Analysis of the District Heating Steam Turbine Unit at CHPP Based on Energy and Exergy Indicators

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DOI https://doi.org/10.15407/pmach2025.02.017
Journal Journal of Mechanical Engineering – Problemy Mashynobuduvannia
Publisher Anatolii Pidhornyi Institute of Power Machines and Systems
of National Academy of Science of Ukraine
ISSN  2709-2984 (Print), 2709-2992 (Online)
Issue Vol. 28, no. 2, 2025 (June)
Pages 17-26
Cited by J. of Mech. Eng., 2025, vol. 28, no. 2, pp. 17-26

 

Author

Andrii O. Mazur, Anatolii Pidhornyi Institute of Power Machines and Systems of NAS of Ukraine (2/10, Komunalnykiv str., Kharkiv, 61046, Ukraine), e-mail: drussmazur@gmail.com, ORCID: 0000-0003-2864-4943

 

Abstract

A 20 MW district heating and condensing steam turbine unit (STU), consisting of the parts of high, medium and low pressure, which is operated at one of the CHPPs in Kharkiv, has been analyzed. According to the scheme, steam from two district heating recovery regulated extraction units is supplied to two network heating units. During the reconstruction of the CHPP, the heaters of the STU regeneration system were dismantled due to their degradation. It has been decided to focus on increasing heat recovery at the CHP plant, so no new high-pressure heaters were installed. In addition, instead of a cooling tower, it was decided to use water from the network for hot water supply in the condenser cooling circuit. An analytical review of the thermal scheme of a district heating STU in terms of energy and exergy indicators is given in the paper, which allowed to identify elements with high exergy cost, which is an indicator of their efficiency. Analytical tables with the exergy parameters of the original scheme element by element and analytical graphs were compiled during the analysis of the options of the thermal scheme of STU. According to the exergy analysis, the highest exergy cost is observed in the energy boiler, but it is known that it can be reduced by reducing exergy destruction in other elements. Therefore, a network heater that is heated by high-pressure steam from the first medium-pressure part of the first extraction was chosen as the element with the greatest potential for increasing the efficiency of the STU. Respectively, the first network heater, which is heated by low-pressure steam from the second low-pressure section, is selected as the second element. We also considered options of the thermal scheme of STU, in which the steam parameters in the turbine extractions (pressure, flow) were varied. It is shown that with a decrease in pressure and a decrease in steam flow in the first extraction, as well as a decrease in steam pressure and an increase in steam flow in the second extraction, the cost of exergy flows in network heaters decreases by almost 5%, the exergy efficiency of the STU increases by 2%, and the electrical efficiency of the unit increases by 2.16% compared to the original scheme.

 

Keywords: exergy, steam turbine unit, exergy cost, efficiency, CHPP.

 

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References

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Received 17 March 2025

Accepted 15 April 2025

Published 30 June 2025