, 13(23), 6180; https://doi.org/10.3390/en13236180
Received: 29 July 2020 / Revised: 30 October 2020 / Accepted: 19 November 2020 / Published: 24 November 2020
This study proposes to use gas-fired boilers as peak shaving heat sources in heating substations due to their capability to increase the reliability, flexibility and heat capacity without the need to change the district heating network (DHN). However, the design and operational requirements with different connection modes for this kind of DH system are still not clear. This paper presents a systematic study on this kind of DH system, analyzes the connection modes of series and parallel connections between the gas-fired boilers and the heat exchangers. For each connection mode, we figured out the thermal balances and obtained the design and operational parameters including the supply temperatures of the heat exchangers, gas-fired boilers and their variations under different network temperature levels and the base load ratios (β). Under the series connection mode, the design supply temperature of the heat exchangers has no relation with the design peak shaving flow ratio (ω′); it decreases linearly along with smaller β, and the decreasing slope is higher with bigger temperature difference (Δt) of the DHN. However, the design supply temperatures of gas-fired boilers increase linearly when β and/or ω′ are smaller, and the increasing speed is proportional to Δt. For the parallel connection mode, the design supply temperatures of the heat exchangers and gas-fired boilers are all affected by β, ω′ and Δt. The former decreases when β and/or ω′ are smaller, while the latter increases at the same time. Finally, the design peak shaving flow ratio ω′ are determined for the peak boilers with series and parallel connection modes. The study provides a theoretical basis for the design and operation of the DH system with peak heating boilers in substations in order to reach a lower investment and higher efficiency. View Full-Text
Keywords: district heating system; heating substation; gas-fired boiler; peak shaving; thermal balance district heating system; heating substation; gas-fired boiler; peak shaving; thermal balance
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MDPI and ACS Style

Li, X.; Wang, H.; Wu, X.; Duanmu, L.; Teppo, E.; Lahdelma, R.; Li, J.; Yu, L. Analysis on the Thermal Balance and Operational Parameters for the District Heating System with Peak Load Boilers in Heating Substations. Energies 2020, 13, 6180. https://doi.org/10.3390/en13236180

AMA Style

Li X, Wang H, Wu X, Duanmu L, Teppo E, Lahdelma R, Li J, Yu L. Analysis on the Thermal Balance and Operational Parameters for the District Heating System with Peak Load Boilers in Heating Substations. Energies. 2020; 13(23):6180. https://doi.org/10.3390/en13236180

Chicago/Turabian Style

Li, Xiangli, Haichao Wang, Xiaozhou Wu, Lin Duanmu, Esa Teppo, Risto Lahdelma, Ji Li, and Li Yu. 2020. "Analysis on the Thermal Balance and Operational Parameters for the District Heating System with Peak Load Boilers in Heating Substations" Energies 13, no. 23: 6180. https://doi.org/10.3390/en13236180

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